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)

“Love hurts”—as the saying goes—and a certain amount of pain and difficulty in intimate relationships is unavoidable. Sometimes it may even be beneficial, since adversity can lead to personal growth, self-discovery, and a range of other components of a life well-lived. But other times, love can be downright dangerous. It may bind a spouse to her domestic abuser, draw an unscrupulous adult toward sexual involvement with a child, put someone under the insidious spell of a cult leader, and even inspire (...) jealousy-fueled homicide. How might these perilous devotions be diminished? The ancients thought that treatments such as phlebotomy, exercise, or bloodletting could “cure” an individual of love. But modern neuroscience and emerging developments in psychopharmacology open up a range of possible interventions that might actually work. These developments raise profound moral questions about the potential uses—and misuses—of such anti-love biotechnology. In this article, we describe a number of prospective love-diminishing interventions, and offer a preliminary ethical framework for dealing with them responsibly should they arise. (shrink)

Incest is a crime in most societies. In the United States, incest is punishable in almost every state with sentences going as far as 20 and 30 years in prison, and even a life sentence. Yet the reasons traditionally proffered in justification of criminalization of incest—respecting religion and universal tradition; avoiding genetic abnormalities; protecting the family unit; preventing sexual abuse and sexual imposition; and precluding immorality—at a close examination, reveal their under- and over-inclusiveness, inconsistency or outright inadequacy. It appears that (...) the true reason behind the long history of the incest laws is the feeling of repulsion and disgust this tabooed practice tends to evoke in the majority of population. However, in the absence of wrongdoing, neither a historic taboo nor the sense of repulsion and disgust legitimizes criminalization of an act. (shrink)

This paper is based on two presentations under the auspices of thf Edinburgh Medical Group in 1976. Dr Noble and Professor Mason, explore the incidence of incest and society's attitudes to it from legal, anthropological, medical and social viewpoints. They place this in a world context by looking at the universal prohibition of incest and the theories related to that taboo. In conclusion, they suggest that there seem to be sufficient sensible grounds on which to base a reappraisal of attitudes (...) to incest. Their conclusions are in turn appraised by brief commentaries from a moral philospher and a psychiatrist. (shrink)

An increasing number of scholars argue that moral judgements are adaptations, i.e., that they have been shaped by natural selection. Is this hypothesis true? In this paper I shall not attempt to answer this important question. Rather, I pursue the more modest aim of pointing out three difficulties that anybody who sets out to determine the adaptedness of moral judgments should be aware of (though some so far have not been aware of). First, the hypothesis that moral judgements are adaptations (...) has been advocated in various different specificities and scopes, and on various different levels. Second, the three kinds of evidence that have most often been appealed to by discussants of this hypothesis require additional arguments. And third, there is significant reasonable disagreement about what moral judgements essentially are. (shrink)

Disgust, the emotion of rotting carcasses and slimy animalitos, finds itself at the center of several critical questions about human culture and cognition. This article summarizes recent developments, identify active points of debate, and provide an account of where the field is heading next.

E.O. Wilson (1975) described humans as one of the four pinnacles of social evolution. The other pinnacles are the colonial invertebrates, the social insects, and the non-human mammals. Wilson separated human sociality from that of the rest of the mammals because, with the exception of the social insect like Naked Mole Rats, only humans have generated societies of a grade of complexity that approaches that of the social insects and colonial invertebrates. In the last few millennia, human societies have even (...) begun to exceed, in numbers of individuals and degree of complexity, the societies of ants, termites, and corals. (shrink)

Westermarck proposed that humans have an incest avoidance instinct, triggered by frequent intimate contact with family members during the first several years of life. Westermarck reasons that familial incest will tend to produce less fit offspring, those humans without instinctive incest avoidance would hence have tended to die off and those with the avoidance instinct would have produced more viable offspring, and hence familial incest would be, as indeed it is, universally and instinctively avoided . Victorian Westermarck claimed this as (...) a human adaptation. Evolutionary psychologists have generalized these claims to Pleistocene humans and their ancestors, to primates, and indeed to animals generally. Yet there is surprisingly little evidence for these claims of universal instinctive avoidance. Considerable inbreeding appears among large, territorial primates and may have been so with early humans and with their ancestors. While there is little reliable non-anecdotal evidence about incestuous behavior or the lack of it among humans, what little there is does not fit well with the Westermarck thesis. (shrink)

Since its inception, donor conception practices have been a reproductive choice for the infertile. Past and current practices have the potential to cause significant and lifelong harm to the offspring through loss of kinship, heritage, identity, and family health history, and possibly through introducing physical problems. Legislation and regulation in Australia that specifies that the welfare of the child born as a consequence of donor conception is paramount may therefore be in conflict with the outcomes. Altering the paradigm to a (...) child-centric model, however, impinges on reproductive choice and rights of adults involved in the process. With some lobby groups pushing for increased reproductive choice while others emphasise offspring rights there is a dichotomy of interests that society and legislators need to address. Concepts pertaining to a shift toward a child-centric paradigm are discussed. (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)

Due to the intense selection pressure against inbreeding, humans are expected to possess psychological adaptations that regulate mate choice and avoid inbreeding. From a gene’s-eye perspective, there is little difference in the evolutionary costs between situations where an individual him/herself is participating in inbreeding and inbreeding among other close relatives. The difference is merely quantitative, as fitness can be compromised via both routes. The question is whether humans are sensitive to the direct as well as indirect costs of inbreeding. Using (...) responses from a large population-based sample (27,364 responses from 2,353 participants), we found that human motivations to avoid inbreeding closely track the theoretical costs of inbreeding as predicted by inclusive-fitness theory. Participants were asked to select in a forced choice paradigm, which of two acts of inbreeding with actual family members they would want to avoid most. We found that the estimated fitness costs explained 83.6% of participant choices. Importantly, fitness costs explained choices also when the self was not involved. We conclude that humans intuit the indirect fitness costs of mating decisions made by close family members and that psychological inbreeding avoidance mechanisms extend beyond self-regulation. (shrink)

The theory of sexual selection suggests several possible explanations for the development of standards of physical attractiveness in humans. Asymmetry and departures from average proportions may be markers of the breakdown of developmental stability. Supernormal traits may present age- and sex-typical features in exaggerated form. Evidence from social psychology suggests that both average proportions and (in females) “neotenous” facial traits are indeed more attractive. Using facial photographs from three populations (United States, Brazil, Paraguayan Indians), rated by members of the same (...) three populations, plus Russians and Venezuelan Indians, we show that age, average features, and (in females) feminine/neotenous features all play a role in facial attractiveness. (shrink)

What is Estonian Philosophy? What is Estonian Philosophy?

Evolutionary theory predicts that humans should avoid incest because of the negative effects incest has on individual reproduction: production of defective offspring. Selection for the avoidance of close-kin mating has apparently resulted in a psychological mechanism that promotes voluntary incest avoidance. Most human societies are thought to have rules regulating incest. If incest is avoided, why are social rules constructed to regulate it? This target article suggests that incest rules do not exist primarily to regulate close-kin mating but to regulate (...) inbreeding between more distant kin and sexual relations between affinal relatives. Three evolutionary hypotheses about cousin marriage and affinal kin mating follow from this suggestion: Rules regulating mating between affinal kin are means of paternity protection. Cousin marriage is regulated because, if it occurs, it can concentrate wealth and power within families to the detriment of the powerful positions of rulers in stratified societies and the relatively equal social statuses of most men in egalitarian societies. Tests using the comparative method on a worldwide sample of 129 societies supported the three hypotheses. Two alternative anthropological hypotheses failed to be supported. (shrink)

The reception so far of Kitcher's Vaulting Ambition reminds me of the old saw about the difference between an optimist and a pessimist. Looking at the same glass of water, the former sees it as half full while the latter sees it as half empty. Some have seen Kitcher's book as a vindication of the possibility of an evolutionary science of human behavior; others have seen it as a devastating critique of the most influential efforts to date to construct such (...) a science. As in the joke about the water glass, both assessments have their point. Sociobiology is a research program, not a unified theory. What one can do is test particular hypotheses within this program and see whether they live up to reasonable standards of rigor and evidence. This is what Kitcher does, with great energy and care. (shrink)

Various anthropologists have alleged that cultural constructions of kinship are at odds with Darwinian understandings of the same phenomena. The argument here is that this is not at all the case if attention is paid to the semantic structure of kinship categories, which reveals that the central members of these categories are indeed close procreative kin. Attention is also drawn to supporting research in cognitive psychology.