Original Article
Kin selection and ethnic group selection

https://doi.org/10.1016/j.evolhumbehav.2017.08.004Get rights and content

Abstract

Ethnicity looks something like kinship on a larger scale. The same math can be used to measure genetic similarity within ethnic/racial groups and relatedness within families. For example, members of the same continental race are about as related (r = 0.18–0.26) as half-siblings (r = 0.25). However (contrary to some claims) the theory of kin selection does not apply straightforwardly to ethnicity, because inclusive fitness calculations based on Hamilton's rule break down when there are complicated social interactions within groups, and/or groups are large and long-lasting. A more promising approach is a theory of ethnic group selection, a special case of cultural group selection. An elementary model shows that the genetic assimilation of a socially enforced cultural regime can promote group solidarity and lead to the regulation of recruitment to groups, and to altruism between groups, based on genetic similarity – in short, to ethnic nepotism. Several lines of evidence, from historical population genetics and political psychology, are relevant here.

Introduction

The theory of kin selection is a central pillar of the current evolutionary synthesis. The theory is important because it explains the widespread phenomenon of kin altruism – the evolution of behaviors geared to the survival and reproduction of an individual's kin, at the expense of the individual's own survival and reproduction.

Ethnicity and ethnocentrism in human societies share some affinities with kinship (Connor, 1993, Horowitz, 1985, Weber, 1978). Ethnic group members often maintain, rightly or wrongly, that they are descended from a common set of ancestors. They often use the idiom of kinship for one another – fellow ethnics are “brothers” and “sisters.” Ethnic identity, like kinship, is commonly seen as a primordial, ascribed, essential status, not easily changed. And ethnic group relations, like relations among kin, often seem to involve something more – and more primal – than the rational pursuit of individual or class interests.

All this has suggested to some evolution-minded authors that ethnicity is kinship, and that the evolution of ethnic sentiments can be explained by the theory of kin selection. An ethnic group is an extended family (so the argument goes), and ethnocentrism is kin altruism, advancing ethnic genetic interests through ethnic nepotism (Harpending, 2002, Rushton, 2005, Salter and Harpending, 2013, Shaw and Wong, 1989, Van Den Berghe, 1981, Vanhanen, 1999, Whitmeyer, 1997). It would be an important development in social theory if any of this turned out to be the case. Is this a real possibility? In the next three sections of this paper, I argue that the answer is No, Yes, and Maybe.

One argument for equating ethnicity and kinship is theoretical. The same mathematical machinery can be used to quantify genetic similarity within individuals and families, and within larger groups ranging from local subpopulations to continent-scale races. Insofar as ethnic groups correspond to population subdivisions, the population genetic definitions of kin relatedness and ethnic group relatedness are the same, allowing for a change of variables. This equivalence suggests that – following the theory of kin selection and assuming that ethnic group relatedness is high enough – we might predict significant altruism within ethnic groups. This possibility is taken up in the next section, where the verdict is negative. In spite of the formal correspondence, there is a quantitative difference between families and ethnic groups that prevents a straightforward application of the theory of kin selection to ethnicity.

The subsequent section arrives at a more positive assessment. It presents an alternative theory in which ethnic nepotism is socially enforced, and favored by ethnic group selection, a subtype of cultural group selection. According to the theory, members of an ethnic group may be cooperative and altruistic toward fellow ethnics based on shared genes. But shared genes are not just a result of genealogical connections, as they are in the standard theory of kin selection. Instead, a theory of ethnic nepotism must take into account some special evolutionary processes at work in human social evolution.

Ethnic group selection is a theoretical possibility; it might or might not have been of any importance in human evolution. Section 4 briefly reviews a few pertinent lines of evidence, from historical population genetics and political psychology.

Section snippets

Relatedness and inbreeding

Hamilton's rule is a simple formula, central to the theory of kin selection (Hamilton, 1964). This section begins with the standard exposition of the rule, and how relatedness relates to inbreeding. The rest of the section shows that the rule can be tricky, so that applying it to ethnicity is not straightforward.

According to Hamilton's rule, an altruistic act that imposes cost cj on benefactor j, while providing benefit bi for beneficiary i, is favored by natural selection as long ascj/bi<rijvi

From cultural group selection to ethnic group selection

The standard theory of kin selection does not yield a theory of ethnic nepotism. In large, long-lasting groups, members may or may not have high coefficients of inbreeding and relatedness as a result of sharing multiple links to distant ancestors, but neither genealogical relatedness nor genetic similarity over the whole genome is a reliable guide to similarities at loci governing sociality. However, the fundamental insight behind the theory of kin selection – that natural selection can favor

Ethnicity and evidence

There is one further difference between kin selection and ethnic group selection. Genetic similarity within families – the basic requirement for kin selection – follows automatically from the way sexual reproduction works. By contrast, genetic similarity within ethnic groups at relevant loci – the basic requirement for ethnic group selection – depends on special conditions that might or might not have held in the evolutionary past. So ethnic group selection is an iffier proposition than kin

Conclusion

Both the study of prehistory and political psychology are changing rapidly in the face of new evidence from biology, especially genetics. It would be intellectually satisfying if we could integrate these findings under the heading of an already existing theory, by equating ethnicity with kinship and applying kin selection theory. But we've seen that this won't work. Ethnicity, like kinship, may have to do with shared genes, and there may be such things as ethnic genetic interests and ethnic

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