Steatopygia

Steatopygia is the state of having substantial levels of fatty tissue on the buttocks and thighs. This can be seen on the buttocks, the inside and outside of the thighs, and the knee.
Steatopygia is an inherited condition of the Khoisan peoples of southern Africa. Charles Darwin wrote about the Khoisan in "The Descent of Man" in 1882, commenting that their steatopygia evolved through sexual selection in human evolution, and that "the posterior part of the body projects in a most wonderful manner".