Viviana A. Weekes-Shackelford

Psychological adaptation to human sperm competition

Abstract Sperm competition occurs when the sperm of two or more males simultaneously occupy the reproductive tract of a female and compete to fertilize an egg. We used a questionnaire to investigate psychological responses to the risk of sperm competition for 194 men in committed, sexual relationships in the United States and in Germany. As predicted, a man who spends a greater (relative to a man who spends a lesser) proportion of time apart from his partner since the couples last copulation reported (a) that his partner is more attractive, (b) that other men find his partner more attractive, (c) greater interest in copulating with his partner, and (d) that his partner is more sexually interested in him. All effects were independent of total time since the couples last copulation and the mans relationship satisfaction. Discussion addresses two failed predictions and directions for future work.

Female coital orgasm and male attractiveness

Female coital orgasm may be an adaptation for preferentially retaining the sperm of males with “good genes.” One indicator of good genes may be physical attractiveness. Accordingly, R. Thornhill, S. W. Gangestad, and R. Comer (1995) found that women mated to more attractive men reported an orgasm during a greater proportion of copulations than did women mated to less attractive men. The current research replicates this finding, with several design variations. We collected self-report data from 388 women residing in the United States or in Germany. Results support the hypothesis that women mated to more attractive men are more likely to report an orgasm at the most recent copulation than are women mated to less attractive men, after statistically controlling for several key variables. Discussion addresses (a) the inability of the present research to specify the causal link between female orgasm and male attractiveness and (b) the proactive nature of female sexuality documented in recent research guided by an evolutionary perspective.

ROMANTIC JEALOUSY IN EARLY ADULTHOOD AND IN LATER LIFE

Young men are more distressed by a partner’s sexual infidelity, whereas young women are more distressed by a partner’s emotional infidelity. The present research investigated (a) whether the sex difference in jealousy replicates in an older sample, and (b) whether younger people differ from older people in their selection of the more distressing infidelity scenario. We presented forced-choice dilemmas to 202 older people (mean age = 67 years) and to 234 younger people (mean age = 20 years). The sex difference replicated in the older sample. In addition, older women were less likely than younger women to select a partner’s emotional infidelity as more distressing than a partner’s sexual infidelity. Discussion offers directions for future work on sex differences and age differences in jealousy.

Methods of filicide: stepparents and genetic parents kill differently.

Stepparents commit filicide at higher rates than do genetic parents. According to M. Daly and M. I. Wilson (1994), motivational differences generate differences in the methods by which stepparents and genetic parents kill a child. Using Canadian and British national-level databases, Daly and Wilson (1994) found that stepfathers were more likely than genetic fathers to commit filicide by beating and bludgeoning, arguably revealing stepparental feelings of bitterness and resentment not present to the same degree in genetic fathers. Genetic fathers, in contrast, were more likely than stepfathers to commit filicide by shooting or asphyxiation, methods which often produce a relatively quick and painless death. We sought to replicate and extend these findings using a United States national-level database of over 400,000 homicides. Results replicate those of Daly and Wilson (1994) for genetic fathers and stepfathers. In addition, we identified similar differences in the methods by which stepmothers and genetic mothers committed filicide. Discussion addresses stepparental psychology in light of the current research, limitations of the current study, and future directions for research on this topic.

Wife killings committed in the context of a lovers triangle

The killing of women by their husbands poses an enigma for social scientists. Why do relationships presumably characterized by love sometimes result in death? A variety of hypotheses have been offered to explain this puzzling pattern. Among the most prominent are (a) sheer proximity and opportunity, (b) epiphenomenal by-products of a male psychology designed for coercive control of women, and (c) evolved mate-killing mechanisms. One way to test these hypotheses is to examine the contexts in which wife killings occur. We secured access to a homicide database that included 345 spouse killings perpetrated by husbands in the context of a lovers triangle, a context that signifies sexual infidelity. Results indicated that a womans age, and hence reproductive status, predicts vulnerability to being killed in the context of a lovers triangle. Discussion focuses on alternative explanations for this finding, as well as findings not explained by existing theories of homicide.

Why Can't We All Just Get Along? Evolutionary Perspectives on Violence, Homicide, and War

We review and discuss the evolutionary psychological literature on violence, homicide, and war in humans and nonhumans, and in doing so argue that an evolutionary perspective can substantially enhance our understanding of these behaviors. We provide a brief primer on evolutionary psychology, describing the basic tenets of the field. The theories of sexual selection and parental investment are explained and subsequently used to highlight the evolutionary logic underlying the use of violence by humans and other animals. Our examination of violent behavior begins with a focus on nonhuman animals, reviewing the different contexts in which violence occurs and discussing how an evolutionary perspective can explain why it occurs in these contexts. We then examine violence in humans and illustrate the similarities and differences between human and nonhuman violence. Finally, we summarize what an evolutionary perspective can offer in terms of understanding violence, homicide, and war, and discuss directions for future research.

Evolutionary perspectives on human sexual psychology and behavior

Section 1: Introduction to Evolutionary Perspectives on Human Sexual Psychology and Behavior.- Evaluating Evidence of Mate Preference Adaptations: How Do We Really Know What Homo sapiens sapiens Really Want?.- Section 2: Sexual Adaptations in Men.- Adaptation and sexual offending.- Sexual selection on human voices.- Agreement and individual differences in mens preferences for womens facial characteristics.- Male adaptations to female ovulation.- (Mis)reading the signs: Mens perception of womens sexual interest.- Bodily Attractiveness as a Window to Womens Fertility and Reproductive Value.- Social and environmental conditions intensifying male competition for resources, status, and mates lead to increased male mortality.- Male production of humor produced by sexually selected psychological adaptations.- Male adaptations to retain a mate.- Section 3: Sexual Adaptations in Women.- Evolutionary psychology and rape avoidance .- Female orgasm.- Female adaptations to ovulation.-Womens preferences for male facial features.- Womens disgust adaptations.- Female Perceptions of Male Body Movements.- Intrasexual Competition and other Theories of Eating Restriction.- Attractiveness and rivalry in womens same-sex friendships.- Section 4: Conclusions and Future Directions for Evolutionary Perspectives on Human Sexual Psychology and Behavior.- Evolutionary perspectives on homosexual psychology and behavior.- Reflections on the Evolution of Human Sex Differences: Social Selection and the Evolution of Competition among Women.

Filicide–Suicide in Chicago, 1870-1930

Filicide (the killing of a child by a parent) followed by the offenders suicide is a tragic but, fortunately, rare event. The contexts and circumstances surrounding filicide–suicide may provide insight into parental psychology. The authors test several hypotheses about filicide–suicide using a database including incident-level information on 11,018 Chicago homicides during 1870-1930. The results provide some support for the hypothesis of differential risk of suicide following filicide by genetic parents and stepparents and replicate previous research indicating that filicides with multiple victims are more likely to end in the offenders suicide than are filicides with a single victim; parents are more likely to commit suicide following the filicide of an older child than of a younger child; and older parents, relative to younger parents, are more likely to commit suicide following filicide. The discussion situates these results within the existing literature and highlights important directions for future research.

Siblicide and Genetic Relatedness in Chicago, 1870-1930

Using a sample of siblicides committed in Chicago from 1870 through 1930, the authors tested two predictions heuristically guided by an evolutionary perspective. They predicted a greater proportion of siblicides of in-law siblings will be perpetrated by beatings, relative to the proportion of siblicides of full siblings. This difference did not reach statistical significance although it was in the predicted direction. They found, as predicted, that a significantly greater proportion of accidental deaths occurred with siblicides of full siblings relative to the proportion of siblicides of in-law siblings. Discussion addresses limitations of this research and the need for a national-level database that codes for the genetic relationship between the siblicide victim and offender to capitalize on greater statistical power.

An Evolutionary Perspective on Why Some Men Refuse or Reduce Their Child Support Payments

This review article begins by highlighting the sociological, macrolevel focus of previous work on the determinants of child support payments. We then highlight the value of addressing these issues from a psychological perspective. We argue that research and policy will benefit by embracing an explicitly evolutionary psychological perspective. We present several evolutionary hypotheses regarding the determinants of child support payments and discuss how previous research informs these hypotheses. Finally, we review proposed solutions for increasing mens compliance with child support orders. We conclude that an evolutionary perspective can inform research not only on the determinants of child support payments but also the social policies that might increase the reliability with which these payments are made.