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Sex equality can explain the unique social structure of hunter-gatherer bands

Science  15 May 2015:
Vol. 348, Issue 6236, pp. 796-798
DOI: 10.1126/science.aaa5139

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Friends and family?

Evolutionary theory stresses the importance of living with kin, not least because they share some of our genes. Nevertheless, a large-scale assessment of contemporary hunter-gatherer societies has established a consistent pattern of unrelated individuals living together. Dyble et al. used a modeling approach to suggest that a possible answer to this conundrum is that cohabitation choices are being governed equally by men and women.

Science, this issue p. 796

Abstract

The social organization of mobile hunter-gatherers has several derived features, including low within-camp relatedness and fluid meta-groups. Although these features have been proposed to have provided the selective context for the evolution of human hypercooperation and cumulative culture, how such a distinctive social system may have emerged remains unclear. We present an agent-based model suggesting that, even if all individuals in a community seek to live with as many kin as possible, within-camp relatedness is reduced if men and women have equal influence in selecting camp members. Our model closely approximates observed patterns of co-residence among Agta and Mbendjele BaYaka hunter-gatherers. Our results suggest that pair-bonding and increased sex egalitarianism in human evolutionary history may have had a transformative effect on human social organization.

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