Recent Advances in the Study of Human Differences, Part 2 of 3: The Biological Basis of Race

Go to Part 1, on gender differences.

Social constructivist orthodoxy has been more successful at shaping popular perceptions of race than of sex. As Murray notes, the idea that “gender is merely a social construct” is widely perceived as too extreme, but many of our contemporaries labor under the mistaken impression that “significant racial differences in cognitive repertoires are known to be scientifically impossible.” (133)

Nevertheless, the author’s discussion of race generously begins with a section entitled “What the Orthodoxy Gets Right.” Richard Lewontin was correct that there is more variation within the major races than between them. Stephen Jay Gould was correct to criticize the theory of polygenesis, viz., that humans evolved independently in Europe, Asia and Africa for hundreds of thousands of years. No one today claims that races can be arranged in an unequivocal hierarchy from “best” to “worst.” But all this merely means that “we have before us an exercise in modifying our understanding of race, not resurrecting nineteenth-century conceptions.” (135)

In 2005, newly acquired data from the sequenced human genome confirmed that Homo sapiens originated in Africa; researchers found that “no origin outside Africa had the explanatory power of an origin anywhere within Africa.” The circumstances of human dispersal from Africa are less clear. Some Homo sapiens seem to have been in the Mideast by about 200,000 years ago. It was long assumed there must have been many distinct migrations out of Africa, but evidence has recently emerged that today’s non-Africans are mostly descended from a single small group:

In 2016, a new whole-genome study based on 300 genomes from 142 diverse populations provided evidence for a one-wave scenario, indicating that just one band of anatomically modern emigrants from Africa has descendants among today’s humans. But, as usual, there were complications. The genomes of Papuans gave signs that about 2 percent of their genomes might have come from an earlier population. That’s not much, but it suggests something more complicated than a single band of emigrants. (147)

Some of the Homo sapiens of Eurasia mated with Neanderthals and Denisovans already there, acquiring useful genes in the process. As the population grew, bands would occasionally split off into new territory, resulting in stepwise increases in genetic drift and decreased genetic diversity; this is called “serial founder effect.” The end result was a species in which differences in gene frequencies increased with distance and were subject to new evolutionary pressures across a wide variety of local environments.

As we know, there is no unequivocal number of human races. In such situations, it is helpful to run a statistical cluster analysis, in which a software program divides members of a sample first into two clusters, then three, increasing the number for “as long as the clusters produced continue to be informative.” (149)

We now turn to the evidence for Murray’s proposition five, viz., “Human populations are genetically distinctive in ways that correspond to self-identified race and ethnicity.”

In 2002, a team of scholars associated with the Human Genome Diversity Project ran a cluster analysis on a sample of 1056 persons from 52 distinct populations, using 377 genetic variants. They found the cleanest set of clusters was produced when K—the number of clusters—was set to five, and that these clusters corresponded to the major continents: Africa, Europe, East Asia, the Americas and Oceania (the Pleistocene continent which included Australia, New Guinea and Tasmania). In general, genetic discontinuities are clearest where they correspond to geographic barriers.

Six years later, following the complete sequencing of the human genome, another group of scholars ran a cluster analysis on the same sample, but taking account of 642,690 variants rather than 377. Murray summarizes the results:

At K = 2, two sets of the 51 populations had virtually no overlap: populations in sub-Saharan Africa versus populations in East Asia plus a few in the Americas. All the other populations were mixtures of the two clusters.

At K=3, the people who showed virtually no admixture across clusters consisted of individuals from sub-Saharan Africa, today’s Europe and Middle East, and the East Asian-Americas group.

At K=4 the Amerindians split off to form a separate cluster.

At K=5, the Oceania populations [=Australian Aborigines, New Guineans, Melanesians, and Micronesians] split off.

At K=6, the Central and South Asians split off.

At K=7, the configuration that the authors assessed as the most informative, those in the Mideast split off from the Europeans. (151)

Nota Bene: At no point does any increase in K fundamentally change the pattern of clusters; each increase splits one of the clusters already obtained, merely adding detail.

Murray draws our attention especially to the last two steps:

As in the 2002 study, the first five clusters corresponded to the five continental ancestral populations… [including] a cluster that corresponded to the classic definition of Caucasian—an odd agglomeration of peoples from Europe, North Africa, the Mideast, South Asia and parts of Central Asia. There had been a reason why physical anthropologists had once combined these disparate populations—all of them have morphological features in common—but it never made much sense to people who weren’t physical anthropologists. With K = 7, one of the new clusters split off the peoples of the Mideast and North Africa and the other split off the people of Central and South Asia—precisely the groups that had always been visibly distinctive from Europeans and from each other in the Caucasian agglomeration. (152)

I am reminded of Steve Sailer’s observation that Luigi Cavalli-Sforza’s laboriously produced map of the world’s “genetic population groups” resembles what Strom Thurmond might have sketched out with a box of crayons. In short, the common man’s perceptions of the races of mankind turn out to be fairly well supported by cutting-edge genetic research.

Recent studies have focused on more fine-grained distinctions. For example, a 2016 review article showed

what happens when several European subpopulations are plotted with different numbers of sites. When only 100 or even 1000 sites are used the subpopulations are indistinguishable. At 10,000 sites, some separation is visible. At 100,000 sites, Italians, Spanish, Germans, and Romanians are all reasonably distinct, with the British, Dutch, Swedish, and Irish fuzzily distinct. (154)

The upshot of these advances is that a geneticist can now say, in effect:

Give me a large random sample of [genetic variants] in the human genome, and I will use a computer algorithm, blind to any other information about the subjects, that matches those subjects closely not just to their continental ancestral populations, but, if the sample is large enough, to subpopulations within continents that correspond to ethnicities.

As the author notes, “if race and ethnicity were nothing but social constructs, that would be impossible.” (156)

Murray’s proposition six states that “Evolutionary selection pressure since humans left Africa has been extensive and mostly local.”

Indeed, the exodus from Africa accelerated evolution: not because mutations became any more common, but because new pressures were applied to pre-existing gene frequencies. For instance, the switch to a cooler Eurasian climate may have made certain previously neutral gene variants valuable, so that they spread within that local population (without necessarily reaching fixity). The transition to agriculture some ten thousand years ago led to a further series of drastic changes in human environments, generating intense new selective pressures and further accelerating evolution.

Before the sequencing of the human genome, researchers had to make educated guesses about where to look for genes recently subject to selection. Today, they can search the entire genome systematically in what are called “genome wide association studies.” Even tiny changes in frequency at individual loci can have large cumulative effects over the whole genome. Geneticists have also developed methods for dating adaptations less than about 30,000 years old.

A 2016 review article summarized the results of 73 studies which have revealed recent adaptations affecting cell function, connective tissue development, the brain and central nervous system, vision, hearing, olfactory receptors, skin pigmentation, immunity and metabolism.

Such adaptations tend to be local, meaning (at a minimum) confined to particular continental races. A 2009 German study found that

68 percent of the regions [of the human genome] under selection were under selection for a single [continental] population. Another 20 percent were under selection in just two of the six. Only 1 percent were under selection in all six populations. (179)

This research is still at an early stage, and we will not know for a long time just how much recent evolution there has been in various geographical regions. But Stephen Jay Gould’s claim that evolution since humans left Africa cannot have been extensive, while perhaps defensible when he made it in the 1980s, is now known to be mistaken.

Murray’s seventh proposition states that “Continental population differences in variants associated with personality, abilities, and social behavior are common.” Here is the evidence.

Research into continental differences in gene variants of all types is becoming more extensive in response to a growing awareness that diseases can affect different racial groups differently. This means that existing genomic data, collected mainly in Europe and the United States, may not be appropriate for use in medical research concerned with other parts of the world. Articles filled with fustian about “institutional racism” in medical science have even begun appearing in the popular press (if geneticists weren’t “racist,” they would presumably have been just as quick to collect samples from the deserts of Central Asia and the African jungle as in their own backyards).

Of course, this kerfuffle is having the positive result that genomic databases drawn from a wider array of racial groups are now being compiled. The goal is improved medical care around the world. But a side effect will be massive amounts of new data about racial differences in gene frequencies, many of which will correlate statistically with differences in personality, abilities and social behavior. Human Diversity provides information for 22 such traits for which evidence is already available (192-193). We cannot assume that all these differences have been produced by natural selection: founder effects and genetic drift probably made a larger contribution to some of them. But they are real racial differences in gene frequencies, whatever their cause.

As of yet, the task of assembling the genetic story for specific phenotypic traits has barely begun, but Murray assures us that “progress is accelerating nonlinearly” (201). By 2030, geneticists will be able to predict personality characteristics, abilities, and social behavior on the basis of genetic information alone, amounting to “an ironclad, you-can’t-get-around-this-one refutation” (300) of social constructivism. The orthodox may still resist the evidence, but they will eventually succumb to the ridicule.