Michael Eisen on Wade’s Leaps of Logic

As my own review of Nicholas Wade’s book suggested, his treatment of genetics has many deep and fundamental problems. And as my blog post noted, many others have called some of those out. I want to call out here a particularly clean such account, which came from evolutionary biologist Michael Eisen a few weeks ago. He cuts right to the nut of one of Wade’s most central and dangerous errors:

It turns out to be far easier to demonstrate that there has been a fair amount of recent natural selection acting on the human population, than it is to pinpoint specific examples, or to rigorously evaluate specific hypotheses. The reason is that different types of evolution (drift, positive selection, purifying selection) leave different fingerprints in the genome, and we can use these to estimate how prevalent each of these forces has been in human history, and, to a lesser extent, identify regions of the genome that have been subject to certain types of selection.

But the effect of specific examples of selection are almost always weak – especially the kinds of transient selection affecting relatively small groups of people on which Wade hangs his speculation. Furthermore, while natural selection leaves a signal behind in the genome, the signal is primarily that it happened – it’s much more difficult to precisely identify what was being selected, let alone why or how.

Knowing that natural selection has occurred, in some cases recently, but being unable to be more specific leaves a huge void – and it is into this void that Wade has inserted himself.

And a bit later:

In making the leap from the broad to the specific – from signature of natural selection in the human genome to explanations of the industrial revolution, Jewish Nobel Prizes and political turmoil in Africa and the Middle East – Wade tries to paint himself as a courageous scholar, going places with modern evolutionary biology that scientists WILL not go. But the truth is that scientists don’t go there, not because we are afraid to, but because we CAN’T. The data we have before us simply do not allow us to reconstruct human evolutionary history in this way.

from Michael Eisen’s On Nicholas Wade and the blurring of boundaries between science and fantasy, which I urge you to read whole.

6 responses

  1. Look there simply is no argument.

    Race IS a social construct even in animals of similar kind of diversity as humans. There are constant problems of classifications in the animal kingdom. The divisions are made based on what use the scientists or whomever the divider wants because its a temporary continuum in the same things, they just pick a point. Dogs for example are created into races(breeds) by humans keeping them apart and selecting for traits. Its not natural. There is not biological point at which race shows up in humans its just a choice of which grain you or racists want to focus on, which is completely temporary SPECIALLY with regards to humans.

    Some temporary genetic cluster of the same alleles between humans on different continents doesn’t mean race is biologically. Somebody just decides depending on what is socially useful for them. Wade does it even in the book itself, sometimes its 3, sometimes its 5, sometimes 7. He even states that its for convenience. Convenience for dividing people that is, because he wants to.

    Thats why Obama is black sometimes and mixed other times. Thats why there were such things as one drop rules, 2% rules, etc etc.

    These guys either want to divide people in order to categorize them, have some sort of power over them, whatever. Its a pure social construct. Its almost the same thing as saying I want to divide people who have blonde hair and construct an identity based on that for them such as the blonde “race”. “My proof is that they have so many more of the same blonde genes in common that others do not at this time, and that I can group them based on it. You are a marxist if you don’t agree.”

    Don’t know why they try so hard…. oh wait I do.

    • ***Race IS a social construct even in animals of similar kind of diversity as humans. There are constant problems of classifications in the animal kingdom.***

      @ Panther Ausf G,

      Sure, but those constructs have an underlying biological component. Hence when conducting a GWAS you need to account for different racial/continental populations because you can get false positives caused by systematic differences in allele frequencies.

      Similarly, if two people from Japan have a child it probably isn’t going to look like a Ugandan or a Swede. There are morphological differences between groups that is linked to regional ancestry. Jerry Coyne had a good post discussing the concept.

      Also, I don’t know why Eisen has such high confidence that group differences like those suggested by Wade couldn’t have arisen. Surely the position at this point is that people can’t say either way in the absence of understanding the genetic architecture of various behavioural traits?

  2. ***But the truth is that scientists don’t go there, not because we are afraid to, but because we CAN’T. The data we have before us simply do not allow us to reconstruct human evolutionary history in this way.***

    Yet, as Steve Hsu notes, in time these questions can be tested in the same manner differences in allele frequencies for height have been examined. Hsu notes:

    “But what about more complicated traits, such as height or cognitive ability or personality? All of these are known to be significantly heritable, through twin and adoption studies, as well as more modern methods.

    We can’t answer the question without understanding the specific genetic architecture of the trait. For example, are alleles that slightly increase height more common in one group than another? We need to know exactly which alleles affect height… But this is challenging as the traits I listed are almost certainly controlled by hundreds or thousands of genes. Could population averages on these traits differ between groups, due to differences in allele frequencies? I know of no argument, taking into account the information above, showing that they could not.

    In fact, in the case of height we are close to answering the question. We have identified hundreds of loci correlated to height. Detailed analysis suggests that the difference in average height between N and S Europeans (about one population SD, or a couple of inches) is partially genetic (N Europeans, on average, have a larger number of height increasing alleles than S Europeans), due to different selection pressures that the populations experienced in the recent past (i.e., past 10k years).

    Many who argue on Montagu’s side hold the prior belief that the ~ 50k years of isolation between continental populations is not enough time for differential selection to produce group differences, particularly in complex traits governed by many loci. This is of course a quantitative question depending on strength of selection in different environments. The new results on height should cause them to reconsider their priors.

    It is fair to say that results on height, as well as on simpler traits such as lactose or altitude tolerance, are consistent with Wade’s theme that evolution has been recent, copious, and regional.

    Further extrapolation to behavioral and cognitive traits will require more data, but:

    1) The question is scientific — it can be answered with known methods. (I estimate of order millions of genotype-phenotype pairs will allow us to extract the genetic architecture of complex traits like cognitive ability — perhaps sometime in the coming decade.)

    2) There is no a priori argument, given what we currently know, that such differences cannot exist. (Cf. Neanderthals!) Note this is NOT an argument that differences exist — merely that they might, and that we cannot exclude the possibility.”

    (What’s New Since Montagu – May 14, 2014)

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