In an article accompanying the initial publication of the human genome sequence in 2001, distinguished evolutionary geneticist Svante Pääbo celebrated the accomplishment, comparing the feat to putting a man on the moon. But he also offered these words of caution:
"As we enter a genomic era in medicine and biology, perhaps the greatest danger I see stems from the enormous emphasis placed on the human genome by the media. The successes of medical genetics and genomics during the last decade have resulted in a sharp shift toward an almost completely genetic view of ourselves. I find it striking that 10 years ago, a geneticist had to defend the idea that not only the environment but also genes shape human development. Today, one feels compelled to stress that there is a large environmental component to common diseases, behavior, and personality traits! There is an insidious tendency to look to our genes for most aspects of our “humanness,” and to forget that the genome is but an internal scaffold for our existence.”
Pääbo's fears could not be better embodied than they were three days later in news peice written by science journalist Nicolas Wade in the New York Times. Titled "The Other Secrets of the Genome," Wade promised readers that the genome sequence would offer insights into the genetic bases of much more than common diseases. Rather, he anticipates that we would find, within the genome, the roots of human intelligence, beliefs, and behaviors. Clearly barely able to wait, he poetically predicts "When fully translated, [the sequence] will prove the ultimate thriller -- the indisputable guide to the graces and horrors of human nature, the creations and cruelties of the human mind, the unbearable light and darkness of being."
Wade now, a little over a decade later, is attemptig to fulfill many of these promises in his new book, A Troublesome Inheritance: Genes, Race and Human History. The thesis of the book is that human races have a genetic basis and that the genetic differences among races account for ethnic, cultural, and geographic differences, including things like governing style and economic system.
The two fundamental problems with this book are that it misunderstands human genetic variation and that it lacks evidence to back up its claims for the genetic basis of behavioral traits. With foresight that now seems nearly uncanny, Pääbo addressed this first issue in the very article mentioned in the opening of this post. He explains that "... it is clear that what is called “race,” although culturally important, reflects just a few continuous traits determined by a tiny fraction of our genes..." and notes that "it is often the case that two persons from the same part of the world who look superficially alike are less related to each other than they are to persons from other parts of the world who may look very different."
In other words, certain genes happen to covary in a way that maps onto historical racial categories, but this is but one of many different patterns of genetic differentiation that reflect human population histories, most of which don't fit typical racial categories. Human genetic variation maps onto geography--continuously, not along borders, and there is more genetic variation within populations than between them.
The strongest signal in human genetic datasets is that the genetic variation outside of Africa largely falls within a subset of variation within Africa. Africa is by far the most genetically diverse geographic region on Earth, which is because it is where our species originated.
Finally, it is worth noting that humans are not even a genetically diverse species. We're a young species and we’re highly interconnected globally. This isn't just recent. Humans have been relatively mobile for most of our history. As a result, we are much more genetically homogenous than any of our ape cousins.
Ironically, back in 2001, Pääbo expressed confidence that the genome sequence would so clearly demonstrate the above true predominant trends in human genetic differentiation that “...stigmatizing any particular group of individuals on the basis of ethnicity or carrier status for certain alleles will be revealed as absurd.” Unfortunately, this message clearly has not been widely received, which raises the question of what the responsibility of scientists is to make sure accurate interpretations of their work are making it into the public sphere.
Sarah Tishkoff, a human evolutionary genetist at University of Pennsylvania Medical School, studies recent human adaptation. Her research group has illuminated recent human genetic changes, like one causing lactase persistance, or the ability to digest dairy as an adult, that vary in modern populations. But, as she told Nature, her work has not turned up any support for genetic variation underlying behavior.
It is not that impossible that genes could influence behavior. Or that genetic varation might contribute to behavioral variation. It may. But little, if any, convicing scientific support for human behavioral differences has been uncovered (though that is a whole other blog post). And, given real patterns of human variation, any such differences that may exist are unlikely to sort along Wade's racial lines.
But Wade cites real scientific studies to back up his claims, which lends his work undeserved authority. Fortunately, the authors of a number of these studies have spoken out.
A letter was published online at the New York Times today in support of a critical review of A Troublesome Inheritance by science writer David Dobbs published earlier in the newspaper. The letter, which will appear in print Sunday, August 10th, 2014, is brief and to the point. The authors argue that Wade misappropriated their research and state that "[w]e are in full agreement that there is no support from the field of population genetics for Wade’s conjectures."
The letter ended up being signed by over 130 population geneticists and evolutionary biologists. Unsurprisingly, Pääbo is among the signatories, as is Tishkoff. Two professors from Yale, Stephen Stearns and Kenneth Kidd are also on the list, along with many huge names in human evolution and genetics like Carlos Bustamante, Michael Hammer, Mary-Claire King, Rasmus Nielsen, David Reich, Anne Stone, Mark Stoneking, and many more. It is great to see all these scientists defend their field of study and decry its misuse.