Journal Article

Stepwise evolution of stable sociality in primates

Opie, Christopher, Shultz, Susanne, Atkinson, Quentin D.

2011

Overview

You scratch my back... Despite long-standing interest in explaining and describing diversity in primate social grouping patterns, the evolutionary history of primate sociality has received little attention. Recent advances in statistical methods allow trait changes to be explicitly modelled on phylogenetic trees and competing evolutionary hypotheses to be tested. Shultz et al . use Bayesian comparative phylogenetic methods to test competing theories for the evolution of social behaviour in primates. They conclude that large groups evolved directly from solitary foraging, with pair living and single-male harems being subsequently derived from the large groups. The shift from nocturnal to diurnal living is linked to the origin of sociality. Although much attention has been focused on explaining and describing the diversity of social grouping patterns among primates 1 , 2 , 3 , less effort has been devoted to understanding the evolutionary history of social living 4 . This is partly because social behaviours do not fossilize, making it difficult to infer changes over evolutionary time. However, primate social behaviour shows strong evidence for phylogenetic inertia, permitting the use of Bayesian comparative methods to infer changes in social behaviour through time, thereby allowing us to evaluate alternative models of social evolution. Here we present a model of primate social evolution, whereby sociality progresses from solitary foraging individuals directly to large multi-male/multi-female aggregations (approximately 52 million years (Myr) ago), with pair-living (approximately 16 Myr ago) or single-male harem systems (approximately 16 Myr ago) derivative from this second stage. This model fits the data significantly better than the two widely accepted alternatives (an unstructured model implied by the socioecological hypothesis or a model that allows linear stepwise changes in social complexity through time). We also find strong support for the co-evolution of social living with a change from nocturnal to diurnal activity patterns, but not with sex-biased dispersal. This supports suggestions that social living may arise because of increased predation risk associated with diurnal activity. Sociality based on loose aggregation is followed by a second shift to stable or bonded groups. This structuring facilitates the evolution of cooperative behaviours 5 and may provide the scaffold for other distinctive anthropoid traits including coalition formation, cooperative resource defence and large brains.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/114/739 / 631/181/2469 / 706/689/19/2472 / Animals / Bayes Theorem / Behavior / Biological and medical sciences / Biological Evolution / Evolution / Female / Fundamental and applied biological sciences. Psychology / Genetics of eukaryotes. Biological and molecular evolution / Group Processes / Humanities and Social Sciences / letter / Male / Markov Chains / Models, Biological / Monkeys & apes / Monte Carlo Method / multidisciplinary / Natural history / Phylogeny / Predatory Behavior / Primates / Primates - anatomy & histology / Primates - physiology / Science / Science (multidisciplinary) / Sex Factors / Social Behavior / Social behavior in animals / Social evolution / Studies / Trees