Adrian V. Bell and colleagues of the University of California, Davis, say behaviors that help unrelated people while being costly to the individual and creating a risk for genetic descendants could not likely be favored by evolution -- at least by common evolutionary arguments.
The researchers used a mathematical equation -- the Price equation -- that describes the conditions for altruism to evolve. This equation motivated the researchers to compare the genetic and the cultural differentiation between neighboring social groups.
Using previously calculated estimates of genetic differences, they used the World Values Survey -- questions are likely to be heavily influenced by culture in a large number of countries -- as a source of data to compute the cultural differentiation between the same neighboring groups.
The researchers found that the role of culture had a much greater scope for explaining pro-social behavior than genetics.
The findings are published in the Proceedings of the National Academy of Sciences.