Contents | April 2001
In This Issue (Contributors)
More on science and technology from The Atlantic Monthly.
The Genetic Archaeology of Race - Page 4
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From Skin Color to Intelligence
eople convinced that human groups differ for genetic reasons in intelligence, aggressiveness, or other complex behaviors have one last recourse. They can assume that the same forces leading to differences in appearance could somehow have influenced mental attributes. Maybe, for example, cold climates exerted some sort of selective pressure on people moving north from the tropics, favoring individuals with greater initiative or intelligence. Or maybe some other genetic process divided cognitive traits unevenly among groups.
The argument doesn't work, for two reasons. First, no mechanism has been identified that could sort complex attributes within such a genetically homogenous species, causing the behavior of one group to differ from that of another. The idea that natural selection favored different cognitive traits on different continents—that selective forces on colder continents led to greater intelligence, for example—seems designed more to justify social prejudice than to establish testable hypotheses. After all, Neanderthals were much better adapted to the cold than modern human beings, yet they weren't able to compete with the newcomers from Africa and eventually became extinct.
Even if a potential differentiating mechanism could be identified, the case for group differences fails for a second reason. There is a fundamental difference between a simple trait such as skin color and a complex attribute such as intelligence. Skin color is determined by a handful of genes and does not depend on the experiences a child has in the womb and while being raised. The development of the brain involves thousands of genes and is indissolubly linked to experience. For this reason it is impossible to parse a particular complex trait into purely genetic and purely environmental components.
Of course, at some point genetic differences must override the effects of experience. Human beings and chimpanzees differ in intelligence. If Neanderthals had survived, their behavior would probably be genetically different from ours. But the genetic differences among modern human beings are so small that group differences in behavior fall entirely within a range attributable to culture.
From the archives:
"Who Owns Intelligence?" (February 1999)
Three unresolved issues will dominate the discussion of intelligence: whether intelligence is one thing or many things; whether intelligence is inherited; and whether any of its elements can accurately be measured. By Howard Gardner
"Academic Ignorance and Black Intelligence," (June 1972)
"The myth of verbal deprivation is particularly dangerous because ... it leads its sponsors inevitably to the hypothesis of the genetic inferiority of black children, which the verbal-deprivation theory was designed to avoid." By William Labov
Take IQ tests as an example. In Japan the Buraku are a caste of people discriminated against in education, housing, and employment. Their children typically score ten to fifteen points below other Japanese children on IQ tests—about the average black-white difference in the United States. Yet when the Buraku emigrate to the United States, the IQ gap between them and other Japanese vanishes.
What if geneticists were to find a particular genetic variant that seems to be associated with a given behavior? Wouldn't that provide evidence for those who believe there are significant genetic differences among groups? In fact, just such an association is about to be made. Within the next few years geneticists will find the specific genetic variants that determine skin color. In the United States, because of the black-white gap on average IQ scores, these variants will be statistically correlated with our most commonly used measure of intelligence. But the genetic variants affecting skin color have nothing to do with the functioning of the brain. They exert their effects entirely through the influence of culture—by sorting people according to the color of their skin.
The complexity of the relationship between genes and behaviors will always confound simple-minded efforts to link the two. Even if a genetic variant seems to cause a particular behavior—such as extroversion or verbal fluency—in one environment, it may have no effect, or the opposite effect, in a different environment. The importance of a person's experiences makes it a fallacy to cite the frequency of certain genetic variants as the cause of group behaviors.
Our knowledge of history argues against any such association. Did the Vikings somehow lose a marauding gene in becoming the laid-back Scandinavians of today? Did the Arabs gain a religiosity gene with the coming of Mohammed? How could Hispanics have any kind of innate characteristics when the group consists of people with varying percentages of European, African, and Native American ancestry? Group attributes change with the alacrity of culture, not with the languor of genes.
There is no need to posit unknown genetic forces to explain the differences among groups. Individuals have unique experiences from the moment of conception. They receive varying levels of nutrition and medical care. They are treated differently every single day by adults, teachers, and peers. They are born into cultures with particular histories and beliefs.
Of course, human history could have worked out differently. Suppose that an archaic species of human beings such as Homo erectus had become firmly established in the Americas during a time of lower sea levels. As sea levels rose and the Bering land bridge became submerged, modern human beings might have ceded the hemisphere to their archaic predecessors and never left the Old World. In that case, when Columbus came ashore in the West Indies, he would not have encountered modern human beings separated from his own ancestors by just a few thousand generations. He would have met slope-browed, linguistically primitive people with a cranial capacity about two thirds of our own. Then we would have a race problem. Instead we have cultural differences masquerading as race problems.
We are highly visual creatures, which makes us very good at spotting differences among people. But researchers who study human fossils and our nonhuman ancestors have a different perspective. They point to the attributes that modern human beings share: our high foreheads, our nuanced languages, the light of intelligence in our eyes.
The Genetic Information Age
ecause of the controversy over the Human Genome Diversity Project, the federal government has so far granted the project relatively little funding. The large-scale effort envisioned by Cavalli-Sforza has not occurred. Paradoxically, the prospects for achieving the project's goals have never been better. Small-scale investigations of genetic variation are thriving. Researchers in other countries have been much more successful than have U.S. investigators at skirting issues of race and genetics. The Center for the Study of Human Polymorphism, based in Paris, now offers DNA samples from populations around the world for research. And the growth of the Internet is changing how genetics research is done. According to Mark Weiss, who oversees a gradually increasing budget for anthropological genetics at the National Science Foundation, the HGDP could go forward as a collection of networked efforts rather than as a single grand undertaking.
But the biggest boost to studies of genetic variation is coming not from anthropology but from medicine. When the project to sequence the human genome began, its organizers anticipated that having a single generic DNA sequence would satisfy most researchers. They have since recognized their short-sightedness. Much of the medical interest in the human genome lies not in the similarities among people but in the differences. If an individual is genetically susceptible to heart disease, cancer, or some other ailment, it is because of particular variants in that person's genes. To understand that susceptibility, researchers need to know about those variants.
Public and private organizations are now feverishly gathering data about human genetic variation. Essentially, they are looking for the same kind of variants involved in skin color and other simple genetic traits: discrete mutations in particular genes that have spread more or less widely in different groups. "Researchers will look at, say, heart patients and controls, or African-Americans with high blood pressure and controls, to find the genetic variants related to those diseases and to find effective therapies," says Lisa Brooks, the director of the Genetic Variation Program at the National Institutes of Health.
Not surprisingly, biomedical researchers are coming up against the same problem that has plagued the Human Genome Diversity Project. How can researchers describe genetic variances among groups without implying that groups are fundamentally different? So far the biomedical world has dealt with the problem largely by wishing it would go away. Investigators using data from the primary database on human genetic variation at the National Institutes of Health, for example, must sign a form saying that they will not try to determine the ethnicity of the people who contributed the DNA (though population geneticists could easily derive the ethnicity by comparing the samples with known sequences).
Maintaining a firewall between anthropology and biomedicine may be politically expedient, but it is intellectually dishonest. To understand the patterns of genetic variation in groups, researchers have to study the history of those groups. "The same evolutionary and historical factors that underlie genetic variation in general underlie the variations responsible for genetic diseases," says Lynn Jorde, a human geneticist at the University of Utah. "The only question is whether we want to be efficient in studying those factors, and to me the answer is sure, why not?"
The privacy and rights of groups need to be protected in these studies, just as do the privacy and rights of individuals. Groups should be involved in the planning and conduct of research, and they need a negotiated measure of control over the uses made of genetic data. Geneticists and anthropologists are in a position to do great harm to groups through irresponsible and unethical actions (though many groups are threatened by societal forces much greater than those any scientists can unleash).
At the same time, groups run a risk by refusing to become involved in genetics research. Such research can have direct medical benefits if it involves diseases affecting the group, or indirect benefits if researchers provide participants with medical care. There can also be commercial dividends if a group retains control over its genetic materials. Besides, there's more than one way to study the genetics of a population. If a group declines to be studied, geneticists can always find more-cooperative members who are outside the group's control.
The rocky history of the Human Genome Diversity Project has demonstrated many of the pitfalls that need to be avoided. First, we have to keep in mind the extreme fluidity of human groups. The word "race," for example, can't begin to capture the commonalities and differences of our shared history. Most African-Americans have European ancestors. All European-Americans have African ancestors. It makes no sense to talk about "races" when we are all complex mixtures of many different peoples.
We also have to remember just how small the genetic differences among groups are. The genetic variants affecting skin color and facial features are essentially meaningless—they probably involve a few hundred of the billions of nucleotides in a person's DNA. Yet societies have built elaborate systems of privilege and control on these insignificant genetic differences.
Finally, as we learn more about our genetic susceptibilities to disease and our relationship to the past, we need to find better ways of putting genetics in context. People tend to attribute great importance to the findings of geneticists. But the striking homogeneity of our DNA actually emphasizes the centrality of the environment and our experiences in determining who we are. Because culture exerts such a profound influence on complex traits, our genetic heritage has little importance in considerations of ethics or public policy.
avalli-Sforza has always believed that if people understood genetics, they couldn't possibly be racists. For that he must certainly be judged naive. Then again, geneticists think in terms of generations, and over that time scale even the staunchest opinions can change. In the 1950s only four percent of white Americans approved of marriages between members of different races. Today the number is close to 50 percent, and it is undoubtedly much higher among young people.
Changing attitudes and new social forces are already having an influence on the collective genome of our species. Barriers that in the past have limited intermarriage among groups are breaking down. Cavalli-Sforza believes that many societies are moving toward what he calls the American model. "Two hundred years from now," he says, "people all over the world will be mixing in the same way that people in the United States are today."
A greater rate of intermarriage will generate great cultural upheavals. Genetically it will matter not a whit. Human beings are so similar that it makes no difference biologically for a white to marry a black, or for an Asian to marry an Australian. More intermarriage will make it harder to figure out an individual's ancestry. But it can only hasten the approach of a color-blind society.
Today most people still bear some traces of group biological history in their faces and skin. Perhaps someday our species will lose those distinguishing characteristics, through either intermarriage or genetic engineering. Until then the study of our genetic differences, if interpreted with care and understanding, could be one of the best ways to appreciate our biological unity.
Copyright © 2001 by The Atlantic Monthly Group. All rights reserved.
The Atlantic Monthly; April 2001; The Genetic Archaeology of Race - 01.04; Volume 287, No. 4; page 69-80.