The evolutionary and ecological roots of human social organization

Abstract

Social organization among human foragers is characterized by a three-generational system of resource provisioning within families, long-term pair-bonding between men and women, high levels of cooperation between kin and non-kin, and relatively egalitarian social relationships. In this paper, we suggest that these core features of human sociality result from the learning- and skill-intensive human foraging niche, which is distinguished by a late age-peak in caloric production, high complementarity between male and female inputs to offspring viability, high gains to cooperation in production and risk-reduction, and a lack of economically defensible resources. We present an explanatory framework for understanding variation in social organization across human societies, highlighting the interactive effects of four key ecological and economic variables: (i) the role of skill in resource production; (ii) the degree of complementarity in male and female inputs into production; (iii) economies of scale in cooperative production and competition; and (iv) the economic defensibility of physical inputs into production. Finally, we apply this framework to understanding variation in social and political organization across foraging, horticulturalist, pastoralist and agriculturalist societies.

Figure 1.

Net food production and survival in human foragers and chimpanzees (adapted from Kaplan et al. 2000). Broken lines, human survival; dotted lines, chimpanzee survival; thick solid line, net production humans; thin solid lines, net production chimpanzees.

Figure 2.

Net caloric resource flows from parents, grandparents and husbands among Tsimane forager–horticulturalists (adapted from Gurven & Kaplan 2008). Filled circles, mother → children; filled squares, father → children; open circles, grandmother → grandchildren; open squares, grandfather → grandchildren; crosses, husband → wife.