Sunday’s New York Times Book Review features a letter signed by 139 population geneticists, including myself. It is, in essence, a group of scientists objecting en masse to Nicholas Wade’s shoddy treatment of race and evolution in his new book A Troublesome Inheritance: Genes, Race, and Human History. 

The book was about the genetics of ethnic and cultural differences, and while it made a valid point that ethnic groups do show small but significant genetic differences across the globe, there was no evidence for Wade’s main thesis: that differences in behavior among groups, and in the disparate societies they construct, are based on genetic differences. While that might in principle be true, we simply have no evidence for that conclusion, and it was irresponsible of Wade to suggest that such evidence existed.

I was asked to review Wade’s book for a major magazine, but after reading it became so dispirited that I simply didn’t have the stomach to eviscerate it (pardon the pun). But Allen Orr did a good job in the New York Review of Books; and it was telling that even the Times’s own review, by David Dobbs, was pretty critical. (The Times Book Review is infamous for going easy on books by the paper’s own writers, and Wade has written for the paper for years.)

At any rate, I’ve put the letter below (link is here), and the list of 139 signatories is here.  I thank the organizers of this venture—which truly was like herding cats—for compiling a list of almost every population and evolutionary geneticist you can think of, and getting nearly all of them to sign. A statement by such a big and influential group of the very people who work on evolutionary genetics—many in humans, some of whose work was cited by Wade—is surely a severe indictment of Wade’s book and scientific acumen.

The letter:

The five  main signatories given above are those who did the heavy lifting, while the rest of us read the letter, made minor suggestions, and signed it.

I’ve been informed that both Science and Nature have written small features about the letter.  The one in Science is called “Geneticists decry book on race and evolution,” and, like the one in Nature, is free.  Some excerpts:

The letter was spearheaded by five population geneticists who had informally discussed the book at conferences, says co-organizer Rasmus Nielsen of the University of California, Berkeley. “There was a feeling that our research had been hijacked by Wade to promote his ideological agenda,” Nielsen says. “The outrage … was palpable.” Molly Przeworski of Columbia University, another organizer, says the group “tried to contact population geneticists whose work had been cited by Wade.” They had no trouble getting signatures, racking up 100 within the first week, she says.

The letter organizers and the editors of the Book Review kept the letter under embargo until its publication today and declined to make it available to Wade for an immediate response. [JAC: he has responded; see below.] But in previous ripostes to the book’s critics, most notably in a 19 June Huffington Post article titled“ Five Critics Say You Shouldn’t Read This ‘Dangerous’ Book,” Wade charged that his critics were “indoctrinated in the social-science creed that prohibits any role for evolution in human affairs” and contended that the book’s central argument “has not been challenged by any serious scientist.”

Letter organizers say they hope to demonstrate that the opposite is true. For example, Sarah Tishkoff of the University of Pennsylvania says she signed the letter because “[m]y own research was used as scientific proof of concepts such as there being between three and five races.” Tishkoff says that her work on the genetics of diverse African populations does not support this claim. Adds David Reich of Harvard University: “Our findings do not even provide a hint of support in favor of Wade’s guesswork.”

Yeah, right! All 139 of us, with diverse views on politics and diverse backgrounds, have been “indoctrinated in the social-science creed that prohibits any role for evolution in human affairs.” What kind of person would say something so fatuous, especially because few of us even have anything to do with the social sciences?

Indeed,  Tishkoff and her team has provided one of the best examples of how evolution played a significant role in human affairs. Populations of humans in Africa that are “pastoral” (i.e., raised sheep and cows for dairy products) evolved the ability to keep digesting the milk sugar lactose after it was normally turned off after childhood in non-pastoral populations. (Early humans didn’t drink milk after weaning, so there was no need to make an expensive enzyme to digest it after you no longer drink it.) Her group even showed that this evolution happened about 8,000-10,000 years ago (it’s described in WEIT), identified the mutations keeping the enzyme turned on, and showed that “turned-on” mutation had a significant selective advantage: allowing up to 10% more offspring than those from people lacking the mutation. (That is a big  evolutionary advantage that can cause rapid change.) This is a splendid example of “gene-culture” coevolution, whereby human cultural practices can affect our genetic constitution.

Ergo, Wade’s claim that we’re all warped by the social sciences to the point where we’d deny the role of evolution in human affairs is simply a stupid claim. This is the last-ditch defense of a man who has no scientific arguments in favor of his hypothesis: when cornered, just question your critics’ objectivity.

The Science piece also ends with a response issued by Wade, which you can find as a separate pdf file here. I won’t duplicate the whole thing, but you can get a sense of it from its beginning:

This letter is driven by politics, not science. I am confident that most of the signatories have not read my book and are responding to a slanted summary devised by the organizers. . . I would urge all the geneticists who signed the letter, several of whom I count as friends, to now read my book and judge to what extent, if any, their condemnation was justified.

I wouldn’t be so sure about that, Mr. Wade! Don’t underestimate scientists’ desires to read  popular books about their field, if for no other reason than to see if our work is represented accurately. In my case, I read the damn thing twice to review it—an experience I wouldn’t want to repeat.

The piece in Nature is called “Geneticists say that popular book misrepresents research on human evolution.”  A few excerpts:

. . .  the letter — signed by a who’s who of population genetics and human evolution researchers, and to be published in the 10 August New York Times — represents a rare unified statement from scientists in the field and includes many whose work was cited by Wade. “It’s just a measure of how unified people are in their disdain for what was done with the field,” says Michael Eisen, a geneticist at the University of California, Berkeley, who co-drafted the letter.

“Wade juxtaposes an incomplete and inaccurate explanation of our research on human genetic differences with speculation that recent natural selection has led to worldwide differences in I.Q. test results, political institutions and economic development. We reject Wade’s implication that our findings substantiate his guesswork. They do not,” states the letter, which is a response to a critical review of the book published in the New York Times.

Several signatories explain how Wade misquoted or misrepresented their findings. Here’s just one, from Graham Coop:

For instance, in making the argument that populations outside of Africa experienced more evolutionary adaptations known as ‘selective sweeps’ than Africans did, Wade quotes a 2002 paper by Coop, in which his team wrote: “A plausible explanation is that humans experienced many novel selective pressures as they spread out of Africa into new habitats and cooler climates … Hence there may have been more sustained selective pressure on non-Africans for novel phenotypes.”

But Coop notes that Wade omitted key caveats, including the statement that African populations may have actually experienced more selective sweeps than non-Africans, but which the researchers missed for technical reasons. “While Wade is obviously welcome to choose his quotes and observations, he consistently seems to ignore the caveats and cautions people lay out in their papers when they do not suit his ends,” Coop says.

And Sarah, whose team did the work on lactose tolerance, damns the book in just a few words (I’ve bolded the money quote):

Tishkoff also acknowledges that natural selection has created biological differences that vary with geography. For example,her team discovered mutations that allows some African populations to digest lactose. But she scoffs at the idea, proposed by Wade, that natural selection has shaped cognitive and behavioural differences between populations around the world. “We don’t have any strong candidates for playing a role in behaviour,” she says.

But she and the other letter signers are most riled by what, they feel, is Wade’s contention that his book is an objective account of their research. “He’s claiming to be a spokesperson for the science and, no, he’s not,” she says.

What is the upshot? As far as the science is concerned, all of the signatories, I think, would agree that evolution has indeed played a significant role in human morphology and biochemistry, producing population differences that have adaptive significance. Differences among groups in skin color and lactose tolerance, for instance, are certainly due to natural selection, though for skin color the story is not as clear as it once seemed (some say darker skin evolved to prevent neural tube defects, for instance, rather than UV-induced melanomas). And the marked differences in physical appearance between groups may have resulted from sexual selection, though that’s pure speculation.

What we do know is that most genes don’t show striking frequency differences among groups, and that “races” are delineated by combining information from many genes, each of which shows relatively small differences among populations. (I’ll add once again that there is no unanimity on how many “races” there are, which is really a semantic question. What we know is simply that populations show genetic differences that correlate with their geographic location.) The genetic information we have, however, is sufficient to give us an idea of the evolutionary history of humans: when they left Africa, when they colonized the New World, where (in some cases) a European can find her ancestors. It’s these genetic differences that, combined, are used by firms like 23andMe to tell you about your ancestry.

But what is even more speculative is Wade’s thesis that behavioral differences between groups, and thus the societies they construct, are based on genetic differences produced by natural selection. Perhaps that is true, but we don’t have a scintilla of evidence for it right now. And we know that those societal and cultural differences can change quite rapidly—much faster than can be explained by natural selection. Perhaps we’ve experienced genetic evolution producing inter-group differences in behavior, but we’ve surely had tons of nongenetic cultural evolution. (Take a look at the penchant for “Hello Kitty” in Japan. That is not based on genes.) For Wade to write a whole book resting on this speculative house of cards—the idea that genes and natural selection are everything in explaining culture—is simply bad popular science.

Wade is fighting back with the only tool he has—ad hominem arguments. But it won’t work, for we simply don’t have the data supporting his thesis. He’ll look very foolish if he, a journalist, continues to claim that he is representing the data correctly, while 139 population geneticists are all wrong. It is Wade’s lack of supporting data that got all of us heated up enough to go public with our criticisms.

Wade should be deeply embarrassed, but, as we know, people are loath to admit that they’re wrong—or that they’ve simply made stuff up to support their pet theory. In his recalcitrance and his propensity for making up stories, Wade resembles a theologian more than a science journalist.