Much clinical and ethnographic evidence suggests that humans, like many other organisms, are selected to avoid close inbreeding because of the fitness costs of inbreeding depression. The proximate mechanism of human inbreeding avoidance seems to be precultural, and to involve the interaction of genetic predispositions and environmental conditions. As first suggested by E. Westermarck, and supported by evidence from Israeli kibbutzim, Chinese sim-pua marriage, and much convergent ethnographic and clinical evidence, humans negatively imprint on intimate associates during a critical period (...) of early childhood.There is also much evidence that, like other social animals, humans do not seek to maximize outbreeding, but rather to maintain an optimal balance between outbreeding and inbreeding.Closeinbreeding reduces fitness through inbreeding depression, butsomeinbreeding brings the benefits of nepotism. For simple, stateless, horticultural societies, the optimal balance seems to be achieved by a combination of precultural inbreeding avoidance of relatives with anr≤·25 and cultural rules of preferential marriage with kin withr≥·25. Adjustment of the coefficient of inbreeding to other ecological settings seems to be largely cultural. An interactive model of “culture in nature” is presented, in which culture is seen as coevolving with genes to produce the maxiniization of individual inclusive fitness. (shrink)

In most cultures, extramarital sex is highly restricted for women. In most of those cultures, men transfer wealth to their own sons. In some cultures extramarital sex is not highly restricted for women, and in most of those cultures, men transfer wealth to their sisters' sons. Inheritance to sisters' sons ensures a man's biological relatedness to his heirs, and matrilineal inheritance has been posited as a male accommodation to cuckoldry—a paternity strategy—at least since the 15th century. However, longitudinal analysis of (...) the cumulative effect of female extramarital sex indicates that matrilineal inheritance is most advantageous for women and would be more accurately considered a grandmaternity strategy. That is, if the probability that men's putative children are their biological children is less than 1, the probabilistic degree of relatedness between a female and her matrilineal heirs is higher than her corresponding relatedness to her patrilineal heirs. The same holds true for men only if ρ is very low. The upshot is that for moderate levels of female extramarital sex, matrilineal inheritance, relative to patrilineal inheritance, is highly advantageous for women and disadvantageous for men. Consideration of female variance in reproductive success beyond the first generation, and of a man's network of obligation to the inclusive fitness of his relatives, suggests that although the establishment of matrilineal inheritance may require extremely high levels of female extramarital sex, once established, it is likely to be maintained at levels of ρ that reasonably characterize many societies in the ethnographic record. New analysis of previously published data shows a strong association between matrilineal inheritance and moderate to low probability of paternity, and an even stronger relationship between patrilineal inheritance and high probability of paternity. (shrink)

Human propensities that are the products of Darwinian evolution may combine to generate a form of social behavior that is not itself a direct result of such pressure. This possibility may provide a satisfying explanation for the origin of socially transmitted rules such as the incest taboo. Similarly, the regulatory processes of development that generated adaptations to the environment in the circumstances in which they evolved can produce surprising and sometimes maladaptive consequences for the individual in modern conditions. These combinatorial (...) aspects of social and developmental dynamics leave a subtle but not wholly uninteresting role for evolutionary biology in explaining the origins of human morality. (shrink)

'At last one of the most famous generalizing works in anthropology by the field's most stimulating and controversial contemporary figure has been translated, beautifully, and with the enlightening preface of the second French edition.