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. 2012 Jun 19;109(25):9923-8.
doi: 10.1073/pnas.1200717109. Epub 2012 May 29.

Human origins and the transition from promiscuity to pair-bonding

Sergey Gavrilets  1
Affiliations

Human origins and the transition from promiscuity to pair-bonding

Sergey Gavrilets. Proc Natl Acad Sci U S A. .

Abstract

A crucial step in recent theories of human origins is the emergence of strong pair-bonding between males and females accompanied by a dramatic reduction in the male-to-male conflict over mating and an increased investment in offspring. How such a transition from promiscuity to pair-bonding could be achieved is puzzling. Many species would, indeed, be much better off evolutionarily if the effort spent on male competition over mating was redirected to increasing female fertility or survivorship of offspring. Males, however, are locked in a "social dilemma," where shifting one's effort from "appropriation" to "production" would give an advantage to free-riding competitors and therefore, should not happen. Here, I first consider simple models for four prominent scenarios of the human transition to pair-bonding: communal care, mate guarding, food for mating, and mate provisioning. I show that the transition is not feasible under biologically relevant conditions in any of these models. Then, I show that the transition can happen if one accounts for male heterogeneity, assortative pair formation, and evolution of female choice and faithfulness. This process is started when low-ranked males begin using an alternative strategy of female provisioning. At the end, except for the top-ranked individuals, males invest exclusively in provisioning females who have evolved very high fidelity to their mates. My results point to the crucial importance of female choice and emphasize the need for incorporating between-individual variation in theoretical and empirical studies of social dilemmas and behaviors.

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Conflict of interest statement

The author declares no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Examples of long-term evolutionary dynamics. (A and C) Small variation among males (σ = 0.25). (B and D) Large variation among males (σ = 1). (A and B) N = 8, ε = 0.05. (C and D) N = 16, ε = 0.1. Other parameters: α = 1, β = 3, γ = 0.5, ω = 1. In A–D, Top shows male provisioning traits pi for males of different rank from low (cyan) to high (magenta), Middle shows female faithfulness trait f, and Bottom shows the average fitness. The colored curves showing mean trait values are superimposed on the graphs to show the distributions of the traits using the gray color scheme. The numbers on top of sets of graphs show the final generation and the average values of p and f at this generation.
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