Why do most Black females have big ole 's?

I heard that it's not actually that they carry more fat there it's because their pelvic bone is at a differnt angle, which gives the bum a curvier shape, but i don't know what evidence backs this up and i don't know why white people don't have this pelvic shape. Maybe it's cultural differnces, a slimmer figure is favoured by western and asian cultures, so those women go on to reproduce more, whereas african/brazil/latino cultures go for more curvier women, so they've ped the gene on to their chidlren and there's more of them