title: The complex structure of hunter-gatherer social networks.
abstract: In nature, many different types of complex system form hierarchical, self-similar or fractal-like structures that have evolved to maximize internal efficiency. In this paper, we ask whether hunter-gatherer societies show similar structural properties. We use fractal network theory to analyse the statistical structure of 1189 social groups in 339 hunter-gatherer societies from a published compilation of ethnographies. We show that population structure is indeed self-similar or fractal-like with the number of individuals or groups belonging to each successively higher level of organization exhibiting a constant ratio close to 4. Further, despite the wide ecological, cultural and historical diversity of hunter-gatherer societies, this remarkable self-similarity holds both within and across cultures and continents. We show that the branching ratio is related to density-dependent reproduction in complex environments and hypothesize that the general pattern of hierarchical organization reflects the self-similar properties of the networks and the underlying cohesive and disruptive forces that govern the flow of material resources, genes and non-genetic information within and between social groups. Our results offer insight into the energetics of human sociality and suggest that human social networks self-organize in response to similar optimization principles found behind the formation of many complex systems in nature.
authors.affiliation: Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA. marcusj@unm.edu
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Hamilton
authors.forename: Bruce T
authors.initials: BT
authors.lastname: Milne
authors.forename: Robert S
authors.initials: RS
authors.lastname: Walker
authors.forename: Oskar
authors.initials: O
authors.lastname: Burger
authors.forename: James H
authors.initials: JH
authors.lastname: Brown
mesh_terms: D019058:Community Networks; D017709:Fractals; D006801:Humans; D012919:Social Behavior