America's modern struggle with race has proceeded on three fronts. The legal battle effectively ended a half-century ago with the Civil Rights Act of 1964. The second front, the battle against private prejudice, has not been won so decisively, but the experiences of Cliven Bundy and Donald Sterling in the past few weeks confirm a longstanding truth about American society: Expressions of racial prejudice by public figures are punished swiftly and severely.
The third front is different in kind. This campaign is waged not against actual violations of civil rights or expressions of prejudice or hatred, but against the idea that biological differences among human populations are a legitimate subject of scholarly study. The reigning intellectual orthodoxy is that race is a "social construct," a cultural artifact without biological merit.
The orthodoxy's equivalent of the Nicene Creed has two scientific tenets. The first, promulgated by geneticist Richard Lewontin in "The Apportionment of Human Diversity" (1972), is that the races are so close to genetically identical that "racial classification is now seen to be of virtually no genetic or taxonomic significance." The second, popularized by the late paleontologist Stephen Jay Gould, is that human evolution in everything but cosmetic differences stopped before humans left Africa, meaning that "human equality is a contingent fact of history," as he put it in an essay of that title in 1984.
Since the sequencing of the human genome in 2003, what is known by geneticists has increasingly diverged from this orthodoxy, even as social scientists and the mainstream press have steadfastly ignored the new research. Nicholas Wade, for more than 20 years a highly regarded science writer at the New York Times, has written a book that pulls back the curtain.
It is hard to convey how rich this book is. It could be the textbook for a semester's college course on human evolution, systematically surveying as it does the basics of genetics, evolutionary psychology, Homo sapiens's diaspora and the recent discoveries about the evolutionary adaptations that have occurred since then. The book is a delight to read—conversational and lucid. And it will trigger an intellectual explosion the likes of which we haven't seen for a few decades.
The title gives fair warning: "A Troublesome Inheritance: Genes, Race and Human History." At the heart of the book, stated quietly but with command of the technical literature, is a bombshell. It is now known with a high level of scientific confidence that both tenets of the orthodoxy are wrong.
Mr. Lewontin turns out to have been mistaken on several counts, but the most obvious is this: If he had been right, then genetic variations among humans would not naturally sort people into races and ethnicities. But, as Mr. Wade reports, that's exactly what happens. A computer given a random sampling of bits of DNA that are known to vary among humans—from among the millions of them—will cluster them into groups that correspond to the self-identified race or ethnicity of the subjects. This is not because the software assigns the computer that objective but because those are the clusters that provide the best statistical fit. If the subjects' ancestors came from all over the inhabited world, the clusters that first emerge will identify the five major races: Asians, Caucasians, sub-Saharan Africans, Native Americans and the original inhabitants of Australia and Papua New Guinea. If the subjects all come from European ancestry, the clusters will instead correspond to Italians, Germans, French and the rest of Europe's many ethnicities. Mr. Lewontin was not only wrong but spectacularly wrong. It appears that the most natural of all ways to classify humans genetically is by the racial and ethnic groups that humans have identified from time out of mind.
Stephen Jay Gould's assurance that significant evolution had stopped before humans left Africa has also proved to be wrong—not surprisingly, since it was so counterintuitive to begin with. Humans who left Africa moved into environments that introduced radically new selection pressures, such as lethally cold temperatures. Surely, one would think, important evolutionary adaptations followed. Modern genetic methods for tracking adaptations have established that they did. A 2009 appraisal of the available genome-wide scans estimated that 14% of the genome has been under the pressure of natural selection during the past 30,000 years, long after humans left Africa. The genes under selection include a wide variety of biological traits affecting everything from bone structure and diet to aspects of the brain and nervous system involving cognition and sensory perception.
The question, then, is whether the sets of genes under selection have varied across races, to which the answer is a clear yes. To date, studies of Caucasians, Asians and sub-Saharan Africans have found that of the hundreds of genetic regions under selection, about 75% to 80% are under selection in only one race. We also know that the genes in these regions affect more than cosmetic variations in appearance. Some of them involve brain function, which in turn could be implicated in a cascade of effects. "What these genes do within the brain is largely unknown," Mr. Wade writes. "But the findings establish the obvious truth that brain genes do not lie in some special category exempt from natural selection. They are as much under evolutionary pressure as any other category of gene."
Let me emphasize, as Mr. Wade does, how little we yet know about the substance of racial and ethnic differences. Work in the decade since the genome was sequenced has taught us that genetically linked traits, even a comparatively simple one like height, are far more complex than previously imagined, involving dozens or hundreds of genes, plus other forms of variation within our DNA, plus interactions between the environment and gene expression. For emotional or cognitive traits, the story is so complicated that we are probably a decade or more away from substantial understanding.
As the story is untangled, it will also become obvious how inappropriate it is to talk in terms of the "inferiority" or "superiority" of groups. Consider, for example, the Big Five personality traits: openness, conscientiousness, extraversion, agreeableness and neuroticism. What are the ideal points on these continua? They will differ depending on whether you're looking for the paragon of, say, a parent or an entrepreneur. And the Big Five only begin to tap the dozens of ways in which human traits express themselves. Individual human beings are complicated bundles of talents, proclivities, strengths and flaws that interact to produce unexpected and even internally contradictory results. The statistical tendencies (and they will be only tendencies) that differentiate groups of humans will be just as impossible to add up as the qualities of an individual. Vive les différences.
The problem facing us down the road is the increasing rate at which the technical literature reports new links between specific genes and specific traits. Soon there will be dozens, then hundreds, of such links being reported each year. The findings will be tentative and often disputed—a case in point is the so-called warrior gene that encodes monoamine oxidase A and may encourage aggression. But so far it has been the norm, not the exception, that variations in these genes show large differences across races. We don't yet know what the genetically significant racial differences will turn out to be, but we have to expect that they will be many. It is unhelpful for social scientists and the media to continue to proclaim that "race is a social construct" in the face of this looming rendezvous with reality.
After laying out the technical aspects of race and genetics, Mr. Wade devotes the second half of his book to a larger set of topics: "The thesis presented here assumes . . . that there is a genetic component to human social behavior; that this component, so critical to human survival, is subject to evolutionary change and has indeed evolved over time; that the evolution in social behavior has necessarily proceeded independently in the five major races and others; and that slight evolutionary differences in social behavior underlie the differences in social institutions prevalent among the major human populations."
To develop his case, Mr. Wade draws from a wide range of technical literature in political science, sociology, economics and anthropology. He contrasts the polities and social institutions of China, India, the Islamic world and Europe. He reviews circumstantial evidence that the genetic characteristics of the English lower class evolved between the 13th century and the 19th. He takes up the outsize Jewish contributions to the arts and sciences, most easily explained by the Jews' conspicuously high average IQ, and recounts the competing evolutionary explanations for that elevated cognitive ability. Then, with courage that verges on the foolhardy, he adds a chapter that incorporates genetics into an explanation of the West's rise during the past 600 years.
Mr. Wade explicitly warns the reader that these latter chapters, unlike his presentation of the genetics of race, must speculate from evidence that falls far short of scientific proof. His trust in his audience is touching: "There is nothing wrong with speculation, of course, as long as its premises are made clear. And speculation is the customary way to begin the exploration of uncharted territory because it stimulates a search for the evidence that will support or refute it."
I fear Mr. Wade's trust is misplaced. Before they have even opened "A Troublesome Inheritance," some reviewers will be determined not just to refute it but to discredit it utterly—to make people embarrassed to be seen purchasing it or reading it. These chapters will be their primary target because Mr. Wade chose to expose his readers to a broad range of speculative analyses, some of which are brilliant and some of which are weak. If I had been out to trash the book, I would have focused on the weak ones, associated their flaws with the book as a whole and dismissed "A Troublesome Inheritance" as sloppy and inaccurate. The orthodoxy's clerisy will take that route, ransacking these chapters for material to accuse Mr. Wade of racism, pseudoscience, reliance on tainted sources, incompetence and evil intent. You can bet on it.
All of which will make the academic reception of "A Troublesome Inheritance" a matter of historic interest. Discoveries have overturned scientific orthodoxies before—the Ptolemaic solar system, Aristotelian physics and the steady-state universe, among many others—and the new received wisdom has usually triumphed quickly among scientists for the simplest of reasons: They hate to look stupid to their peers. When the data become undeniable, continuing to deny them makes the deniers look stupid. The high priests of the orthodoxy such as Richard Lewontin are unlikely to recant, but I imagine that the publication of "A Troublesome Inheritance" will be welcomed by geneticists with their careers ahead of them—it gives them cover to write more openly about the emerging new knowledge. It will be unequivocally welcome to medical researchers, who often find it difficult to get grants if they openly say they will explore the genetic sources of racial health differences.
The reaction of social scientists is less predictable. The genetic findings that Mr. Wade reports should, in a reasonable world, affect the way social scientists approach the most important topics about human societies. Social scientists can still treat culture and institutions as important independent causal forces, but they also need to start considering the ways in which variations among population groups are causal forces shaping those cultures and institutions.
How long will it take them? In 1998, the biologist E.O. Wilson wrote a book, "Consilience," predicting that the 21st century would see the integration of the social and biological sciences. He is surely right about the long run, but the signs for early progress are not good. "The Bell Curve," which the late Richard J. Herrnstein and I published 20 years ago, should have made it easy for social scientists to acknowledge the role of cognitive ability in shaping class structure. It hasn't. David Geary's "Male/Female," published 16 years ago, should have made it easy for them to acknowledge the different psychological and cognitive profiles of males and females. It hasn't. Steven Pinker's "The Blank Slate," published 12 years ago, should have made it easy for them to acknowledge the role of human nature in explaining behavior. It hasn't. Social scientists who associate themselves with any of those viewpoints must still expect professional isolation and stigma.
"A Troublesome Inheritance" poses a different order of threat to the orthodoxy. The evidence in "The Bell Curve," "Male/Female" and "A Blank Slate" was confined to the phenotype—the observed characteristics of human beings—and was therefore vulnerable to attack or at least obfuscation. The discoveries Mr. Wade reports, that genetic variation clusters along racial and ethnic lines and that extensive evolution has continued ever since the exodus from Africa, are based on the genotype, and no one has any scientific reason to doubt their validity.
And yet, as of 2014, true believers in the orthodoxy still dominate the social science departments of the nation's universities. I expect that their resistance to "A Troublesome Inheritance" will be fanatical, because accepting its account will be seen, correctly, as a cataclysmic surrender on some core premises of political correctness. There is no scientific reason for the orthodoxy to win. But it might nonetheless.
So one way or another, "A Troublesome Inheritance" will be historic. Its proper reception would mean enduring fame as the book that marked a turning point in social scientists' willingness to explore the way the world really works. But there is a depressing alternative: that social scientists will continue to predict planetary movements using Ptolemaic equations, as it were, and that their refusal to come to grips with "A Troublesome Inheritance" will be seen a century from now as proof of this era's intellectual corruption.