Nicholas Wade in The New York Times:
The scientists, at the University of Oxford in England, looked at the evolutionary family tree of 217 primate species whose social organization is known. Their findings, published in the journal Nature, challenge some of the leading theories of social behavior, including:
¶ That social structure is shaped by environment — for instance, a species whose food is widely dispersed may need to live in large groups.
¶ That complex societies evolve step by step from simple ones.
¶ And the so-called social brain hypothesis: that intelligence and brain volume increase with group size because individuals must manage more social relationships.
By contrast, the new survey emphasizes the major role of genetics in shaping sociality. Being rooted in genetics, social structure is hard to change, and a species has to operate with whatever social structure it inherits. If social behavior were mostly shaped by ecology, then related species living in different environments should display a variety of social structures. But the Oxford biologists — Susanne Shultz, Christopher Opie and Quentin Atkinson — found the opposite was true: Primate species tended to have the same social structure as their close relatives, regardless of how and where they live.