In my post below responding to David Goldstein's implication that intelligence has been subject to strong directional selection I put up a chart from the GSS which illustrated the fact that women who have weaker vocabularies tend to have more children. If you don't believe that intelligence "means anything," and that it isn't heritable, read no further.
On the other hand, if you think intelligence as measured by something like a vocabulary test is important and that it is heritable, below the fold I've placed some charts which show the same relationship between number of children and vocab score as the more general data set (though all are limited to women). Again, on the X axis you have the CHILDS variable from the GSS, that is, 0 to 8 or more children. On the Y axis you have WORDSUM, which shows the mean number correct for each class of women with a particular number of children. I have filtered by variables to show how the trends play out. I've also dropped WORDSUM mean scores where the N for the category was less than 10. I do caution not to over-read every twist and turn of these trends too seriously because of small N's, especially as the number of children increases (e.g., women in graduate school have a very mean low fertility which drops off very quickly).
Highest level of education attained
Race
Political views
Religious views
Observation: I think the educational data tell us quite a bit and suggest that socialization and expectations are very important, more important than the lack of foresight one assumes is more common among the less intelligent. A quick regression suggests that this is so. The beta for WORDSUM is around 0 and not statistically significant when DEGREE is included as another independent variable when CHILDS is the dependent that these two are predicting (albeit, they still don't predict much of the variation in CHILDS).
Methodological note: Remember that the data plotted above are the mean WORDSUM scores within each category of children. The number of individuals within each category doesn't show up here.
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It is one of the most unexpected and important facts of human biology that IQ - having been adaptive for (at least) several million years of human history - became fitness-reducing as soon as contraception began to become available and/or death rates declined sufficiently, and that trend has continued and strengthened. Of course this has been known for a century and more; but it still strange and still not fully explained. I think it tells us something fundamental about humankind, but I'm not yet sure what...
It is one of the most unexpected and important facts of human biology that IQ - having been adaptive for (at least) several million years of human history - became fitness-reducing as soon as contraception began to become available and/or death rates declined sufficiently, and that trend has continued and strengthened. Of
1) i think there was a fair amount of "balancing" dynamics for what we call "general intelligence" over human history (as laid out in the goldstein post). so i don't think it is necessarily fitness enhancing for most of the past 2 million years (i think analogy to height/size is probably apropos). IOW, i'd be willing to bet money that the current dysgenic trend in the modern world is simply recapitulating something that has occurred before many times.
2) in england i believe that the dysgenic trend occurred in the late 19th century during the demographic transition; before effective contraception, right?
Re: 1 - I presume there were several speciation-related increases in IQ over the past 5 million years since humans were (more or less) chimps, as well as more recent amplificiations since out-of-Africa.
2. My understanding from Richard Lynn's Dysgenics and elsewhere is that the demographic transition started with the highest classes. They increasingly used contraception in the 19th century and there were probably other factors. But it may be that it was the huge reduction in death rates that made a decisive difference.
So differential birth rates increasingly came to dictate fitness, rather than differential mortality (since increasing IQ certainly correlates negatively with all cause mortality and mortality from accidents - probably in all societies).
I presume there were several speciation-related increases in IQ over the past 5 million years since humans were (more or less) chimps, as well as more recent amplificiations since out-of-Africa.
*shrug* i don't see the point in talking about "IQ" when it comes to comparing chimps vs. humans. in any case, my point is that there is no reason to presuppose that there has been any sort of unidirectional selection for IQ within the span of the last few tens of thousands of years. i gave the reasoning in my previous post. that doesn't mean that that model is falsified; just that if we assume IQ to be a subset of a class of phenotypes then those are phenotypes which we know seem not to be characterized by persistent unidirectional selection. IOW, the dynamics we observe from 1870 on are not necessarily exceptional or of significant note. they may be recapitulating a tendency for societies to swing between different optimal "set points" of IQ.
My understanding from Richard Lynn's Dysgenics and elsewhere is that the demographic transition started with the highest classes. They increasingly used contraception in the 19th century and there were probably other factors
no, that's my understanding. but i have a narrow conception of what 'contraception' might mean. assumed you meant it was the later adoption of the pill and widespread usage of condoms.
"the dynamics we observe from 1870 on are not necessarily exceptional or of significant note. they may be recapitulating a tendency for societies to swing between different optimal "set points" of IQ."
I think you are probably correct - and if so this is very important and will take a lot of coming-to-terms-with.
The idea coming from the work of Ian Deary in his numerous collaborations (including Linda Gottfredson, who has stated it most clearly) is that the major fitness-related role of IQ may be in reducing age-specific mortality (and thereby increasing longevity) - presumbly this also applies to mothers reducing the mortality of their young offspring.
So, given that IQ comes at a cost (the cost of larger brains, plus presumably other fitness-reducing aspects about which I am not clear at present) it would make sense that the adaptiveness of IQ will vary according to the magnitude of age-specific mortality.
When mortality rates are high, differential IQ may be the most powerful determinant of differential reproduction. But when mortality rates are low, differential fitness is more powerfully affected by birth rates than by IQ.
On the other hand, when mortality rates in childhood become *very* high, then this kind of *extreme* r selection probably accelerates human development to reach sexual maturity at an earlier age with lower average IQ (and reduced average life expectancy) as seems to have happened with pygmies.
http://www.human-evol.cam.ac.uk/Members/migliano/walkeretal2006growthra…
http://www.human-evol.cam.ac.uk/pygmies/am/pnas_2007_life_history_pygmi…
So I guess we might have some kind of inverted U shaped relation between human IQ and mortality rates - highest in societies with moderate mortality, lower in societies with very low or high mortality.
But the interesting twist would be if high IQ humans in modern societies learn this information (which has been knocking around for more than 100 years) and 'decide' to make cultural or social changes to alter differential birth rates according to IQ. This is why I am so interested in the US Mormons, because it seems they *may* have made such a social change, to produce a positive correlation between IQ and fertility.
When mortality rates are high, differential IQ may be the most powerful determinant of differential reproduction. But when mortality rates are low, differential fitness is more powerfully affected by birth rates than by IQ.
if i understand you by this logic the "old stock" of american settlers should be less intelligent than their parent stock in the british isles. the american settler populations experienced a massive demographic expansion between 1650-1850. the most extreme cases might have been in new england between 1650-1700 (see albion's seed).
Well, my argument only apples ceteris paribus; and long distance migration introduces a very powerful kind of population sampling - so no, I would not expect that "the "old stock" of american settlers should be less intelligent than their parent stock in the british isles" - quite the reverse. Although this sampling may be one root of the greater contemporary religiousness in the USA.
But clearly I need to read Albion's Seed - starting in about 2 hours time...
and long distance migration introduces a very powerful kind of population sampling
new england was strongly sampled toward the middle and upper middle classes who were literate, so yes. OTOH, the south was far less so. the people of the southern uplands were the poor and those without means from ulster and the borders. those in the lowlands were divided between the planter aristocracy, and their peasant retainers who they brought or the descendants of indentured white servants. the middle atlantic was more mixed, though more typified by artisans from the midlands.
Disclaimer; not a geneticist or scientist here. Regular working Joe.
I just want to note that having more babies is not necessarily the single criterion (or even the best) for measuring the success of a population.
For example: slaves in the Old South had far more children than the white plantation owner class, but you could not argue that therefore the slaves were more successful as a social group than the landowners.
In other words, sheer numbers are not the gold standard. Another example: India vs the USA. In India you have 600 million people living in poverty who have on average, many more kids per family than in the USA, which has under half the number of people total. It cannot be argued that the half billion impoverished Indians are more successful than the quarter billion Americans because they have more offspring.
This thing could work out to show that smaller populations of more intelligent individuals are better able to adapt to changes imposed by their physical, economic, and social circumstances, and therefore, more fit to survive.
Huge, impoverished populations seem more prone to disease pandemics, or are more adversely affected by natural catastrophes. I would like to see studies of the average number of persons killed or displaced by say, a 6.0 Richter scale earthquake in an impoverished area versus an area where the population is better educated. Or compare deaths from major typhoons in poor areas to correspondingly powerful hurricanes in the US. Or compare the differences in deaths caused by Category 3,4,and 5 hurricanes in the US with corresponding data from Haiti, Dominican Republic, or other poor Caribbean countries where the birthrate is higher and average level of education is lower.
In other words, don't rush to the conclusion that the intelligent are less fit simply because they don't produce as many offspring.
Indulge me for one further thought, if you will:
I think you can see where my logic is going.
Consider: which is more successful in terms of survival and quality of life:
1. A small planet with one billion educated intelligent citizens, or
2. The same small planet with six billion mostly uneducated, impoverished citizens?
yogi-one, you're right that quality is as important a factor as quantity, but ultimately it's about whatever dominates the gene pool. Unless the increased quality grants an increased survival chance greater than increasing quantity, the genetic traits associated with that strategy will tend to be lost in population fluctuations.
If the trait doesn't perpetuate itself as effectively as alternatives, it'll die off eventually.
It is one of the most unexpected and important facts of human biology that IQ - having been adaptive for (at least) several million years of human history - became fitness-reducing as soon as contraception began to become available and/or death rates declined sufficiently, and that trend has continued and strengthened. Of course this has been known for a century and more; but it still strange and still not fully explained. I think it tells us something fundamental about humankind, but I'm not yet sure what...
It's not necessarily fitness-reducing, even in the strictest sense. As an extreme example: Suppose that the average family that produces five children loses three to famine or disease before puberty, but the average family producing four children loses only one. In this case, having fewer children means higher fitness. Resource availability matters, and we're not the only species that requires parental care.
At any rate, simple mathematical models of fitness are extremely useful for making and testing predictions about populations, but in a species that can manipulate its environment the way we can, their uses have limits. Quality of human life, as yogi-one pointed out, is not determined solely by how many descendants one leaves. And one doesn't have to deny the heritable component of IQ to consider an IQ test score to be at best an incomplete predictor of a person's survival probability, economic prospects, or level of social function.
slaves in the Old South had far more children than the white plantation owner class, but you could not argue that therefore the slaves were more successful as a social group than the landowners.
i believe this is false. american slaves did reproduce above replacement by the 18th century, but note that this was a very exceptional case for new world slave populations, most of whom had to be replenished by importation lest their numbers decline through attrition. i have read a few books on american slavery recently and it seems rather clear by inference that free populations, especially elite free populations, had far higher rates of replacement than slaves. do you have a citation?
btw yogi, the rest of your post addresses something totally different than what i'm talking about here.
The 'dysgenic' evidence is not straightforward. The relation between IQ and fertility is probably not linear. The results of different studies (and in different countries) vary, but there is some evidence that the very dim (retarded) on average have few children; the moderately dim have a lot; the prudent lower-middle-middle classes have few; while the upper-middle-upper have more than the average, once they get started.
yogi-
Nature will not care quality of life. Bacteria might have terrible quality of life with short life span and mass death. But as species, germs might be winner over millions years history of life on earth. Dinosaurs had better quality life, less in number compared to roaches. At end, dinosaurs extint. Roaches still roaming around.
Winner of evolution is not determinded by wishful thinking.
Razib- your findings are consistent with Rushton's theory again.
The findings from the GSS don't seem to align with the results from the NLSY, where there is no apparent dysgenic effect for whites:
"50 percent of white children were born to women with IQs below the white mean."
"50 percent of white children were born to women with IQs below the white mean."
depends on the nature of the distribution, right?
Fitness (or the tendency to leave offspring) is a slippery concept. A trait, or allel, that may be very fitness producing in a population over a number of generations may turn out to be completely irrelevant in the face of some new environmental challenge, as for example, a new disease causing agent. Suddenly a trait which in the past may have had little or no value is the be-all and end-all.
So I guess the more interesting question is which trait variations (not gone to fixity) tend to have fitness value over a long historical (or geological) period of changing environments? Intelligence would seem to fit the bill for human beings, all else being equal: smart people can cope better with new environmental challenges, regardless of whether they grow fruitful and multiply, or merely limp along at replacement levels of reproduction.
So maybe fitness should be measured in longevity measured in generations rather than in number of progeny?
Just a hazy thought in a hazy mind.
IOW, i'd be willing to bet money that the current dysgenic trend in the modern world is simply recapitulating something that has occurred before many times.
Could you explain that? I'm aware that Rome may have had a similar problem during the late Republican and earlier Imperial period, and that Sparta did too (if you assume that high Helot birthrates and low Spartan birthrates were dysgenic - I'm sure the Spartans would have). I'll bet all urbanized societies had that problem. But generally, prior to the 20th century our ancestors were mostly farmers in a relatively static, hierarchical society, and before that they were hunter-gatherers. Why would the IQ sweet spot have changed, other than during the transition to agriculture?
But generally, prior to the 20th century our ancestors were mostly farmers in a relatively static, hierarchical society, and before that they were hunter-gatherers. Why would the IQ sweet spot have changed, other than during the transition to agriculture?
in farewell to alms greg clark makes the case that the upper gentry outreproduced both the upper classes and the middle to lower classes. so that subsequent generations were mostly descended from the upper gentry. primogeniture meant that most of the lower classes were descended from upper gentry. since they lived in the country they didn't die in the cesspools that were cities. around 1800 i believe the blooded aristocrats started breeding like crazy; i think some of this can be attributed to the relative demilitarization of the nobility (or at least reduced morality). by the late 19th century the upper classes as a whole, gentry and aristocracy, were dropping in fecundity. so in this specific case you see lots of variation in terms of who is reproducing the most.
as for your point about cities, yes, to a great extent near the climax and through the 'decline' phase of any empire i assume that cities were population sinks. many enterprising and intelligent people were sucked into them and left few if any descendants. in contrast, during expansionary phases i assume that the the malthusian hells were not so extreme and many elites might have initially been more dispersed in the cities.
What about cottage industry? "Until the rise of industrial capitalism in the late 1800s, successful entrepreneurs would increase their workforce by having larger families" (from Peter Frost's blog).
[quote]It is one of the most unexpected and important facts of human biology that IQ - having been adaptive for (at least) several million years of human history - became fitness-reducing as soon as contraception began to become available and/or death rates declined sufficiently, and that trend has continued and strengthened. Of course this has been known for a century and more; but it still strange and still not fully explained.[/quote]
Razib mentions Farewell to Alms and downward mobility in comments, for which I thank her. I think the modern welfare state goes far in explaining any fitness reduction in IQ. On one end, if a person can't or won't work, they can get food, housing and medical care regardless. On the other end, if someone can and will work, they're going to have one quarter to one half of their income taxed away, putting off the day they can afford to raise children of their own.
So there's potentially a perverse selection effect going on, if the pressure is strong enough.
Birth control could be a factor also, but I tend to think it would correct itself in the absence of other distortion.* Consider the grandchild effect: if you only have two children, but they both get every advantage in education, inheritance and society, so that they both find mates and have two and only two children, that may offset the advantage of having more children, not all of whom may have children at all.
*In fact, there's an argument that abortion is slowly correcting itself already, which might explain the slow, general red-state shift in American politics.
For example: slaves in the Old South had far more children than the white plantation owner class, but you could not argue that therefore the slaves were more successful as a social group than the landowners.
Evolution does not really select for 'social group' (though of course social group can help survival), it selects for genetic success. It is not at all impossible that the genes of southern slaves are much more widely distributed in the modern population (including people classified as 'white') than the genes of their plantation owners.