[This piece was submitted to Foreign Affairs, which rejected it Email them.]
Jerry Z. Muller a professor at Catholic University, ("Us and Them,", Foreign Affairs, March/April 2008, and "Replies," July/August 2008) argued that the power of ethnic nationalism "will drive global politics for generations to come" because it "corresponds to some enduring propensities of the human spirit," which often manifests in the "need for each people to have its own state." His essay provided a valuable corrective to the position that ethnic identity is a mere social construction that globalization will steadily eradicate.
But Muller's argument would have been strengthened by understanding why people prefer genetic similarity in others.
Ever since the 1994 publication of The History and Geography of Human Genes by Stanford University geneticist Luigi Cavalli-Sforza, it has been possible to measure genetic distances between population groups in terms of family equivalents. Anthropologist Henry Harpending showed that against the background of worldwide genetic variance, the average similarity between people within a single population is the same as that between half-siblings. Political scientist Frank Salter calculated that compared to the Danes, any two random English people have a kinship of 1/32 of a cousin. Two English people become the equivalent of 3/8 of a cousin by comparison with people from the Near East, 1/2 cousin by comparison with people from India, half-siblings by comparison with people from China, and like full-siblings compared with people from sub-Saharan Africa.
Thus, the aggregate of genes people share with co-ethnics dwarfs those shared with extended families. Rather than being a poor relation of family nepotism, ethnic nepotism is virtually a proxy for it.
The pull of genetic similarity explains why members of ethnic groups move into the same neighborhoods, join together in clubs and societies, and are prone to develop ethnocentric attitudes toward those who differ in dress, dialect, and other appearance. In The Ethnic Phenomenon (1981), by Pierre van den Berghe, a sociology and anthropology at the University Of Washington, found that even relatively open and assimilative groups "police" their boundaries against invasion by strangers using cultural "badges" to mark group membership, such as scarification, linguistic accent, and clothing style. Another study calculated coefficients of consanguinity within and between Eskimo tribes in the Hudson's Bay region of Canada and found prosocial behavior such as wife exchange, and anti-social behavior such as genocidal killing during warfare, followed lines of genetic distance, albeit mediated by ethnic badging such as dialect and appearance. [A study in the evolution of ethnocentrism, by C. J. Irwin, in The Sociobiology of Ethnocentrism, 1987]
From an evolutionary perspective, the reason why people construct ethnic identities and engage in ethnic nepotism is that by doing so they increase the survival of their genes. Central to discussion is the concept of inclusive fitness.
As Richard Dawkins explicated in his 1976 book, The Selfish Gene, it is genes that survive and are passed on across generations. Some of the individual's most distinctive genes will be found in fellow ethnics as well as in offspring, siblings, nephews, cousins, and grand-children. By benefiting extended kin, people benefit copies of their genes.
Of course, altruism has always posed a conundrum for Darwinism. How could altruism evolve through "survival of the fittest" if altruism means self-sacrifice? If the most altruistic members of a group sacrifice themselves for others, they will leave fewer offspring to pass on the genes that made them altruistic. At first glance, it would seem that altruism could not evolve, while selfishness would.
Yet altruism is common in all animals, even to the point of self-sacrifice. When bees defend their hive and sting intruders, the entire stinger is torn from the bee's body. Stinging an intruder is an act of altruistic self-sacrifice. In ants, if nest walls are broken open, soldiers pour out to combat foragers from other nests; at the same time, worker ants repair the broken walls, in the process leaving the soldiers outside to die.
Evolutionary psychology answers the Darwinian conundrum. From an evolutionary point of view, an individual organism is only a vehicle, part of an elaborate device, which ensures the survival and reproduction of genes with the least possible biochemical alteration. So even when an altruist sacrifices its life for its kin, it ensures the survival of common genes. In this case, the vehicle has been sacrificed to preserve copies of its precious cargo.
Patriotism is traditionally seen as a virtue and extension of family loyalty, typically preached using the terminology of kinship. Nations are referred to as the "motherland" and "fatherland," while members call each other "cousin," "brother," and "sister." Although ethnic groups and nations appear and disappear, they break-up and coalesce anchored in the reality of socially perceived biological descent.
While descent often has an element of fiction, pure fiction seldom flies. When resources are plentiful, conflict is minimal. As resources become scarce, individuals compete more intensely, and they do so in groups of extended kin. Ethnic hatred and warfare are the "dark side" of human altruism.
Genetic distance studies have confirmed (and disconfirmed) many ideas about people's origins. For example, in the case of both the Indian caste system and the Jews, traditional views have been confirmed.
Even though they have been scattered around the world for two millennia, Jews from Iraq and Libya share more genes with Jews from Germany, Poland, and Russia than either group shares with the non-Jewish populations among whom they have lived for centuries. Israel is a new state, yet one which is built on an ancient tradition of ethnicity and nationhood.
Some Jews have greeted the genetic "validation" positively because it affirms the organic nature of the Jewish people. It is also recognized as a two-edged sword that could be invoked to claim "conspiracy" from certain quarters.
Surveys carried out by political scientist Robert Putnam suggest that too much ethnic diversity seriously undermines the trust and social bonds within a community. The more diverse a community, the less likely its inhabitants are to trust others, from next-door neighbors to local governments. Individuals become more wary even of members of their own ethnic group, as well as people from different backgrounds. People like to live within a "comfort zone" of others like themselves.
Other surveys show that, in multiethnic countries, people prefer same-race health providers and perceive them as more trustworthy. On the positive side, research with adolescents has shown that ethnic pride helps teenagers maintain confidence when faced with stress.
The pull of genetic similarity has been demonstrated to occur not only in large groups, both national and international, but also in dyads such as marriage partners and friendships. Of all the decisions people make that affect their environment, choosing friends and spouses are among the most important.
Reviews of the literature consistently show that spouses and best friends are most similar on socio-demographic variables such as age, ethnicity, and educational level (r = .60), next most on opinions and attitudes (r = .50), then on cognitive ability (r = .40), and least, but still significantly so, on personality (r = .20) and physical characteristics (r = .20).
Studies of adoptees, and of monozygotic or MZ twins (who share 100% of their genes) and dizygotic or DZ twins (who share 50% of their genes), show the human preference for similarity is heritable. Psychologist David Rowe studied similarity between best friends in several hundred twin pairs. He found not only a genetic contribution to antisocial behavior, but that adolescents genetically inclined to delinquency were genetically inclined to seek each other out as friends.
A study of adopted and non-adopted siblings found that whereas biological siblings (who share genes as well as environments) had friends who resembled each other, adoptive siblings (who share only environments) had friends who were not at all similar to each other.
A 2005 study of twins in Psychological Science [PDF]looked at spouses as well as best friends. All the respondents completed questionnaires measuring their personality and social attitudes. The results showed: (a) friends and spouses were about as similar as siblings (r = .25), a level of similarity not previously recognized; and (b) MZ twins chose more similar friends and spouses to their co-twin than did DZ twins. People's choices were found to be over 30% heritable.
A genetic contribution to mate choice has been shown by similarity being more pronounced on the more heritable attributes within sets of homogeneous traits. In a study of physical characteristics, people had chosen their spouses more on the basis of the more heritable features such as middle-finger length (80% heritable) than on the less heritable features such as upper-arm circumference (50% heritable).
In a study of personality and leisure time pursuits, spousal similarity was greater on the more heritable items such as enjoying reading (41% heritable) than on the less heritable items such as having many different hobbies (20% heritable).
In a study of cognitive ability, spousal resemblance was greater on the most heritable of 26 subtests. Other studies found that degree of genetic matching not only predicted the occurrence of marriage but also its stability and happiness.
Even when people marry across ethnic lines, they prove rather than disprove the rule. One analysis of the large Hawaii Family Study of Cognition found that spouses who married across race were more similar to each other in personality than those marrying within race. The researchers suggested that couples "made up" for their dissimilarity on the racial dimension by choosing spouses more like themselves in other respects.
Conclusion: the reason people engage in ethnic nepotism, as well as marry similar others, and like, make friends with, and help the most similar of their neighbors, is that doing so benefits copies of their genes.
The sense of a common ethnicity remains a major focus of identification for individuals today. It is no more likely to diminish in the future than is that of the family.
Genetic similarity theory explains why.
J. Philippe Rushton (E-mail him) is a professor of psychology at the University of Western Ontario, London, Ontario, Canada. and the author of Race, Evolution, and Behavior: A Life History Perspective. His most recent work on the evolution of ethnonationalism appeared in Nations and Nationalism (2005) and the Biological Journal of the Linnean Society (2009).