[Notable New Media]
by Kenneth W. Krause.
Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer. Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes regularly to Skeptic as well. He may be contacted at firstname.lastname@example.org.
If we inherit from our parents traits typically associated with “race,” including skin, hair, and eye color, why do most scientists insist that race is more social construct than biological reality? Are they suffering from an acute case of political correctness, perhaps, or a misplaced paternalistic desire to deceive the irresponsible and short-sighted masses for the greater good of humanity? More ignoble things have happened, of course, even within scientific communities. But according to geneticist Daniel J. Fairbanks, the denial of biological “race” is all about the evidence.
In Everyone is African: How Science Explodes the Myth of Race (Prometheus 2015), Fairbanks points out that, although large-scale analyses of human DNA have recently unleashed a deluge of detailed genetic information, such analyses have so far failed to reveal discrete genetic boundaries along traditional lines of racial classification. “What they do reveal,” he argues, “are complex and fascinating ancestral backgrounds that mirror known historical immigration, both ancient and modern.”
In 1972, Harvard geneticist Richard Lewontin analyzed seventeen different genes among seven groups classified by geographic origin. He famously discovered that subjects within racial groups varied more among themselves than their overall group varied from other groups, and concluded that there exists virtually no genetic or taxonomic significance to racial classifications. Later characterizing that conclusion as “Lewontin’s Fallacy” in 2003, Cambridge geneticist A.W.F. Edwards reminded us how easy it is to predict race simply by looking at people’s genes.
So who was right? Both of them were, according to Lynn Jorde and Stephen Wooding at the University of Utah School of Medicine. Summarizing several large-scale studies on the topic in 2004, they confirmed Lewontin’s finding that about 85-90% of all human genetic variation exists within continental groups, while only 10-15% between them. Even so, as Edwards had insisted, they were also able to assign all native European, east Asian, and sub-Saharan African subjects to their continent of origin using DNA alone. In the end, however, Jorde and Wooding revealed that geographically intermediate populations–South Indians, for example–did not fit neatly into commonly conceived racial categories. “Ancestry,” they concluded, was “a more subtle and complex description” of one’s genetic makeup than “race.”
Fairbanks concurs. Humans have been highly mobile for thousands of years, he notes. As a result, our biological variation “is complex, overlapping, and more continuous than discreet.” When one analyzes DNA from a geographically broad and truly representative sample, the author surmises, “the notion of discrete racial boundaries disappears.”
Nor are the genetic signatures of typically conceived racial traits always consistent between populations native to different geographic regions. Take skin color, for example. We know, of course, that the first Homo sapiens inherited dark skin previously evolved in Africa to protect against sun exposure and folate degradation, which negatively affects fetal development. Even today, the ancestral variant of the MC1R gene, conferring high skin pigmentation, is carried uniformly among native Africans.
But around 30,000 years ago, long after our species had first ventured out of Africa into the Caucasus region, a new variant appeared. KITLG evolved in this population prior to the European-Asian split to reduce pigmentation and facilitate vitamin D absorption in regions of diminished sunlight. Some 15,000 years later, however, another variant, SLC24A5, evolved by selective sweep as one group migrated west into Europe. Extremely rare in other native populations, nearly 100% of modern native Europeans carry this variant. On the other hand, as their varied skin tones demonstrate, African and Caribbean Americans carry either two copies of an ancestral variant, two copies of the SLC24A5 variant, or one of each. Asians, by contrast, developed their own pigment-reducing variants–of the OCA2 gene, for example–via convergent evolution, a process where similar external traits result independently among different populations due to similar environmental pressures.
So how can biology support traditional notions of race when the genetic signatures of those notions’ most relied upon trait–that is, skin color–are so diverse among people sharing the same or similar degree of skin pigmentation? Fairbanks finds such ideas utterly bankrupt “in light of the obvious fact that actual variation for skin color in humans does not fall into discrete classes,” but rather “ranges from intense to little pigmentation in continuously varying gradations.”
To long-time science journalist, Nicholas Wade, who, in his recent book, A Troublesome Inheritance, judged that biological races are real and can be distinguished genetically at the continental level, Fairbanks offers the following reply: “Traditional racial classifications constitute an oversimplified way to represent the distribution of genetic variation among the people of the world. Mutations have been creating new DNA variants throughout human history, and the notion that a small proportion of them define human races fails to recognize the complex nature of their distribution.”