Scientists at the University of Oxford in England conducted a survey in which they observed two hundred seventeen primate species' evolutionary family trees. The species they observed have distinct and scientifically-known social structures and behaviors. What scientists found when they looked at these evolutionary family trees was quite surprising: related species have similar social structures. This suggests that common ancestry genetically determines social behaviors.
These findings are incredibly important because they come in direct conflict with some of the leading theories of social behavior. They challenge the theory that social behaviors and structures are determined by the environment. Researchers found that in spite of vastly different ecology, Old World monkeys still have very similar social systems. The findings also challenge the social brain hypothesis, which claims that intelligence and brain volume directly correlate with group size, because members of the group must learn how to engage in more complex social relationships. The findings, however, suggest that there has not been a steady increase over all primate species from small groups to large groups.
The study also verifies the social structure of humans. As part of the primate family, the organization of human society is likely to have a genetic basis as well. However, the fact that human society seems to be so socially diverse must be considered. Scientists of this survey argue that while social behavior among humans too is genetically determined, "cultural variation hides both the social unity of humankind and its biological foundation."