A large literature proposes that preferences for exaggerated sex typicality in human faces (masculinity/femininity) reflect a long evolutionary history of sexual and social selection. This proposal implies that dimorphism was important to judgments of attractiveness and personality in ancestral environments. It is difficult to evaluate, however, because most available data come from largescale, industrialized, urban populations. Here, we report the results for 12 populations with very diverse levels of economic development. Surprisingly, preferences for exaggerated sex-specific traits are only found in the novel, highly developed environments. Similarly, perceptions that masculine males look aggressive increase strongly with development and, specifically, urbanization. These data challenge the hypothesis that facial dimorphism was an important ancestral signal of heritable mate value. One possibility is that highly developed environments provide novel opportunities to discern relationships between facial traits and behavior by exposing individuals to large numbers of unfamiliar faces, revealing patterns too subtle to detect with smaller samples.facial attractiveness | evolution | cross-cultural | aggression | stereotyping

No abstract

Cave bears, an extinct subgenus (Spelearctos) of Ursus, were versatile enough to inhabit large areas of the northern hemisphere during the middle and late Pleistocene, yet they had evolved a specialized dentition that emphasized grinding functions, implying a heavy dietary reliance on tough, fibrous foods (i.e., plants). Isotope studies have yielded conflicting results on cave bear diet, however, often without consideration of the provenance of the samples or the possible contradictions that taphonomic and morphologic evidence might pose to dietary interpretations. It is likely that cave bear habits varied somewhat in response to environmental circumstance, and the limits on their abilities to do so remain unknown. If the larger goal of paleontological inquiry is to reconstruct the adaptations of cave bear species, then variation and commonalities among populations must be tracked closely, and the disparate lines of evidence currently available examined together on a case by case basis. Clearly, no single analytical technique can achieve this. By way of example we present the results of a cross-disciplinary collaboration that combines osteometric, isotopic, and taphonomic approaches to studying the paleoecology of a bear assemblage from Yarimburgaz Cave in northwest Turkey. Reference information on the linkages between diet, hibernation, and population structure in modern bears provides test implications for the investigation. Osteometric techniques demonstrate the presence of two coextant middle Pleistocene bear species in the sample–Ursus (Spelearctos) deningeri, a form of cave bear, and U. arctos or brown bear–the former abundant in the sample, the latter rare. An attritional mortality pattern for the bears and the condition of their bones show that most or all of the animals died in the cave from nonviolent causes in the context of hibernation. The study also elucidates several characteristics of the cave bear population in this region. Osteometric techniques show that the adult sex ratio of the cave bears is only slightly skewed toward females. This pattern lies near one extreme of the full range of possible outcomes in modern bear species and can only reflect a strong dietary dependence on seasonally available plants and invertebrates, showing that hibernation was a crucial overwintering strategy for both sexes; the results specifically contradict the possibility of regular, heavy emphasis on large game (hunted or scavenged) as a winter food source. The nature of wear and breakage to the adult cave bear teeth indicates that food frequently was obtained from cryptic sources, requiring digging and prying, and that extensive mastication was necessary, leading to complete obliteration of some cheek tooth crowns in old individuals. The patterns of tooth damage during life corroborate the dietary implications of the adult sex ratio and also argue for a diet rich in tough, abrasive materials such as nuts, tubers, and associated grit. The carbon and oxygen isotopic compositions of cave and brown bear tooth enamel from the site are virtually identical, and there is no evidence of a strong marine signal in either species, despite the cave's proximity to a modern estuary of the Sea of Marmara; nitrogen isotope ratios could not be examined because of poor protein preservation. The isotope results suggest that both bear species were highly omnivorous in the region during the middle Pleistocene and obtained nearly all of their food from terrestrial and fresh-water habitats. Bone pathologies, usually originating from trauma, occur in some of the adult bears, testifying to long lifespans of some individuals in this fossil population. The Yarimburgaz cave bears also exhibit great size dimorphism between the sexes, based on weight-bearing carpal bone dimensions, with adult males attaining roughly twice the body mass of adult females.

Polygyny can increase, decrease, or have no effect on fertility. Understanding how this can occur requires consideration of both the proximate determinants of fertility and the ultimate effects of polygyny as a female reproductive strategy. Several factors reduced the fertility of polygynous women in 19th century Utah, including marrying at an older age, marrying older men, and conflict between co-wives. Sterility did not explain the reduced number of children in polygynous women, nor is there evidence of a "dilution effect" from sharing a husband. If women could anticipate a reduction in their own fertility, why would they still choose polygyny? Evidence suggests that they chose it because the children of polygynous men had increased fertility, high enough to offset the low fertility of polygynous women themselves.

Estimating the degree of sexual dimorphism is difficult in fossil species because most specimens lack indicators of sex. We present a procedure that estimates sexual dimorphism in samples of unknown sex using method-of-moments. We assume that the distribution of a metric trait is composed of two underlying normal distributions, one for males and one for females. We use three moments around the mean of the combined-sex distribution to estimate the means and the common standard deviation of the two underlying distributions. This procedure has advantages over previous methods: it is relatively simple to use, specimens need not be assigned to sex a priori, no reference to living species analogs is required, and the method provides conservative estimates of dimorphism under a variety of conditions. The method performs best when the male and female distributions overlap minimally but also works well when overlap is substantial. Simulations indicate that this relatively simple method is more accurate and reliable than previous methods for estimating dimorphism.