In the comments section of another thread over at Pandas' Thumb, I asked leading ID proponent Paul Nelson to explain why he thinks the differences between humans and chimps represent macroevolution and not microevolution. Dr. Nelson responded to my question. The terms microevolution and macroevolution are so frequently used in the context of creationism, Intelligent Design, and evolution, so I thought it might be a good idea to move the topic to a new thread.
In addition to linking to Paul's comment, I'll also reproduce it in full at the end of this post. That should make it easier for people to see what he said in its entirety, without my commentary.
My question to Dr. Nelson was this:
While you're here, and this is genuine curiosity on my part, could you take a couple of minutes to elaborate on exactly why you believe that human-chimp divergence is macroevolutionary rather than microevolutionary?
I asked that because he had just written a blog post in which he classified (more than once) the divergence of chimps and humans as "macroevolutionary." The beginning of his response to my question is somewhat dismissive:
Micro, macro, tomato, tomahto..."I am apt to suspect there enters somewhat of a dispute of words into this controversy" (Hume 1779).
I've spent the last two years studying evolutionary biology, molecular ecology, speciation, and related subjects at the graduate level. My interest in evolution started well before that, and I've been following the various creation-evolution controversies for a solid decade now. I have absolutely no problem with the idea that the distinction between macro- and microevolution is nothing more than a dispute over words.
The thing is, they're not my words.
Microevolution and macroevolution are words that are sometimes used by evolutionary biologists, but they're more often used by anti-evolutionists, usually in a very specific context. I cannot count the number of times that anti-evolutionists have assured us that they have no problem with the idea of microevolution, and that they simply do not accept the idea that macroevolution can account for the biodiversity we see in the world today. The issue was raised by the Discovery Institute during textbook hearings in Texas. It came up more than once during the Kansas Kangaroo Kourt hearings. The Institute for Creation Research's website has hundreds of references to macroevolution. I'm not sure if (or how often) the words are used in Mike Behe's new book, but the idea that there's a hard boundary beyond which evolution doesn't work is the central thesis of The Edge of Evolution. I, personally, do think that this is a word game, but I'm not the one playing it.
But seriously: my first introduction to King & Wilson 1975 was, IIRC, reading Gould's Ontogeny and Phylogeny (1977) as a college student, which then sent me back to the original paper. Gould was so excited about King & Wilson 1975 that he used it to launch the book's epilogue (and thanked King and Wilson in his acknowledgments for providing the launching point) about searching for evolutionary mechanisms to explain the "phenomena of saltation" (p. 409):
Although the differences between humans and chimps may be quantitative only, the two species as adults do not look much alike and their adaptive differences are, to say the least, profound (no monkey, despite the common metaphor, will ever type -- much less write -- the Iliad). Yet King and Wilson (1975), reviewing evidence for the astoundingly small differences in structural genes between the two species, have found that the average human polypeptide is more than 99 percent identical with its counterpart in chimps....For 44 structural loci, the average genetic distance between chimps and humans is less than the average distance between sibling species barely, if at all, distinguishable in morphology - and far less than the distance between any measured pair of congeneric species.
What, then, is at the root of our profound separation? King and Wilson argue convincingly that the decisive differences must involve the evolution of regulation....Of the nature of our regulatory differences, King and Wilson profess ignorance: "Most important for the future study of human evolution would be the demonstration of differences between apes and humans in the timing of gene expression during development of adaptively crucial organ systems such as the brain" (p. 114).
I think King and Wilson 1975 was deeply prescient -- a great paper, deservedly a classic. But the puzzle they posed is still unsolved today. Sorry, Toejam, but that's the truth; don't gripe to me, take it up with Massimo Pigliucci:
The argument here. and please do correct me if I'm wrong, seems to be that macroevolution is any evolution where we don't entirely understand the exact mechanism that caused the changes. That particular line of argument reminds me of a signature file that Sverker Johansson used on talk.origins:
Micro-evolution: evolution for which the evidence is so
overwhelming that even the ICR can't deny it.
Macro-evolution: evolution which is only proven beyond
reasonable doubt, not beyond unreasonable doubt.
The language of Dr. Nelson's argument may differ from Sverker's sig quote, but the spirit seems to be more or less the same. We don't understand something or another about the difference, therefore it's macroevolution.
Actually, I hope I really am misunderstanding Paul's argument, because if I'm not it's embarrassingly bad. If the major difference between microevolution and macroevolution is based more on our imperfect human understanding of biology than on any objective differences between species, it's nothing more or less than an argument from ignorance. That's poor form in logic, debate, and philosophy. It certainly has no place in science.
Paul Nelson's original comment in full:
Hi Mike, You asked:
could you take a couple of minutes to elaborate on exactly why you believe that human-chimp divergence is macroevolutionary rather than microevolutionary?
Micro, macro, tomato, tomahto..."I am apt to suspect there enters somewhat of a dispute of words into this controversy" (Hume 1779). But seriously: my first introduction to King & Wilson 1975 was, IIRC, reading Gould's Ontogeny and Phylogeny (1977) as a college student, which then sent me back to the original paper. Gould was so excited about King & Wilson 1975 that he used it to launch the book's epilogue (and thanked King and Wilson in his acknowledgments for providing the launching point) about searching for evolutionary mechanisms to explain the "phenomena of saltation" (p. 409):
Although the differences between humans and chimps may be quantitative only, the two species as adults do not look much alike and their adaptive differences are, to say the least, profound (no monkey, despite the common metaphor, will ever type -- much less write -- the Iliad). Yet King and Wilson (1975), reviewing evidence for the astoundingly small differences in structural genes between the two species, have found that the average human polypeptide is more than 99 percent identical with its counterpart in chimps....For 44 structural loci, the average genetic distance between chimps and humans is less than the average distance between sibling species barely, if at all, distinguishable in morphology - and far less than the distance between any measured pair of congeneric species. What, then, is at the root of our profound separation? King and Wilson argue convincingly that the decisive differences must involve the evolution of regulation....Of the nature of our regulatory differences, King and Wilson profess ignorance: "Most important for the future study of human evolution would be the demonstration of differences between apes and humans in the timing of gene expression during development of adaptively crucial organ systems such as the brain" (p. 114).
I think King and Wilson 1975 was deeply prescient -- a great paper, deservedly a classic. But the puzzle they posed is still unsolved today. Sorry, Toejam, but that's the truth; don't gripe to me, take it up with Massimo Pigliucci: http://life.bio.sunysb.edu/ee/pigliuccilab/Lectures_files/lecture-evono… See slides 11 and 18-20. Consider an anatomical character that, except under pathologic circumstances, is universally shared in Homo sapiens, our white sclera: http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&T… How did this character arise, and how was it fixed, in our common ancestry with chimps (who lack the character)? Various adaptive hypotheses exist about the communication function of white sclera. These however tend to be of the "it's good to have that trait, so we have it" sort. Given that other primates have pigmented sclera, it is likely that the common ancestor of chimps and humans also had pigmented sclera. The character "white sclera" must then have evolved on the branch leading to Homo sapiens. How did that happen? Anybody? Doc Bill, you asked about "astonishment."
My conversations about King & Wilson 1975 have typically gone (roughly) like this [EA, evolution activist; PN, me]:
EA: King & Wilson showed that we're basically chimps. You know, the "third chimpanzee," as Jared Diamond put it. 99 percent identical genetically.
PN: Actually, the main point of their paper was to argue that significant evolutionary change must arise from mutations in "regulatory," not structural, genes, and that how this happens, and what these loci are, is an open puzzle.
EA: Say what? About like that. This conversation does not occur with evolutionary biologists of my acquaintance who have read King & Wilson 1975.
All this strikes me as somewhat disingenuous. We're really talking here about the subjective appreciation of differences. Chimps look very different - they're shorter, they behave differently, they're much hairier, the tasks they do well are very different from the tasks we do well. From an intensely self-centered frame of references, these differences are clearly macro. Contrast this with sharks - creationists have no problem associating (say) sand sharks and whale sharks as the same "kind" because, hey, they're both sharks. All bacteria are the same "kind" because these are so nonhuman their differences don't matter.
I wonder how Paul would classify the occasional atavistic human - born with obviously chimp-like characteristics to normal human parents. When "macro" depends on hair, or ability to write like Homer, is it any wonder we "classify" such individuals by looking the other way and not mentioning them?
Excellent post Mike. It is worth repeating that scientists do science, while IDers play word games. They need to be called on that more often.
Perhaps someone with the necessary knowledge should put together a list of species within "kinds" that are further apart genetically than are chimps and humans. I believe rats and mice qualify, as do most bacteria.
Since no two creationists can agree on what a "kind" is, no such list can be compiled. In fact, most individual creationists cannot agree with what they themselves said on a different day. Behe, for example, has gone from arguing that whales are a separate kind from other mammals to arguing that phyla are separate kinds.
Worst case: one particularly stupid creationist of my unfortunate acquaintance asserted in the scope of a single paragraph that eagles and hawks were two different kinds, then that all birds were one kind. He then went on to claim that the kind was a genus, and gave us an example, lions and housecats. When I pointed out that lions and house cats were not in the same genus, he replied (grammar intact): "That you problem. I have define kind."
My head still hurts thinking about it.
But if a definitive list is impossible, at least we can manage some trends.
As was observed above, creationist "kinds" get bigger the farther away from humans you are. Also, the more humans like or care about the group, the more attention it gets, the more likely it is to be divided narrowly.
Hominids are generally "kinds" vary narrowly, less than a genus, with "huge, unbridgeable gaps" everywhere you look. (Never mind that they can't seem to *find* any of these huge, obvious gaps.)
Other apes are kinds at about the genus level. Gotta keep them diverse!
Most other mammals can be safely labeled kinds based on the family. There are exceptions. Farm animals will likely be split at the genus level from their wild relatives. Rodents and bats, being less familiar and of less interest, may well be lumped into order-sized kinds.
I see little consistency in the treatment of birds. Many creationists seem content to make one bird kind, or split them at orders. Creationists who are aware of just how much diversity there is in the Passerines are likely to suggest cutting that up as well, but I've never encountered a creationist familiar enough with birds to actually present a splitting.
Reptiles can be safely divided somewhere between orders and class. Turtles are usually regarded as different from the others, but "Lizards" (frequently including crocodilia) may or may not be split from snakes. Creationists with an ounce of sense do not cluster crocodilia and lizards, but "has an ounce of sense" is hardly a common merit in the group. I've never encountered a creationist who had even heard of a tuatara or amphisbaena.
(If you haven't, good reader, look them up! They're neat, but oh, so often ignored.)
Amphibians are easy: Two kinds, frogs and salamanders. Wait, there's a third group? Since when! Okay, 3!
(While you're looking up tuatara and amphisbaena, check out caecilians. Amphibian snakes! There's so much neat wildlife out there.)
Fish are lumped very broadly. Many creationists will accept fish as one kind totally. Henry Morris, for example, once suggested that all fish, ALL FISH, could have microevolved from salmon in less than 500 years. Anyone who can swallow batfish, sharks, rays, guppies, flounder, and piranha all being one kind, but finding evolution between chimps and humans impossible is in serious denial. Many creationists will assert narrower splits, though, at least getting the cartilaginous and jawless fishes away from the bony ones.
After that, it's a game of Russian roulette. I've never met a creationist who understood invertebrates of plants well enough to split them. Those that even remember that they exist are likely to make three kinds out of invertebrates: Bugs, worms, and (if you're lucky) mollusks. I've never met one who remembered sponges, echinoderms, or cnidarians without prompting, much less one who had a clue just how much was being stuffed into "worms" and "bugs".
Naturally, no creationist has heard of Trichoplax or can explain how it isn't a perfect transition stage between protists and animals. (Genetically, it isn't, but physically, it shows perfectly that such a transition could have been easily accomplished. Poor creationists, nature just doesn't seem to want to give them any gaps at all.)
Plants? They're all green, right? Creationists ignore them so much I can't really identify any trends. They're all over the board the few times I've seen them brought up.
Protists and fungus, may well be lumped together. Algae, also green (wait, aren't there non-green algae? DON'T CONFUSE ME!), probably go in the plants though. Maybe. Or not.
Bacteria are sometimes green so... OH JUST FORGET IT!
Seriously, I've only seen one creationist address bacterial kinds. There was only one bacteria kind. Just one.
Get this. Bacteria include more biochemical diversity than the entire rest of life on earth put together without even trying. I absolutely do not comprehend how a creationist can swallow a single kind that would require COMPLETELY rewiring every biochemical system the organism has, but find that humans cannot be apes because we have less hair, larger brains, and are a bit straighter in the back. It's like proclaiming that driving from Alaska to Tierra del Fuego is easy, but driving across Mayberry is impossible.
They're using a folk biology of a not-very-biodiverse arid region and trying to apply it to the entire biosphere.
It's classic "ask a stupid question..." territory.
I think a simple way for them to define 'kind' is to use chromosomal numbers as the separating factor. Its pretty easy to measure in animals and plants and in animals at least different chromosome numbers will have a distinct effect on the ability of very similar species to interbreed, i.e. dog and wolf can have fertile offspring but not dog and fox.
If they can agree on that then they can get to work counting up the actual number of 'kinds' that Noah took on the ark!
Why do people think writing the Iliad is something that comes naturally to humans? As if someone who grew up without being taught to read, write, speak, etc would suddenly be able to do so, simply because they're human. In order to see natural behaviors between the two, ape and human comparisons must be made with a cultural filter.
By the way, what about the bonobo who could understand human speech very well and could type (using symbols instead of letters)?
Posted by MartinC
I think a simple way for them to define 'kind' is to use chromosomal numbers as the separating factor.
Doesn't work. There are many examples of species that breed readily despite greatly differing chromosome counts. As a simple example, XYY human males have no trouble having children with regular human women. (The same isn't true of XXY males, though, in which number I may end up being counted; I get tested next week.) This, despite vertebrates being relatively picky about such things. There is a at least one species of butterfly where the chromosome counts are extremely variable, but which have no problem breeding with other members of the same species that have two or three times the available genetic material!
Posted by soteos
By the way, what about the bonobo who could understand human speech very well and could type (using symbols instead of letters)?
Creationists don't like to admit bonobos exist. They attack pretty much all of the fundamentalist party line!
Michael, I wouldnt describe chromosomal number as the ultimate and only defining factor but it is one of the best. The XYY or XXY situation is hardly a common karyotype in humans and wouldn't be used if you are going to define humans by their 'normal' 46XX or 46XY karyotype. Perhaps we cant use this method to define some plants or insects as you have described but for a lot of species I think it is about the most useful means to differentiate them.
I think a simple way for them to define 'kind' is to use chromosomal numbers as the separating factor.
Unfortunately some plants have very variable chromosome numbers, e.g. sugar cane has 40 - 128 chromosomes. Then there are things like triploid bananas and tetraploid lilies that I think most creationists would be reluctant to consider 'separate kinds".
I am glad it is a problem for creationists, not for biologists!
Paul Nelson provides IMHO the best example why creationists definition of micro- and macroevolution is an impossible distinction:
Consider an anatomical character that, except under pathologic circumstances, is universally shared in Homo sapiens, our white sclera [...] How did that happen? Anybody?
Yes, let us consider white sclera. It is a phenotype among other colored sclera in several animals, for example horses.
Is evolution of sclera color, specifically white sclera, among horses micro- or macroevolution, Paul? Is evolution of sclera color, specifically white sclera, among hominids micro- or macroevolution, Paul?
The XYY or XXY situation is hardly a common karyotype in humans and wouldn't be used if you are going to define humans by their 'normal' 46XX or 46XY karyotype.
But you would still not explain Robertsonian translocations:
Although people with these translocations have only 45 chromosomes in each of their cells, all essential genetic material is present, and they appear normal.
Their children, however, may either be normal and carry the fusion chromosome, or they may inherit a missing or extra long arm of an acrocentric chromosome. The distribution of a Robertsonian translocation chromosome at meiosis can cause serious medical problems or no problems at all!
Organisms can have different chromosome arrangements and still retain the same phenotype.
I once got William Harris to say that microevolution happens within species, while macroevolution happens between species. He, of course, had problems with macroevolution. When I told him about all the research in which species boundries are broken down or created, he admitted he wasn't familiar with any of it. I wasn't surprised.
There are examples of sexual dimorphism that make the opposite sexes of the same species that make the human/chimp morphological differences look small. There are also species for which we don't even know what the male looks like.
macroevolution obviously means "evolution that can't happen". You get a more direct discussion by framing the more direct question "which aspect of the chimp/human difference is impossible via 'microevolution'".
I have bookmarked Michael Suttkus's excellent discussion of kind
Some creationists use the term "baramin" rather than "kind." Check out http://www.conservapedia.com/Baramin for a revealing explanation. [chortle]
Torbjorn, you forgot to mention one salient point regarding Robertsonian translocations, namely that individuals with this karyotype have fertility problems. They need to pass on the Robertsonian chromosome when mating rather than a combination of the Robertsonian and one of the other D group chromosomes. I used to work as a cytogeneticist, looking for karyotypic abnormalities as an explanation for infertility in apparently healthy couples and the discovery of an underlying Robertsonian translocation in one of the partners was not an uncommon finding. It obviously doesn't make you completely infertile but it will seriously impact your overall fertility. In an inbred population, however, the 46 chromosome karyotype can go to 45(Robertsonian) to 44, in the course of three generations if there is a mating between two 45(Robertsonian) siblings (or between a parent and child who both have this karyotype). The resultant individual can have great difficulty in breeding with anyone but carriers of the Robertsonian. Here is a study in mice that illustrates this effect.
Obviously chromosomal numbers do not distinguish ALL species but for many situations it is a good rule of thumb.
Torbjorn, you forgot to mention one salient point regarding Robertsonian translocations,
I thought it was sufficient to leave the part about children to show that it isn't problem free. But you are correct, I haven't noticed that inbreeding isn't stable - I didn't consider the implications of how RT is passed along. Thank you, MartinC.
So I concede the point, it isn't pertinent if it isn't stable and dominant so characterizing a population.
Btw, in my eyes worse (because I learned something new here!) was that I claimed "the same phenotype". I guess it is instead likely that RT will differ some in regulation, so it is only roughly the same.
I've never come across a coherent, meaningful Creationist account of the difference between micro- and macroevolution. Eldredge (Macroevolutionary Dynamics, 1989) said that Dobzhansky "saw macroevolution as the accumulation of microevolutionary changes over periods of time extending far beyond human capacity for direct experimentation and observation." However, he considered this definition to require some modification when digging into the details of evolution. For one thing, at the larger scale, accumulation of complex adaptations can occur and it is also at the larger scale that mass extinctions occur. Mass extinctions, Eldredge claims, provide opportunity for truly novel adaptations.
The ultimate irony of the creationist distinction between species and 'kinds' is that the people who invented the Genesis myth probably had a better grasp of the concept of species than modern creationists do. IIRC, SJ Gould reported some of the anthropological data on small, non-Western groups in at least one column for Natural History. The bottom line was that people living close to nature were quite aware of species (i.e., naturally breeding populations) and generally defined exactly the same species as biologists did. In at least one case when their definition of a particular species differed from the biologists', it turned out the tribe or clan had simply discovered a species previously unknown to science.
Given that, it seems hugely likely that the people who first came up with the Genesis myth were referring to something very close to the modern scientific concept of species when they used the word 'kind' (or whatever Hebrew word later got translated into 'kind.')
I guess the creationists have gotten so used to misquoting and quote-mining scientists that they just slipped into doing the same thing with the bible.
MartinC, Torbjorn--there are a few mammal species with well-documented chromosomal variability that doesn't significantly inhibit reproduction--best examples are house mice and Brazilian marsh rats. There is a short essay by Jim Patton that reviews chromosomal speciation issues in mammals, with good references, at http://www.scielo.org.ar/scielo.php?pid=S0327-93832004000200001&script=…
Look, I am a graduate of SOEST. The morphological differences between chimps and humans are mostly described by selection. Not evolution in the genetic sense. Chimps normally walk on branches using their hands to balance on branches above the branch they are walking on. Watch the animal channel for examples. They simply selected the trait in the same way we select dogs for favored traits. A lasopso (sp) is a haisbreath away genetically from a great dane but sexually differentiated. We cannot breed a small dog with a large dog without congenital defects, some awfull. The only seriously different change between chimps and humans is the brain. Of course I am simplifying things, Chimps and humans are not sexually compatable 3 million years of separation guarantee that. but genetically we are very similar. It is no surprize.
I would not be surprized to find out that the difference betweem the chimp genome and the human genome is less than the difference between siblings. but that difference is dramatic.
The morphological differences between chimps and humans are mostly described by selection. Not evolution in the genetic sense. Chimps normally walk on branches using their hands to balance on branches above the branch they are walking on. Watch the animal channel for examples.
Or you may read the article in the 1 June 2007 issue of Science by Thorpe, Holder, & Crompton, "Origin of Human Bipedalism as an Adaptation for Locomotion on Flexible Branches."
Does micro lead to MACRO? No, it does not:
"As encompassed by the âSynthetic Theoryâ (or âModern Synthesisâ) of evolutionary biology, the 20th century has provided a thorough understanding of the mechanisms of microevolution (Dobzhansky, 1937; Mayr, 1942; Simpson, 1944; Mayr and Provine, 1980). It is relatively well known how organisms adapt to their environment and, arguably, even how new species originate. However, whether this knowledge suffices to explain macroevolution, narrowly defined here to describe evolutionary processes that bring about fundamental novelties or changes in body plans (Theissen, 2006), has remained highly controversial." - Journal of Experimental Botany, 2006 57(13):3531-3542
Ah, a creationist troll posts on a long-moribund thread!
The concluding remarks to the same paper:
Due to the large time-scales and diverse mechanisms involved, studying macroevolution is hardly a trivial task. Reconciling macroevolution with population genetics appears to be a considerable challenge for the future (Nutt et al., 2006; Theissen, 2006). The Spe variety of C. bursa-pastoris shows a rare, yet potentially evolutionarily important, phenomenon, specifically the occurrence of a homeotic variety apparently forming stable populations in the wild. A detailed study of the Spe variety may not only tell us more about the developmental genetic mechanisms that generate novel structures in the first place, but also indicate whether, and if so how, drastic morphological variants are established in natural populations.
However, in discussions with colleagues we are occasionally told that even clarifying the molecular mechanism that brings about the Spe phenotype, and demonstrating that Spe plants currently have a fitness in the wild that is at least as high as that of wild-type plants of C. bursa-pastoris, would not suffice to make a convincing case for Spe being a hopeful monster. Rather, one would have to demonstrate that Spe is still flourishing in, say, one million years time. However, we do not agree, because it is a characteristic feature of homeosis or other saltational changes in evolution that they readily produce morphological novelties within a short period of time. While these novelties may strongly influence the probability of short-term survival of the affected population, its long-term survival will much more depend on all kinds of contingencies rather than on the newly established morphological feature; hence long-term survival is irrelevant for the plausibility of saltational evolution.
To summarize, someone dishonestly quote-mines a real piece of research to try and make it look like real science agrees with creationism. Gee, we've never seen that before have we?