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.