Schmitt recognized that research is needed to identify other factors associated with sex ratio and with sociosexuality that may explain cross-cultural variation in sexual behavior. One such factor may be the risk of sperm competition. Sperm competition theory may lead us to a more complete explanation of cultural variation in sexual behavior.

Men who spend a greater proportion of time apart from their female partner since the couple’s last copulation are at greater “objective” sperm competition risk. We propose a novel cue to sperm competition risk: the time she spends with her male friends. Four hundred and twenty men in a committed, heterosexual, sexual relationship completed a questionnaire. The results indicate that men at greater objective sperm competition risk report less time desired until the couple’s next (...) copulation, greater interest in copulating with their partner, and greater anger, frustration, and upset in response to their partner’s sexual rejection, but only among men whose partner spends more time with her male friends. These results remain after controlling statistically for the participant’s age and their partner’s age. We discuss limitations of the current research, and discuss how research in human sperm competition can inform social issues, including men’s partner-directed sexual coercion. (shrink)

This study investigates changes in sexual motivation over the duration of a partnership in a population sample stratified by age. The results replicate and extend the findings of a previous study that was based on a sample of college students. In the samples of 30- and 45-year-olds, male sexual motivation remains constant regardless of the duration of the partnership. Female sexual motivation matches male sexual motivation in the first years of the partnership and then steadily decreases. In the sample of (...) 60-year-olds, male sexual motivation always exceeds female sexual motivation, and both are little affected by duration of the partnership. This pattern is clearly evident for some measures of sexual motivation and less so or not at all for others. Interpretations of the current results from social constructivism or from mainstream psychology are difficult to conceive. The results seem more intelligible from an evolutionary perspective as reflections of evolved design for sexual motivation, fine-tuned to the different conditions governing the reproductive success of males and females. In this view male sexual motivation promotes a constant frequency of copulation in order to guard against cuckoldry. Female sexual motivation, in contrast, promotes copulation to solve the adaptive problem of procuring male resources by establishing and maintaining a pair bond. (shrink)

Rape of women by men might be generated either by a specialized rape adaptation or as a by-product of other psychological adaptations. Although increasing number of sexual partners is a proposed benefit of rape according to the “rape as an adaptation” and the “rape as a by-product” hypotheses, neither hypothesis addresses directly why some men rape their long-term partners, to whom they already have sexual access. In two studies we tested specific hypotheses derived from the general hypothesis that sexual coercion (...) in the context of an intimate relationship may function as a sperm competition tactic. We hypothesized that men’s sexual coercion in the context of an intimate relationship is related positively to his partner’s perceived infidelities and that men’s sexual coercion is related positively to their mate retention behaviors (behaviors designed to prevent a partner’s infidelity). The results from Study 1 (self-reports from 246 men) and Study 2 (partner-reports from 276 women) supported the hypotheses. The Discussion section addresses limitations of this research and highlights future directions for research on sexual coercion in intimate relationships. (shrink)

Using a sample of 652 college students, we examined several implications of the hypothesis that the shape of the human penis evolved to enable males to substitute their semen for those of their rivals. The incidence of double mating by females appears sufficient to make semen displacement adaptive (e.g., one in four females acknowledge infidelity, one in eight admit having sex with two or more males in a 24-hour period, and one in 12 report involvement in one or more sexual (...) threesomes with two males). We also document several changes in post-ejaculatory behavior (e.g., reduced thrusting, penis withdrawal, loss of an erection) which may have evolved to minimize displacement of the male’s own semen. Consistent with predictions derived from a theoretical model (Gallup and Burch 2006), we discovered that most females report waiting at least 48 hours following an instance of infidelity before resuming sex with their in-pair partners. (shrink)

Studies of multiple paternity in mammals and other animal species generally report proportion of multiple paternity among litters, mean litter sizes, and mean number of sires per litter. It is shown how these variables can be used to produce an estimate of the probability of reproductive success for a male that has mated with a female. This estimate of male success is more informative about the mating system that alternative measures, like the proportion of litters with multiple paternity or the (...) mean number of sires per litter. The probability of success for a mated male can be measured both theoretically and empirically, and gives an estimate of the intensity of sperm competition and of a male's “confidence of paternity” upon mating. The probability of success for mated males for ten “exemplar” species of mammals is estimated and they are compared for insights into the functioning of their mating systems. (shrink)

Reproductive proteins maintain species‐specific barriers to fertilization, affect the outcome of sperm competition, mediate reproductive conflicts between the sexes, and potentially contribute to the formation of new species. However, the specific proteins and molecular mechanisms that underlie these processes are understood in only a handful of cases. Advances in genomic and proteomic technologies enable the identification of large suites of reproductive proteins, making it possible to dissect reproductive phenotypes at the molecular level. We first review these technological advances (...) and describe how reproductive proteins are identified in diverse animal taxa. We then discuss the dynamic evolution of reproductive proteins and the potential selective forces that act on them. Finally, we describe molecular and genomic tools for functional analysis and detail how evolutionary data may be used to make predictions about interactions among reproductive proteins. (shrink)

Mating activity of a wild Mueller’s gibbon group was observed in the Danum Valley Conservation Area, Sabah, Malaysia. The purpose of this study was to investigate the function of copulation calls in gibbons. The female emitted copulation calls at the time of intromission and pelvic thrusting. Copulation calls were composed of two notes and one of them was sung only while mating. Approximately half of copulation calls were sung near the range boundary. Mating with copulation calls sometimes occurred while singing. (...) According to the model that female copulation calls have evolved under the selective pressures of risk of infanticide and sperm competition, copulation calls should be rare in species with little female promiscuity. As gibbons usually live in pair-living social organization and have a monogamous mating system, no vocal signals by female gibbons are considered to be needed. However, clear copulation calls were emitted by the female. It suggests that the relationship between paired gibbons is unstable. Copulation calls by the female Mueller’s gibbon may function to increase mate guarding and strengthen the pair bond. (shrink)

Drosophila males sing a courtship song to achieve copulations with females. Females were recently found to sing a distinct song during copulation, which depends on male seminal fluid transfer and delays female remating. Here, it is hypothesized that female copulation song is a signal directed at the copulating male and changes ejaculate allocation. This may alter female remating and sperm usage, and thereby affect postcopulatory mate choice. Mechanisms of how female copulation song is elicited, how males respond to copulation (...) song, and how remating is modulated, are considered. The potential adaptive value of female signaling during copulation is discussed with reference to vertebrate copulation calls and their proposed function in eliciting mate guarding. Female copulation song may be widespread within the Drosophila genus. This newly discovered behavior opens many interesting avenues for future research, including investigation of how sexually dimorphic neuronal circuits mediate communication between nervous system and reproductive organs. (shrink)

What explains the distinctive features of human behavior? In this book, Stewart-Williams aims to answer this ambitious question. This book is an engaging addition to the already long list of recent attempts to provide an evolutionary explanation of human uniqueness. It is organized into six chapters, plus two appendices. These chapters address several key topics in evolutionary theory, sex differences and sexual behavior, altruism, and cultural evolution, albeit with varying degrees of detail and depth. These topics include sexual selection, kin (...) selection, Hamilton’s rule, reciprocal altruism, costly signaling theory, group selection, gene-centered views of evolution, inclusive fitness, proximate and ultimate evolutionary explanations, inbreeding avoidance, the Westermarck effect, jealousy, sperm competition, mating and parenting effort, cumulative cultural evolution, imitation and learning biases, evolutionary mismatch theories, and more. (shrink)

Cuckoldry is an adaptive problem faced by parentally investing males of socially monogamous species (e.g., humans and many avian species). Mate guarding and frequent in-pair copulation (IPC) may have evolved as anti-cuckoldry tactics in avian species and in humans. In some avian species, the tactics are used concurrently, with the result that mate guarding behaviors and IPC frequency are correlated positively. In other avian species, the tactics are compensatory, with the result that mate guarding behaviors and IPC frequency are correlated (...) negatively. The relationship between mate guarding and IPC frequency in humans is unknown. Avian males that use these tactics concurrently share with human males an inability to guard a female partner continuously during her peak fertile period. We hypothesized, therefore, that men’s mate guarding and IPC frequency function as concurrent anti-cuckoldry tactics, resulting in a positive correlation between them. Study 1 (n=305) secured men’s self-reports of mate guarding and IPC frequency. Study 2 (n+367) secured women’s reports of their partners’ mate guarding and IPC frequency. The concurrent tactics hypothesis was supported in both studies: Men’s mate guarding and IPC frequency are correlated positively, and this association is not attributable to male age, female age, relationship satisfaction, relationship length, or time that the couple spends together. The Discussion section addresses potential limitations of this research and future research directions. (shrink)

The evolution of a female penis is an extremely rare event and is only known to have occurred in a tribe of small cave insects, Sensitibillini (Psocodea: Trogiomorpha: Prionoglarididae). The female penis, which is protrudable and inserted into the male vagina‐like cavity during copulation to receive semen, is thought to have evolved independently twice in this tribe, in the Brazilian Neotrogla and the African Afrotrogla. These findings strongly suggest that there are some factors unique to Sensitibillini that have facilitated female (...) penis evolution. Here, several hypothetical factors are presented that may have enabled the evolution of the female penis in Sensitibillini. The female–female competition for nutritious semen, the oligotrophic environment, and the twin insemination slots with switching valve are considered to be the driving factors for female penis evolution. Additionally, the following factors are considered responsible for relaxing the constraint against female penis evolution: preexistence of the female‐above mating position, the elongated duct connecting the female pre‐penis with the sperm storage organ, and the small male genital cavity accepting the female genital tubercle bearing the opening of this duct. Understanding the factors enabling female penis evolution may also shed light on the evolution of the male penis. (shrink)

Errol Lord explores the boundaries of epistemic normativity. He argues that we can understand these better by thinking about which mental states are competitors in rationality’s competition. He argues that belief, disbelief, and two kinds of suspension of judgment are competitors. Lord shows that there are non-evidential reasons for suspension of judgment. One upshot is an independent motivation for a certain sort of pragmatist view of epistemic rationality.

The dominant view on the ethics of cognitive enhancement (CE) is that CE is beholden to the principle of autonomy. However, this principle does not seem to reflect commonly held ethical judgments about enhancement. Is the principle of autonomy at fault, or should common judgments be adjusted? Here I argue for the first, and show how common judgments can be justified as based on a principle of service.

BackgroundHuman female orgasm is a vexed question in the field while there is credible evidence of cryptic female choice that has many hallmarks of orgasm in other species. Our initial goal was to produce a proof of concept for allowing females to study an aspect of infertility in a home setting, specifically by aligning the study of human infertility and increased fertility with the study of other mammalian fertility. In the latter case - the realm of oxytocin-mediated sperm retention (...) mechanisms seems to be at work in terms of ultimate function while the proximate function remains unresolved.MethodA repeated measures design using an easily taught technique in a natural setting was used. Participants were a small, non-representative sample of females. The introduction of a sperm-simulant combined with an orgasm-producing technique using a vibrator/home massager and other easily supplied materials.ResultsThe sperm flowback (simulate... (shrink)

Is it a requirement of justice to democratize private companies? This question has received renewed attention in the wake of the financial crisis, as part of a larger debate about the role of companies in society. In this article, we discuss three principled arguments for workplace democracy and show that these arguments fail to establish that all workplaces ought to be democratized. We do, however, argue that republican-minded workers must have a fair opportunity to work in a democratic company. Under (...) current conditions, this means that a liberal order must actively promote workplace democracy. (shrink)

Understanding religion requires explaining why supernatural beliefs, devotions, and rituals are both universal and variable across cultures, and why religion is so often associated with both large-scale cooperation and enduring group conflict. Emerging lines of research suggest that these oppositions result from the convergence of three processes. First, the interaction of certain reliably developing cognitive processes, such as our ability to infer the presence of intentional agents, favors—as an evolutionary by-product—the spread of certain kinds of counterintuitive concepts. Second, participation in (...) rituals and devotions involving costly displays exploits various aspects of our evolved psychology to deepen people's commitment to both supernatural agents and religious communities. Third, competition among societies and organizations with different faith-based beliefs and practices has increasingly connected religion with both within-group prosociality and between-group enmity. This connection has strengthened dramatically in recent millennia, as part of the evolution of complex societies, and is important to understanding cooperation and conflict in today's world. (shrink)

Newsome ((2003). The debate between current versions of covariation and mechanism approaches to causal inference. Philosophical Psychology, 16, 87-107.) recently published a critical review of psychological theories of human causal inference. In that review, he characterized covariation and mechanism theories, the two dominant theory types, as competing, and offered possible ways to integrate them. I argue that Newsome has misunderstood the theoretical landscape, and that covariation and mechanism theories do not directly conflict. Rather, they rely on distinct sets of reliable (...) indicators of causation, and focus on different types of causation (type vs. token). There are certainly debates in the research field, but the theoretical landscape is not as fractured as Newsome suggests, and a potential unifying framework has already emerged using causal Bayes nets. Philosophical work on causal epistemology matters for psychologists, but not in the way Newsome suggests. (shrink)

Stimuli that resemble humans, but are not perfectly human-like, are disliked compared to distinctly human and nonhuman stimuli. Accounts of this “Uncanny Valley” effect often focus on how changes in human resemblance can evoke different emotional responses. We present an alternate account based on the novel hypothesis that the Uncanny Valley is not directly related to ‘human-likeness’ per se, but instead reflects a more general form of stimulus devaluation that occurs when inhibition is triggered to resolve conflict between competing stimulus-related (...) representations. We consider existing support for this inhibitory-devaluation hypothesis and further assess its feasibility through tests of two corresponding predictions that arise from the link between conflict-resolving inhibition and aversive response: 1) that the pronounced disliking of Uncanny-type stimuli will occur for any image that strongly activates multiple competing stimulus representations, even in the absence of any human-likeness, and 2) that the negative peak of an ‘Uncanny Valley’ should occur at the point of greatest stimulus-related conflict and not (in the presence of human-likeness) always closer to the ‘human’ end of a perceptual continuum. We measured affective responses to a set of line drawings representing nonhuman animal-animal morphs, in which each continuum midpoint was a bistable image (Exp. 1), as well as to sets of human-robot and human-animal computer-generated morphs (Exp. 2). Affective trends depicting classic Uncanny Valley functions occurred for all continua, including the nonhuman stimuli. Images at continua midpoints elicited significantly more negative affect than images at endpoints, even when the continua included a human endpoint. This illustrates the feasibility of the inhibitory-devaluation hypothesis and the need for further research into the possibility that the strong dislike of Uncanny-type stimuli reflects the negative affective consequences of cognitive inhibition. (shrink)

Whether or not capitalism is compatible with ethics is a long standing dispute. We take up an approach to virtue ethics inspired by Adam Smith and consider how market competition influences the virtues most associated with modern commercial society. Up to a point, competition nurtures and supports such virtues as prudence, temperance, civility, industriousness and honesty. But there are also various mechanisms by which competition can have deleterious effects on the institutions and incentives necessary for sustaining even (...) these most commercially friendly of virtues. It is often supposed that if competitive markets are good, more competition must always be better. However, in the long run competition enhancing policies that neglect the nurturing and support of the bourgeois virtues may undermine the continued flourishing of modern commercial society. (shrink)

In Republic 1, Thrasymachus makes the radical claim that being just is ‘high-minded simplicity’ and being unjust is ‘good judgment’ (348c–e). Because injustice involves benefiting oneself, while justice involves benefiting others, the unjust are wise and good and the just are foolish and bad (348d–e). The “greedy craftsperson” argument (1.349b–350c) attempts to show that the unjust person's desire to outdo or have more than ( pleon echein) everyone is a symptom of her ignorance. Many commentaries have found the argument problematic (...) and unclear. However, this paper argues that the greedy craftsperson argument defends plausible constraints on the nature of justice and wisdom. (shrink)

In Denmark and Sweden sperm donation is the most debated and contested of the reproductive technologies that are currently in use. Although the two countries are neighbouring welfare states with public healthcare in common, policies and practices of sperm banking and sperm donation differ strongly. Drawing on ethnographic fieldwork, this article explores how the sperm used for donor insemination is narrated, chosen, produced and consumed at sperm banks in Denmark and Sweden.The analysis illustrates that marginalization (...) and stigmatization of infertile men, donors, single women, lesbians and donor children not only takes place in the media and during debates in the Danish and Swedish parliaments where the technology has historically been contested, but also at the sperm banks and fertility clinics. This article therefore calls for more inclusive stories on sperm donation to be narrated. (shrink)

(2009). Sports Rules, Their Spirit and the Oldest Knockout Competition of Them All. Sport, Ethics and Philosophy: Vol. 3, No. 1, pp. 1-2. doi: 10.1080/17511320902752300.

The E.U. is shortly before implementing the Digital Markets Act (DMA), which aims to regulate digital markets and (ideally) rein in the power of big tech gatekeepers. Several researchers claim that this proposal – and especially its goal to ensure the contestability and fairness of digital markets – is ordoliberal in nature, yet what is missing in the academic literature is a closer look at the parallels (and differences) between the E.U.’s competition policy (and the DMA) and ordoliberalism. This (...) paper tries to close the gap and help answer the question of whether the DMA is indeed standing in an ordoliberal tradition. Furthermore, it evaluates the Act’s institutional strengths and weaknesses – as seen from an ordoliberal perspective – and points out potential ways to strengthen E.U. competition policy (and the DMA) and bring it closer to the ordoliberal ideal. (shrink)