Why Human Brains Vary

Nice post.

I wonder if more cesarean sections are allowing for larger brains (or at least larger heads) than would be the case under natural conditions.

Also, the fact that Neanderthals seemed to have bigger brains than modern Homo sapiens seems to drive a nail into the coffin of brain size and intelligence.

Gould once wrote an interesting piece on women's brains, if you haven't already read it.

Deacon's book is excellent. A very good recommendation. It ages well, so it is not a problem that it is not super up-to-fate on latest research - the main points are still correct.

In a sense Deacon was/is so far ahead of his time that it's not really out of date. I'm very fortunate to have had the opportunity to work with him (teaching) for several years.

On Gould's essay: He makes a fundemental mistake in arguing that while females have relatively larger brains than males they are not smarter. Clearly, they are smarter. See:

http://scienceblogs.com/gregladen/2009/06/women_are_smarter_than_men_we…

What if women's brains are just more shapeable by their culture?

Greggo, I am not entirely surprised that you're arguing more for the cultural side, since you're an anthropologist, and perhaps I am also biased too since I argue for the biological side, but it appears to me that you have got this wrong.

Genetic variation does in fact explain brain differences. The question is by what mechanism.

Down's syndrome folks have trisomy 21. In every case of trisomy 21, it is linked to Down's syndrome. The severity varies with the person, but they have the same symptoms and only differences in degree, not type. This is not inherited from their parents, but it is a genetic defect caused by nondisjunctions in a gamete!

An inherited brain issue is fatal familial insomnia, which clearly screws up the brain.

So genetic variation DOES explain brain differences.

I think, in addition, you're pussyfooting a bit around how significant brain size is, which it isn't, within a certain range. Whether one race has a bigger brain than another is probably of no consequence if they are not much bigger, and intelligence is about quite a bit more than brain size.

And before anyone goes all 'WHARRGARBL DOWN'S SYNDROME ISN'T A DEFECT', yes it is if it produces shit that's totally maladaptive.

Katharine, before making insinuations that say more about the basis of your opinions, you might want to note that Greg is a biological anthropologist. You also seem to have missed the paragraph about genetic abnormalities.

He makes a fundemental mistake in arguing that while females have relatively larger brains than males they are not smarter. Clearly, they are smarter.

Sure. Just ask Harry Belafonte.

"You also seem to have missed the paragraph about genetic abnormalities."
Which is a total cop-out. The distinction between polymorphism and mutation is just whether we're talking about >1% or <1% of the population.
You say abnormality, I say variation. Mutations are normal.

Never mind about genetic contributions to possible rare cognitive phenotypes that are defects on an individual basis, but adaptations on a collective one. Or adaptive for specific environments, but detrimental in others.
There's no reason to think these sorts of mutations don't exist for cognitive features other than intelligence (been following the orchid vs. dandelion bit over at Neuron Culture?); so why couldn't they be there for any-cognitive-capacity-being-termed-intelligence-in-a-given-setting?
The more fundamental question is that, given the tremendous variation of mechanisms of cognition at both the genetic and environmental levels, is there anything common enough to different people's thought processes that defining intelligence is remotely useful?
None of which is to say environment can't be more important than genes; just that I don't think we can say something like "only people with e.g. Down's syndrome are limited by their genes". I think we're ALL limited; just in different ways. If you come up with a specific enough cognitive test, you'll find lots of 'normal' people with defective brains. It's the workarounds that are interesting from a neural signaling perspective.

I kept all my dead neurons in a shoe box with a list of withered connections.

-----
There wouldn't need to be umpteen million genes to specify how many neurons to create or how many interconnections. Only a few to say "go multiply" and "multi-connect" with many switches and genes for region control, couldn't there?

Thank you Greg for a very thought provoking post and I have to say I agree with you.

Whilst there may be some genetically determined factors, the motherâs diet, her general well being, her avoidance of alcohol and other substances, her access to fresh unpolluted air and water, and avoidance of harmful chemicals, radiation etc during pregnancy will give the developing brain a head start (excuse the pun).

Once born, for the developing brain to reach maximum potential needs a similar environment; high levels of nutrition and oxygen, well being, (stress and disease free) and a caring, loving environment, rich in language, education, creativity and culture. These optimum circumstances for the really intelligent brain are difficult to achieve in first world countries, let alone the third world.

"Dat's right! De woman is sma-tah, dat's ri . . ."

Oh, Sven has that covered.

*I can remember telling Ma how much I liked the way that man sings. She said she liked it too. Back when the song was new, she played that record nearly every day.*

I keep wondering if a brain of comparable capacity and expression to ours could arise from a sufficient number of connections between "artificial neurons." If some clever coding could replicate genetic instruction to create a sufficiently complex substrate might something astounding (and ultimately, sobering) happen?

What would it take to initiate the process? Would it be merely reaching some level of interconnectedness? Would it take some separate initiator or would an ego just fall out of the jumble? And if the ego did just "fall out" on its own, imagine the mad scurrying and editing and ass covering that would suddenly overcome the larger half of humanity!

Why, the implications for (discipline goes here) alone are staggering.

Nice post, Greg.

Becca, what percentage of cases of a variation have to lead to spontaneous abortion before it becomes abnormal?

Nice article. I am working on a write-up of how nitric oxide is related to neuronal remodeling. (hint, it is highly related)

I must completely agree with Greg that most variation in brain structure is not genetic. Monozygous twins can be discordant for autism. Monozygous twins can be discordant for anencephaly.

The term âenvironmentalâ needs to be understood to include the in utero environment also. There are a handful of in utero exposures that are known to affect long term brain function. Exposure to flu in utero leads to an increased incidence of schizophrenia, a number of teratogens cause autism (thalidomide, valproate), low folate causes neural tube defects. Exposure to stress in utero increases the incidence of autism too. Exposure to violence produces a more violent adult.

The âcycle of violenceâ is well observed. There must be physiology that transduces the signal of violence on the pregnant mother into a violent adult phenotype in the in utero fetus. That canât be genetic.

Genes simply canât determine brain structure with the kind of detail necessary to âcauseâ intelligence (or most other emergent properties of adult brains). Genes may produce a brain structure that is conducive to developing into an intelligent brain (of certain types) given the proper environment, but any genotype can also produce a completely unintelligent brain.

A lot of the adult phenotype is produced through epigenetic programming of genes during development. Epigenetic programming is known to affect the adult physiology of the heart, liver, vasculature, endocrine system, and a great many other things. Presumably it affects the brain as well.

Somehow, genes can code for species-specific differences in spider webs. A spider web is not so much an object as a very complex behavior. This behavior is somehow stored in a spider's nervous system. Somehow genes direct the development of that nervous system in such a way as to store it. I don;t know how many neurons a spider's got but I bet not that many.

Until we can figure out how genes do stuff like that, it seems way premature to decide what they can and can't do in human brains.

For one, it's not the penetrance of the genotype, it's the prevalence of the phenotype that would make it abnormal (let me know if that's too genetics jargon-y; I don't know what your background knowledge is on this topic).
For another, as you point out, it's not *really* simply the prevalence of the phenotype, so much as whether we decide the phenotype is remarkable and bad, that cause us to call it abnormal.
However, recall that spontaneous abortions are actually an exceedingly common outcome in early pregnancy- I'm not sure it's because anything "abnormal" is happening (I'd bet that many in the world at large are probably a reflection of the actions of highly adaptive genes getting rid of a fetus because a certain threshold of favorable conditions are not met).
Personally, I only accept "normal" as a statistical term. It's a philosophical position necessitated by my own freakishness.

Sven, the process of creating a spider web isn't that complex, although the result is pretty, and some of the variety is caused by variety in the shape of the spiders. As for the argument from personal incredulity, maybe you should read the book before deciding what is presumption.

When I think about the apparent sparseness of complexity in genetic coding as compared to the much greater level of complexity of brains in general I get the impression that the genes don't accomplish the making of a brain but rather create a potential for behaviors that by their actions accomplish the task.

Maybe I'm thinking along the lines of Conway's Game 'O Life but there are certainly systems less complex than, say, a centipede's brain that show amazingly complex behavior. Small internal combustion engines, stringed instruments, slime molds, flocks of birds and the brains of most animals are all relatively simple systems that display a variety of behaviors that aren't obvious or expected upon inspection of the parts and configurations.

I keep thinking about how biology is chemical based. Chemistry falls out of physics and physics seems to fall out of the fabric of the universe. You can tell that I'm not a scientist (engaged enthusiast would be more apt) so there are wide gaps in my grasp of subtleties that others here eat with breakfast. The notion that brains and minds exist seems no more (or less) astounding than does the existence of particles, elements, energy and empty spaces. Given the building blocks and a large enough workshop it may be only a matter of time before some system becomes self aware. At least, it's happened in this neck of the woods, arm of the galaxy, warm, wet planet.

Katherine, my name is Greg, not Greggo, and I am a biological anthropologist which does not in any way predict that I would argue "the cultrural side." Nor is my argument anything like what cultural anthropologists (which are not biological anthropologists) say, to my knowledge.

Yes, as I have acknowledged, broken genes can break brains. That is not relevant to this discussion at all, though at this point in the argument it often is dragged out of the closet!

I don't understand the point you are making about brain size. I did not discuss the brain size vs. intelligence connection or lack thereof.

Hey, go read Deacon's book. He's a biologist. Neurobiologist, actually.

Oh, and another thing Katherine, as a biologist you should know that it is inappropriate (i.e. kinda dumb) to declare that we definitely know that there is a genetic-phenotype connection and in the same paragraph declare that we merely need to discover the mechanism.

Genetic determination of phenotype is a mechanism. You can't say "oh, yes, we know there is a mechanism. ... we just don't know what the mechanism is." without revealing that your basic approach is ... what... religious? predetermined bias? Unmitigated BS?

I'm sure you didn't mean to say what you said. We are looking forward to the correction. Thank you very much.

Beckee-baby, you've got to be kidding. Trisomy is not a mutation, sweetiecakes. It's a chromosomal disjunction.

(Ooops, did I overstep my bounds there in diminishing the person I'm arguing with by using what sounds like a pet name that I don't have permission to use?... Bwahahahaha!)

And no, it is not a cop out. Broken systems, especailly neural systems, have historically informed us about how brains work to a useful but limited degree, but typically then have led us astray.

Hey, read the book. Terry uses somme brain 'abmormality' insights in the book.

daedalus2u:

The âcycle of violenceâ is well observed. There must be physiology that transduces the signal of violence on the pregnant mother into a violent adult phenotype in the in utero fetus. That canât be genetic.

One study (regretfully unpublished, I think) looked at head injury in a very specific population. The study was able to document a few (two/three?) generations of psychopathy linked to head injury, passed on from father to son. The starting points for each lineage were mutli-violent murder felons labled as psychopaths in a major penitentiary. Some of them had dads who were also psychopaths, and grand dads as well. If you just gave the data as "trait present or absent" it would resemle at first blush a "familial" bias and all the TEH GENES DAYZ EXPLAINZ EVERYTHINGZ" wonks would call it genetic. But the mechanism of transmission was beating your son enough times that he obtained head injuries that fucked him up for life.

It certainly makes a lot of evolutionary psychology look silly, when the mind is viewed this way.

I had a hunch this would turn into a gender thing soon. I am curious what greg has to say about that (well, I am expecting posts about it, considering how the comments are starting to sound).

skeptifem: About which, evo-psycho or the gender thing?

I'll assume the former for now.

Modules are great ideas. The brain has modules. Like the module to read and the closely related module to write. How did they get there? Not the way the Evo-psychos would presume, I think!

Sven DiMilo: There has been a fair amount of research on how genetic variation causes things like spider web building (or foraging by fruit fly larvae, etc.) It is not unexplored territory.

A few points should be made:

Yes, there are almost no neurons in a spider or a fruit fly larva. More neruons are used to remember a bad dream in a human than to program most of the behavior of one of those larvae. The neural organs are not the same ... at all ... mammalian cortical tissue. Even bird cortical strucures (birds are the only other creatures with "neocortex" are different enough from mammalian in their ontogeny that they serve as poor models.

You see, it is almost like neurons allow the formation of an entirely novel set of structures that were difficult (but not impossible) using proteins or non-neural cells. Once these started to 'deploy' in an evolutionary sense, this new tissue type formed many different organs. The nerual cortext is not comparable to the ganglia of spiders any more than the tetrapod skeletal system is comparable to the rasping organ of a slug or the shell of a snail.

So the spider analogy is barely useful as a philosophical tool but falls way short looking at the biology of the problem.

And, as Stephanie pointed out, spider webs are actually simple.

Where did I say trisomy is a mutation?
I said mutations are normal, and that I favor the hypothesis that different people have genetic differences that limit their cognition (much more broadly than trisomy).
If you like, we're all a little broken. Or, more accurately, we all have different shapes for our building blocks. That we mostly get useful and analogous structures out of them is a minor miracle (in a totally non-religious way).

Also, I put forth that it's bad form to call me pet names to make a point to Katherine, unless you're referring to your legacy as greggie, in which case you should make that explicit, for those following along at home.
As a random side note, I went home for birthdays and everyone was calling me becky. It's weird how there's now that extra-split-second of pause in reaction time where I try to figure out who they are talking to.

I read the first few pages of Deacon on Amazon. That's one I will NOT be getting from ILL. It's painful. Incredibly, horribly, awful. Full of so many preposterous pompous presumptions in one page I can't imagine why you even brought him up. Seriously, WTF??

Also, I put forth that it's bad form to call me pet names to make a point to Katherine, unless you're referring to your legacy as greggie

I was indeed doing that, and further, in reference to the discussion between Stephanie and Bryan on QM.

You telling me that I need to be less obscure in my discourse is making me LOL, by the way.

So, other than some religious belief in genes, and putting aside Down Syndrome, what is your evidence that allelic variation across humans explains, say, IQ variation between populations? I ask because what you are saying in your comment, given the context of the comment, clearly intends to support that argument. So let's hear it.

I'm going to put this another way so even the dim can understand. (Sorry, The Vikings have put me in a pissy mood .... grrrrr)

Saying that genes shape brains in a way that would cause significant variations in intelligence (like, enough to qualify/disqualify one for a job at a corporation, as our friend Bryan claims would be the case with IQ's that vary by 10 points or so) is like saying that the avialable palate of colors and size/shape of canvass determines the difference between a Picasso and a Miro. Yes, the colors and canvases are relevant in some way (Miro was more into primary colors and large canvases, for instance) but the paints to not make the painting and the alleles do not make the thinking brain.

The way human cortical structures (our thinking brain) forms is from information provided primarily by the environment. This is what people who study human brain ontogeny have known for decades. Any theory of brain variation that ignores this is perilous.

I didn't say you shouldn't be obscure, just that this particular reference ought to be explained. And the intention was to be amusing.

ANYWAY. One of my points is that I don't see why anyone is talking about IQ variation- it simply isn't that interesting a metric. Further, as other people have pointed out, and I tend to agree, the culturally convenient groupings of populations by 'race' is rarely an accurate reflection of genetic status. So I am not making any claims whatsoever about the allelic variation and IQ variation between identified populations. I will thank you to not tell me what arguments I am clearly intending to support.

Further, it is not a 'religious' belief in genes to hold the view that function follows form. Basically, if your proteins are shaped differently, your neurons will get laid down differently, and you'll think differently. (thus my analogy with the building blocks). That isn't to say most thinking differently is the result of different shaped proteins, though I suppose it could be for all you or I can prove.

"There certainly are genetic abnormalities that cause abnormalities in human brains, but just as a gene that cause a person to be born without legs is not assumed to have alleles that affect running abilities, a gene that if "broken" causes a "broken" brain can not be assumed to be a gene with allelic variation that affects day to day normal brain function. Genes don't work that way, bodies don't work that way."
So a genetic abnormality, like say an excess of DYRK1A due to trisomy 21, would never be seen for a gene for which certain SNPs are associated with measurable personality differences*, right?

*like conscientiousness(Mol Psychiatry. 2008 Oct 28.
Genome-wide association scan for five major dimensions of personality.
Terracciano A, Sanna S, Uda M, Deiana B, Usala G, Busonero F, Maschio A, Scally M, Patriciu N, Chen WM, Distel MA, Slagboom EP, Boomsma DI, Villafuerte S, Sliwerska E, Burmeister M, Amin N, Janssens AC, van Duijn CM, Schlessinger D, Abecasis GR, Costa PT Jr.)

the paints to not make the painting and the alleles do not make the thinking brain.
Yes, but have you ever tried to make a proper great lakes sky without colbalt blue??!!!

Does the average neuron really have up to 2000 connections? O.o

No.

You know, the 50 to 100 billion neuron number is probably good (though even 10 billion would be imporessive) but the number of connections is from a different source and now that you point it out it is probably bogus. I was hoping Joe Marcus would show up and tell us about this. He knows more than anyone (not kidding here, he does) about how many neurons and connections there are in mammalian cortex, being the only person who has done a large scale study of it.

You know, the 50 to 100 billion neuron number is probably good (though even 10 billion would be imporessive)

But do they rub together?

I need to save this post and flash it at the next person who pretends interests and aptitudes are not influenced by what children are exposed to or encouraged to/rewarded if they participate in. A lot of people really seem to believe that interests form in a vacuum.

I believe that there is a definite genetic factor to intelligence, though I don't buy the IQ stuff (culturally biased, and measures only IQ). This doesn't mean that I believe that races have different intelligences, or that races even exist.

Assuming human intelligence is an evloved trait, and that inheritance is genetic, one must find that intelligence is genetic. I completely agree with you that the vast majority of differences in intelligence are explained by environmental factors such as nutrition and experience.

There is a bias against research into intelligence and genetics which was commented on in my neuroscience seminars - it's a touchy subject area, and there are certainly some who are biased in their research (and I freely confess my lack of knowledge of the area - my background is in neuroscience, but I never really studied intelligence apart from it coming up in a few courses).

I do think it's unfortunate that any bias exists among researchers, and that students need to be cautioned about studying any aspect of psychology/biology due to the political/sensitive nature of the area. Ideally the subject would be studied without any special concern, as just another topic, providing potential insights into how the brain works and how we evolved.

Assuming human intelligence is an evloved trait, and that inheritance is genetic, one must find that intelligence is genetic.

This is the kind of belief that becomes "conventional wisdom" because it just sounds plausible and "everyone says" it and "it stands to reason, don't it?" and too few people bother to test it or ask whether it's been tested. Sort of like that old "conventional wisdom" that sex-ed encourages promiscuity -- it SOUNDS plausible, even irrefutable, but actual observation shows it just ain't so. Yes, given what we know of how genes work, it certainly is possible, in theory, for intelligence to be determined by genes; but where is the actual research and observation showing real, significant specific variations determined by genetic factors?

becca writes:

Basically, if your proteins are shaped differently, your neurons will get laid down differently, and you'll think differently.

Oh dear Lord, no. An onion has way more genes than you do. There isn't nearly a one-to-one correspondence between what you are describing - the genes responsible for neuron formation in development - and the mechanisms responsible for differential survival of particular neurons, which is a big part of what determines the most robust, best-connected, fastest-acting neuronal pathways, and thus is responsible for a great deal of what people refer to as "intelligence."

Of course there are genes responsible for neuron formation in development, but any significant mutations there are far more likely to show up as wholesale problems than as anything subtle enough to account for a couple of questions' worth of difference on an IQ test. (Thus Greg's admonition that problems such as Down's Syndrome aren't that closely related to the topic of genetic determinacy of intelligence within the "normal" range.)

Raging Bee:
Yes, given what we know of how genes work, it certainly is possible, in theory, for intelligence to be determined by genes; but where is the actual research and observation showing real, significant specific variations determined by genetic factors?

I agree that actual research would be great, but what would such work entail? Intelligence in non-humans is hard to define (heck, it's hard in humans), and we can't go doing selection experiments on people, leaving us with quasi-experimental results at best.

Before any examples of evloution were actually observed in laboratories the principles and the observation of evidence supporting the theory from different lines of evidence were enough to support the theory. I do think theere is ample evidence of the changing brains structure/size of hominoids to infer that at least that aspect has evolved, and there is evidence that humans are more intelligent (at least as we define it) than the creatures we are most related to (chimpanzees, for example). Attributing some difference(s) in intelligence(s) between humans and chimpanzees to genetic differences doesn't sound like it is reaching to me. It isn't just empty theorizing - we share a common ancestor with them, and something happened "on the way" to being human (not implying a directional evolution, but in retrospect) that we can see in the fossil lineage. What that thing would be a great scientific mystery to solve (and hopefully we will solve it), but that it has a genetic component doesn't seem to me in the same vein as your sex-ed example.

It's not just plausible; we have a starting point (some shared relative of ours and an example species, like a great ape) and two end points, with differences that are attributed according to theory by selection pressures, and that result largely from genetic change. To accept that most of the changes are genetic but exclude intelligence from those changes seem to me the odder of the two choices.

Assuming human intelligence is an evloved trait, and that inheritance is genetic, one must find that intelligence is genetic.

Here we have a basic misunderstanding. Let's take a very simple case: Style of earrings. In order for there to even be earrings, there must be ears, and indeed, genetically speaking there must be ear lobes. Some people don't have ear lobes because they have some crazy strange gene. So would we then say that style of earrings is genetic?

No.

We we ask "is intelligence genetic" we actually using that for a short hand for "is variation in intelligence caused by underlying allelic variation in genes"

There need not be. We should only make the claim if there is evidence for it, and if there is some evidence for some genetic factor controlling variation in intelligence, it is not appropriate (i.e. scientifically wrong) to then make the leap that all or most variation in intelligence (or as you point out that racial variation in intelligence, etc.) is caused by genes.

Becca:

"Basically, if your proteins are shaped differently, your neurons will get laid down differently, and you'll think differently."

Really? Huh. New theory.

Now let the real Becca out of the closet and untie her.

I can't let the real Becca out- I didn't hear the safe word.

Let's take a very simple case: Style of earrings. In order for there to even be earrings, there must be ears, and indeed, genetically speaking there must be ear lobes. Some people don't have ear lobes because they have some crazy strange gene. So would we then say that style of earrings is genetic?

I think this is a little unfair as a comparison - style of earings may even be heritable, but they are a peculiarly human acoutrement with no analogues in other species. Intelligence is something that occurs across species. I was talking about the evidence of intelligence difference across species.

We we ask "is intelligence genetic" we actually using that for a short hand for "is variation in intelligence caused by underlying allelic variation in genes"

Agreed, that seems like a fine definition. What I was trying (perhaps clumsily?) to say was that we have evidence that suggests that species differ in intelligence, and fossil evidence that suggests a gradual change in the human lineage in the organ suspected to house intelligence, as well as a diffrence in intelligence between humans and their closest relatives. These closest relatives of humans have brains more similar to early human relatives than late human relatives.

These changes are accepted as being inherited (hence the ability to change over time in a manner that seems directional, and was likely selected for.) This suggests that at some level, intelligence is likely to be genetic.

I am not saying that it's the case that any significant proportion of human variation in intelligence is genetic. That is an interesting question, and unfortunately one that is fraught with difficulties in addressing, not the least of which (from examples of research) is individual bias influencing the attempts to answer it.

It is possible that human variation in intelligence has no genetic component (aside from disorders) - perhaps we went through a bottleneck and are so completely conserved in this area (and/or changes are so deleterious) that there is essentially no variation. Or perhaps it does have substantial variation - but not across "racial" lines, merely having a nice distribution in all populations.

I certainly don't want to be miscast here - I was bringing up the issue to set a sort of lower bound on inheritance - there must be some degree of genetics involved, or it wouldn't have been an evolvable trait. If people wish to say that it is idle speculation to assume that intelligence did evolve at all, I can't help that. I don't think one can discount all inheritance and would be very interestied in knowing more about it, though I too am very suspicious of anyone claiming to have found racial differences.

On a different note, I do like how simple systems can provide complex seeming results - spiderwebs, fractals, attractors and so on. One question is how complex a system is needed to generate the apparently complex thing we call intelligence; I've been having fun reading Hofstadter's I am a Strange Loop, and I wonder how complex intelligence really is. Is it possible that some very simple rules are generating what appears to be a complex system? His observation that we tend to infer desires into systems with observable feedback (like a top maintaining its spin) is interesting, in that it takes very little for us to begin such attributions; a top that is jostled is easily said to be "trying" to remain upright. If we are fooled by inanimate systems into lending them this illusion of consciousness and desire, what level of complexity is truly necessary to seem "intelligent" in the first place?

Becca, try "banana." Or "avocado."

Agreed, that seems like a fine definition.

It is not a fine distinction. It is one of the most fundamental errors people make in trying to grasp things like heritiblity and selection.

I am not saying that it's the case that any significant proportion of human variation in intelligence is genetic.

Why any at all, other than variation caused by genetic disorders?

It is possible that human variation in intelligence has no genetic component (aside from disorders) - perhaps we went through a bottleneck and are so completely conserved in this area

Here you are assuming that there is a way for there to be variation caused by genes. You tossed out my analogy of earrings before you understood it. In my analogy, assume that earring style is caused by earring manufacturers not the alleles of the wearer, to make the thought experiment even more fool proof. It is not the case that there is no allelic veriation causing significant intelligence variation in humans because it is a trait that went through a bottleneck. It is the case that very little variation in human intelligence can because by genes because human intelligence emerges in a different way than eye color.

The fact that the human brain has evolved does not obviate this. Again, go back and try to understand the earring/earlobe parable.

there must be

there must be

there must be

there must be

there must be

say it as often as you want!!!11!! OH man.

I know that you are understanding this better than most people do. I get that there is seemingly a conflict between the idea that a trait evolves and the idea that allelic variation (which we associate with evolution/selection) is uninvolved. But there are lots and lots and lots of "traits" where 100% of the observed reaction norms in day to day populations is not allelic.

One question is how complex a system is needed to generate the apparently complex thing we call intelligence

According to the actual evidence we seem to have, a fairly simple set of growth and directionality rules cause patterns of extension and exploration among neurons (not "laying down by proteins") which result in a brain capable of doing little more than keeping a heart beating and that sort of thing. And even that information comes not entirely from genes but also from the fact that the heart exists. Or the eyes, or ears, or olfactory bulbs, etc. Then, what we think of as the highly complex thing called "human intelligence" is "coded for" by genes which make a very simple blank pattern that has no inherent intelligence whatsoever, and the complex nature of (and interaction with) culture and environment.

And when I say "culture" I simply mean the vast field of information about the world we live in that is the outcome of human behavior, I'm not trying to define it in any particular way.

I dunno...

There aren't enough genes to deterministically control the placement and connection of a hundred billion neurons. The most the genes can do is establish general rules for the construction of a brain.

Environment must play a massive roll in this. Poor nutrition obviously can have an effect. The type of learning environment will have an effect.

But even so it seems unlikely that there would not be genetic differences that have reasonably large effects. In fact the claim that there cannot be seems kind of strange. I mean what other measurable thing would you make this kind of claim?

Take basketball playing ability. Would anyone claim that M Jordan has no genetic advantage over most of us? Would anyone really claim that we all started as a basketball blank slate?

But so what? We are all individuals. Short, tall, fat, thin or whatever. Environment has an effect on all of these. So do genes. You treat people as the individuals that they are.

I am not saying that it's the case that any significant proportion of human variation in intelligence is genetic.

Why any at all, other than variation caused by genetic disorders?
Because there is evidence that allelic variations do affect cognitive functions, whether that be in the form of sensitivity to environment in determining risk of depression (you *did* read the orchid vs. dandelion thing, right?) or particular aspects of whatever it is we're measuring in personality tests (e.g. "conscientiousness"). Because this IS how genes work. It IS how bodies work. They are highly variable. Little differences- alleles, CNR, SNPs, mutations- add up to enormous diversity.
Look, of course intelligence isn't eye color. It's an extremely complex trait of many genes, highly modified by the environment. That doesn't mean there isn't a genetic basis. Do you know ANYTHING about molecular epidemiology of cancer susceptibility?

"According to the actual evidence we seem to have, a fairly simple set of growth and directionality rules cause patterns of extension and exploration among neurons (not "laying down by proteins") which result in a brain capable of doing little more than keeping a heart beating and that sort of thing."
And where, pray tell, is the information for these growth and directionality rules kept? There's a blueprint, but no designer (since we're all operating off the assumption of no god here)?
And yet Hox genes, and all the other proteins that I was taught *do* affect cell polarity and differentiation, and therefore cell development and therefore neuronal connectivity, those proteins are all irrelevant to the magical intelligence that is completely divorced from the physical reality of neurons and brains?
Religious faith in dualism between mind and body does not become a skeptic.

And, as an aside, why do you assume any neurons are needed to keep a heart beating? Cardiomyocytes will beat in a petri dish.

Stephanie- Avacado? I'd rather go with Hyacinthe.

turnike,turnikeler,turnike sistemleri,turnikeli geçiŠsistemleri
Thank you very much for this great blog. How you can pr 7 this blog?
I see your other blog. It is too high pr.

Actually, ppnl, with this kind of a plastic, self-pruning and organizing system, it's a bit of a jump to argue that any genetic differences would result in large-scale effects. In a system that has--as its primary characteristic--reactivity to environment, differences would tend to get buried in the noise.

It is the case that very little variation in human intelligence can because by genes because human intelligence emerges in a different way than eye color.

Ok, I think I get at least one of your points, which is that alleles don't exist in a one-to-one relationship with the traits observed - and that I do understand.

I know that genes and the environment interact to produce phenotype; even in instances of strong, single gene effects like phenylketonuria, a dietary approach can limit the effect of this genetic change. There is a tendency for more complex phenomena to have more of an environmental effect I suspect, in that there are more areas for deficiencies or changes due to environmental factors; height is an example of an inheritable trait that is polygenic, but also strongly influenced by environmental factors. And the coloration of flamingos depends on the genes of another creature in the food supply; vary the shrimp colouration (albino shrimp?) and you vary the coat colour of the flamingo without needing to alter the flamingo's alleles at all.

I get that there is seemingly a conflict between the idea that a trait evolves and the idea that allelic variation (which we associate with evolution/selection) is uninvolved.

Indeed - maybe I'm missing something here. I'd appreciate being brought up to speed if that's the case (honestly!). I read as much as I can on evolution and it's something I enjoy learning about.

I can believe that the vast majority of variation is due to environment, but if intelligence was selected for (and it appears to have been), as much as you object to my saying "there must be"; I can't help but think that there must be a genetic component.

But there are lots and lots and lots of "traits" where 100% of the observed reaction norms in day to day populations is not allelic.

Well yes, but are they traits that are selectable? You can't breed for a given pattern of dots in a dalmatian or pattern of splotches in a calico cat. I can think of many cases of variation without allelic change - but they couldn't be selected for. I have no issue with the fact that variation can exist without allelic change, nor with the fact that alleles can change without observable effect.

I do admit that there I have as an assumption that humans did evolve intelligence - it seems well supported by evidence. I'd need some evidence that it isn't the case to be able to let go of that assumption.

As for the complexity required for intelligence; I wasn't talking purely about laying out a rough plan, directing nerves to connect, but also the pruning of these nerves in such a way so that intelligence results. The number of connections we make in development is as you most likely know orders of magnitude more than we end up conserving, and the process of paring these connections down is likely critical, and may be more complex.

OK, we are getting off track again. I am not saying that there can not be genetic factors that affect the brain. I am saying something quite different and quite specific, and the differences matter.

First, the assertion that "there must be" or "there certainly is" or "of course there is" X,Y, or Z are usually linked beyond the assertion to a series of other specific assertions. Like this one: Genes determine intelligence, intelligence is measured accurately by IQ, and IQ is shown by hundreds of studies to be different based on race (race = "oriental" "black" and "white") and so on.

I allow for the possibility that something like IQ-measured "intelligence" is affected by genes, but I see no evidence for it. Yet, Becca insists that the way the brain works is affected by allelic variation because depression and other "disorders" are fammilial and there is a well demonstrated genetic link (not just a familial link). But do you (Becca, others) understand that linking MDO or depression, etc. to genes is an entirely different question than intelligence, and is an entirely different question than linking inherited states of the brain to race?

If you need to believe that intelligence is determined by protein shape laying down neurons in a "more intelligent" way in, say, white brains than in, say, black brains ... because this belief makes you feel better, or simply because it is the received knowledge you grew up with, or because you've been convinced that "if you don't understand that this is true than you don't understand evolution" and you want to appear to understand evolution, then it will be very easy for you to take chromosomal disorders or inherited psychological conditions and map that on to individual of population level IQ values.

In the case of being Becca, you are kind of stuck, because you have an (inherited?) pathology of having to disagree with ... people with Y-chromosomes? People named Greg? Bloggers? whatever... So Becca, you are going to have to accept the fact that skin color predicts the presence of alleles that determine IQ to the extent that depending on the skin color of a sample of people, their average IQ can vary by as much as 35 points. Because THAT is the position I'm arguing against. So, start reconciling yourself to that position.

Now Becca will start with the absurd sophistic retorts (No, greggie, when you said X you meant Y and therefore Z and on and no) which shall be summarily ignored.

Uffda.

But even so it seems unlikely that there would not be genetic differences that have reasonably large effects.

"It seems unlikely?" Is that all you've got? Look at the available evidence and tell us: what "reasonably large effects" are there, and what evidence is there that they are the effects of genetic differences?

In fact the claim that there cannot be seems kind of strange.

It's not so strange when you consider all the evidence that supports it.

I mean what other measurable thing would you make this kind of claim?

A measureable thing that acts a lot like intelligence? Just a guess.

Argument from incredulity is a logical fallacy. And "it seems unlikely" and "it seems kind of strange" and "it seems reasonable to suppose (without verification)" are nothing but arguments from incredulity.

This article, just published, says up to 10,000 connection per neuron.

http://futurity.org/top-stories/mature-brain-recycles-embryonic-circuit…

Becca, you've read the orchid/dandelion stuff far enough to know that it doesn't affect intelligence, yes? Depression centers around other parts of the brain, with other patterns of development. It isn't all this plastic, or we'd be born requiring life support until we learned how to breathe.

Stephanie

I don't see much difference between the brain and the rest of the body in that respect. The body must also have "reactivity to the environment". The body has specific structures that are useful for interacting with the environment in specific ways.

Same thing with the brain. If the brain started as just a homogeneous collection of neurons it wouldn't need thousands of genes to code for it. It needs those genes to create specific structures to react to the environment in specific and complex ways. Slight differences in the genes can cause slight differences in those structures.

With many thousands of genes involved it seems genetic drift alone would create massive genetic diversity.

And I do expect that difference to be buried in the noise if we still lived in the environment in which we evolved. But we don't. We live in an environment in which we are more likely to have similar levels of nutrition and access to education.

And thats the strange part. The more egalitarian the society we live in the more visible the genetic differences will be.

Even so they seem fairly small.

ppnl, with all due respect, you're way off in your comparison of the brain to the other parts of the body. You're getting into "not even wrong" territory. You're also out there on modern versus ancient inequality. The kinds of intrasocietal environmental inequalities we see today are a very modern invention in terms of human evolution.

The way human cortical structures (our thinking brain) forms is from information provided primarily by the environment. This is what people who study human brain ontogeny have known for decades. Any theory of brain variation that ignores this is perilous.

But this is misleading, in that it implies genetics aren't also part of the picture. Of course environment has the most influence on the structure of the brain, the impact of genetics doesn't have the sort of time frame that the environment does. That doesn't mean that genetics can't have a rather profound effect on neurological function.

There is increasing evidence that a propensity for certain neurological issues is genetic, while the actual expression of those neurological issues are triggered or not, by environmental input. There is also evidence to suggest that genetics influence our personal strengths - not intelligence persay, but what we are actually good at.

I really don't have the time to go into this now - we are heading to a challenger simulated mission to mars right sudden here and I really am devoting most of my time while they are here to my boys. But I would definitely like to address this further in a couple of days, with citations.

The bottom line though, is that the evidence would suggest that genetics has a rather profound impact on how a given brain is likely to develop, while environment and environmental input actually does the shaping.

Assuming human intelligence is an evolved trait, and that inheritance is genetic, one must find that intelligence is genetic.

Greg made a good comparison to height, let me make another one. Is a height of 1.783427 meters genetic? Is having 4,305 hairs growing on your head genetic?

To some extent, height and hair growth is genetic; however genomic DNA does not exert control over height to 1 micron precision or hair abundance to single strands.

Brain size certainly has genetic components. But what part of the brain is big in the adult depends on the details of neural proliferation, differentiation, and apoptosis; how the different parts work together depends on neuronal remodeling, all of which is activity dependant. A big visual cortex might give you good vision and might help you read fast, but you canât speak with it. A big motor region might give you good eye-hand coordination but you canât smell with it.

We know there are individuals with extreme, genius level intelligence in some areas but with profound weaknesses in others.

http://en.wikipedia.org/wiki/Kim_Peek

How do individuals such as Kim Peek fit into a âgenetics controls intelligenceâ conceptual paradigm? I donât think they do. If you then say that the âgenetics controls intelligenceâ paradigm only works for ânormalâ individuals, then by what basis is what is ânormalâ defined? The circular definition that something is normal because if fits the normal paradigm? No, that is fail. As you add more and more details, you will eventually get to a group size so small as to be useless.

It seems that the major differences in Kim Peekâs brain were the result of what would otherwise be called âdamageâ, that is a disruption of the ânormalâ neurodevelopmental paradigm. If âdamageâ or âdisruptionâ can cause superior performance, by what basis are we calling it âdamageâ? Degraded performance in one area (motor ability to button a shirt) may free up brain volume to use for other things (remembering information). That trade-off is considered a deficit when testing for shirt-buttoning ability; it is considered a superior ability when testing for sports trivia. Assigning an arbitrary linear weighting and averaging those two abilities is useless, foolish and wrong.

The observation that there are people like Kim Peek, illustrates what might be expected from cognition as an emergent property of neurodevelopment along the lines that Greg has outlined. It is not consistent with a âgenes control everythingâ paradigm. There are no genes for ability at reading because reading is a very recent development. There are no genes for baseball trivia.

The problem with considering intelligence to be primarily genetic is that there are very many environmental factors that affect adult intelligence, some affect it up, some affect it down, some affect is sideways. Some do all 3 but differently at different times. We know that adult intelligence is an emergent property resulting from the interactions of multiple non-linear coupled phenomena (genes and environment). Such systems are inherently chaotic, that is they are fundamentally not predictable long term. They are sensitive to differential changes in initial conditions, the âbutterflyâ effect. Certainly neurodevelopment in utero has to be chaotic in a mathematical sense. That is why differential environmental effects in utero can produce monozygous twins that are discordant for anencephaly. If differential environmental effects can produce such extremes of phenotype, presumably they can also produce less extreme differences.

The argument that because intelligence must have evolved, that present differences must be due to genes also doesnât work. The context those genes evolved is very different than what is going on now. Intelligence evolved under conditions in âthe wildâ where food was scarce, disease was common, and physical survival was difficult. A large brain with âplasticityâ was likely more important than a large brain with âintelligenceâ. A brain that can adapt to changing circumstances is a lot better survival factor than a brain with only the hammer of âintelligenceâ. We may use that plasticity now for learning information, what did that plasticity evolve for in the first place? Most likely to learn detailed social information; not âbook learningâ (because there were no books).

The fundamental concepts of IQ, and g, have not been demonstrated to actually exist and to then actually have the properties that proponents claim. The idea that there is such a thing as a unitary âintelligenceâ, a âgâ, is a myth. A statistical myth as has been demonstrated many times, going as far back as EB Wilson in 1928. People working with g, are doing what Harriet Hall (of Science Based Medicine) calls âTooth Fairy Scienceâ. Feynman called it âCargo Cult Scienceâ. It is going through the motions of using scientific methods, but without the intellectual honesty or intellectual rigor to consider the fundamental aspects of what you are doing, and are those fundamentals correct or not.

I think the reason that the field of genetics and intelligence is considered âtaintedâ is because for the most part it is tainted. It is generally understood that scientists working in a field, those who know the most about it, must also be the ones who are most skeptical about their findings and who must be the most rigorous in trying to falsify their hypotheses. When this does not happen, then those who are not expert in the field have the right (and obligation to self) to be even more skeptical of results in that field. When the peers in the field (i.e. those that do peer review), are insufficiently rigorous, then that field is lost until a new group of peers arise that are sufficiently rigorous. There are many things that are known to affect academic and intellectual performance, and it is known how to improve them. Why all of those are ignored and the focus made on a mythic g (which supposedly cannot be changed) is not a question about the scientists, but about the motivations of the scientists choosing what to study and how to study it.

If you want to be a scientist, and to do good work, you canât work with a mentor who is a member of a scientific cult. You canât get funding in a field where all the peers are members of a scientific cult. You canât get papers published if the reviewers are members of a scientific cult. So what do you do? You pick a non-cultish field and avoid the cultish ones. If you have good ideas that canât be published because the peer reviewers are caught up in their cultish groupthink, you publish it on a blog as the writer of âg, a statistical mythâ did.

http://cscs.umich.edu/~crshalizi/weblog/523.html

Like this one: Genes determine intelligence, intelligence is measured accurately by IQ, and IQ is shown by hundreds of studies to be different based on race (race = "oriental" "black" and "white") and so on.

Well, that's just silly. Yes, of course there are idiots who spout that kind of garbage. The racist "logical" chain is broken in several places, it doesn't matter whether the first argument (intelligence is genetic) is true or false, the whol argument is bogus.

Raging Bee

Yes "it seems unlikely" is pretty much all I have. And yes an argument to incredulity is a logical fallacy. But I didn't intend it as a logical necessary conclusion. Just an expectation based on a limited understanding of how the brain is built.

You have many thousands of genes controlling the construction of the brain. It is difficult to believe that there is not substantial genetic differences in any aspect of its performance.

How is performance on an intelligence test different from performance on a basketball court?

As for differences in intelligence between races I don't know. There is no reason why not in principle. It wouldn't really surprise me. But it seems likely to be small compared to the differences between individuals which is in turn fairly small. And it is likely to be lost in the noise caused by the necessary difference in environment.

A more important question is who really cares? Is there any good reason that we should be obsessed over such small theoretical differences?

DuWayne, your genes totally affect what you're good at. Exhibiting coordination means you're likely to play more sports, which means you're developing spacial skills. Having two X chromosomes affects your access to math-rich environments, and having one X and one Y can affect your access to verbally rich environments. There are plenty of genetic effects, but they're not acting directly on the brain.

Since you won't bother looking up the orchid/dandelion bit: The serotonin pathway contains genes that have polymorphisms. One particular allele of one gene is associated with *susceptibility to environment*, not with depression per se. That is, people with this allele raised in abusive environments are more likely to get depressed; but people with this allele raised in good environments are more resistant to depression. I fail to buy the argument we must dismiss such variations as 'defects'.
Given the intensely complex and highly environmentally influenced nature of emotional temperment, I think it is reasonable to draw a parallel between it and cognitive capacities I would refer to as intelligence (which might include, but are CERTAINLY not limited to, those measured by IQ tests).
I don't buy that personality tests measure personality, or intelligence test measure intelligence. But whatever those test measure, we will find meaningful correlations with outcomes on those tests and different genetic alleles.
So yes, I GET that the cognitive variations people have that are currently known to be correlated with allelic variation are not the same as the cognitive variations that affect cognitive speed or flexibility or performance on IQ tests... but I don't think you GET how far-fetched it is to say that genes influence all these other things (albeit in a complex way with critical environmental contributions), but NOT intelligence.

And yes Greg, of course that is an "entirely different question than linking inherited states of the brain to race". That is the POINT. In arguing against the link of inherited states of the brain to race, you have gone out on a limb and stated things about how Genes Are and Bodies Are that are simply NOT TRUE. I am not calling bullshit on your entire argument, and as far as race and IQ we're on the same side (albeit for slightly different reasons)... but you don't get a pass to make up misleading bullshit just because you're on my side.

ppnl: I don't see much difference between the brain and the rest of the body in that respect. The body must also have "reactivity to the environment". The body has specific structures that are useful for interacting with the environment in specific ways.

Same thing with the brain.

It is true that a number of different biological systems grow/develop in response to the environment, etc. But "Not seeing that much difference" is more a problem with what you are seeing than what is there. Neural systems are famous for being explorative, adaptive, sculpted, and so on orders of magnitude more than other cell systems. But yes, exploration and adaptation in growth and development and communication, and feedback from communication to exploration growth etc. are common to all cells, but neural system have at least one or two levels of functional connectivity added to this.

It is a little like the difference between a bunch of kindergarteners organizing themselves around a table of food and the scientists at CERN organizing itself to figure search for the Higgs Boson. Same thing, really. Not.

"misleading bullshit"?

Oh boy, this should be fun!

BTW... wonder how this fits in the discussion:

http://johnhawks.net/weblog/reviews/brain/genetics/surface-area-cortica…

Becca, like Sven and spider webs, you're imputing a complexity to the production of emotion that isn't well-represented in reality. Inducing emotion is often as simple as manipulating the senses in some well-known ways.

Emotions can affect how intelligence is shaped, but it still isn't the direct effect of the genes. As in the example you give, the effect isn't determined by the gene but by environment.

mk, I've said it elsewhere, but it's definitely worth repeating here:

Twin studies are very good for ruling out genetic causes, but for reasons discussed in the previous thread (i.e., degree of shared prenatal environment, action of traits known to be genetic on the environment), they are insufficient to prove a genetic link. At best, they can identify a possible genetic link to look for.

Ask and receive! Ain't the web a cool place?

Thanks Stephanie.

Stephanie,

Why is a comparison of the brain to other body parts off base?

A person can have the genetics to be taller and thus genetically be a better basketball player than average even if they never play the game. They may be short due to poor nutrition. But genetically they have better basketball potential.

If a person has a genetic difference in their language center they may be more able to learn different languages. They may never be exposed to a different language but the genetic potential is there.

What is the difference?

And there is nothing modern about racism, bigotry, sexism or general nastiness. In the past they were so prevalent that they were invisible. We live in a far more egalitarian society today where these things are seen as bad. Today a woman with a talent for math has a reasonable chance of making it work. A hundred years ago it would have been very difficult. Much before that it was essentially impossible. That is how the environment has changed.

And I repeat, the more egalitarian the society the more purely genetic differences will show.

A person can have the genetics to be taller and thus genetically be a better basketball player than average even if they never play the game.

Are you making a claim about the genetics of stature?

And I repeat, the more egalitarian the society the more purely genetic differences will show.

Interesting hypothesis. I did not happen to see that during the years I lived in what is generally accepted to be the worlds' most egalitarian society, but it would have been difficult to measure.

This does remind me of a problem: We don't live in an egalitarian society. We live in a society in which privileged individuals manage society in such a way as to keep it from being egalitarian. The science shows that brains do not develop in individuals in a way that supports the idea that "Africans" are an average of 35 IQ points below "Whites" yet our modern discourse .... and discourse matters ... includes the ongoing assumption, often insistence, that it does. And individuals who participate in perpetuating this assumption, often for their own personal and sometimes quirky reasons (that may not have much to do with a conscious effort to perpetuate racial thinking) have to ask themselves what the fuck they think they are doing.

ppnl, it's not a valid comparison for the reason I've already mentioned. If other parts of the body ranked anywhere near the plasticity of the parts of the brain that are under discussion here, we would die. It's like saying a bicycle and a car are both pieces of mechanical equipment used in transportation, so looking at a bike must tell us something about internal combustion engines.

And the reason this degree of disparity in environment is modern (and modern does not mean industrial, but recent in human evolution) is that we've seen improvement on the high end of the scale. We've still got children who starve. Now we also have children who eat diverse food from all over the world. We have a less egalitarian society, which is why we treat equality as a value rather than taking it for granted.

ppnl, a point about language, essentially any infant can learn essentially any language as a first language, and do so nearly as good as anyone else with no accent. Essentially every adult cannot learn a single new language without an accent.

These differences between infants and adults are not genetic; they are developmental and shared by essentially all humans.

If an adult retains an infant-like ability to learn new languages without an accent, what test would we use to determine if that is genetic, or environmental?

If we do a thought experiment, and have multiple clones of a phenotype that is capable of learning multiple languages as an adult without an accent, would each clone have that ability irregardless of environment? I donât think so.

One of the reasons that some speakers of certain languages have difficulty with certain sounds is because their first language didnât contain them, so the neural networks that detect those sounds did not develop. Presumably that applies to concepts more complicated than sounds, if a neural network is not present to detect them, they cannot be detected.

If one of the clones is raised where his/her first language does not include certain sounds, then those sound-detecting neural networks wonât develop and presumably that individual would be unable to hear that sound with sufficient fidelity to make that sound appropriately in learning a new language where it is used.

There is some evidence for a familial aspect of super-language learning abilities. There is a small number of people (scattered across the "races" I quickly add, so you privileged white people don't assume this is about you) who can do simultaneous translation, and some have argued that this kind of thing is familial, and thus maybe genetic. I'm not stipulating that it is, but assume for a moment that it is so.

There are two or three dimensions of variability in language function in humans (putting aside people with abnormalities). There is what I just mentioned: Ability to simultaneously translate, there is ease of learning new languages, there is which language you speak,and there is how many languages you speak, for example.

These variability sets are primarily explained by experience, as daedalus2u points out. The super-abilities (simultaneous translators, etc) ... that is primarily determined by gender, IIRC.

However, I guarantee that those who need genes to determine intelligence will ignore the fact that the vast majority of language variation across our species is determined by environment and focus on a few studies showing that maybe there is inheritance of some rare and quirky phenomenon.

Apparently, with privilege comes insecurity.

I'll reply to what was addressed to me.

Sven, the process of creating a spider web isn't that complex, although the result is pretty,

First, your implication that I think spider webs are complex because they're pretty is insulting. Second, you really want to argue about what is "complex" and what is "simple"? These are opinions. Building a web may not be astrophysics, but it is a stereotyped behavior that is far more complex than undertaken by any other individual arthropod.
But it doesn't matter. "Complex" wasn't the point. In fact, my point is made even better if you want to insist that spider-web building is "simple," because my point was that we have basically no freaking idea how even such a "simple" behavior is coded by genes. Yet it is.

and some of the variety is caused by variety in the shape of the spiders.

So what? Some of it isn't. Some of it is caused by species-specific differences in gene-encoded behavior. This style of argument-by-nitpicking is wearisome.

There has been a fair amount of research on how genetic variation causes things like spider web building (or foraging by fruit fly larvae, etc.) It is not unexplored territory.

Did I say it was unexplored territory? Here, I'll modify my statement to reflect this fair amount of research: Nobody has much of a clue about how, mechanistically, behavior is coded in genes. Do you deny that? People are still ablating single Aplysia neurons and running them in T-mazes, for chrissakes. Please admit that not only do you not know how genes encode behavior (and therefore neural development), in any organism, but that nobody knows. OK? That's my point. Nobody knows how even these much simpler systems work. What you claim to know about what is and what isn't possible for genes to do to the vastly more complicated human cerebral cortex is not something that it's possible for you to know. *shrug*

Once these started to 'deploy' in an evolutionary sense, this new tissue type formed many different organs.

...thanks to heritable variation in neural structure (and presumably function) the whole way...

The nerual cortext is not comparable to the ganglia of spiders any more than the tetrapod skeletal system is comparable to the rasping organ of a slug or the shell of a snail.

uh...what? That's absurd hyperbole and really crappy typing. Neurons, synapses, and a variety of neurotransmitters and receptors are homologous in spiders and mammals, even if specific ganglia are not.

So the spider analogy is barely useful as a philosophical tool but falls way short looking at the biology of the problem.

OK. Here's what I want to conclude from the spider analogy: Genes can in fact affect neural function, in ways that we understand very poorly at any explanatory level. That's it.

I then want to make the jump from that to: Statements to the effect that genetic variation cannot possibly affect variation in neural function among individual humans are wildly premature and presumptuous. I base this not on the little tiny bit we know about how brains (and ganglia) develop and function, but rather on the humbling magnitude of our ignorance on the subject.

As for the argument from personal incredulity, maybe you should read the book before deciding what is presumption.

Sorry, it's a book club? Which book were we supposed to read before commenting? Have you read it?
In any case, for reasons outlined above, I'm going to stick with my current opinion of "presumption," at least until I get around to reading the book. Whatever it is.

A small number scattered across the races doesn't sound like Mendelian inheritance, which is really the only kind of inheritance that is well established.

The so-called "complex genetic traits" look a lot more like environmentally determined traits to me. That is really what I think they are.

Wow, Sven, way to forget all about the original post in commenting. And to forget that you haven't been advocating for a neutral position on gene-intelligence interaction while more evidence comes in. You walked into this stating it was absurd to think there was no connection. I'm not sure how "the humbling magnitude of our ignorance on the subject" supports that position better than Greg's. It does, however support the causes of the racists, which is an excellent argument for policing your own presumptions.

And I happen to think spider webs are pretty.

Greg L.

Yes I believe the genetic component to height is well established. There is also an environmental component. According to a recent Sciam article 60% to 80% of the differences in height are due to genetic factors while 20%-40% are due to environmental factors. Mostly nutrition.

The point I'm trying to make is that as you equalize the environmental factors the genetic component rises toward 100%. In a society of the very rich and the very poor height will correlate with wealth rather than genetic factors. Equalize the access to nutrition and height will no longer correlate with wealth.

I agree we do not live in a perfectly egalitarian society. But it is probably a massive improvement over most of the societies of the past. Depending on what you mean by egalitarian it isn't even clear that it is desirable. Something better than what we have probably is desirable.

As for racial differences in IQ I doubt it is large enough to allow it to be untangled into environmental and genetic components if it exists at all. Thats a very difficult thing to do and the result simply isn't that interesting.

I agree that neural systems are very adaptable. A good mathematician can do mental feats that leave me breathless. But then M. Jordan could leave me breathless as well. I don't see any real difference in principle. Both have a variable genetic component, a cultural component and a simple practice component. We can't all be world class mathematicians any more than we can all play on M. Jordan's level.

There have been many cases where children have learned multiple languages before the age of ten. Are you saying this is environmental? If this is genetic isn't this as big a difference as there is between a short wide slow white guy and M. Jordan? What is the difference in principle?

I'm not sure how much of a genetic component there is in intelligence. But there seems to be a non-trivial genetic.

We know that small genetic changes in other species can substantially alter intelligence levels (as measured to perform specific classes of tasks). See for example http://www.nature.com/news/2009/091014/full/461862a.html which discusses this for mice.

How substantial the genetic component is seems to be up in the air. However, it seems that there's pretty heavy ideological motivations for people arguing in either direction.

Claims of racial based genetic differences are a completely separate claim. However, given how little understanding we have of the genetic component of intelligence, it seems really stupid to try to make any claims about racial groups having differences in their genetic make-up that impact intelligence.

Stephanie -

There are plenty of genetic effects, but they're not acting directly on the brain.

Bullshit. What do you think makes for coordination? What do you think mediates the hands and the eyes? And there are other skills that I had in mind, more on that later.

Joshua Z - what type of intelligence are you talking about? There are many different ways people can express intelligence, most of which are virtually impossible to account for with standardized IQ tests.

Yes, DuWayne, I should have been more precise. They're not acting directly on anything we'd call intelligence. They act on intelligence only by acting on the environment.

And really, you should catch up on the discussion around here before jumping in. The newer post on racial traits will give you a heads up as to why you need to be very clear on what you are and aren't arguing. This is one of those cases where precision is called for.

I am most certainly not talking about race - though it should be noted that some people from different populations (ie. people who lived for tens, if not hundreds of thousands of years with minimal interaction with populations that wandered to other parts of the globe) do tend to have varying degrees of various neurological disorders, something I am very interested in studying one day. But in regards to skill sets and differences in intelligence, that is completely irrelevant.

I do however, still have some issues with this notion that genetics doesn't play a significant role in neurodevelopment. Daedelus mentions some possible causes for autism and schizophrenia above, that fail to account for very strong genetic correlations for both. ASDs are often found in conjunction with parents who show signs of ASDs and in many cases family histories show evidence that a grandparent exhibited symptoms of ASDs - there are marked differences in expression of symptoms when you go back a couple generations, but there were also marked differences in stimuli that would cause reactions and ASDs tend to be very sensory oriented. As for schizophrenia, there is a great deal of correlation between persons with schizophrenia and family histories of often rather significant mood disorders.

Attention deficit disorders tend to be even more profound, especially when certain traits combine. Some people with attention deficit issues seem to manage to pass it along rather strongly - my paternal siblings almost all have attention deficit issues, including the girls. Out of nine confirmed (asshat was prolific) from five different women, one boy and one girl do not have attention deficit issues and as far as I know, all of us have mood disorders as well. And the offspring of a parent with attention deficit issues and a parent with an ASD will almost always have attention deficit issues - couplings between persons with autism spectrum issues and persons with attention deficit issues are not all that uncommon.

Mood disorders also have strong familial correlations, as do early onset alzheimers, obsessive compulsive disorders and pathological aggression. While the exact mechanisms are little understood, it is assumed that for many of these neurological issues carry a genetic propensity and may or may not be triggered by environmental influences. It is unquestionable that environment has a profound impact on the expression of symptoms.

The problem that I have with discussions of intelligence, is that there are very different types of intelligence and I see little reason to assume that genetics doesn't play a role in them. For example, there are people who have profound abilities in certain arenas that are exhibited at an extremely early age - usually in the arts or mathematics. I use these as an example for what I suspect is widespread and that there is evidence to suggest is widespread. Someone who can, for example, paint with remarkable skill and a flair for abstraction at age five or six, didn't just pick something up from their environment. Someone who can manage remarkably complex mathematics at the same age, is just as unlikely to have picked that up from their nurture.

This is not to say that there are inherent differences in the level of intellectual abilities. I worked with a guy who would probably score more than one, possibly two standard deviations low on most standardized IQ tests, who could intuitively rip apart complex machinery that had failed and fix it - often enough improvising parts. Not machinery he had necessarily repaired before and without ever having the least bit of training in any sort of repairs - he had the equivalent of a fifth grade education and couldn't read words he didn't recognize the whole of. I would argue he is as intelligent as any Mensa member, though he can barely string together a coherent sentence. He just happens to exhibit engineering brilliance - best I can figure, when it comes to his abilities at structural engineering, is that he just "sees" the math and does it without really being cognizant of it.

Intelligence comes in all sorts of flavors and as far as I can tell, has nothing to do with social constructs. Nor, as far as I can figure, do divergent populations have anything to do with it. That does not mean that genetics can't possibly influence the flavor someone happens to have...

hundreds of thousands of years with minimal interaction with populations that wandered to other parts of the globe

Are you talking about HUMAN populations that have lived apart for hundreds of thousands of years? For the record, this is inaccurate.

DuWayne, what makes for most good eye-hand coordination is practice, practice, practice. What the practice does is cause neuronal remodeling that tunes the neural networks to work better, to work better "in sync".

All humans have self-tuning neural networks. All humans exhibit improved performance in all tasks with practice. The unpracticed ability might have a pretty strong genetic component, but after a few thousand hours of practice, it is mostly the practice. People get tens of thousands of hours of practice at thinking by the time they are 5 years old. Is thinking ability then due to genetics or due to practice?

It isn't just "practice" that makes perfect, it is "perfect practice makes perfect". There may be differences in the number of repetitions it takes to perfect a technique. Maybe there is a genetic component in how many reps it takes, and some people can perfect a technique in 10 reps that might take someone else 10,000. A differential effect of efficiency of repetitions isnât what is thought of as âintelligenceâ.

I posted a link to the wiki page on Kim Peek (that comment still hasnât made it out of moderation). He had an eidetic memory so he could memorize material with a single trial, a whole page of text in ~10 seconds. Did that make him very intelligent? Was that ability genetic? Or was it due to some aspect of neurodevelopment? If the ability to memorize a page in 10 seconds is from a non-genetic fluke of neurodevelopment, by what basis are smaller differences considered to be caused by genetics?

I have really good technical intuition. I got that intuition by never considering something to be counter-intuitive. If my intuition was wrong, it was the fault of my intuition and so I changed it. I have done that my whole life, as long as I can remember. Is my intuition genetic, or is it due to practice? Does it matter?

Oh, that book. Yeah, I forgot all about the OP.

So is it really your belief that every (non-pathological) individual human is born with the same potential for brain development, and that therefore any differences in cortical function we can discern or measure among individuals must be due entirely to environmental effects on brain development?

Because yes, I think that kind of blank-slatism is an absurd belief. I think that because of everything else I know about physiology and development in animals (which is even more than most biological anthropologists). Obviously I don't have the smoking-gun proof at hand, but that's only because these are really hard questions to answer about really complex systems. Time will tell, I guess.

As for policing presumptions lest racists gain support, um, nah. Go ahead and check off the "science ain't PC" box on your bingo card. Acknowledging the probability of genetically based individual variation in human intelligence (or whatever) is not in any way racist. Conversely, defeating "scientific" racist arguments does not require denying the possibility of genetic variation in cognitive function.

Sven, you are completely missing the point, a lot of environmental exposure happens in utero. No, not everyone is born with the same potential because a lot of it has all ready be determined in utero. Fertilized eggs have much more nearly equal potential than do new born infants, but even fertilized eggs have epigenetic programming from the two parents. Of course providing two identical environments is not possible and would not produce identical outcomes because many of the developmental pathways are chaotic, they are inherently not predictable long term. All systems of coupled non-linear parameters exhibit chaos. Development is no exception.

The genetics of autism is something that has been very seriously studied and which I have read a lot about. There is no âautism geneâ. There are a modest number of single gene issues that cause autism-like symptoms. Rett Syndrome is one of them, is caused by the deletion of the MeCP2 gene which codes for a protein necessary for reading out methylated DNA. It only shows up in females because the MeCP2 gene is on the X chromosome and XY boys with the deletion donât survive (mostly). In females the X chromosome is turned of at random, so the active MeCP2 gene in the mosaic females rescues the phenotype from death, but causes Rett Syndrome. All together the total known genetic âcausesâ of autism only amount to about 15%. Virtually all of those are characterized by dysmorphic features and are singleton; that is they are mostly found sporadically (not always but usually). None of them individually amount to more than a percent or so (statistics on this are bad though).

Some teratogens (thalidomide, valproate, misoprostol) can cause autism if given during certain periods of neurodevelopment (first trimester). These cases are obviously not genetic, but they produce long lasting changes that result in the autism phenotype.

The majority of autism is found in multiplex families, where there are multiple closely related individuals that show autism symptoms to a greater or lesser degree. This autism is not associated with dysmorphic features. Only when those symptoms reach clinical significance is the person said to have autism. Even though there is strong familial linkage, the genetics of these autism cases is completely impenetrable, with no gene accounting for more than a few percent of the loading.

Identical twins can be discordant for autism, that is identical genotypes can be discordant for the autism phenotype.

There has been a lot of work on autism genetics, thousands of people with autism and their extended families have had whole genome scans done. So far there is no âsmoking gunâ.

The genetics of autism parallels the genetics of other major diseases, heart disease, hypertension, kidney failure, Alzheimerâs. Even in multiplex families there is no âsmoking gunâ. These disorders are all called âcomplex genetic disordersâ, with the fundamental premise being that the must be genetic, but no genes can be found.

The obvious question then comes up, how can common diseases have complex genetics? That is how can a âdiseaseâ be âcausedâ by so many genes and still be common? I appreciate this will sound like an argument from personal incredulity, but if common genes cause a disease, how can there be so many of them? By what mechanism did those genes that cause this disease become common? They could only have become common if they were selected for (or actually, not selected against), but if the cause a disease how can they be selected for? The other alternative is that the disease is an emergent property of many genes working in concert. But then one would expect the disease to appear infrequently, and to be a unique and idiosyncratic emergent property of the specific genes that âcauseâ the disease. How can these complex genetic diseases be so common, and have such a common development trajectory?

My conclusion is that these disorders are fundamentally not genetic in nature, but are developmental and environmental. They result from normal and idiosyncratic differences in regulation of important pathways, and the pathways are still operating ânormallyâ, and in their normal active range, just that the setpoint of the regulatory pathway is in a non-physiological place for long term good health. Restore the normal setpoint and health will return to normal (provided there is sufficient plasticity and there hasnât been too much damage).

All systems of coupled non-linear parameters exhibit chaos. Development is no exception.

I suppose sometimes a baby seal shows up in the maternity ward...right?

Greg -

I was thinking it was (thus why I was so ambiguous), but could not remember my timelines (the National Geographic genetics project). I wrote that after spending the night with a feverish and fitful two year old waking me up every hour or more and then keeping me up with his poking and kicking during naptime as well - not to mention his having peed on me and, after 25 minutes of reading books while he was sitting on the potty in vain, his wandering off five minutes after the diaper was on, to take a dump in the corner. Yesterday was a long fucking day...

Daedalus -

DuWayne, what makes for most good eye-hand coordination is practice, practice, practice.

That is simply not the case for everyone. There are people who have various types of hand eye coordination that really does come quite naturally to them. For my own part, the first time I picked up a rifle and did some target shooting, I was able to fire in close pattern - same with handguns. By the same token, knowing how the fingering goes with guitars and keyboards, I am still unable to play either - though if I practiced enough, I could probably manage. One of my best friends from childhood, on the other hand, could watch someone playing the piano and play back what they had played perfectly - with perfect rhythm - when he was six.

All humans have self-tuning neural networks. All humans exhibit improved performance in all tasks with practice.

The first part is quite true, the second is not - at least not as simply as you make it sound. Abilities exist on a spectrum for people and for any given person, there are abilities that are going to take a prohibitive amount of practice to accomplish.

Is thinking ability then due to genetics or due to practice?

Both - I am not trying to claim that genetics are the endall - I said as much. Environment has a profound effect on neurodevelopment.

A differential effect of efficiency of repetitions isnât what is thought of as âintelligenceâ.

Never said it was.

He had an eidetic memory so he could memorize material with a single trial, a whole page of text in ~10 seconds. Did that make him very intelligent?

Not the least bit intelligent - which is not to say he wasn't intelligent, just that memory has little to nothing to do with intelligence. And eidetic memory can actually interfere rather profoundly with intellectual expression.

Was that ability genetic? Or was it due to some aspect of neurodevelopment?

Probably both. Or possibly just one or the other. I don't know enough about eidetic memory to say.

If the ability to memorize a page in 10 seconds is from a non-genetic fluke of neurodevelopment, by what basis are smaller differences considered to be caused by genetics?

You are really missing my point. I am not saying that anything is purely genetics. It is exceedingly unlikely that genetics is the whole story - it is just equally unlikely that genetics doesn't play a significant role in neurodevelopment. It is completely fucking ridiculous to think that it doesn't.

Is my intuition genetic, or is it due to practice? Does it matter?

Again with the assumption that it is either or. I have very little doubt that genetics played a significant role in your baseline abilities, while practice - developing the underlying neuropathways dramatically improved it.

PlaydoPlato[35]:

If larger brains correlate with greater intelligence

They don't

if, according to this table, Whites have larger brains

They don't

how do we explain the election of George W. Bush

DuWayne, I am not trying to say that there is no genetic components to any mental activity. The problem with biological research right now is that nearly everyone has a DNA fetish. Every medical and biological problem is being looked at with the hammer of gene sequencing. From a scientific standpoint we need to know the genetics of stuff, in no way am I disputing that genes are not important and are not worth knowing about. The problem is the gene sequencers are telling the funding agencies that all problems can be solved best through genetics, so give us all the money, we will sequence the genes, and then by glancing at the genes we will know and understand how to cure every disease. That ainât going to happen. The idea that by glancing at the genome emergent properties of organisms will jump out at us is complete nonsense, nonsense brought about by the arrogance of ignorance, by the extreme hubris of the gene sequencers.

There is a quote I like that illustrates this. When George Weinstock, the head of the consortium of 174 collaborators that sequenced the honeybee genome was asked âWhat was the biggest surprise about the beeâs genome?â his response was âThat we did not come up with breakthroughs in understanding social behaviour of the bee. Many small changes account for this and it is possible that this reflects our limited knowledge of behavioural genetics.â (Nature, Vol 443, Issue no. 7114, 26 October 2006)

George Weinstock is a very senior scientist. He has been involved in the sequencing of many genomes. His knowledge of genomics is probably second to none. I want to be clear that I have enormous respect for him and his work and all that he has accomplished, and I donât want what I am to say next to detract the slightest bit from what he has done.

But to expect to understand the emergent properties of systems of many individuals from their genetics shows a naiveté that to me is breathtaking. The properties of a protein are not understood from its sequence. In other words, the functions of the proteins that comprise the receptors in the bee nervous system canât be deduced from their sequence. The properties of a nerve cell cannot be deduced from the properties of the proteins that comprise it. The properties of a neural network canât be deduced from the properties of the neurons that comprise it. What basis is there for expecting the emergent properties of a society of organisms, their social behaviors, to be obvious from an inspection of their genome? None, other than a breathtaking sense of hubris.

In basic research, all of us are naïve or the research wouldnât be worth doing. Funding usually does go to the people who are most confident about what the research will show. The fetish of âhypothesis driven researchâ dictates that someone who just says we need to know the sequence of the honeybee genome just because wonât get funded but someone who says the sequence of the honeybee genome will allow us to understand social behaviors of bees will. Naiveté and hubris in basic research isnât that bad once you learn how to see through it. If you donât, that is a problem.

When that kind of naiveté and hubris are applied to human problems and human behaviors, you get crap research. That is why the genetics work on âcomplex genetic diseasesâ isnât going anywhere. The diseases are fundamentally not âgeneticâ in nature, but the gene sequencers are too enamored with there sequencing hammer to see that. Throw in a little racism and you get crap like Rushtonâs work. Crap that racists in policy positions can use to justify racist policies with the imprimatur of âscienceâ.

In terms of human neurodevelopment, it is like a chain, every link in the chain is important. The chain is only as strong as the weakest link. What racists hear when they listen to people like Rushton speak, is that in blacks, the gene link to intelligence is so weak that there is no need to educate blacks because that weak genetic link cannot be made up for. That is already their default hypothesis. A hypothesis not based on data, but on belief, the belief in the statistical myth of g.

How someone ends up being a smart adult really doesnât matter to me, whether they do it via good genes, good prenatal nutrition, good parenting, good schooling, good work/study habits. I would like to foster all of those things for everyone. Genes is the one thing that canât be changed in individuals; everything else that matters can be worked on and improved and we know how to do it. Why waste policy-mental-space on the one thing that canât be changed?

Just a quick comment: The fact that brains are "sculpted" by development is not a slam dunk for the nature vs. nurture debate, as Greg seems to imply in his post. I mean, that is pretty much the message of evo-devo: Development works in conjunction with the genotype to manifest the phenotype, with no simple one-way relationship with one dictating the course of the other. The relationship can be cyclical even.

For instance, many genes would likely manifest differently if the environment in the womb were radically different, but it's a safe bet that any organism with a human genotype developed inside a human womb -- that womb in turn being a product of both genes and environment. (Of course, in this case, it's the genes of the mother, not the developing organism itself)

So I'm not really buying the connection between Greg's argument and his conclusion. Yes, in order to be useful our brains must develop in ways that cannot possibly be directly and explicitly dictated by the genome. From this, it does not in any way follow that nearly all brain structure is shaped by culture. That's a monumental leap that, IMO, betrays a poor understanding of developmental biology.

Daedalus -

Got to head for the hills (with sleds) so I will be brief.

The reason I think understanding the genetic component is important, is the same reason I am going into neuropsychology and linguistics and hope to eventually move into evolutionary psychopathology. I believe there is a great deal of value to so called neurological disorders. I believe that by untangling the skein of causality, it will be possible to more fully appreciate the benefits, while minimizing the negative aspects of neurological issues.

I want to understand as much as possible the genetics of psychopathology, because I believe in neurodiversity and genetics is a piece of the puzzle that will help society benefit more fully from it.

James Sweet, no one is arguing that genes have no effect what-so-ever on adult behaviors. Gregâs argument (as I understand it and with which I agree) (I donât presume to be speaking for Greg, just my interpretation of what he has said) is that there is no real data showing a genetic involvement in adult behaviors (data really would have to fit Stephanieâs criteria to count as ârealâ, correlations that could be due to other things doesnât count, those other things have to be excluded (by data of course, not by incredulity)). Of course the course of neurodevelopment is directed by genes, that is not the point. The question is âare differential adult behaviors due to differential genetics or to differential developmentâ

There are plenty of hypotheses that there are genetic components to behavior, but none of those hypotheses have real genetic data to back them up. I mentioned the cycle of violence; Greg mentioned the anecdote of âheritableâ murderous psychopathology likely mediated through brain trauma. Greg is not rejecting the hypothesis that there are genetic components to adult behaviors; he is just not accepting that as received wisdom in the virtually complete absence of any real data.

There is lots and lots of real data on neurodevelopment, on neuronal plasticity, on how nurture, diet, environment, education, etc, etc, etc, etc, etc. affect adult behaviors. There is no corresponding data on how genes affect adult behavior. Maybe they do, but it would be nice to have some data before saying they do, and even nicer to have some data before making policy decisions that assumes that they do.

If we do look at the data of adult behaviors, we donât find that there are some behaviors that are completely and uniquely associated with a certain genotype and completely absent in all others. We donât find behaviors that are transmitted by Mendelian genetics. We do find a lot of very similar life courses; people who end up in prison as violent offenders were very likely abused as children. People raised in a French speaking household learn to speak French. Maybe someone whoâs ancestors have lived in France for the last 20 generations can learn to speak French slightly better than someone with ancestors from a different region (but probably not because 20 generations is pretty short for a gene to become common, and language isnât stable for much longer than 20 generations), but that effect would be very small and hard to find. It is pretty hard to imagine how a single gene could improve an ability to speak French anyway. It would need to be a cluster of genes, and then how do those clusters of genes interact singly and in concert with clusters of genes for other languages? Combining genes for thinking in Cartesian coordinates with genes for thinking in radial coordinates might produce someone who could think in neither. A better evolutionary strategy is likely to evolve a flexible phenotype, one that can adapt to what ever environment it is in. That is what it appears humans have, a flexible phenotype. Essentially any human can learn essentially any language as a first language, including non-audible languages such as ASL. ASL is a synthetic language, it became a real language when it was learned as a first language by children. They modified it and (in the words of the skin horse) "made it real". There were no unique genes in that cohort of children that did that. Essentially any cohort of essentially any children would have accomplished essentially the same thing. Not exactly the same thing because it is chaotic and the path is not predictable from the initial conditions. The initial conditions do specify that there is a path, just not which path or where it leads to exactly.

When social animals are raised in isolation, their social abilities are greatly stunted, but their non-social intellectual abilities are enhanced.

http://www3.interscience.wiley.com/journal/109704771/abstract

That isnât genetics that is development. The genotype does specify the size of the phenotype-space, development determines which phenotype develops. The phenotype-space is very large. In the citation I linked to, the social phenotype and the isolated phenotype both can develop from the same genotype.

DuWayne, I deliberately left that fairly open. I agree that IQ measures a very narrow set of (possibly culturally dependent) abilities. So focusing on that would be bad. The point is that in animal models many things that we would consider signs of intelligence have genetic bases.

It's worth a reminder that genetic causes for some developmental disabilities are clearly recognized. The genetic impact on adult cognition that we're talking about here, the needle in this race-intelligence haystack, is something shy of being pervasive enough to be labeled a developmental disability but big enough to still be seen after the environment has had its way with adding and subtracting neuronal connections, increasing and decreasing the "sensitivity" of synapses by changing how chemicals are produced and received and eliminated, changing signal speeds by changing myelination, and some other stuff that environment has already been shown to do. Once all that happens, you still have to be able to find a genetic effect to say that genes directly affect normal cognition.

This isn't arrogance or wishful thinking in saying that a direct genetic affect is highly unlikely. It's a look at how small our "genes of the gaps" would have to be if they aren't large enough to screw everything up.

James: From this, it does not in any way follow that nearly all brain structure is shaped by culture. That's a monumental leap that, IMO, betrays a poor understanding of developmental biology.

That would be a monumental leap and would betgray a poor understanding of developmental biology. What we have here, actually, is a monumentally foolish and inadequate reading. Which is annoying because what you are really asking me to do is to say it again and again, more slowly and more simply each time so that you can understand it. Or, you could just pay more attention.

I think the big problem I have with this conversation Stephanie - and this is not at all the fault of people not trying to perpetuate ignorant fucking bullshit about social constructs and intellectual abilities - is that there is a valid discussion to be had about this outside the context of race/ethnicity/region of origin. Not some vague concept like intelligence, which is ultimately just another social construct - but relatively inherent abilities that environment cannot fully explain. Developmental disabilities is in my mind a copout, because there are developmental disabilities that could very likely be anything but if we understood them better.

And that aside, there are simply people out there who have very specific talents that are expressed at such an early age, that it is a stretch to assume that those talents have no genetic basis. People who are not necessarily particularly capable in other realms or even in any serious academics. And it is equally obvious that most people have specific areas in which they excel and areas in which they really don't - regardless of their desire or attempts to engage in areas they just don't have the ability.

Is it really all that ridiculous to consider whether or not the type of intelligence people have might not have a genetic component? Especially when it is very likely that various neurological issues have rather significant genetic components - neurological issues that often come with specific intellectual abilities common to people with those neurological issues. Could it not be that many people have the same sorts of genetic influences to their neurological makeup, that just aren't accompanied by rather obvious neuropathologies? This is not to say that environmental influences aren't playing a profound role in neurodevelopment - we know full well they do. But the notion that genetics don't play a role seems rather fucking ridiculous.

DuWayne, I think you're underestimating a couple of things: (1) how rare truly special abilities are and (2) the role of environment in developing "special" kids. Despite the news reports, most of the kids who do something unusual have a parent or friend of the family who encouraged something smart and cute the first seventeen times they saw it. Then someone got serious about it.

None of this is to say that neurological conditions identified as abnormal can't come with some side benefits. I've seen and lived the reality of that, and it's cool. It's just not what we're talking about right now. And yeah, I find the need to have this discussion this way probably about as annoying as you do. However, when talking with people who use imprecision as a tool to avoid the need to prove their claims, one has to be precise sometimes.

@Greg-getting back to this kind of late- but yeah, I was referring to evolutionary psych being silly. When you view nurture as a hugely important element in things like IQ (and a lot of other behavior) it doesn't make sense to evaluate it from an evopsych point of view. Not to mention how far we are from really coherently describing most of the behavior that evolutionary psychology claims to explain...

Anyway- regarding the importance of genetics: I drew a conclusion about this a long time ago, when I read a bunch of my mom's books about development & education. She put a lot of effort into finding out how to help her kids reach their full potential, so I had a wealth of material before me by the time I could read it. The difference that attention & education made for special needs children was especially striking, but it applied pretty much across the board. When culture gives a shit about children and helps them learn and understand the world they go very far (this is a reason feminism is very important). Another interesting thing to look into is the plasticity of the young brain in the face of things like brain injury; mental functions that are less ambiguous than intellect (like motor control) can be examined this way. The brain never really loses all of its plasticity, but in children it is very pronounced. they can regain functions that you would not anticipate because of the flexibility of the functions of this organ, it seems to be an inherent feature of the brain that makes the genetic component a lot more mysterious. We still don't understand epigenetics either (where genes are altered depending on forces of nurture), so that some genetic component of IQ is a result of culture rather than being one or the other only. It is a big complex problem and I am not certain that it will ever be answered in a satisfactory way.

HOWEVER, the idea of natural inferiority has been a mainstay of every single organized form of oppression in existance. For a long time the inferiority attributed to oppressed groups was usually explained via religion (god had cursed them, or made them to fufill the role imposed on them, etc). But biology has been used to explain why it is ok to oppress and hurt other people; that science explains their inferiority. There currently isn't definitive proof that groups like brown folks/women/gays/jews are inferior, and that kind of proof would be pretty hard to come by. It seems to me that the only ethical assumption to make is that there isn't a natural inferiority for certain groups until there is some very convincing evidence, because of the kind of evil that has been done in the name of this idea make it a worrying conclusion to prefer. People who flock to assume that there IS such a difference worry me greatly.

The problem of the âgenes explain everythingâ is exactly like Stephanie says, it is a âgenes of the gapsâ, just like âGod of the gapsâ explains everything that is just beyond our current knowledge. Saying âgenes did itâ is almost as empty an explanation as saying âGod did itâ.

There are things like synapse strength, nerve conduction velocity, etc, etc, etc, things we know âmustâ affect things like cognition and neuronal information processing. Why are those not candidates for direct genetic control? Because they are so important that they are all regulated. Everything in physiology that is important is regulated (that means everything is regulated). The more important it is, the better the regulation. Really important stuff like virtually every single aspect of brain function is regulated by feedback control. That feedback control is part of the neuronal remodeling system which is going on all the time. (as an aside, much of that feedback control is mediated through nitric oxide, which couples to the basal level and is how global control of things happens).

You can screw up that regulation, for example with drugs like morphine, but then the remodeling goes on and the brain changes the numbers of receptors, changes how they are connected to things, changes what happens when they are triggered, and you get increased tolerance to morphine. The brain has remodeled to cope with a certain dose of morphine. The remodeling of the brain to cope with ongoing stuff is extremely robust. That is why people are so resistant to drugs and why dying nerves donât cause the brain to fail, why people can recover some function after strokes (and also why they lose function immediately after a stroke, there is pruning of cells to maintain the stability of overall brain function at the expense of loss of function). That is why there is excitotoxicity. It is a pruning mechanism to get rid of nerve cells that are insufficiently reliable.

DuWayne, you canât have a genetically determined superior cognitive trait suddenly appearing in isolation. Early positive traits do not have to be due to genetics, any more than early negative traits have to be due to genetics.

Genetics do play a role, but it is a subtle role, not on the level of gross function. Teratogens like thalidomide exert their effects with no effects on genes. The effect of thalidomide and most other teratogens is not genetic. The loss of things like hands due to thalidomide is due to subtle changes in apoptosis and regulation of cells.

The thalidomide phenotype is specified by the genome under the environmental influence of thalidomide. That is what the environment can do. The thalidomide phenotype is part of the phenotype-space specified by the genome. The genome doesnât specify a phenotype, it specifies a path that leads to a phenotype.

Stephanie and Daedalus -

I am not talking about anything particularly special or superior - everyone - and I mean absolutely everyone, with the exception of people born with serious brain abnormalities, has the potential for particular cognitive functionality. The fact that someone might have innate abilities that are oriented towards art, as apposed to math doesn't mean either has superior cognitive function - it means they have different cognitive strengths.

And I am most assuredly not, I repeat for the bajillionth time, not claiming that it is all genetics. I recognize and have recognized in all my comments the profound affect that environment plays on neurodevelopment. All that I am saying is that there is absolutely no reason to assume that genetics doesn't play a rather profound role in the potential of development. This is shown in a great many neurological issues such as attention deficit, mood disorders, psychotic disorders, obsessive disorders, ASDs and many more. It is also shown in certain addiction disorders.

Despite the news reports, most of the kids who do something unusual have a parent or friend of the family who encouraged something smart and cute the first seventeen times they saw it.

So someone who can compose an aria at age four had some remarkable teacher? Someone who can paint virtual perfection at age five was somehow taught? I have no doubt that someone noticing these abilities at an early age has to encourage a child to engage in them, but that doesn't mean there isn't likely a genetic component to the underlying ability that allows them to actually paint, or perform complex mathematics at such a young age. And I am not saying that such abilities are rare - quite the opposite, I think they are very common, given that I assume that all humans have such genetic influences. Unfortunately, most kids aren't encouraged in those directions at a young age and many kids have environmental influences that run directly counter to healthy neurodevelopment.

There are things like synapse strength, nerve conduction velocity, etc, etc, etc, things we know âmustâ affect things like cognition and neuronal information processing. Why are those not candidates for direct genetic control? Because they are so important that they are all regulated. Everything in physiology that is important is regulated (that means everything is regulated). The more important it is, the better the regulation. Really important stuff like virtually every single aspect of brain function is regulated by feedback control. That feedback control is part of the neuronal remodeling system which is going on all the time. (as an aside, much of that feedback control is mediated through nitric oxide, which couples to the basal level and is how global control of things happens).

So what you are saying is that there are no neurological developmental problems. That in effect no neurological disorders exist. Because if the degree of regulation you are talking about exists, it would make all of them impossible - unless really powerful chemicals are thrown into the mix. Please understand that this flies directly in the face of our best understanding of neuropsychology. It has long been recognized that there are familial correlations to a great many neurological issues that simply cannot be explained away by environmental influences.

So someone who can compose an aria at age four had some remarkable teacher? Someone who can paint virtual perfection at age five was somehow taught?

Find me some who didn't, and who didn't have a neurological disorder. Even Mozart grew up in a house that was all music, with a professional teacher for a father who gave up his career (and teaching his daughter) to teach his son. He was never not being taught music. And realistic art from a very early age are one of the hallmarks of ASD--objects get depicted realistically because of the deficit in symbolic processing.

Basic musical abilities are rare among Westerners, but in many (most?) societies music is basic and engaged in by everyone. Everyone grows up tonal, with pitch perception that is near perfect or perfect, and with rhythm because these things are part of day to day life from infancy and instead of watching TV or being on the soccer team one engages in other activities, frequently, one of them being music.

Putting this a slightly different way: There is variability in musical ability, ranging from nil to excellent with an added virtuoso at the excellent end of the scale, like this:

Nil-----Good-----Exc----------super.

In the US most people are between Nil and Good on this scale with a handful of people Excellent and fewer Super duper. If you know basis stats, which I do and have even taught despited Mr. Bryan's idiotic missives, you know that this = high variance.

In many (most) other cultures, most people are around Good to Excellent, with almost no one at Nil and, again, rarely at super-duper.

Less variance.

There is more variance in western culture than in "traditional cultures" that have been studied by anthropologists with western culture showing a general deficit.

This variation and Western Inferiority is obviously RACIAL AND GENETIC!!!!!

Right?

Or is there another explanation.

Think, Bryan, think. Think. Think. Think.

Can't think of it? The answer is culture. Cultural variation explains this variation in musical ability. The explanation of cultural variation pulls your white nuts out of the fire of genetic determination.

Too bad you won't let cultural variation matter to women or non-whites.

DuWayne, there are many thousands of parameters that must be specified and regulated to produce a functioning brain. The dynamic range required for virtually all of them is too large to be specified genetically. In large part the specific parameter must be regulated locally because different cells need different values of that parameter. For example mitochondria number. Every cell needs to have enough mitochondria to supply enough ATP. In some nerve cells the number of mitochondria can be different by 4 orders of magnitude. A motor neuron with a meter long axon needs a lot more mitochondria than a neuron with just a cell body and 10 microns of axon. The number of mitochondria in a nerve cell cannot be regulated genetically because it has to be regulated locally by closed-loop feedback control because only local closed-loop feedback control can provide the precision necessary.

There are disorders where the regulation of the number of mitochondria is screwed up; ALS for example. Is ALS genetic? Sometimes, the most common familial cause is a mutation in the Cu, Zn, superoxide dismutase. But the mutation doesnât cause a loss of SOD activity, it is a âgain in functionâ, and can be cause by any of over 100 different mutations spread out all across the molecule, not at the active site. But then there are environmental influences too, sun exposure increases ALS, so does physical exertion of certain types, soccer players seem to have a higher incidence. Mitochondria number is also screwed up in other neurodegenerative diseases, Alzheimerâs, Lewy body neuropathies, Huntingtonâs. Are those genetic? Well, Huntingtonâs is, but it doesnât show up until late middle age. Alzheimerâs? The genetics of Alzheimerâs looks pretty impenetrable, nothing even remotely obvious.

The same holds true for things like receptor number. The right nerve cells need the right number of receptors of the right kind to receive the right neurotransmitters. These are regulated locally. Some cells have none, some have a few, some have a lot. These numbers change over time due to local regulation. In the case of receptors that are sensitive to nicotine, there are a number of them, and when people are exposed to nicotine, the regulation of those receptors is perturbed such that the person becomes addicted to nicotine.

Gregâs information on musical ability is interesting. My suspicion is that it relates to in utero exposure to sounds of different types, perhaps related to how many conversations the mother has and the frequency, intensity, duration, etc, etc, etc, of those sounds during particular developmental windows in utero. The timing of when those developmental windows are open might be under genetic control, so fraternal twins might have the same windows open at different times, and so the same stimulus might have different effects because the two fraternal twins are slightly out of sync. This is the chaotic nature of development, differential effects early on can have macroscopic effects later. A zygote from an egg that fertilized 3 hours later than its fraternal twin might have different responses to the same environment of its 3 hour older fraternal twin. Those difference might look âgeneticâ even when they are not.

Wow, I'm getting popcorn here for the argument that whatever made Shakespeare Mozart and Einstein world class had zero to do with some extra-ordinary innate ability on their parts.

d: we do actually know something about how these things develop in indiduals, and it does relate to exposure, though I'm not sure what current research shows on the timing.

Please note that most English Only Americans are too stupid on tone to ever really speak most languages without a terrible accent and, actually, just getting it wrong most of the time. But non westerners tend to be forgiving in that area. Its a genetic gtings. White westerners have the assole allele at a higher frequencey.

And my point, Stephanie, is why should we assume that all intellectual predispositions are accompanied by overt neurological disorders? My suspicion would be that everyone has some degree of "atypical" neurological function, most just aren't expressed to a pathological degree. Twenty five years ago, a lot of people with an ASD weren't diagnosed as such, because we didn't realize the spectrum existed as it does. We also didn't have diagnosis for bipolar or understand that bipolar is also a spectrum. Schizophrenia is also considerably different than it was just a few decades ago, the diagnosis becoming rather rare - not because there are no longer so many people with what used to be diagnosed such, but because we now recognize that there is a spectrum to that as well.

The bottom line is that if we parse people down enough, it turns out that most anyone can be diagnosed with something, because their personality and general behavior fit within various diagnostic criteria.

As for the teaching, there is only so much a four, five or six year old can absorb to attribute it to teaching alone. There is however, the reasonable assumption that a given child already had a propensity for particular abilities that caused there to be little training required.

Daedalus -

DuWayne, there are many thousands of parameters that must be specified and regulated to produce a functioning brain. The dynamic range required for virtually all of them is too large to be specified genetically.

Do you somehow believe that genetics is somehow particularly simple?

More importantly, I am not claiming that all parameters are specified genetically. For the umpteenbajillionth time, I am not claiming that genetics are the end of the story - I am fully cognizant that environmental input is a huge part of it all. All that I am saying, is what seems reasonably obvious to me and most anyone who studies science based psychology - genetic influences play significant roles and environmental influences play significant roles in neurodevelopment.

You are asking if neurodegenerative diseases are genetic - some are and some we can even identify, such as Huntington's. There is correlational evidence that heritability may play a role in early onset Alzheimerâs - correlations that are not evident in normal onset Alzheimer's. There are some neurodegenerative diseases that we already understand the genetics of. Why would you assume that just because we haven't for others, there is no genetic component?

You also seem to be assuming that there is some singular gene that produces the propensities I am talking about. I doubt very much it is that simple. Genetics isn't as simple as saying this gene produces this effect and this effect only. Genes that are largely recognized for producing a particular effect also influence other aspects of who we are. Genes that produce red hair also tend to increase the fairness of skin so that redheads tend to have problems with sunburn. It just isn't as simple as pointing to a gene and saying this is what causes people to have bipolar disorder, for example.

As for your point about dizygotic twins, there is also the plain fact that they simply do not get the same genetic coding. Ultimately monozygotic twins who get the exact same coding are exceedingly rare - theirs are considerably closer, but they are not exact - having different fingerprints, slightly different DNA and different eyeprints. There are twins for whom those are all exact matches, but they are extremely uncommon. But even the latter, exceedingly rare twins do not have precisely the same brain and other differences arise with time, because of environmental influences.

As for the teaching, there is only so much a four, five or six year old can absorb to attribute it to teaching alone. There is however, the reasonable assumption that a given child already had a propensity for particular abilities that caused there to be little training required.

Really? What's the limit to immersive learning at that age? More importantly, what's the limit to immersive learning at an even earlier age? We don't know. We do know that child prodigies get that kind of immersive learning, however, and that they not only display skill at an early age, but also have adults around them who display that skill to the world.

One of the things I hate about the Michael Jordan thing that people keep bringing up is that it grossly undercredits him with the work that he's done to develop his skills. It also undercredits the people around him who taught him and motivated him and gave him additional opportunities they didn't give to other people. He might have been born with a physical advantage or two, but nobody is born, much less conceived, with the strategy and muscle memory to be a top-ranked basketball player.

And a word about visual savants. That isn't a skill. That is simply how the brain works in the absence of symbolic processing. That's different from someone learning to how to look at all of the individual bits of whatever they want to draw and see how it all comes together. They may produce the same result, but they aren't the same process. That isn't to say there's no value in seeing the world that way, but the impairment is different than the learned behavior.

I wonder what the pro-racialist side hopes the upshot of their striving might be, should they succeed? Never mind, that's too disturbing to contemplate.

As far as exceptional, prodigious ability goes, I think there's obviously much to be discovered about the relative weight of nature or nurture. Nevertheless, as a child I was horrified to discover that IQ was apparently 100% correlated with wealth, when I was inducted into the gifted school, along with nearly all of my fellow mates from the wealthy neighborhood, and about none of the kids from the lower classes. I actually quit the program eventually because a new principal arrived who started spouting a bunch of bullshit about how special we were, compared to "normals".

(Just to specify: I quit the program because it was an unethical diversion of public resources to the most privileged 1% of families; that I could see that it was unethical relates to my own experience of "the other side of the tracks"--not to any innately superior moral sense. This anecdote doesn't bear on the question under discussion; but it might elucidate some pretty fundamental things about society for a few of the commenters.)

Bryan, where do you get that? Ability is a property of a phenotype, not a genotype.

I write as a layman, but as someone who has read a lot of Pinker and others who seem to think that there is a genetic component to a lot of brain function. I was impressed by Pinker, but Greg seems to be saying that he was totally wrong - that there is a blank slate, in fact.

Do not Pinker's claims about identical twins brought up apart imply a genetic input? Or are they bunk? - which would surprise me.

Do children adopted very young share show intellectual abilities correlated with their birth parents? Their adopted parents? Or a bit of both, as I would suspect?

In a hypothetical case where a mother had a couple of kids, one by her - for the sake of argument - not very bright husband, and the other as the result of a one night fling with a highly intelligent man, and both parents assumed the children were the children of the husband and wife (the wife might suspect, I suppose) would none of the intellectual traits of the father of the bastard child show through?

None of the intellectual traits of sperm donors?

OK, I know I am presenting an argument from incredulity. But I'd take a lot of convincing that there is no genetic input to brain differences.

More than Greg's opening post provides.

David B

David, I really suggest reading comment threads, particularly when the blog writer participates. Start with comments 49 and 65, then go back and reread the second-to-last paragraph of the OP. Ta da! No need to start over at square one in the conversation.

I was impressed by Pinker, but Greg seems to be saying that he was totally wrong - that there is a blank slate, in fact.

The alternatives are not "Pinker is right" vs. "There is a blank slate."

But Pinker is wrong in a lot of ways. For instance, he does an excellent job of writing about creole as evidence for innateness of language ... and language capacity certainly is innate ... but if you go beyond what Steve writes, read the original sources, and read the critiques, you will find that is argument is very deeply flawed and you will be very disappointed.

Pinker has a lot of it right about how language works, but his module based, evo-psycho view of how it develops in an individual and how it evolved is just plain wrong. Read Fodor and Deacon.

Do not Pinker's claims about identical twins brought up apart imply a genetic input? Or are they bunk? - which would surprise me.

Ask yourself this: How do you get a study sample that is worth anything from ID twins who have had their cultural and linguistic environments randomized? How do you match these separated twins up? Think about it. Where do you get the twins from?

The criteria for "separated at birth" is laughable. I was amused to discover that by the criteria used for those studies my brother and I (we're not twins, but still) were "raised apart" because we had different addresses, and he "lived with my grandmother" and I "lived with my parents"

We would have qualified (if we were twins) to be counted as separated. First, I ask you: Is being raised by granma vs. parents really culturally/environmentally different?

No, probably not. But in our case, we actually WERE all raised by my parents, but we lived in a duplex (and grandma lived there) that we happen to have been using like a single family dwelling. We STILL would have qualified as raised separately. There are "twins separated at birth" in those studies who GREW UP IN THE SAME FUCKING HOUSE!!!!! Others grew up down the street from each other. Others were raised by different relatives across town.

So yes, David, be surprised. I certainly was when I found out what the twin studies were about. I totally bought into them until I read the literature.

Do children adopted very young share show intellectual abilities correlated with their birth parents? Their adopted parents? Or a bit of both, as I would suspect?

I really don't think we know that at this point. I also think that proclivities and "innate abilities" can potentially be inherited, but the vast majority (repeat: vast majority) of the cultural traits we see in people are 'inherited' from their adoptive parents if the kids are adopted as infants.

Do you really, seriously, not know any people who were adopted? It is quite possible that you do and just don't know it because the person you know acts so ... non-mayan, or non-sudanese, or non-east asian, or non-whatever.

In a hypothetical case where a mother had a couple of kids, one by her - for the sake of argument - not very bright husband, and the other as the result of a one night fling with a highly intelligent man, and both parents assumed the children were the children of the husband and wife (the wife might suspect, I suppose) would none of the intellectual traits of the father of the bastard child show through?

I would guess that you would see the signal of the cuckolder in the child, although how strong is hard to say. But that is not the issue here The issue here is does "race" determine intelligence at the level of 30 IQ points.

Did you know, David, that somewhere between 10 and 25% of Americans are fathered by a person other than the person everyone thinks is the father? If the paternal signal was really strong, wouldn't that be part of our general knowledge about each other? Make a list of 20 people you know, where you know them well, and you know the siblings as well, and the sibs are also on the list. Start with your own family and work your way out. Cross off people you know were adopted and cross off step sibs. (Add back to the list to bring it up to nearly 20). Between 2 and 5 of those people were not fathered by the putative father. If variation in personality and ability and intellect and linguistic features were inherited genetically in any meaningful, obvious way, would that not be obvious looking at that list? You ma well notice it now that I've pointed it out, but you will primarily focus on physical features first then later, after thinking about it, you will be able to name behavioral traits. That will be primarily confirmation bias (as was you not seeing the traits to begin with!)

I'm making these arguments that relate to personal experience to you because it is probably faster than other ways to realize that it is just possible that humans are the product of their environment more than any other thing. Or at least, you should consider this as a primary first order observation that is, when you think about it, rather in your face.

But I'd take a lot of convincing that there is no genetic input to brain differences.

More than Greg's opening post provides.

My argument is not a moving target, and I would appreciated it if you did not qualify it that way. Do you want "none"? I can't give you none. Do you want "more or less than I provide?" I did not provide a value.

The majority of variation in human brain function (culture, measured intelligence, linguistic details, etc) is shaped by experience in a normal person. And the 70-105-110 range of means of IQ caused by genes across a Black-White-Oriental sample model is totally wrong.

You are partly arguing from incredulity, but what you are really doing, which is a serious misunderstanding, is saying that since you have some belief (based on your reading of Pinker as well as incredulity) that genes can cause SOME of the behavioral features we see in growd-up normal humans that genes are therefore very important and seemingly more important than experience.

Realize that for every 1% point Pinker can show that a difference is caused by genes, the relevance of anthropology diminishes by 1% point.

I don't think appeal to authority is a fallacy, and I think I will appeal to Pinker here. Meant to bring him up earlier (regarding his prominent debate with someone else on whether sex differences are biological or social-- the video is on the web).

Realize that for every 1% point Pinker can show that a difference is caused by genes, the relevance of anthropology diminishes by 1% point.

How does that work? Do you know what anthropology is? Are you confusing hard core sociocultural anthropology with anthropology more generally? Do you think that anthropologists do not know about genes? The Bryan Pesta view of Anthropology is revealed. We are not impressed.

I don't think appeal to authority is a fallacy, and I think I will appeal to Pinker here. Meant to bring him up earlier (regarding his prominent debate with someone else on whether sex differences are biological or social-- the video is on the web).

I see your Pinker and raise a Fodor and a Deacon.

Fodor's modularity of mind was a great read. Too bad the science has moved past him.

A few week's ago, I thought anthro was science; not so sure now. I wish I were alive 100 years from now, not because this debate will still be going, but to see how marginalized your field has become.

HNY!

So Dr Bryan, this is you "back on your meds" eh? Maybe cutting back on them is in order, you petulant little jack-off.

Bryan: Great come back!

First of all, I'd like to thank you for the trouble of making such a long response to my first comment on this blog.

Clearly I have a lot of thinking and reading to do.

Second, that I've never been convinced that the alleged racial differences in IQ are genetic in origin, because I wouldn't deny that culture is very important to brain development.

Third - I'd better go back to Pinker and check out some of his sources, and criticisms of them.

But now to get onto your final para -

'You are partly arguing from incredulity, but what you are really doing, which is a serious misunderstanding, is saying that since you have some belief (based on your reading of Pinker as well as incredulity) that genes can cause SOME of the behavioral features we see in growd-up normal humans that genes are therefore very important and seemingly more important than experience.'

Well, there's more to it than that. One thing being that I was brought up by a couple of teachers who were firmly convinced that there was a lot of heredity involved in intelligence among their pupils, sometimes over more than one generation. Which no doubt has left its mark on me, and I have to consider that they may have radically over-estimated heredity vis-a-vis environment.

Another thing is that I have not just read Pinker - reading people like Geoffrey Miller and Steven Mithen I've also found interesting, and from them and Pinker I've developed a working hypothesis that sexual selection for (among other things) intelligence has been a major factor in the development of humanity. Which wouldn't be much of an idea if intelligence isn't inherited.

This I might need to rethink.

And then again, the cases of bastardy and adoption that I do know well have tended to reinforce my belief that genes do indeed have a considerable input into intelligence, and into other traits.

Could be confirmation bias, of course.

Thanks again - very thought provoking.

David

firmly convinced that there was a lot of heredity involved in intelligence among their pupils, sometimes over more than one generation

We all observe that kids resemble their parents but consider that kids speak the same exact language as their parents, and that is not coded for by genes. It is rather arbitrary to put one behavioral trait into the genetic camp and another into the culture camp, but that is often what people do.

Mithin is derivative of Barkow, Toobey, Cosmides, Pinker. So you didn't really read two differen things.

Go read deacon!

Off topic, but serendipity is a wonderful thing.

Despite the vid staying firmly on Deacon, so one can't see what was on his illustrations, my quick google search gave me http://video.google.com/videoplay?docid=-4692166850538046905# which was fascinating.

When I take 'Greatest Show on Earth' back to the library, I'll see what they can find for me by Deacon. Might not be much over here in Britain, but I'll certainly go seek.

Ah, brings back memories.

Greg, still speaking as a scientific layperson here, but also as someone very much aware of the hidden (and not so hidden) "stakes" in this conversation, there is an aspect that has not been mentioned. And that is the question of whether "success" may have a social and personal "cost" as well as "benefit" - and whether people in different social groupings (also known as "races" in American parlance) might rate such costs/benefits differently.

I know myself, that my actual performance/interest in maths never lived up to the potential apparently indicated by my (1977) SAT scores. And whether I was conscious of it or not (on the whole, probably not), there was an equation to be made. To do well at maths might, it seemed, in some undefined way, diminish my claim to feminity - ie such "success" might have a social/personal cost. Obviously such equations are not weighed up in the rational mind, but so long as such costs are levied, then individuals will weigh them up. The heavier the cost, the fewer will be found willing to pay. That is to say, some women will find this cost either irrelevant, or worth paying, but to the extent that it remains a cost, many more won't.

The few times that I have been in the States, it was clear to me that the terms "Black" and "White" (along with many other similar terms) in the usage of those I met, described that peculiarly American thing, an "identity." ie - membership in a social grouping strongly organised around a cluster of experience. And those same Americans often agonised deeply about these "identities" - whether this "identity" trumps or precludes that "identity". Or accused one another, or celebrities of being "traitors" to such and such an "identity." (It's a style of discourse seldom encountered in Ireland).

It strikes me as not unreasonable to suppose that there might be a social/personal cost for a "Black"-identified person who becomes too successful in "White"-identified education/jobs/etc. Perhaps they may be suspected of "getting above themselves" or "forgetting their roots," or (maybe this phrase will date me) "becoming The Man". In any case the possibility of social exclusion from an identity deeply invested in must surely be investigated as a confounder in the studies we've been talking about.

If IQ predicts academic success, job success, wealth acquisition, etc, and if all of these measures of success are "White" defined, then the consistently lower group scores of those sharing the "Black" identity (even if their genes are, for all practical purposes indistinguishable from people around them who self-identify as "White") are an exact measure of how much more such "White"-defined "success" costs "Black" people than "White" people.

Ways to test this might include - using control groups with "Black" testers/"Black" subjects - "Black" testers/"White" subjects - "White" testers/"Black" subjects - "White" testers/"White" subjects. Also, the information provided to test subjects could be carefully varied - eg. researchers could say: a) this particular test has shown "Black" people scoring consistently higher than "White" people, and we're doing research to find out whether there is something about this test that particularly suits them or b) vice versa. (I presume most people take these tests with a fairly well established awareness of b).

I would hypothesize (and anyone with oodles of industry money to spend on IQ testing can have this idea for free) that varying the visible "identities" of the testers, and/or the "expectations" set up before the test, so as to prevent any "cost" being levied on "Black" identity (the presence of "Black" researchers/testers, an overtly expressed expectation of success due to one's "Blackness") might make huge differences to the results.

Scot your points are very similar to Wade Boykin's cultural explanation (he's an african american scholar, I think at harvard).

he's an african american scholar, I think at harvard

Actually, he's a psychologist, not an afro-am scholar. Howard, not Harvard. and he co-authored this:

http://en.wikipedia.org/wiki/Intelligence:_Knowns_and_Unknowns

(Well, that's the wikipedia write up on it but it isprobably on the web somewhere. )

Scotlyn - not Scot, not Scott. Thanks.

Wow Bryan, just wow. So in just a few weeks you have read and understood enough of the breadth and depth of the anthropology literature to conclude that anthropology might not be a science?

We are supposed to take you seriously when you say shit like that? What it tells us is that we can take nothing that you say seriously. What is also says is that when you donât understand or donât know something, you dismiss it as either wrong, or not worth knowing or not science. You wish to see the scientific progress of 100 years just so you can gloat over the people you now perceive to be working down dead ends? If that is what is driving your "quest for knowledge", you are going to remain ignorant for a long time.

And you believe there is some kind of zero-sum game going on between genes and anthropology? I guess that explains the mindset of the âauthoritiesâ you hangout with and respect in your field. They are not concerned with scientific accuracy, or with describing reality as it actually exists, they are concerned with turf.

If your âauthoritiesâ are so concerned with âturfâ in one area, that explains their racism and why they canât address fundamental flaws in their field, such as the myth of g. They cling to their beliefs so as to cling to their turf, to avoid the narcissistic injury that comes from admitting one was wrong.

I just came across this clip of Bertrand Russell from 50 years ago.

http://www.youtube.com/watch?v=2aPOMUTr1qw&feature=player_embedded

He makes quite a good case for only believing in things because they are true, not because they are useful.

Oh, and Bryan/Greg - thanks to both of you for the hat tip.

Sorry Scotlyn-- I will remember not to shorten your name.

Bryan, it occurs to me that, instead of shrugging your shoulders about it, you are in an ideal position to cast some light on the really interesting phenomenon you described - ie that you have higher numbers of female "black" identified students enrolling/succeeding in your business programme than male "black" identified students.

If you were to relinquish your interest in marketing your "expertise" to the clientele you have aptly described as "those not wanting to spend 6 figures in court for permission to apply discriminatory tests in the workplace" (my paraphrase), in exchange for experiencing the simple curiosity of a true scientist, and the willingness to follow wherever the data lead, you might find it interesting to see what emerges if you were to hypothesise that "success" may be less threatening to the female "black" identity than the male one. That for "black" identified men, "success" may involve more danger of foregoing the goodwill and trust of people they care about, more danger of being perceived to be a "race" traitor, than for "black" identified women, leading to fewer "black" men willing to pay that "cost."

Think about it. It is a fascinating fact crying out to be explained.

***However, large brains persist. There is some literature suggesting that some "races" have smaller brains than others. As far as I know these assertions are very suspicious, and while brain size varies across different samples, there is no reliable data suggesting that there are major population level differences in human brain size. Some of the differences that have been asserted in the literature have involve very poor data and very inappropriate manipulation of the data to make it look like there are significant population differences in brain size.***

There is a review of that literature here.

"FollowingWorldWar II (1939â1945) and the revulsion evoked by Hitlerâs racial policies, craniometry became associated with extreme forms of racial prejudice. Research on brain size and intelligence virtually ceased, and the literature underwent vigorous critiques (Gould, 1978, 1981; Kamin, 1974; Tobias, 1970). However, as we shall show, modern studies confirm many of the earliest observations...

Rushton (1997) analyzed population group differences from birth to age
7 years using measurements of head circumference and GMA gathered on
40,000 children by the U.S. Collaborative Perinatal Project (Broman et al., 1987). The results showed that at birth, 4 months, 1 year, and 7 years, the East Asian children averaged larger cranial volumes than White children who averaged larger cranial volumes than Black children (Figure 5). Within each group, children with larger head sizes obtained higher IQ scores. Moreover, the East Asian children, who averaged the largest craniums, were the shortest in stature and the lightest in weight, whereas the Black children, who averaged the smallest craniums, were the tallest in stature and the heaviest in weight; the differences in brain size were not due to body size." (page 708)

"Dozens of studies from the 1840s to the 1990s, using four different methods
of measuring brain sizeâMRI, endocranial volume measured from empty
skulls, wet brain weight at autopsy, and external head size measurementsâall
yield similar results. Using MRI, for example, Harvey et al. (1994) found that
41 Africans and West Indians in the United Kingdom had a smaller average
brain volume than 67 Caucasians, although Harvey et al. provided no details
on how, or if, the samples were matched for age, sex, or body size. In another British study, Jones et al. (1994) found a (not significant) trend for Whites to average a 30 cm3 larger intracranial volume and smaller ventricles than Afro-Caribbeans.

Measuring endocranial volume, the American anthropologist Samuel George Morton (1849) filled over 1,000 skulls with packing material and found that Blacks averaged about 5 cubic inches less cranial capacity than Whites.

These results have stood the test of time (Gordon, 1934; Simmons, 1942; Todd, 1923). The largest study of race differences in endocranial volume was by Beals et al. (1984) with measurements of up to 20,000 skulls from around the world. They found that East Asians, Europeans, and Africans averaged cranial volumes of 1,415, 1,362, and 1,268 cm3, respectively.

Weighing brains at autopsy, Broca (1873) found that Whites averaged heavier brains than Blacks and had more complex convolutions and larger frontal lobes. Subsequent studies have found an average BlackâWhite difference of about 100 g (Bean, 1906; Mall, 1909; Pearl, 1934; Vint, 1934). Some studies have found that the more White admixture (judged independently from skin color), the greater the average brain weight in Blacks (Bean, 1906; Pearl, 1934). In a study of 1,261 American adults, Ho et al. (1980) found that 811 White Americans averaged 1,323 g and 450 Black Americans averaged 1,223 g (Figure 1). Since the Blacks and Whites were similar in body size, differences in body size cannot explain away the differences in brain weight.

The largest autopsy study, as yet unpublished, is by anthropologist Ralph Holloway at Columbia University Medical School (personal communications, March 16, 2002, August 26, 2004). He found that in both men and women aged 18â65 years, 615 Blacks, 153 Hispanics, and 1,391 Whites averaged brain weights of 1,222, 1,253, and 1,285 g, respectively. The population groups were all of similar body size. There were also a large number (N = 5,731) of brain weights from 15- to 50-year-old Chinese from Hong Kong and Singapore that averaged 1,290 g." (708-709).

"Populationâgroup differences may have originated from evolutionary pressures presented in colder climates (Rushton, 1995; Templer & Arikawa, 2006). Of course, brain size and intellectual performance are also affected by nutrition and experience (Flynn, 2007; Sternberg, 2004)." (p 712)

Rushton, J. P., & Ankney, C. D. (2009). Whole-brain size and general mental ability: A review. International Journal of Neuroscience, 119, 691-731.

http://psychology.uwo.ca/faculty/rushtonpdfs/2009%20IJN.pdf

Scotlyn:

I think you misunderstood me. I've done three cases as an expert. In two of them, I was an expert for the people who were discriminated against (I provided expert testimony for the victims of discrimination; no company paid me; in fact, the big $ was on the other side).

I made about 3k for 20 hours work in the Gottermeyer case (the only time a company "gave me money"; and it had nothing to do with IQ tests. It was a statistical analysis on an age discrimination claim-- the plaintiff claimed the company's layoff created AI. It did not).

I'm not sure I ever will do a study on race and IQ again. I hope to produce lots on intelligence in general, though.

Your hypothesis re black males could be correct. I don't see it as an explanation for race differences on ECTs though.

***I would hypothesize (and anyone with oodles of industry money to spend on IQ testing can have this idea for free) that varying the visible "identities" of the testers, and/or the "expectations" set up before the test, so as to prevent any "cost" being levied on "Black" identity (the presence of "Black" researchers/testers, an overtly expressed expectation of success due to one's "Blackness") might make huge differences to the results.

Posted by: Scotlyn | January 1, 2010 5:06 PM***

Scotlyn,

Would that explain the differences on reaction time measures? Or why the BlackâWhite difference is greater on backward than on forward digit span memory tests?

"Reaction time is one of the simplest culture-free cognitive measures. Most reaction time tasks are so easy that 9- to 12-year-old children can perform them
in less than 1 s. But even on these very simple tests, children with higher IQ scores perform faster than do children with lower scores, perhaps because reaction time measures the neurophysiological efficiency of the brainâs capacity to process information accuratelyâthe same ability measured by intelligence tests (Deary, 2000; Jensen, 1998b). Children are not trained to perform well on reaction time tasks (as they are on certain paper-and-pencil tests), so the advantage of those with higher IQ scores on these tasks cannot arise from practice, familiarity, education, or training....

Lynn and his colleagues carried out a series of reaction time studies on over 1,000 nine-year-old East Asian children in Japan and Hong Kong, White children in Britain and Ireland, and Black children in South Africa (summarized by Lynn & Vanhannen, 2002, pp. 66â67). The Progressive Matrices were given as a nonverbal test of intelligence, along with the simple, choice, and odd-man-outtasks. Reaction times and variabilities were measured by computer and hence were not subject to any human error in recording. For details, see Shigehisa and Lynn (1991) for Japan; Chan and Lynn (1989) for Hong Kong and Britain; Lynn (1991) for Ireland; and Lynn and Holmshaw (1990) for South Africa.

The correlations between IQ and reaction times for the five countries are summarized in Table 1. The East Asian children in Hong Kong and Japan obtained the highest IQs, followed in descending order by the White children in Britain and Ireland, and then the Black children in South Africa. The medians for simple reaction time, choice reaction time, and odd-man-out reaction time follow the same descending order as the IQs. Because all the tasks take less than 1 s, all children found them easy. The variabilities in the three reaction time measures for the three groups follow the same general descending trend.

The same pattern of average scores on these and other reaction time tasks (i.e., East Asians faster than Whites faster than Blacks) is found within the United States. Jensen (1993) and Jensen and Whang (1994) examined the time taken by
over 400 schoolchildren ages 9 to 12 years old in California to retrieve overlearned addition, subtraction, or multiplication of single digit numbers (from 1 to
9) from long-term memory. All of the children had perfect scores on paper-andpencil tests of this knowledge, which was then reassessed using the Math Verification Test. The response times significantly correlated (negatively) with Raven Matrices scores, whereas movement times have a near-zero correlation.

The average reaction times for the three racial groups differ significantly (see Figure 2). They cannot be explained by the groupsâ differences in motivation because the East Asian children averaged a shorter response time but a longer
movement time than did the Black children." (page 245)

Rushton, J. P., & Jensen, A. R. (2005). Thirty years of research on race differences in cognitive ability. Psychology, Public Policy, and Law, 11, 235-294.

http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf

Would that explain the differences on reaction time measures? Or why the BlackâWhite difference is greater on backward than on forward digit span memory tests?

Yes, through differential anxiety and distraction. In fact, reaction times are so responsive to extrinsic factors (I haven't checked on the memory tests) that I was stunned to learn that anyone thought they were a valid test of intrinsic differences.

There is a quote that recognizes this.

Baseball is ninety percent mental and the other half is physical.
Yogi Berra

The mental part of the game is disrupting your opponents' concentration, so they screw-up. If it works in something as simple as baseball, why wouldn't it work in something more complex like IQ tests?

*** Would that explain the differences on reaction time measures? Or why the BlackâWhite difference is greater on backward than on forward digit span memory tests?

Stephanie Z wrote:

Yes, through differential anxiety and distraction. In fact, reaction times are so responsive to extrinsic factors (I haven't checked on the memory tests) that I was stunned to learn that anyone thought they were a valid test of intrinsic differences.***

Note that Ian Deary found they predict lifespan even better than IQ:

"The researchers learned that those with higher IQ scores lived longer, a result consistent with other studies. The study also showed that characteristics significantly related to death included male gender and smoking. But Deary and Der also found something new - faster reaction times seemed an even better predictor of long life than IQ.

There are different ways the results could be interpreted. Slow reaction times could reflect a degeneration of the brain, which in turn could reflect degenerating physical health (an obvious possible cause of earlier mortality). But in another study the IQs of 11-year-old subjects also were found to predict life span length, just as accurately as it did for the middle-aged participants in Deary and Der's 14-year study.

Future studies of reaction times in younger-aged people may shed more light on the IQ-mortality connection."

http://www.news-medical.net/news/2005/02/03/7612.aspx

A more recent paper by Deary is:

"Higher cognitive function is associated with faster choice reaction time (CRT), and both are associated with a reduced risk of mortality from all-causes and cardiovascular disease (CVD)...These analyses suggest that CRT, a moderately high correlate of intelligence, is an important risk factor for death from all-causes and CVD."

Cognitive epidemiology: Its rise, its current issues, and its challenges Personality and Individual Differences, In Press, Corrected Proof, Available online 14 December 2009
Ian J. Deary

Deary also notes in this paper (Inspection time and cognitive abilities in twins aged 7 to 17 years:
Age-related changes, heritability and genetic covariance Intelligence 36 (2008) 210â225) that increased myelination may drive age related increases in reaction time. That would fit with Thompson's work showing the association of myelination quality and cognitive abilities:

"to make predictions about localisation. Because it has
been hypothesised that the development in speed of
processing may be associated with age-related increases
in myelination, we would expect white matter particularly
to be implicated. In future work we intend to look
at the relationship between white matter tracts and
inspection time by analysing Diffusion Tensor Image
(DTI) scans that give detailed information about white
matter tracts and their connections...

8.8. Conclusions

In conclusion, the results indicate that inspection
time improves across the age range of 7 to 17 years; that
inspection time is related to cognitive abilities in
childhood as well as in adulthood; that inspection time
is moderately heritable, and that genetic and non-shared
environmental factors underlie the relationship between
inspection time and IQ."

152.98.160.29/contents/p/staff/edmonds_intelligence.pdf

Observer, the age-of-death correlation is an argument against a genetic influence on IQ, right?

***Observer, the age-of-death correlation is an argument against a genetic influence on IQ, right?

Posted by: Stephanie Z | January 4, 2010 1:41 AM***

One of the suggestions Deary makes in the paper is that more efficient processing (as shown on reaction time measures) reflects some other aspect of bodily integrity. Here is the pdf of the paper (http://www.psychologicalscience.org/pdf/ps/reaction_time.pdf).

That idea is further discussed in the interesting paper below by Arden, Gottfredson & Miller.

Arden, R., Gottfredson, L. S., & Miller, G. (2009). Does a fitness factor contribute to the association between intelligence and health outcomes? Evidence from medical abnormality counts among 3,654 US veterans. Intelligence, 37(6), 581-591.

http://www.udel.edu/educ/gottfredson/reprints/2009fitness.pdf