How can non-human primates inform evolutionary perspectives on female-biased kinship in humans?

The rarity of female-biased kinship organization in human societies raises questions about ancestral hominin family structures. Such questions require grounding in the form and function of kin relationships in our close phylogenetic relatives, the non-human primates. Common features of primate societies, such as low paternity certainty and lack of material wealth, are consistent with features that promote matriliny in humans. In this review, I examine the role of kinship in three primate study systems (socially monogamous species, female-bonded cercopithecines and great apes) that, each for different reasons, offer insights into the evolutionary roots of matriliny. Using these and other examples, I address potential analogues to features of female-biased kinship organization, including residence, descent and inheritance. Social relationships are biased towards matrilineal kin across primates, even where female dispersal limits access to them. In contrast to the strongly intergenerational nature of human kinship, most primate kin relationships function laterally as the basis for cooperative networks and require active reinforcement. There is little evidence that matrilineal kin relationships in primates are functionally equivalent to descent or true inheritance, but further research is needed to understand whether human cultural constructs of kinship produce fundamentally different biological outcomes from their antecedents in primates. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'.

Winning friends and influencing peers: Strategies of peer influence in late childhood

We divided children ( N = 719, grades 3–6) into five control types based on the degree to which they reported employing prosocial (indirect, cooperative) and coercive (direct, hostile) strategies of control (prosocial controllers, coercive controllers, bistrategic controllers, noncontrollers, and typicals). We tested for differences across the five types on personal characteristics, friendship motivations, wellbeing, and social integration, expecting specific patterns according to whether control is wielded, and whether coercive or prosocial behaviour (or both) is employed. Prosocial controllers revealed positive characteristics (e.g., social skills, agreeableness), intrinsic friendship motivations, and positive wellbeing. In contrast, coercive controllers revealed negative characteristics (e.g., hostility), extrinsic friendship motivations, and ill-being. Bistrategic controllers, as expected, reported the highest control, and revealed characteristics associated with both prosocial and coercive orientations. Noncontrollers, in contrast, did not report having these characteristics and felt the least effective in the peer group. Our evolutionary perspective offers unique predictions of how prosocial and coercive children are similar in terms of their instrumental goals and the consequences of using both strategies or neither.

Sex and age differences in juvenile social priorities in female philopatric, nondespotic blue monkeys

Juveniles should choose social partners on the basis of both current and future utility. Where one sex is philopatric, one expects members of that sex to develop greater and sex-typical social integration with group-mates over the juvenile period. Where a partner's position in a dominance hierarchy is not associated with services it can provide, one would not expect juveniles to choose partners based on rank, nor sex differences in rank-based preferences. We tested these ideas on 39 wild juvenile (3.2-7.4 years) blue monkeys (Cercopithecus mitis stuhlmanni), cercopithecines with strict female philopatry and muted hierarchies. We made focal animal observations over 6 months, and computed observed:expected amounts of proximity time, approaches and grooming given to various social partners. Overall, our results agree with the hypothesis that juvenile blue monkeys target social partners strategically. Spatial proximity, approaches and active grooming showed similar patterns regarding juvenile social preferences. Females were far more sociable than males, groomed more partners, reciprocated grooming more frequently, and preferred-while males avoided-infants as partners. Older juveniles (5-7 years) spent more time than younger juveniles (3-4 years) near others, and older females were especially attracted to infants. Close kin, especially mothers and less consistently adult sisters, were attractive to both male and female juveniles, regardless of age. Both sexes also preferred same-sex juveniles as social partners while avoiding opposite-sex peers. Juveniles of both sexes and ages generally neither preferred nor avoided nonmaternal adult females, but all juveniles avoided adult males. Partner's rank had no consistent effect on juveniles' preference, as expected for a species in which dominance plays a weak role. Juveniles' social preferences likely reflect both future and current benefits, including having tolerant adult kin to protect them against predators and conspecifics, same-sex play partners, and, for females, infants on which to practice mothering skills. Am. J. Primatol. 72:193-205, 2010. (c) 2009 Wiley-Liss, Inc.