Applications of sexual selection theory to humans lead us to expect that because of mammalian sex differences in obligate parental investment there will be gender differences in fitness variances, and males will benefit more than females from multiple mates. Recent theoretical work in behavioral ecology suggests reality is more complex. In this paper, focused on humans, predictions are derived from conventional parental investment theory regarding expected outcomes associated with serial monogamy and are tested with new data from a postreproductive cohort (...) of men and women in a primarily horticultural population in western Tanzania (Pimbwe). Several predictions derived from the view that serial monogamy is a reproductive strategy from which males benefit are not supported. Furthermore, Pimbwe women are the primary beneficiaries of multiple marriages. The implications for applications of sexual selection theory to humans are discussed, in particular the fact that in some populations women lead sexual and reproductive lives that are very different from those derived from a simple Bateman-Trivers model. (shrink)

The fundamental postulate of sociobiology is that individuals exploit favorable environments to increase their genetic representation in the next generation. The data on fertility differentials among contemporary humans are not cotvietent with this postulate. Given the importance ofHomo sapiensas an animal species in the natural world today, these data constitute particularly challenging and interesting problem for both human sociobiology and sociobiology as a whole.The first part of this paper reviews the evidence showing an inverse relationship between reproductive fitness and “endowment” (...) in contemporary, urbanized societies. It is shown that a positive relationship is observed only for those cohorts who bore their children during a unique period of rising fertility, 1935–1960, and that these cohorts are most often cited by sociobiologists as supporting the central postulate of sociobiology. Cohorts preceding and following these show the characteristic inverse relationship between endowment and fertility. The second section reviews the existing so-ciobiological models of this inverse relationship, namely, those of Barkow, Burley, and Irons, as well as more informal responses among sociobiologists to the persistent violation of sociobiology's central postulate, such as those of Alexander and Dawkins. The third section asks whether the goals of sociobiology, given the violation of its fundamental postulate by contemporary human societies, might not be better thought of as applied rather than descriptive, with respect to these societies. A proper answer to this question begins with the measurement of the pace and direction of natural selection within modern human populations, as compared to other sources of change. The vast preponderance of the shifts in human trait distributions, including the IQ distribution, appears to be due to environmental rather than genetic change. However, there remains the question of just how elastic these distributions are in the absence of reinforcing genetic change. (shrink)

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)

Menstrual taboos are nearly ubiquitous and assume parallel forms in geographically distant populations, yet their function has baffled researchers for decades. This paper proposes that menstrual taboos are anticuckoldry tactics. By signaling menstruation, they may advertise female reproductive status to husbands, affines, and other observers. Females may therefore have difficulty in obfuscating the timing of the onset of pregnancy. This may have three consequences: (a) males are better able to assess their probabilities of paternity and to direct their parental investment (...) toward genetic offspring; (b) adulterous pregnancies are more easily detected and penalized, enhancing sexual fidelity; and (c) males avoid marrying pregnant females by relying on menstruation as evidence of nonpregnancy. This hypothesis is tested with 29 months of field data on menstrual taboos among the Dogon of Mali. Key results include the following: (a) cuckoldry is a major Dogon concern, (b) menstrual huts advertise female reproductive status, (c) husbands impose the taboos upon their wives, (d) female defiance of the taboos is undetectable and probably rare, and (e) informants think that the taboos help husbands and patrilineages to avoid cuckoldry. Thus the anti-cuckoldry hypothesis provides helpful insight into the menstrual taboos of the Dogon and should be tested among other populations. (shrink)

We conducted a meta-analysis of 17 studies that tested for an association between grandparental survival and grandchild survival in patrilineal populations. Using two different methodologies, we found that the survival of the maternal grandmother and grandfather, but not the paternal grandmother and grandfather, was associated with decreased grandoffspring mortality. These results are consistent with the findings of psychological studies in developed countries (Coall and Hertwig Behavioral and Brain Sciences 33:1-59, 2010). When tested against the predictions of five hypotheses (confidence of (...) paternity; grandmothering, kin proximity, grandparental senescence, and local resource competition), our meta-analysis results are most in line with the local resource competition hypothesis. In patrilineal and predominantly patrilocal societies, the grandparents who are most likely to live with the grandchildren have a less beneficial association than those who do not. We consider the extent to which these results may be influenced by the methodological limitations of the source studies, including the use of retrospective designs and inadequate controls for confounding variables such as wealth. (shrink)

This article argues that feminist analyses of patriarchy should be expanded to address the evolutionary basis of male motivation to control female sexuality. Evidence from other primates of male sexual coercion and female resistance to it indicates that the sexual conflicts of interest that underlie patriarchy predate the emergence of the human species. Humans, however, exhibit more extensive male dominance and male control of female sexuality than is shown by most other primates. Six hypotheses are proposed to explain how, over (...) the course of human evolution, this unusual degree of gender inequality came about. This approach emphasizes behavioral flexibility, cross-cultural variability in the degree of partriarchy, and possibilities for future change. (shrink)

Understanding female sexuality and mate choice is central to evolutionary scenarios of human social systems. Studies of female sexuality conducted by sex researchers in the United States since 1938 indicate that human females in general are concerned with their sexual well-being and are capable of sexual response parallel to that of males. Across cultures in general and in western societies in particular, females engage in extramarital affairs regularly, regardless of punishment by males or social disapproval. Families are usually concerned with (...) marriage arrangements only insofar as those arrangements are economically or politically advantageous, but females most often have a voice in arranged marriages. Extended families also concentrate on a couple’s future reproduction rather than on sexual exclusivity. Although marriage for females is often compromised by male or family reproductive interests (which may not in fact differ from female interests), females appear to exercise their sexuality with more freedom than has previously been suggested. Notions of human females as pawns in the male reproductive game, or as traders of sex for male services, should be dispelled. (shrink)

In modern Indian political discourse the custom of dowry is often represented as the cause of serious social problems, including the neglect of daughters, sex-selective abortion, female infanticide, and the harassment, abuse, and murder of brides. Attempts to deal with these problems through legislative prohibition of dowry, however, have resulted in virtually no diminution of either dowry or violence against women. In contrast, radically different interpretations of dowry can be found in the literatures of structural-functionalist anthropology, economics, and human behavioral (...) ecology which muster wide-ranging forms of qualitative and quantitative evidence to support functional models of dowry as a form of inheritance or investment in daughters and/or their children. This paper argues that a functionalist perspective on dowry could lead to improved dowry policy, and that an approach based in human behavioral ecology (HBE) is uniquely suited to this task. After reviewing the relevant literature on dowry in South Asia, I discuss current dowry legislation and its limitations. I then develop a behavioral ecology model of Indian dowry and test it with quantitative and qualitative data. I conclude that if dowry legislation is to achieve broad support or bring about effective social change, it must address and support the positive motivations for and effects of dowry and take a targeted approach to dowry violence, which is not uniformly distributed across regions, castes, or social classes. (shrink)

In most social species, position in the male social hierarchy and reproductive success are positively correlated; in humans, however, this relationship is less clear, with studies of traditional societies yielding mixed results. In the most economically advanced human populations, the adaptiveness of status vanishes altogether; social status and fertility are uncorrelated. These findings have been interpreted to suggest that evolutionary principles may not be appropriate for the explanation of human behavior, especially in modern environments. The present study tests the adaptiveness (...) of social status with actual mating and reproductive data in a representative sample of males from an industrial society. Reproductive success, even when assessed by a more reliable measure ofactualmale fertility than the one commonly used, fails to correlate with social status. In striking contrast, however, status is found to be highly correlated withpotentialfertility, as estimated from copulation frequency. Status thus accounts for as much as 62% of the variance in thisproximatecomponent of fitness. This pattern is remarkably similar to what is found in many traditional societies and would result in a substantial positive relationship between cultural and reproductive success in industrial populations were it not for the novel conditions imposed by contraception and monogamy. Various underlying mechanisms are suggested for these findings, illustrating the value of current behavioral and reproductive data in the study of adaptation. It is concluded that evolutionary explanations of human behavior remain entirely relevant in modern societies. (shrink)