This might seem simple, as if ethnic identity can be reduced to counting genes. That is not how the human Homo Sapien) mind works. Suffice it that descent is what defines and motivates kinship systems. Members of an ethnic group believe that they share common ancestors, as well as sharing culture. This perceived kinship, expressed in folkloric metaphors such as “shared blood”, explains why ethnic and tribal motivation can be so strong. Knowledge of genetics might now, in principle, substitute for folklore but has not been necessary for thousands of years. By and large, beliefs about ancestry are accurate, so that folkloric beliefs about ethnicity generally correspond to genetic identity. This contradicts the sociological theory that ethnicity and race are socially constructed with no role for biology.
Frank Salter presents a powerful case for the adaptiveness of ethnocentrism. Different human ethnic groups and races have been separated for thousands of years, and during this period they have evolved some genetic distinctiveness. This genetic distinctiveness constitutes a storehouse of genetic interest. A quick look at the historical record shows that conflict between different groups has been common throughout human history. Tribalism seems to be the default mode of human political organization. The world’s largest land empire, that of the Mongols, was a tribal organization. But tribalism is hard to abandon, again suggesting that an evolutionary change may be required. Cooperative defense by tribal peoples is universal and ancient and it is bound to have boosted the genetic fitness of those who acted to further the interests of their group. Under such circumstances it would be odd indeed if natural selection did not mold the human mind to be predisposed to ethnocentrism.
In other words, people have an interest in their ethnic group in exactly the same way that parents have a genetic interest in raising their children: In raising their children, parents ensure that their unique genes are passed on to the next generation. But in defending ethnic interests, people are doing the same thing ensuring that the genetic uniqueness of their ethnic group is passed into the next generation. When parents of a particular ethnicity succeed in rearing their children, their ethnic group also succeeds because the genetic uniqueness of their ethnic group is perpetuated as part of their child’s genetic inheritance. But when an ethnic group succeeds in defending its interests, individual members of the ethnic group also succeed because the genetic uniqueness that they share with other members of the ethnic group is passed on. This is the case even for people who don’t have children: A person succeeds genetically when his ethnic group as a whole prospers.