Way I figure, the common traits for any given part of the world where as much influenced by the isolation of groups as environmental factors. Back in primitive times it could take months wandering before you happened across another group, and even then there may be ‘untrusted tribe’ type conflicts.

It still shows up today in how rural isolated communities tend to foster more prejudiced attitudes towards people different from them. But now we can move all over quickly and communicate instantly, so there’s a less concentrated effect by location. Plus the whole advent of ordered society and the host of factors that brings into play.