Social behavior among primates — including humans — has a substantial genetic basis, a team of scientists has concluded from a new survey of social structure across the primate family tree.

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.