Females' tendency to place a high value on protecting their own lives enhanced their reproductive success in the environment of evolutionary adaptation because infant survival depended more upon maternal than on paternal care and defence. The evolved mechanism by which the costs of aggression (and other forms of risk taking) are weighted more heavily for females may be a lower threshold for fear in situations which pose a direct threat of bodily injury. Females' concern with personal survival also has implications for sex differences in dominance hierarchies because the risks associated with hierarchy formation in nonbonded exogamous females are not offset by increased reproductive success. Hence among females, disputes do not carry implications for status with them as they do among males, but are chiefly connected with the acquisition and defence of scarce resources. Consequently, female competition is more likely to take the form of indirect aggression or low-level direct combat than among males. Under patriarchy, men have held the power to propagate images and attributions which are favourable to the continuance of their control. Women's aggression has been viewed as a gender-incongruent aberration or dismissed as evidence of irrationality. These cultural interpretations have “enhanced” evolutionarily based sex differences by a process of imposition which stigmatises the expression of aggression by females and causes women to offer exculpatory (rather than justificatory) accounts of their own aggression.

Campbell's analysis of the evolution of human sex differences to include selection pressures on the female is generally welcomed. This commentary raises some specific issues about the evidence cited: the impact of paternal death on survival prospects; a possible mechanism underlying a sex difference in fear; the selective advantage of dominance hierarchies; and the absence of evidence that testosterone causes human aggression.

Campbell's evolutionary explanation of women's typically lower rates of interpersonal aggression is plausible, but some supporting evidence requires scrutiny. Women may not commit less interpersonal violence than men against small children. Women are more vulnerable than men in same-sex encounters. The link between dominance and reproductive success for males is less secure than was once thought.

In Homo sapiens and other species, promiscuity, risk-taking, and aggression are less matters of sex (having XX vs. XY) than gender (giving PI vs. resources and/or genes). Classic role reversals include: sea-horses, polyandrous birds, and a few heiresses in England and Rome. Unlike other females, but like many males, they are assertive, they take chances, and they are not chaste.

The development of physical traits and the formation of alliances are two important means of attaining status for both sexes. The types of physical traits and alliances that are linked with status, however, differ for the two sexes. Sex differences in the characteristics that lead to the acquisition of status must be considered before concluding that females are less concerned than males with status.

The view that female mammals are more docile appears to arise in part from imposing human values on animal studies. Many reports of sexual dimorphism in physical aggression favouring the male in laboratory rodents appear to select circumstances where that expectation is supported. Other situations that favour the expression of conflict in females have been (until recently) relatively little studied. Although female rodents generally do not show the “ritualised” forms of conflict that characterise male sexual competition, they can use notably damaging strategies (especially if they are of short duration). Such considerations might weigh in the selection of strategies by our own species.

Sex differences in willingness to take physical risks and in concern for peer esteem may be relevant to whether women should serve in combat, since two major fears soldiers experience are of being injured and of not measuring up as warriors. Women's relative aversion to nonphysical risk may have workplace implications, since risk taking is an attribute of most successful executives.

We applaud Campbell's cogent arguments for the evolution of female survival mechanisms but take issue with several key conceptual claims: the treatment of patriarchy; the implicit assumption that women are passive pawns in a male game of media exploitation; and the neglect of the possibility that media images exploit existing evolved psychological mechanisms rather than create them.

A single evolved psychological mechanism, social identity, may help explain the development of salient sex differences in aggression. Bearing children automatically provides a basis for positive social identity for females. Masculine identity is more problematic, especially where the range of possible cultural roles is small. Ethnohistorical data provides insight into the overlap between masculine values and warrior values.

Men are more physically aggressive and more risk-prone than women, but are not necessarily more competitive. New data show the gender difference in competitiveness to be one of kind rather than degree, with women and men competing in different ways and, to some extent, over different objectives, but not differing in overall strength of competitive feeling.

The same aggressive act will – all else being equal – have a different behavioral significance according to whether it is performed by a man or a woman. Such a perspective should have profound implications for legal and psychiatric practice, and for social policy in general.

This commentary focuses on the role played by constructions of women's violence in the maintenance of male control over women. While actual women's violence tends to be denied, pathologized or minimized, cultural constructions (particularly in the media) of women's violence tend to demonize it. Both of these androcentric cultural processes fail to illuminate the actual sources of the gender gap in violent behavior and instead tend to normalize male aggression and to cultivate female passivity.

The ultimate causes of sex differences in human aggressive behavior can lie mainly in evolved, inherited mechanisms that differ by sex or mainly in the differing placement of women and men in the social structure. The present commentary contrasts Campbell's evolutionary interpretation of aggression sex differences with a social structural interpretation that encompasses a wider range of phenomena.

Points of criticism of the target include: the extreme violence of females in defence of young despite high potential cost, the reality of female dominance striving, differences in male and female ritualization of aggression, the real existence of institutionalized female instrumental aggression, and the uselessness of “patriarchy” as defined as a category for differential analysis. It is concluded that it may in fact be the decline of patriarchy in the strict sense that leads to the female use of exculpatory explanations for aggression, thus reversing Campbell's proposed causal sequence.

Campbell's ambitious target article attempts to explain gender differences in both aggressive behavior and cultural representations of aggressive behavior. I comment on some of the specific arguments that require further clarification, some areas that merit expanded discussion, some topics which should be mentioned, and some research and theoretical questions raised by the article.

Why is female violence a taboo? We suggest that both men and women actively contribute to the creation of this stigma. Men may benefit because nonaggressive women may make better mothers and be more faithful and fertile. Females may benefit by downplaying their aggressive nature because they will be perceived as more valuable mates and because they will be more accepted within female social groups.

In contrast to evidence for evolved sex differences, support for the argument that female aggression was suppressed by patriarchial ideologies is thin. One empirical test of the differential stigmatization hypothesis is proposed, utilizing the four standard criteria for judgments of abnormality.

Gender differences in aggression are highly variable; there is significant evidence that this variability is as much a function of social and cultural conditions as evolutionary processes. While some of these conditions may reflect resource scarcities as Campbell proposes, others are inconsistent with her perspective or are explained equally well by other perspectives.

Campbell's target article significantly advances the field but fails to give adequate weight to individual differences. Moreover, there is no convincing rationale why males gain by making females less aggressive than they would otherwise be. It is also as likely that patriarchal ideology serves women's interests by canalizing genetic influences on individual differences within a more adaptively circumscribed range as it is to counter their interests by preventing them from challenging male hegemony.

Sociobiology has ignored the results of psychology, which is the discipline between biology and society. Campbell's target article fills some of the gaps beautifully, but the fact that women's direct and physical aggression has increased during the past 20 years, undermines Campbell's evolutionary explanation of female aggression. The two classical types of theoretical explanations of aggression are that (1) aggression is a drive and (2) aggression is instrumental behavior. Expressive aggression, assumed to be typical of women, is no more drive aggression than is men's aggression.