I ask three questions related to the claims made within the staying alive theory : Is survival more fitness-enhancing for females than for males? Does the historical record on sex differences in mortality support the SAT? Is it possible to talk about “independent selective pressures on both male and female traits” when all we have are sex/gender comparisons?

Income inequality has been empirically linked to interpersonal competition and risk-taking behaviors, but a separate line of findings consistently shows that individuals have inaccurate perceptions of the actual levels of income inequality in society. How can inequality be both consistently misperceived and yet a reliable predictor of behavior? The present study extends both these lines of research by evaluating if the scope of input used to assess income inequality (i.e., at the national, state, county, or postal code level) can account (...) for perception discrepancies and if actual/perceived inequality is associated with female intrasexual competition. Female participants recruited online from the general US population (_n_ = 691) provided demographic information, measures of perceived income inequality, and measures of intrasexual competition attitudes and behavior. Actual and perceived income inequality (at any level) did not predict negative attitudes toward other women or female weighting of physical appearance as a desirable trait. Perceived income inequality and actual county-level inequality was, however, predictive of female competition in the form of self-sexualization clothing choice. Further analyses found that age and importance placed on physical attractiveness also predicted women’s clothing choices. Perceptions of income inequality were predicted not by actual Gini indices, but by beliefs about the levels of poverty and income gaps. These results highlight the importance of better understanding the proximate cues by which people perceive environmental features such as inequality, and how those cues are used to adjust interpersonal behaviors. (shrink)

Several theories claim that dreaming is a random by-product of REM sleep physiology and that it does not serve any natural function. Phenomenal dream content, however, is not as disorganized as such views imply. The form and content of dreams is not random but organized and selective: during dreaming, the brain constructs a complex model of the world in which certain types of elements, when compared to waking life, are underrepresented whereas others are over represented. Furthermore, dream content is consistently (...) and powerfully modulated by certain types of waking experiences. On the basis of this evidence, I put forward the hypothesis that the biological function of dreaming is to simulate threatening events, and to rehearse threat perception and threat avoidance. To evaluate this hypothesis, we need to consider the original evolutionary context of dreaming and the possible traces it has left in the dream content of the present human population. In the ancestral environment human life was short and full of threats. Any behavioral advantage in dealing with highly dangerous events would have increased the probability of reproductive success. A dream-production mechanism that tends to select threatening waking events and simulate them over and over again in various combinations would have been valuable for the development and maintenance of threat-avoidance skills. Empirical evidence from normative dream content, children's dreams, recurrent dreams, nightmares, post traumatic dreams, and the dreams of hunter-gatherers indicates that our dream-production mechanisms are in fact specialized in the simulation of threatening events, and thus provides support to the threat simulation hypothesis of the function of dreaming. Key Words: dream content; dream function; evolution of consciousness; evolutionary psychology; fear; implicit learning; nightmares; rehearsal; REM; sleep; threat perception. (shrink)

Archer recognizes that sexual selection theory is sensitive to the effects of ecologies on sex differences, yet he does not explain the impact of such variation. For example, to what degree are there sex differences in aggression in polygynous and monogamous societies? I demonstrate how differences in mating perceptions affect the traditional dichotomy that males compete for and females choose mates.

The pregnancy compensation hypothesis provides a mechanistic explanation for the evolution of sex differences in immune system functioning, the excess of women experiencing autoimmune disease, and why this is observed only in industrialized nations; none of which can be explained by the staying alive theory, as proposed by the authors of the target article.

Martínez-Manrique contends that we overlook a possible nonconnectionist vehicle theory of consciousness. We argue that the position he develops is better understood as a hybrid vehicle/process theory. We assess this theory and in doing so clarify the commitments of both vehicle and process theories of consciousness.

Sex/gender is a continuous variable that researchers frequently treat as dichotomous. This practice can mask continuous underlying adaptive traits and yield spurious dichotomous “sex differences.” As such, many sex differences in self-protection may be evolutionary by-products of underlying adaptations rather than adaptations themselves. Binary analysis of continuous sex/gender is ill-considered science that can contribute to inequality and counterproductive public policy.

Several theorists have tried to model anorexia on Wasser and Barash’s (1983) “reproductive suppression model” (RSM). According to the RSM, individual females adaptively suppress their reproductive functioning under conditions of social or physiological stress. From this perspective, mild anorexia is viewed as an adaptive response to modern conditions; more severe anorexia is viewed as an adaptation gone awry. Previous models have not, however, examined the full richness of the RSM. Specifically, Wasser and Barash documented not only self-imposed reproductive suppression, but (...) also manipulative reproductive suppression of subordinate females by dominants. I propose that the modern “epidemic” of anorexia is explained neither by adaptive self-suppression nor by environmental mismatch (an adaptation gone awry); I propose that the “epidemic” levels of anorexia seen in modern western society are a direct consequence of intrasexual competition, the scope of which has been enhanced by the power and reach of modern communications media. According to this perspective, anorexia, even in its mild forms, is a manipulative strategy imposed on subordinates by dominants. Anorexia is, in both senses, a “losing” strategy. (shrink)

Defense of reproductive choice is an important motivation in women's self-protection psychology for which the “staying alive theory” cannot fully account. Evidence indicates that some elements of women's self-protection psychology function to protect reproductive choice rather than survival, or may be equally well explained by either motivation. Integrating perspectives will result in greater explanatory breadth and precision in theory testing.

The target article presented a plausible argument that females' susceptibility to threats might be self-protection for staying alive, but some evidence requires scrutiny. We need to consider the biases of narrative reviews, subjective life quality, and the shadow side of extreme reactions to threats before concluding that females' threat-based response is a self-protection mechanism that promotes survival.

Life history data, attractiveness ratings of male photographs, and attitudes towards partnership and child-rearing of 321 women were used to test four evolutionary models (quantitative reproductive strategy, male short-age, polygyny indication, and maternal reproductive interests) which attempt to explain the influence of family composition on reproductive strategies. Links between early menarche and other markers of reproductive strategy were investigated. Childhood stress and absence of a father figure, whether genetically related or not, were found to have accelerated menarche whereas having younger (...) siblings decelerated it. Early menarche was associated with attractiveness ratings, the number of partners desired for the immediate future, and the early onset of intimate relationships. It was not linked with sociosexual orientation, mate choice criteria, and investment in the subjects’ own children, but these three markers were interrelated. The implications of the findings for the four evolutionary models are discussed. (shrink)

Sex differences in physical and indirect aggression have been found in many societies but, to our knowledge, have not been studied in a population of hunter-gatherers. Among Aka foragers of the Central African Republic we tested whether males physically aggressed more than females, and whether females indirectly aggressed more than males, as has been seen in other societies. We also tested predictions of an evolutionary theory of physical strength, anger, and physical aggression. We found a large male bias in physical (...) aggression. Controlling for anger, we found an adult female bias in indirect aggression. Physical strength predicted anger, which predicted hitting, although results were sensitive to the inclusion or exclusion of traditional healers, who were physically and emotionally distinct from other Aka. With some important caveats, our results generally support the predicted sex differences in physical aggression and indirect aggression, and the predicted relationships among anger, strength, and aggression. (shrink)

The authors propose that many morbidities higher in women than men are adaptations protecting survival, selected because survival has been especially crucial to mothers' reproductive success. Following their lead, I pursue variation in tradeoffs between reproduction and survival recognized by Darwin that were likely central to the evolution of many traits that distinguish us from our great ape cousins.

We argue that Benenson et al. need to consider not only sex differences in the effects of care on offspring survival but also in age-specific fertility when predicting how longevity affects fitness. We review evidence that staying alive has important effects on both women's and men's fitness, and encourage consideration of alternative explanations for observed sex differences in threat responses.

Venturing into novel terrain poses physical risks to a female and her offspring. Females have a greater tendency to avoid physical harm, while males tend to have larger range sizes and often outperform females in navigation-related tasks. Given this backdrop, we expected that females would explore a novel environment with more caution than males, and that more-cautious exploration would negatively affect navigation performance. Participants explored a novel, large-scale, virtual environment in search of five objects, pointed in the direction of each (...) object from the origin, and then navigated back to the objects. We found that females demonstrated more caution while exploring as reflected in the increased amounts of pausing and revisiting of previously traversed locations. In addition, more pausing and revisiting behaviors led to degradation in navigation performance. Finally, individual levels of trait harm avoidance were positively associated with the amount of revisiting behavior during exploration. These findings support the idea that the fitness costs associated with long-distance travel may encourage females to take a more cautious approach to spatial exploration, and that this caution may partially explain the sex differences in navigation performance. (shrink)

Benenson et al. amass impressive evidence of robust sex differences as support for expanding “staying alive” theory. We argue for a broader and more domain-specific conceptualization focusing on life history tradeoffs between survival and mating success. Using three examples – women's disgust, fear of rape, and cultivation of bodyguards – we illustrate these tradeoffs and suggest a broader theoretical framework.

This commentary cites evidence to argue that girls growing up in a competitive and aggressive environment are more likely to shift to avoidant attachment than to ambivalent attachment in middle childhood. These avoidant women are also more likely to favor a short-term mating strategy. The role of oxytocin (OT) and early experience in shaping an avoidant attachment in females is also discussed.

Males in many non-monogamous species have larger ranges than females do, a sex difference that has been well documented for decades and seems to be an aspect of male mating competition. Until recently, parallel data for humans have been mostly anecdotal and qualitative, but this is now changing as human behavioral ecologists turn their attention to matters of individual mobility. Sex differences in spatial cognition were among the first accepted psychological sex differences and, like differences in ranging behavior, are documented (...) for a growing set of species. This special issue is dedicated to exploring the possible adaptive links between these cognitive and ranging traits. Multiple hypotheses, at various levels of analysis, are considered. At the functional (ultimate) level, a mating-competition hypothesis suggests that range expansion may augment mating opportunities, and a fertility-and-parental-care hypothesis suggests that range contraction may facilitate offspring provisioning. At a more mechanistic (proximate) level, differences in cue availability may support or inhibit particular sex-specific navigation strategies, and spatial anxiety may usefully inhibit travel that would not justify its costs. Studies in four different cultures—Twe, Tsimane, Yucatec Maya, and Faroese—as well as an experimental study using virtual reality tools are the venue for testing these hypotheses. Our hope is to stimulate more research on the evolutionary and developmental processes responsible for this suite of linked behavioral and cognitive traits. (shrink)

The target article claims that evolutionary theory predicts the emergence of sex differences in aggression in early childhood, and that there will be no sex difference in anger. It also finds an absence of sex differences in spousal abuse in Western societies. All three are puzzling from an evolutionary perspective and warrant further discussion.

The target article interprets women's lower competitiveness than men's as evidence of adaptation to help women avoid physical conflicts and stay alive. This commentary advances the additional hypothesis that strategically suppressing competitiveness, thus signaling egalitarian intentions, could be an adaptation to catalyze cooperative behavior from males and females, turning natural competitors into allies and men into supportive partners.

Supporting a mediating role for fear in inhibiting female aggression, a recent study shows that aversion to impulsivity completely mediates the sex difference in direct aggression but not in angry acts where dangerous retaliation is unlikely. A more inclusive use of the term to encompass reproductive advantage would recognise females' crucial role in nurturing and protecting offspring.

Incorporating theoretic insights from ageing biology could advance the “staying alive” hypothesis. Higher male extrinsic mortality can weaken selection against ageing-related diseases and self-preservation, leading to high male intrinsic mortality. This may incidentally result in female-biased longevity-promoting traits, a possibility that will require rigorous testing in order to disentangle from the adaptive self-preservation hypothesis presented in the target article.

We extend Benenson et al.'s hypothesis from the individual level to the societal level. Because women have highly limited reproductive rates, societies have generally prioritized female survival and regarded males as expendable. We describe various lines of evidence that are consistent with this hypothesis, and we offer additional predictions about differential attitudes toward male versus female endangerment.

Many male traits are well explained by sexual selection theory as adaptations to mating competition and mate choice, whereas no unifying theory explains traits expressed more in females. Anne Campbell's “staying alive” theory proposed that human females produce stronger self-protective reactions than males to aggressive threats because self-protection tends to have higher fitness value for females than males. We examined whether Campbell's theory has more general applicability by considering whether human females respond with greater self-protectiveness than males to other threats (...) beyond aggression. We searched the literature for physiological, behavioral, and emotional responses to major physical and social threats, and found consistent support for females' responding with greater self-protectiveness than males. Females mount stronger immune responses to many pathogens; experience a lower threshold to detect, and lesser tolerance of, pain; awaken more frequently at night; express greater concern about physically dangerous stimuli; exert more effort to avoid social conflicts; exhibit a personality style more focused on life's dangers; react to threats with greater fear, disgust, and sadness; and develop more threat-based clinical conditions than males. Our findings suggest that in relation to threat, human females have relatively heightened protective reactions compared to males. The pervasiveness of this result across multiple domains suggests that general mechanisms might exist underlying females' unique adaptations. An understanding of such processes would enhance knowledge of female health and well-being. (shrink)

Extending Campbell's (1999) staying alive theory (SAT) beyond aggression, we reviewed evidence that females are more self-protective than males. Many commentators provided additional supporting data. Sex differences in life-history adaptations, in the optimal relation between survival and reproduction, and in the mechanisms underlying trade-offs involved with self-protection remain important topics with numerous opportunities for improved understanding.

Archer presents a traditional view of intrasexual competition. Knowledge of a species' social structure provides a more complete picture. Human males compete against individuals with whom they may cooperate later in inter-group aggression. By contrast, females compete against individuals for a mate's continued support. Females' aggression may aim at eliminating the competition, whereas males simply may attempt to dominate others.

Evolutionary theory makes further predictions about conflict. It predicts sex differences in the proclivity to attack and defend. It further suggests complementary biases in what we expect of the sexes. Finally, it suggests that the forms of human facial expressions of anger and happiness may have coevolved with the regularity of conflict as a means of signaling, bluffing, and defusing attack.

My response is organized into three sections. The first revisits the theme of the target article, the explanatory power of sexual selection versus social role theory. The second considers the range and scope of sexual selection, and its application to human sex differences. Two topics are examined in more detail: (1) the paternity uncertainty theory of partner violence; (2) evolution of inter-group aggression. Section 4 covers ultimate and proximal explanations and their integration within an ethological approach. I consider the development (...) of sex differences in aggression, and their causal mechanisms, within this framework. (shrink)

I argue that the magnitude and nature of sex differences in aggression, their development, causation, and variability, can be better explained by sexual selection than by the alternative biosocial version of social role theory. Thus, sex differences in physical aggression increase with the degree of risk, occur early in life, peak in young adulthood, and are likely to be mediated by greater male impulsiveness, and greater female fear of physical danger. Male variability in physical aggression is consistent with an alternative (...) life history perspective, and context-dependent variability with responses to reproductive competition, although some variability follows the internal and external influences of social roles. Other sex differences, in variance in reproductive output, threat displays, size and strength, maturation rates, and mortality and conception rates, all indicate that male aggression is part of a sexually selected adaptive complex. Physical aggression between partners can be explained using different evolutionary principles, arising from the conflicts of interest between males and females entering a reproductive alliance, combined with variability following differences in societal gender roles. In this case, social roles are particularly important since they enable both the relatively equality in physical aggression between partners from Western nations, and the considerable cross-national variability, to be explained. (shrink)

Extended staying alive theory (SAT) raises the issue of the extent to which its various attributes are linked or whether they provide alternative means to the same adaptive ends. Theories such as SAT that consider an array of sex differences may benefit from the application of the multivariateDstatistic, rather than using a series ofdvalues, as is common at present.

Block explains the conflation of phenomenal consciousness and access consciousness by appeal to the ambiguity of the term “consciousness.” However, the nature of ambiguity is not at all clear, and the thesis that “consciousness” is ambiguous between phenomenal consciousness and access consciousness is far from obvious. Moreover, the conflation can be explained without supposing that the term is ambiguous. Block's argument can thus be strengthened by avoiding controversial issues in the semantics of “consciousness.”.

Women have consistently higher levels of disgust than men. This sex difference is substantial in magnitude, highly replicable, emerges with diverse assessment methods, and affects a wide array of outcomes—including job selection, mate choice, food aversions, and psychological disorders. Despite the importance of this far-reaching sex difference, sound theoretical explanations have lagged behind the empirical discoveries. In this article, we focus on the evolutionary-functional level of analysis, outlining hypotheses capable of explaining why women have higher levels of disgust than men. (...) We present four hypotheses for sexual disgust and six for pathogen disgust, along with testable predictions. Discussion focuses on additional new hypotheses and on future research capable of adjudicating among these competing, but not mutually exclusive, hypotheses. (shrink)