Two scientists, Dr. Betti and Dr. Manica, conducted a study of 348 female human skeletons from all around the word in order to compare and contrast each body's structure. All in all, they found that not only were the pelvic structures different, but that arm and leg length also varied significantly in each separate population. Narrowing it down, they realized that pelvic structure relied on the geographical location of the individual, "People of sub-Saharan origin generally had the deepest pelvises back-to-front, while Native Americans had the widest side-to-side. Europeans, North Africans and Asians fell in the middle of the range". On a genetic level, the scientists discovered that a fluctuation in gene frequency was related to the variation in pelvic shape. Dr. Betti also believes that geographical natural selection has something to do with the shape of the pelvis as well and use the example of a siberian woman tending to have a birth canal that is much wider at the top because it will, "make the individual stockier" and hold weight better to keep her warm.