Science · 2011 · 868 citations · 17 references
Life SciencesBiologyEvolutionary BiologyCoevolutionEvolutionary EcologyHuman EvolutionBehavioral EvolutionCommunity StructureEvolution Of CooperationHuman-animal InteractionsKinship NetworksSocial CooperationAncestral Population StructureEvolution Of Social BehaviorHuman Behavioral EcologyInclusive Fitness TheoryKinship Co-residenceSocial AdaptationSocial Interaction NetworksSocial Learning Evolution
Human biological success derives from cumulative culture and cooperation, traits that may trace back to ancestral group structures. We examined co‑residence patterns across 32 contemporary foraging societies, totaling 5,067 individuals, to investigate these ancestral structures. Hunter‑gatherers display a unique social structure in which either sex may disperse or stay, siblings often co‑reside, and most group members are unrelated, forming large interaction networks that challenge inclusive‑fitness explanations for cooperation yet may underpin the evolution of social learning and cumulative culture.
Contemporary 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.
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