AbstractContemporary humans exhibit spectacular biological success derived from cumulative culture and cooperation. The origins of these traits may be related to our ancestral group structure. Because humans lived as foragers for 95% of our species’ history, we analyzed co-residence patterns among 32 present-day foraging societies (total n = 5067 individuals, mean experienced band size = 28.2 adults). We found that hunter-gatherers display a unique social structure where (i) either sex may disperse or remain in their natal group, (ii) adult brothers and sisters often co-reside, and (iii) most individuals in residential groups are genetically unrelated. These patterns produce large interaction networks of unrelated adults and suggest that inclusive fitness cannot explain extensive cooperation in hunter-gatherer bands. However, large social networks may help to explain why humans evolved capacities for social learning that resulted in cumulative culture.
Update (Mar 17): Blackbird, who runs some interesting blogs on non-human animals you may want to check, mentions that our Pan sp. cousins, both chimpanzees and bonobos, may not be as gender biased as we used to think in regards on who moves and who lives in the established community. The following paper addresses this matter a bit and also includes an interesting analysis of haploid genetics among bonobos (all of which live in D.R. Congo):
Jonas Erikson et al, Y-chromosome analysis confirms highly sex-biased dispersal and suggests a low male effective population size in bonobos (Pan paniscus). Molecular Ecology 2006. [doi: 10.1111/j.1365-294X.2006.02845.x]
He (Blackbird) suggests, and he may be right I’d say, that this ambiguity of locality is similar to what Hills observes for Homo sapiens and may therefore be a shared pattern among the super-genus.