I looked all over, but even my precious scientific journal databases have failed me! I can't identify the genes responsible for butt size.
There's a trait in some African populations called steatopygia.
The word translates as 'fat butt'. Really. Both men and women tend to store fat in their backside and surrounding areas (upper thighs, lower abdomen). It's most pronounced in people whose recent ancestors were hunter-gatherers and did not practice agriculture, which led to the theory that the fat storage helped them survive during a drought. So that's sort of what you're looking for -- I think the majority of European, Asian and other populations relied on agriculture before the majority of African populations did. We didn't need the fat storage as much, so we lost it.
I have a vague recollection that there's also a difference in the arrangement of the gluteal muscles -- something about the gluteus maximus being located higher up in people of African descent. This memory is very old. I may have been about ten years old when I heard it. I only mention it in case you could be bothered researching that possibility, since I certainly can't.
Sorry for the lack of credible sources and the overload of half-formed theories. Not my best work, but the best I can do at the moment.
· 1 decade ago