Cooperative breeding in South American hunter–gatherers

Abstract

Evolutionary researchers have recently suggested that pre-modern human societies habitually practised cooperative breeding and that this feature helps explain human prosocial tendencies. Despite circumstantial evidence that post-reproductive females and extra-pair males both provide resources required for successful reproduction by mated pairs, no study has yet provided details about the flow of food resources by different age and sex categories to breeders and offspring, nor documented the ratio of helpers to breeders. Here, we show in two hunter-gatherer societies of South America that each breeding pair with dependent offspring on average obtained help from approximately 1.3 non-reproductive adults. Young married males and unmarried males of all ages were the main food providers, accounting for 93-100% of all excess food production available to breeding pairs and their offspring. Thus, each breeding pair with dependants was provisioned on average by 0.8 adult male helpers. The data provide no support for the hypothesis that post-reproductive females are the main provisioners of younger reproductive-aged kin in hunter-gatherer societies. Demographic and food acquisition data show that most breeding pairs can expect food deficits owing to foraging luck, health disabilities and accumulating dependency ratio of offspring in middle age, and that extra-pair provisioning may be essential to the evolved human life history.

Nutritional values of tortoises relative to ungulates from the Middle Stone Age levels at Blombos Cave, South Africa: Implications for foraging and social behaviour

“…A review of the ethnographic literature with a particular focus on South Africa has shown that women also provide a great deal of meat resources through less-prestigious activities such as snaring, trapping, and collecting of shellfish (Wadley, 1998). For at least some huntergatherer groups, provisioning from older, post-reproductive females is one of the most important sources of nutrition for a family unit (Hawkes et al, 1998;Hill and Hurtado, 2009) . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65…”

Gene-culture coevolution in the age of genomics

“…Cooperative breeding seems to have been essential to provide food supplements to mothers and juveniles to support the expansion of brains (41). In anatomically modern humans, at least to judge by well-studied ethnographic examples, adult male hunters produced a large surplus of meat and fat that was channeled to women and children (36,42). To reduce the risk of biggame hunting, males cooperated in band-sized units including several good hunters.…”

Testing the Affiliation Hypothesis of Homoerotic Motivation in Humans: The Effects of Progesterone and Priming

“…The affiliation hypothesis thus proposes that natural selection co-opted this reward system as a means of promoting same-sex social bonds. In small-scale societies that resemble those characteristic of ancestral human populations, social bonding and alliance formation play a number of critical roles, including advantage in violent inter-coalition conflict (Bowles, 2009;Van Vugt, 2009), buffering against food shortfalls (see Hill & Hurtado, 2009), alloparenting (Hrdy, 2009), and insuring against illness and injury (Sugiyama, 2004). Moreover, while some aspects of these patterns are uniquely human, the fundamental link between social connectedness and fitness has a very deep phylogeny, as there is evidence that, among both male and female nonhuman primates, social bonds translate into enhanced survival and reproductive success (Kuhle & Ratdke, 2013;Silk, Alberts, & Altmann, 2003;Silk et al, 2010).…”