Evolution & Human Behavior RSS feed: Current Issue. Evolution and Human Behavior is an interdisciplinary journal, presenting research reports and theory in which evolutionary perspectives are brought to bear on the study of human behavior. It is primarily a scientific journal, but submissions from scholars in the humanities are also encouraged. Papers reporting on theoretical and empirical work on other species will be welcome if their relevance to the human animal is apparent. http://www.ehbonline.org/?rss=yesElsevier Inc.en © 2012 Elsevier Inc. All rights reserved. Evolution & Human Behavior1090-5138331January 2012 © 2012 Elsevier Inc. All rights reserved. healthpermissions@elsevier.comhttp://www.ehbonline.org/article/PIIS1090513811000250/abstract?rss=yesAbstract: It has been hypothesized that female orgasm evolved to facilitate recruitment of high-quality genes for offspring. Supporting evidence indicates that female orgasm promotes conception, although this may be mediated by the timing of female orgasm in relation to male ejaculation. This hypothesis also predicts that women will achieve orgasm more frequently when copulating with high-quality males, but limited data exist to support this prediction. We therefore explored relationships between the timing and frequency of women's orgasms and putative markers of the genetic quality of their mates, including measures of attractiveness, facial symmetry, dominance, and masculinity. We found that women reported more frequent and earlier-timed orgasms when mated to masculine and dominant men—those with high scores on a principal component characterized by high objectively-measured facial masculinity, observer-rated facial masculinity, partner-rated masculinity, and partner-rated dominance. Women reported more frequent orgasm during or after male ejaculation when mated to attractive men—those with high scores on a principal component characterized by high observer-rated and self-rated attractiveness. Putative measures of men's genetic quality did not predict their mates' orgasms from self-masturbation or from non-coital partnered sexual behavior. Overall, these results appear to support a role for female orgasm in sire choice.Men's masculinity and attractiveness predict their female partners' reported orgasm frequency and timingDavid A. Puts, Lisa L.M. Welling, Robert P. Burriss, Khytam Dawood10.1016/j.evolhumbehav.2011.03.003Evolution & Human Behavior 33, 1 (2012)2011-06-10Evolution & Human Behavior2011-06-10331S1090-5138(11)X0007-7Original Articles19http://www.ehbonline.org/article/PIIS1090513811000419/abstract?rss=yesAbstract: We use data from the National Incident-Based Reporting System to examine the effects of offender and victim age on whether male offenders commit sexual assault while robbing women. Restricting analyses to robberies reveals the offenders' age preferences since it allows one to control for the effects of opportunity. We find that robbers of all ages are most likely to sexually assault women at ages 15–29 years, ages when their reproductive potential is highest. However, in contrast to the idea that rape is a direct adaptation, victims are no more likely to be raped than sexually assaulted at these ages. The age of the offender is also a strong predictor of sexual assault. The likelihood that a robber commits a sexual assault increases from age 12 years until he reaches his early thirties when it begins to decline. This age pattern corresponds, to some extent, to age differences in the male sex drive.Age and sexual assault during robberiesRichard B. Felson, Patrick R. Cundiff10.1016/j.evolhumbehav.2011.04.002Evolution & Human Behavior 33, 1 (2012)2011-07-22Evolution & Human Behavior2011-07-22331S1090-5138(11)X0007-7Original Articles1016http://www.ehbonline.org/article/PIIS1090513811000432/abstract?rss=yesAbstract: Friendship is a core aspect of human social life. Friends form long-term, cooperative relationships, and provide material and emotional support for one another. Previous research in social psychology suggests that people prefer balanced relationships over unbalanced relationship with friends, but at the same time, friendship is defined by an absence of direct reciprocity and careful tracking of favors given and received. The goal of this study was to distinguish between differences in tracking and tolerance of imbalances among friends and strangers. We conducted parallel behavioral economic experiments in three different urban cultural settings, USA, Japan and China, in an effort to expand our understanding of the dynamics of human friendship. Across all sites, we found that subjects monitored their friends less carefully than they monitored strangers, were more generous to friends than to strangers and that friends were more tolerant of imbalances in payoffs than strangers were. Although there were differences in the extent of tracking among friends and strangers, tracking did occur among friends. Our study extends the understanding on the dynamics of human friendship and emphasizes the need for further investigation on how friends balance vigilance and tolerance in real-life interactions.The role of tracking and tolerance in relationship among friendsMing Xue, Joan B. Silk10.1016/j.evolhumbehav.2011.04.004Evolution & Human Behavior 33, 1 (2012)2011-07-21Evolution & Human Behavior2011-07-21331S1090-5138(11)X0007-7Original Articles1725http://www.ehbonline.org/article/PIIS1090513811000456/abstract?rss=yesAbstract: The natural experiments created by the Israeli Kibbutzim and Taiwanese minor marriages provide unique testing grounds for investigating the mechanisms governing sibling detection, inbreeding avoidance and kin-selected altruism. Here we present two studies conducted on the coreared peers of Israeli Kibbutzim. We examined how coresidence duration — a cue that would have indicated genetic relatedness in ancestral environments — impacts the development of kin-directed behaviors. In both studies, we found that coresidence duration predicts levels of altruism and sexual aversions directed toward peers. We also investigated the relationship between personal sexual aversions and moral attitudes relating to peer sexual behavior. The absence of norms proscribing sex between peers on the Kibbutz allows for a more tightly controlled investigation of this relationship. We found that total coresidence duration with opposite-sex peers predicts the intensity of moral wrongness associated with third-party peer sexual behavior, but not other behaviors, including sibling incest. More directly, we found that the summed sexual aversion felt toward all opposite-sex peers predicts levels of moral wrongness associated with third-party peer sex. Mediation analyses confirmed that personal sexual aversions mediate the relationship between coresidence duration and moral attitudes regarding peer sex. These results bolster Westermarck's original claims that childhood coresidence serves as a kinship cue, leading to greater sexual aversions and altruistic motivations, and that personal sexual aversions shape attitudes relating to third-party sexual behavior.Kinship on the Kibbutz: coresidence duration predicts altruism, personal sexual aversions and moral attitudes among communally reared peersDebra Lieberman, Thalma Lobel10.1016/j.evolhumbehav.2011.05.002Evolution & Human Behavior 33, 1 (2012)2011-08-05Evolution & Human Behavior2011-08-05331S1090-5138(11)X0007-7Original Articles2634http://www.ehbonline.org/article/PIIS1090513811000468/abstract?rss=yesAbstract: The persistence of left-handers in every human population studied to date is an evolutionary puzzle in light of evidence of survival costs associated with left-handedness. Associations between left-handedness and socioeconomic advantages have been observed in Western countries and could provide left-handers fitness benefits through higher survival chances and greater reproductive success. We aimed to explore the generality of this result in another culture. For this purpose, we investigated several socioeconomic status indicators and the number of children alive for 917 men and women in Uzbekistan and compared results for two different measures of handedness: hand preferences for writing and for knife use. Among both men and women, left-handed writers were significantly more likely to own a car, own a washing machine and have a bank account. Left-handed women (using both measures) had a higher income than right-handed women. Among men, left-handers for knife use had a higher income than right-handers. The results of our study suggest that the previously observed socioeconomic advantage of left-handers in Western populations also applies to non-Western populations, at least in the urban environment studied. However, we did not detect any difference in the number of children. We discussed how the frequency-dependent socioeconomic status advantage could be responsible for the persistence of left-handers throughout human evolution.Handedness and socioeconomic status in an urban population in UzbekistanCharlotte Faurie, Violaine Llaurens, Tatyana Hegay, Michel Raymond10.1016/j.evolhumbehav.2011.05.003Evolution & Human Behavior 33, 1 (2012)2011-08-16Evolution & Human Behavior2011-08-16331S1090-5138(11)X0007-7Original Articles3541http://www.ehbonline.org/article/PIIS109051381100047X/abstract?rss=yesAbstract: Human speech evidently conveys an adaptive advantage, given its apparently rapid dissemination through the ancient world and global use today. As such, speech must be capable of altering human biology in a positive way, possibly through those neuroendocrine mechanisms responsible for strengthening the social bonds between individuals. Indeed, speech between trusted individuals is capable of reducing levels of salivary cortisol, often considered a biomarker of stress, and increasing levels of urinary oxytocin, a hormone involved in the formation and maintenance of positive relationships. It is not clear, however, whether it is the uniquely human grammar, syntax, content and/or choice of words that causes these physiological changes, or whether the prosodic elements of speech, which are present in the vocal cues of many other species, are responsible. In order to tease apart these elements of human communication, we examined the hormonal responses of female children who instant messaged their mothers after undergoing a stressor. We discovered that unlike children interacting with their mothers in person or over the phone, girls who instant messaged did not release oxytocin; instead, these participants showed levels of salivary cortisol as high as control subjects who did not interact with their parents at all. We conclude that the comforting sound of a familiar voice is responsible for the hormonal differences observed and, hence, that similar differences may be seen in other species using vocal cues to communicate.Instant messages vs. speech: hormones and why we still need to hear each otherLeslie J. Seltzer, Ashley R. Prososki, Toni E. Ziegler, Seth D. Pollak10.1016/j.evolhumbehav.2011.05.004Evolution & Human Behavior 33, 1 (2012)2011-08-01Evolution & Human Behavior2011-08-01331S1090-5138(11)X0007-7Original Articles4245http://www.ehbonline.org/article/PIIS1090513811000481/abstract?rss=yesAbstract: Reasoning about the evolution of our species' capacity for cumulative cultural learning has led culture–gene coevolutionary (CGC) theorists to predict that humans should possess several learning biases which robustly enhance the fitness of cultural learners. Meanwhile, developmental psychologists have begun using experimental procedures to probe the learning biases that young children actually possess — a methodology ripe for testing CGC. Here we report the first direct tests in children of CGC's prediction of prestige bias, a tendency to learn from individuals to whom others have preferentially attended, learned or deferred. Our first study showed that the odds of 3- and 4-year-old children learning from an adult model to whom bystanders had previously preferentially attended for 10 seconds (the prestigious model) were over twice those of their learning from a model whom bystanders ignored. Moreover, this effect appears domain-sensitive: in Study 2 when bystanders preferentially observed a prestigious model using artifacts, she was learned from more often on subsequent artifact-use tasks (odds almost five times greater) but not on food-preference tasks, while the reverse was true of a model who received preferential bystander attention while expressing food preferences.Prestige-biased cultural learning: bystander's differential attention to potential models influences children's learningMaciej Chudek, Sarah Heller, Susan Birch, Joseph Henrich10.1016/j.evolhumbehav.2011.05.005Evolution & Human Behavior 33, 1 (2012)2011-08-16Evolution & Human Behavior2011-08-16331S1090-5138(11)X0007-7Original Articles4656http://www.ehbonline.org/article/PIIS1090513811000493/abstract?rss=yesAbstract: Evolutionary theories (e.g., the challenge hypothesis) suggest that testosterone plays an important role in intrasexual competition. In addition, those theories suggest that testosterone responses during competition should depend upon the presence of potential, immediate mating opportunities associated with the competition. The current research tested the hypothesis that the sex composition of individuals at a competition (ratio of opposite-sex, potential mates to same-sex individuals) would influence changes in competitors' testosterone levels. Consistent with our hypotheses, higher ratios of opposite- to same-sex individuals at an ultimate frisbee tournament were associated with greater increases in salivary testosterone among competitors. The relationship between sex ratio and increased salivary testosterone was observed for both male and female competitors and occurred regardless of whether competitors won or lost. Findings are consistent with the hypothesis that testosterone responses during competition are influenced by cues of potential, immediate mating opportunities.Adaptive attunement to the sex of individuals at a competition: the ratio of opposite- to same-sex individuals correlates with changes in competitors' testosterone levelsSaul L. Miller, Jon K. Maner, James K. McNulty10.1016/j.evolhumbehav.2011.05.006Evolution & Human Behavior 33, 1 (2012)2011-08-16Evolution & Human Behavior2011-08-16331S1090-5138(11)X0007-7Original Articles5763http://www.ehbonline.org/article/PIIS109051381100050X/abstract?rss=yesAbstract: Cooperative hunting is often assumed to be mutualistic, maintained through returns to scale, where, by working together, foragers can gain higher per capita return rates or harvest sizes than they can by hunting alone. We test this hypothesis among Martu hunters and find that cooperation only provides increased returns to poorer hunters while disadvantaging better hunters. Even so, better hunters still cooperate as frequently as poorer hunters. We ask whether better hunters are advantaged in secondary sharing distributions or whether they bias their partner choice to kin or household members. We find that better hunters are not more likely to pair up with kin and they do not gain consumption benefits from acquiring more. They share a greater proportion of their harvest than poorer hunters: no matter how much one produces — better hunter, worse hunter, cooperator, solitary hunter — all eat the same amount in the end. Such a result suggests the hypothesis that cooperation might be a costly signal of commitment to the public interest on the part of better hunters, which generates trust among camp members and facilitates strong social networks, particularly among women, who cooperate more than men. While some foragers may benefit through cooperation from returns to scale or risk reduction, others may benefit more through signaling commitment and generating trust.The hierarchy of virtue: mutualism, altruism and signaling in Martu women's cooperative huntingRebecca Bliege Bird, Brooke Scelza, Douglas W. Bird, Eric Alden Smith10.1016/j.evolhumbehav.2011.05.007Evolution & Human Behavior 33, 1 (2012)2011-08-16Evolution & Human Behavior2011-08-16331S1090-5138(11)X0007-7Original Articles6478http://www.ehbonline.org/article/PIIS1090513811000444/abstract?rss=yesBefore Principles of Social Evolution, when social scientists or economists asked me to recommend a book on the evolution of cooperation, I never quite knew what to say. , the stalwart of undergraduate Zoology courses, is an excellent, example-laden introduction to social evolution and the wider field, but is too basic for most. he Major Transitions in Evolution (1995) illustrates the importance of sociality but lacks the conceptual framework that explains how it evolves. At the other extreme, oundations of Social Evolution (1998) explains the theory but does not discuss any empirical work. I usually suggest this trilogy and some more recent review papers (e.g. ). Now I will just direct people to the Principles of Social Evolution. This highly readable account uses the conceptual framework of inclusive fitness theory, combined with a wealth of empirical examples, to illustrate the common principles that underlie the evolution of sociality at all levels of complexity.Life: social to its coreClaire El Mouden10.1016/j.evolhumbehav.2011.05.001Evolution & Human Behavior 33, 1 (2012)2011-08-05Evolution & Human Behavior2011-08-05331S1090-5138(11)X0007-7Book Review7980http://www.ehbonline.org/article/PIIS1090513811001206/abstract?rss=yesAcknowledgment of Reviewers10.1016/j.evolhumbehav.2011.11.005Evolution & Human Behavior 33, 1 (2012)2012-01-01Evolution & Human Behavior2012-01-01331S1090-5138(11)X0007-7Acknowledgment of Reviewers8183