The uses of natural selection argument in politics have been constant since Charles Darwin’s times. They have also been varied. The readings of Darwin’s theory range from the most radically individualist views, as in orthodox socio-Darwinism, to the most communitarian, as in Peter Kropotkin’s and other socialist perspectives. This essay argues that such diverse, contradictory, and sometimes even outrageous political derivations from Darwin’s theory may be partially explained by some incompleteness and ambivalences underlying Darwin’s concepts. “Natural selection,” “struggle for existence,” and “survival of the fittest” are open concepts and may suggest some hierarchical and segregationist interpretations. Circumstantially, Darwin accepted social “checks,” such as discouraging marriage of “lower” individuals to prevent them from reproducing, in a vein of Malthusian politics. This makes Darwin’s theory of selection by struggle collide with his theory of social instincts, by which he explains the origins of morality. It also favors reading Darwin’s On the Origin of Species or The Descent of Man from opposite, mostly ideological perspectives. Darwin’s position is ambivalent, although hardly unreasonable. The recognition he makes of social instincts, as well as the use of the concept of artificial selection, entails accepting the role of human consciousness, by which social evolution cannot be reduced to natural evolution, as socio-Darwinians did next and as some neo-Darwinists seem to repeat. On these grounds, this essay argues the inadequacy of the conventional model of natural selection for understanding politics. If we want to describe politics in Darwin’s language, artificial rather than natural selection would be the concept that performs better for explaining the courses of politics in real society.

Psychological adaptation underlies all human behavior. Thus, sexual coercion by men could either arise from a rape-specific psychological adaptation or it could be a side-effect of a more general psychological adaptation not directly related to rape. Determining the specific environmental cues that men's brains have been designed by selection to process may help us decide which these rival explanations is correct. We examine six testable predictions against existing data: (1) Both coercive and noncoercive will be associated with high levels of sexual arousal and performance in men. (2) Achieving physical control of a sexually unwilling woman will be sexually arousing to men. (3) Young men will be more sexually coercive than older men. (4) Men of low socioeconomic status will likewise be more sexually coercive. (5) A man's motivation to use sexual coercion will be influenced by its effects on social image. (6) Even in long-term relationships men will be motivated to use coercion when their mates show a lack of interest in resistance to sex because these are interpreted as signs of sexual infidelity. Current data support all six predictions and are hence consistent with the rape-specific hypothesis, but this does not eliminate the side-effect hypothesis, which is likewise compatible with the findings, as well as with the further evidence that forced matings increased the fitness of ancestral males during human evolution. We suggest some research that may help decide between the two hypotheses.

Human ethology is defined as the biology of human behavior. The methods it employs and the questions it poses are elaborations of those generally used in the various fields of biology, but especially adapted to the study of man. Observation and experimentation in the natural and seminatural setting as well as the comparative method derived from morphology play important roles in human ethology, and the exploration of phylogenetic adaptations constitutes one of its focal interests. On the basis of observations on experientially deprived and nondeprived children, comparative primate and animal behavior studies, and cross-cultural investigations, certain universal phylogenetic adaptations (in terms of fixed action patterns, innate releasing mechanisms, releasers, innate motivating mechanisms, and innate learning dispositions) have been found to occur. However, human ethology does not restrict itself to the investigation of phylogenetic adaptations. The question as to how a behavior pattern contributes to survival can be posed with respect to cultural patterns as well. Similar selection pressures have shaped both culturally and phylogenetically evolved patterns. Through cross-cultural studies a number of universal social interaction strategies have been discovered.

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 (especially cousin categories) and sexual relations between affinal relatives (often nonkin). Three evolutionary hypotheses about cousin marriage and affinal kin mating follow from this suggestion: (1) Rules regulating mating between affinal kin are means of paternity protection. Cousin marriage (inbreeding) is regulated because, if it occurs, it can concentrate wealth and power within families to the detriment of (2) the powerful positions of rulers in stratified societies and (3) 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 (derived from Freudian theory and alliance theory) failed to be supported.

Darwin, Sex and Status argues that a human sociobiology that mistakes evolutionary theory for theories of psychology and culture is wrong, as are psychologies that could never have evolved or social sciences that posit impossible psychologies. Status develops theories of human self-awareness, cognition, and cultural capacity that are compatible with evolutionary theory. Recurring themes include: the importance of sexual selection in human evolution; our species' preoccupation with self-esteem and relative standing; the individual as an active strategist, regularly revising culturally provided information; and awareness as an impressionmanagement device. Culture is a somewhat structured information pool that itself evolves, often in ways that reduce the genetic fitness of its participants.

This paper examines the strengths and weaknesses of one of science's most pervasive and flexible metaprinciples; optimality is used to explain utility maximization in economics, least effort principles in physics, entropy in chemistry, and survival of the fittest in biology. Fermat's principle of least time involves both teleological and causal considerations, two distinct modes of explanation resting on poorly understood psychological primitives. The rationality heuristic in economics provides an example from social science of the potential biases arising from the extreme flexibility of optimality considerations, including selective search for confirming vidence, ex post rationalization, and the confusion of prediction with explanation. Commentators are asked to reflect on the extent to which optimality is (1) an organizing principle of nature, (2) a set of relatively unconnected techniques of science, (3) a normative principle for rational choice and social organization, (4) a metaphysical way of looking at the world, or (5) something else still.

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 of actual male fertility than the one commonly used, fails to correlate with social status. In striking contrast, however, status is found to be highly correlated with potential fertility, as estimated from copulation frequency. Status thus accounts for as much as 62% of the variance in this proximate component 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.

We present a general framework for analyzing the contribution to reproductive success of a behavioural action. An action may make a direct contribution to reproductive success, but even in the absence of a direct contribution it may make an indirect contribution by changing the animal's state. We consider actions over a period of time, and define a reward function that characterizes the relationship between the animal's state at the end of the period and its future reproductive success. Working back from the end of the period using dynamic programming, the optimal action as a function of state and time can be found. The procedure also yields a measure of the cost, in terms of future reproductive success, of a suboptimal action. These costs provide us with a common currency for comparing activities such as eating and drinking, or eating and hiding from predators. The costs also give an indication of the robustness of the conclusions that can be drawn from a model. We review how our framework can be used to analyze optimal foraging decisions in a stochastic environment. We also discuss the modelling of optimal daily routines and provide an illustration based on singing to attract a mate. We use the model to investigate the features that can produce a dawn song burst in birds. State is defined very broadly so that it includes the information an animal has about its environment. Thus, exploration and learning can be included within the framework.

A new theory of attraction and liking based on kin selection suggests that people detect genetic similarity in others in order to give preferential treatment to those who are most similar to themselves. There are many sources of empirical and theoretical support for this view, including (1) the inclusive fitness theory of altruism, (2) kin recognition studies of animals raised apart, (3) assortative mating studies, (4) favoritism in families, (5) selective similarity among friends, and (6) ethnocentrism. Specific tests of the theory show that (1) sexually interacting couples who produce a child are genetically more similar to each other in blood antigens than they are either to sexually interacting couples who fail to produce a child or to randomly paired couples from the same sample; (2) similarity between marriage partners is most marked in the more genetically influenced of sets of anthropometric, cognitive, and personality characteristics; (3) after the death of a child, parental grief intensity is correlated with the child's similarity to the parent; (4) long-term male friendship pairs are more similar to each other in blood antigens than they are to random dyads from the same sample; and (5) similarity among best friends is most marked in the more genetically influenced of sets of attitudinal, personality, and anthropometric characteristics. The mechanisms underlying these findings may constitute a biological substrate of ethnocentrism, enabling group selection to occur.

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 of Homo sapiens as 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” (i.e. wealth, success, and measured aptitudes) 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.

In most cultures, extramarital sex is highly restricted for women. In most of those cultures, men transfer wealth to their own sons (patrilineal inheritance). In some cultures extramarital sex is not highly restricted for women, and in most of those cultures, men transfer wealth to their sisters' sons (matrilineal inheritance). 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 (ρ = probability of paternity) 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 (< 0.46). 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.

The Strange Situation procedure was developed by Ainsworth two decades agoas a means of assessing the security of infant-parent attachment. Users of the procedureclaim that it provides a way of determining whether the infant has developed species-appropriate adaptive behavior as a result of rearing in an evolutionary appropriate context, characterized by a sensitively responsive parent. Only when the parent behaves in the sensitive, species-appropriate fashion is the baby said to behave in the adaptive or secure fashion. Furthermore, when infants are observed repeatedly in the Strange Situation,the pattern of behavior is said to be highly similar, and this pattern is said to predict the infants' future behavior in a diverse array of contexts. After an exhaustive review of the literature, it is shown that these popular claims are empirically unsupported in their strong form, and that the interpretations in terms of biological adaptationare misguided. There is little reliable evidence about the specific dimensions of parental behavior that affect Strange Situation behavior, although there does appear to be some relationship between these constructs. Temporal stability in security of attachment ishigh only when there is stability in family and caretaking circumstances. Likewise, patterns of Strange Situation behavior only have substantial predictive validity in similarly stable families. Implications for future research and theorizing — particularly as they relate to the use of evolutionary biology in psychological theory — are discussed.

Sociopaths are “outstanding” members of society in two senses: politically, they draw our attention because of the inordinate amount of crime they commit, and psychologically, they hold our fascination because most ofus cannot fathom the cold, detached way they repeatedly harm and manipulate others. Proximate explanations from behavior genetics, child development, personality theory, learning theory, and social psychology describe a complex interaction of genetic and physiological risk factors with demographic and micro environmental variables that predispose a portion of the population to chronic antisocial behavior. More recent, evolutionary and game theoretic models have tried to present an ultimate explanation of sociopathy as the expression of a frequency-dependent life strategy which is selected, in dynamic equilibrium, in response to certain varying environmental circumstances. This paper tries to integrate the proximate, developmental models with the ultimate, evolutionary ones, suggesting that two developmentally different etiologies of sociopathy emerge from two different evolutionary mechanisms. Social strategies for minimizing the incidence of sociopathic behavior in modern society should consider the two different etiologies and the factors that contribute to them.

In both biology and the human sciences, social groups are sometimes treated as adaptive units whose organization cannot be reduced to individual interactions. This group-level view is opposed by a more individualistic one that treats social organization as a byproduct of self-interest. According to biologists, group-level adaptations can evolve only by a process of natural selection at the group level. Most biologists rejected group selection as an important evolutionary force during the 1960s and 1970s but a positive literature began to grow during the 1970s and is rapidly expanding today. We review this recent literature and its implications for human evolutionary biology. We show that the rejection of group selection was based on a misplaced emphasis on genes as “replicators” which is in fact irrelevant to the question of whether groups can be like individuals in their functional organization. The fundamental question is whether social groups and other higher-level entities can be “vehicles” of selection. When this elementary fact is recognized, group selection emerges as an important force in nature and what seem to be competing theories, such as kin selection and reciprocity, reappear as special cases of group selection. The result is a unified theory of natural selection that operates on a nested hierarchy of units.

The vehicle-based theory makes it clear that group selection is an important force to consider in human evolution. Humans can facultatively span the full range from self-interested individuals to “organs” of group-level “organisms.” Human behavior not only reflects the balance between levels of selection but it can also alter the balance through the construction of social structures that have the effect of reducing fitness differences within groups, concentrating natural selection (and functional organization) at the group level. These social structures and the cognitive abilities that produce them allow group selection to be important even among large groups of unrelated individuals.

Social dilemmas occur when the pursuit of self-interest by individuals in a group leads to less than optimal collective outcomes for everyone in the group. A critical assumption in the human sciences is that people's choices in such dilemmas are individualistic, selfish, and rational. Hence, cooperation in the support of group welfare will only occur if there are selfish incentives that convert the social dilemma into a nondilemma. In recent years, inclusive fitness theories have lent weight to such traditional views of rational selfishness on Darwinian grounds. To show that cooperation is based on selfish incentives, however, one must provide evidence that people do not cooperate without such incentives. In a series of experimental social dilemmas, subjects were instructed to make single, anonymous choices about whether or not to contribute money for a shared “bonus” that would be provided only if enough other people in the group also contributed their money. Noncontributors cited selfish reasons for their choices; contributors did not. If people are allowed to engage in discussion, they will contribute resources at high rates, frequently on irrational grounds, to promote group welfare. These findings are consistent with previous research on ingroup biasing effects that cannot be explained by “economic man” or “selfish gene” theories. An alternative explanation is that sociality was a primary factor shaping the evolution of Homo sapiens. The cognitive and affective mechanisms underlying such choices evolved under selection pressures on small groups for developing and maintaining group membership and for predicting and controlling the behavior of other group members. This sociality hypothesis organizes previously inexplicable and disparate phenomena in a Darwinian framework and makes novel predictions about human choice.