Hype vs. content.

I think I should clarify my position on the human evolution acceleration issue, because I don’t want my comments about nonsense in the press to be misconstrued as a rejection of the study. The basic theoretical arguments make good sense, and I am eagerly awaiting (peer-reviewed) commentary regarding the particular method and dataset. As far as whether I accept the possibility of recent selection among humans, allow me to start by showing three slides that I use in my section on human history. These were presented three weeks ago, before I knew anything about the Hawks et al. paper.



If the Hawks et al. study holds up by next fall, I will add some slides about it specifically, because I think it nicely brings together ideas about adaptive peaks, population size, and selection.

My problem, as noted, is with the hype in the press, most of it direct quotes of the authors. Over at evolgen, Hawks suggests that “Most [bloggers] seem to be reacting viscerally to the idea that evolution could ‘accelerate’ by as much as we claim. That’s a deficiency of theory and/or knowledge about human history, which we’re trying as hard as we can to make a dent in.”

Maybe so. But that’s not the case with me, as should be obvious from above. But let’s evaluate how well these authors are succeeding in clarifying misconceptions about human evolution.

“History looks more and more like a science fiction novel in which mutants repeatedly arose and displaced normal humans – sometimes quietly, by surviving starvation and disease better, sometimes as a conquering horde. And we are those mutants.”

Now imagine you’re not a biologist. Your concept of “mutant” is based on what you know from science fiction. And a scientist tells you that human history really did include stampeding hordes of mutants, right out of science fiction. Does this help you to understand that it is an *allele* that is a mutant, and what really happened is that some of us, though more than in the past, are descendants who carry these alleles?

“Five thousand years is such a small sliver of time – it’s 100 to 200 generations ago,” he says. “That’s how long it’s been since some of these genes originated, and today they are in 30 or 40 percent of people because they’ve had such an advantage. It’s like ‘invasion of the body snatchers.’”

Again with the science fiction. I have absolutely no idea how allele frequencies changing *over many generations* by normal vertical inheritance is anything remotely like body snatchers.

“We found very many human genes undergoing selection,” says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million genes showing the most variation. “Most are very recent, so much so that the rate of human evolution over the past few thousand years is far greater than it has been over the past few million years.”

A few million years ago there we no humans. Six (or so) million years ago, there would have been one species that eventually branched into the lineage of which humans are currently the only representative, and the one of which chimps and bonobos are the only extant examples. The *rate* of allele frequency change may be the highest it has ever been, but these statements are unbelievably misleading.

“In the last 40,000 years humans have changed as much as they did in the previous 2 million years.”

Modern humans, as a species, have existed for about 200,000 years or so. More than 90% of the history covered in this claim includes Homo habilis and Homo erectus. Allele frequency changes *may* be faster and more abundant now than during all that time, but this is hardly as significant under the normal conception of “evolutionary change” as the actual origin of two new species, including our own.

Their paper may be great. What they have been stating about it is irresponsible.


7 comments to Hype vs. content.

  • RPM

    the team that analyzed the 3.9 million genes showing the most variation

    So, the pop press thinks SNP=gene?

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  • Anonymous

    “In the last 40,000 years humans have changed as much as they did in the previous 2 million years.”

    That is preposterous. In terms of cultural-biological evolution, is the Upper Paleolithic, the Neolithic revolution, and urbanization really more important than mastery of fire, large game hunting, the invention of clothing, or the diversification of lithic toolkits? Is the morphological evolution of the last 40,000 years greater in magnitude than the two million before that?

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  • Anonymous

    What coauthors have stated in their AAPA 2007 abstracts:

    Understanding human races: the retreat of neutralism.
    Henry Harpending

    “…(H)uman are more, not less, differentiated than other large mammal species. … It appears that there is a lot of ongoing evolution in our species and the loci under strong selection on different continents only partially overlap. Human race differences may be increasing rapidly.”

    Acceleration of adaptive evolution in modern humans.
    J. Hawks and G. Cochran

    “… In genomic and craniometric terms, the origin of modern humans was a minor event compared to more recent evolutionary changes.”

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  • Larry Moran

    Ryan, I admire your restraint. You are willing to grant the authors the benefit of the doubt.

    In spite of the fact they have been widely quoted saying very foolish things about evolution you still believe that the paper itself is theoretically sound.

    Sometimes I wish I could be that generous. I tend to be of the opinion that what people say “off the record” is far more likely to reflect their real beliefs than what they say in a scientific paper that has to pass by reviewers.

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  • TR Gregory

    Hi Larry,

    That’s for sure. But we can’t dismiss the double helix structure because Watson says ridiculous things. I will wait to pass judgment on the paper once I have seen the reaction from other experts. The very basic theory behind it isn’t troubling, but whether the actual numbers reported are sensible remains to be determined. I am, however, able to pass judgment on the nonsense they have said about their work to a susceptible media.

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  • Marco F

    Did you read the paper yet, Mr. Gregory? I’d really like to have your opinion on the Real McCoy (you know, I have to write a short news about it) 8-)

    Marco Ferrari (greetings from Italy)

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