In this paper we outline the activities of young girls in a Toba community of northern Argentina and examine the effect of girl helpers on time allocation of nursing women. Activity budgets were obtained for 41 girls aged 3 to 15 using spot observations. Girls spent substantial portions of observations engaged in helping behaviors. Individual values varied with age, anthropometric characteristics, and birth order. Activity budgets of 21 nursing women were obtained through focal observation sessions. Women living in households with (...) girls aged 7 to 15 allocated 17% less time to domestic work and 9% more time to socializing during afternoon observation sessions. For nursing women in this community, direct childcare (provided by the infant’s own mother) seemed to be a priority. Living with a girl helper did not have any measurable effect on the frequency or duration of nursing, or on the time that women spent caring for their infants. Based on these findings, hypotheses are outlined for future work on the effect of girl helpers on women’s fertility. (shrink)

Previous research in North America has supported the view that male involvement in committed, romantic relationships is associated with lower testosterone (T) levels. Here, we test the prediction that undergraduate men involved in committed, romantic relationships (paired) will have lower T levels than men not involved in such relationships (unpaired). Further, we also test whether these differences are more apparent in samples collected later, rather than earlier, in the day. For this study, 107 undergraduate men filled out a questionnaire and (...) collected one saliva sample (from which a subject’s T level was measured) at various times across the day. As in previous studies, men involved in committed, romantic relationships had lower salivary T levels, though only during later times of the day. Furthermore, additional analysis of the variation among unpaired subjects indicated that men without prior relationship experience had lower T levels than experienced men. Finally, while paired men as a group had lower T levels than unpaired men, those men at the earliest stage (less than six months) of a current relationship had higher T levels than unpaired men as well as men in longer-term relationships. These results suggest that variation in male testosterone levels may reflect differential behavioral allocation to mating effort. (shrink)

The probability of lineal extinction is sensitive to all the moments of the reproductive success probability distribution. In particular, high variance in reproductive success is associated with high probability of lineal extinction. Where male variance in reproductive success exceeds female variance, strictly patrilineal lines of descent will become extinct more rapidly than strictly matrilineal lines of descent. Patrilineal genealogies will be expected to be shallower and broader than matrilineal genealogies under such conditions. Potential implications of this genealogical asymmetry for human (...) descent systems include the greater information content of patrilineal kinship reckoning compared with any other unilineal system and the greater effectiveness of patrilineal kinship as a vehicle for corporate action. (shrink)

The nervous system and the endocrine system interact to integrate behavior and physiolo­gy. Hormones play an important role in this interaction, particularly steroid hormones. Other molecules, notably oxytocin, can serve both as hormones in the soma and neuro­modulators in the central nervous system. Understanding the influence of the endocrine system on human behavior, both individual and social, has been a primary focus of behav­ioral endocrinology for many decades, though technical and methodological challenges have been formidable. The recent enthusiasm for enzyme-linked (...) immunoassay kits for measuring steroid hormones in saliva has been found to be largely unsound, for example. Despite these difficulties, advances in many areas have been made and new areas, such as the endocrinology of paternal behavior and the role of oxytocin in social interactions, have emerged. Reproductive ecology provides a theoretical framework for integrating the di­verse content of human behavioral ecology. (shrink)