I believe that every aspect of any culture anywhere in the world can be boiled down to the one factor that progenated all of them:
survival, both personal and of the race itself
Can’t culture be traced back to that one thing? Are cultural similarities due to the existence of this common root? Variations in culture are merely reflections of the approaches to meeting these survival needs since this inception of mankind. It is how we choose, as a group, to meet this natural stimuli with the express purpose of survival. Everything stems from there.
However, it does seem that cultural variations are on the upward slope of merging with one another, as if we are returning to this common base, thousands of years after the inception of culture.