More than 130 leading population geneticists have condemned a book arguing that genetic variation between human populations could underlie global economic, political and social differences.
A Troublesome Inheritance, by science journalist Nicholas Wade, was published in June by Penguin Press in New York. The 278-page work garnered widespread criticism, much of it from scientists, for suggesting that genetic differences (rather than culture) explain, for instance, why Western governments are more stable than those in African countries. Wade is former staff reporter and editor at the New York Times, Science and Nature.
But the letter — signed by a who’s-who of researchers in population genetics and human evolution — and published in the 10 August issue of the 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 helped to draft 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 IQ test results, political institutions and economic development. We reject Wade’s implication that our findings substantiate his guesswork. They do not,” write the authors of the letter, which is a response to a critical review of the book published in the New York Times.
“This letter is driven by politics, not science,” Wade said in a statement. “I am confident that most of the signatories have not read my book and are responding to a slanted summary devised by the organizers.”
Wade added that he had asked the letter’s authors — Eisen and Graham Coop, a population geneticist at the University of California, Davis — for a list of errors so that he could correct future editions of the book. According to Wade, Coop did not reply and Eisen promised a response but has yet to deliver one.
The book, Wade said, “argues that opposition to racism should be based on principle, not on the anti-evolutionary myth that there is no biological basis to race”.
Coop says the idea for the letter emerged over discussions at conferences. “There was a strong feeling that we as a community needed to respond,” he says. Like many of the signers, Coop is not pleased about how his research was explained by Wade.
The first portion of the book summarizes recent research in human population genetics, to support the author’s argument that geographically defined ‘races’ are supported by patterns of genetic variation, and that the different environments encountered by these groups led to genetic adaptations after humans left Africa more than 50,000 years ago — such as lighter skin or the ability to digest milk sugar (lactose) into adulthood.
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.
Sarah Tishkoff, a population geneticist at the University of Pennsylvania in Philadelphia who studies human variation in Africa, finds the book’s efforts to explain race in genetic terms to be problematic.
Wade cites a study from another team that analysed genome data from 1,056 humans from around the world using a computer program that divides people into clusters on the basis of their genetic similarity. If the researchers instructed the program to put people into five clusters, the assignments corresponded to continental groups — Africa, East Asia, Europe and the Middle East, the Americas and the Pacific Islands. Wade cited that study and others as evidence for the existence of five human races.
But Tishkoff says that the five clusters are somewhat arbitrary. In a 2009 study that included numerous African populations, her team found that 14 clusters (most of them composed of Africans) were a better explanation for global genetic diversity. “You may see that individuals cluster by major geographic regions. The problem is, there are no firm boundaries,” she says.
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.