American Scientist

HOW TO ARGUE WITH A RACIST: What Our Genes Do (and Don’t) Say about Human Difference. Adam Rutherford. 221 pp. The Experiment, 2020. $21.95.

Adam Rutherford describes his recent book, How to Argue with a Racist: What Our Genes Do (and Don’t) Say about Human Difference, as a “tool kit” of scientific knowledge that can be used to challenge incorrect claims about race, genes, and ancestry. As a geneticist and evolutionary biologist, he is well qualified to provide the necessary information, and he is an excellent science communicator. His tool kit arrives at an opportune time, when open expression of bigotry is increasingly pushing its way into popular discourse.

The book groups misunderstandings about race into four subject areas— pigmentation, ancestry, sports, and intelligence—and devotes a chapter to each. Skin color (and eye color) have long been used to sort humans into a small number of “races,” even though skin color varies continuously across our species. People interested in genealogy—particularly those who are white supremacists—have often extended their attitudes about race into the distant past to claim ancestral racial “purity” or lineal descent from special individuals. Some sports fans believe that top African athletes are endowed with special physical abilities that derive from race. And it has been alleged throughout history that differences in intelligence between groups result from biological factors that have a racial basis. Rutherford notes that although it is easy to make race-based claims, it is much more difficult to refute them. But by deploying a sophisticated understanding of genetics, biology, and behavior, he demonstrates convincingly that those claims are not scientifically valid.

Rutherford explains that race is an imprecise, poorly defined term, used colloquially in ways that conflict with what we know about human variation from genetics. Along with words like Black, white, and Asian, race is an unscientific descriptor. Nevertheless, race is a very real social construct, and people do have a common informal understanding of these descriptors, so it is hard to avoid using them when trying to clarify underlying biological realities across human populations. Stereotypes, myths, and assumptions about race have deep roots in Western culture, and pseudoscience has long been used to defend those assumptions. Well-meaning people as well as overt racists often insist that racial categories are rooted in biology. The claims persist in part because the physical traits used to lump people into crude racial categories are, in fact, determined in part by genetic variation. The important question, Rutherford says, is this: “Are there essential biological (that is, genetic) differences between populations that account for socially important similarities or divisions within or between those populations?”

Here is how Rutherford deconstructs race as a biological concept: Historically, he explains, the word race served as a rough synonym for categories that were more scientific, such as subspecies of animals or varieties of plants—genetically distinct subgroups with multiple correlated characteristics. For members of such subgroups, one expects to be able to correctly predict nontrivial things about the organism’s physiology and behavior just by looking at it. For example, someone who is familiar with dog breeds can identify a springer spaniel and a border collie, and knows which is a hunting dog and which is a herding dog. However, the surface features that we use to put humans into racial categories do not allow us to make accurate predictions about the people in a given category. Rutherford also notes that geographical distance, rather than the boundaries between geographic areas, best accounts for the genetic variation we see among humans. His discussion of supposed racial traits is up to date, clear, and complete.

Recent genetic research shows that few genes code for a single trait, and that few traits are coded for by a single gene. Moreover, biological features are the product both of development and of interactions between genes and the environment. Therefore, genetic differences are not organized and distributed across humankind in neat packages that correspond to racial categories. Also, no links have been found between genes and body types, or between genes and particular behaviors, that would support simplistic racist ideas.

Rutherford rejects on multiple grounds the theory that evolutionary selection among slaves was the source of athletic prowess among African Americans today.

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In the chapter on ancestral purity, Rutherford takes the reader on a startling toboggan ride through family trees and the results of commercial DNA testing. This discussion is a highlight of the book. Every time one goes back a generation in a family tree, the number of ancestors doubles. Going back a thousand years puts genealogical slots for more than a trillion ancestors into the tree. Clearly, most of those slots for ancestors are filled by a small number of individuals. And the further back one goes, the more it will be the case that the people in one person’s family tree will also appear in the family trees of large numbers of other people. Eventually, the genetic isopoint will be reached: the point in time at which every member of the entire historical population of a geographic area was an ancestor of the entire current population of the area. The isopoint for living Europeans occurred a little over a thousand years ago. The global isopoint occurred much more recently than you might assume; let’s just say that the members of a club of white supremacists meeting in a shack in the woods in Michigan today and the contemporary inhabitants of a Maasai village in Tanzania are related thousands of times over within a timeframe that postdates the rise of civilization.

Racist thinking rests on particularly thin ice in the area of sports. Consider running: There has not been a white athlete fast enough to set an Olympic record for sprinting in four decades, which has led many people to jump to the conclusion that speed is race-based. In the area of endurance, many recent international marathons have been won by Kenyans or Ethiopians. Similar observations have been made across a range of sports. Being of African descent has ostensibly predisposed African Americans genetically to have a physiology that is athletically advantageous. Dozens of genes have been identified in elite athletes that appear to relate to speed and endurance, but it has not been shown that those genes are concentrated in particular ethnic populations. Also, the presence of a given genetic allele may be necessary but not sufficient to promote speed or endurance. Obviously, additional physical factors (such as body shape, metabolic efficiency, and adaptation to altitude) contribute to athletic success, and nurture may be just as important as nature.

One race-based explanation for the high level of performance among African-American athletes is the idea that centuries of slavery “bred” individuals with those specific traits, which rests on two assumptions: that slaves with a particular combination of size, strength, and power would have had an evolutionary advantage, and that this ideal slave phenotype somehow turned out to be the perfect phenotype for all of the different modern sports at which African-American athletes excel. Rutherford points out that if certain genes have made members of some races into superior runners, then there should be dozens, maybe hundreds, of populations contributing to the record books, because those genes are widely distributed. He also provides a better explanation for the dominance of particular populations in certain Olympic sports: Many of the most successful athletes come from countries that provide highly specialized training programs for promising individuals.

Rutherford rejects on multiple grounds the theory that evolutionary selection among slaves, whether it occurred naturally or through breeding programs, was the source of athletic prowess among African Americans today: A few centuries is not a long time in evolutionary terms, and the slave population in the United States was highly diverse genetically; also, physical strength would not necessarily have been an advantage among house slaves.

Variation in intelligence between racial groups has been measured with IQ tests, and the assessment of that variation is much more complex than is the analysis of variation in sports prowess. IQ is much more difficult to measure than speed on a race track, and we don’t know a great deal about what causes differences between groups in performance on IQ tests. Indeed, because IQ tests provide highly variable results, it is common to scale the results for a given version of the test so that the average score is 100 and the other scores fall into a normal distribution (a bell curve). Black populations around the world have been found on average to score 10 to 15 points lower than other groups on IQ tests. Genetic factors probably don’t account for this, because African countries are so genetically diverse; it seems much more likely that environmental factors have created the discrepancy. Dozens of genetic variants have been found to correlate with performance on cognitive tests, but we don’t know what most of those genes do.

In the book’s conclusion, Rutherford observes that “Race is real because we perceive it. Racism is real because we enact it. Neither race nor racism has foundations in science.” We have a duty, therefore, “to contest the warping of scientific research . . . to justify prejudice.”

Those are strong words, and true ones. I highly recommend this book.