The buttocks allow primates to sit upright without needing to rest their weight on their feet as four-legged animals do. Females of certain species of baboon have red buttocks that "blush" to attract males. In the case of humans, females tend to have wider and thicker buttocks due to higher subcutaneous fat and wider hips.
Some baboons and all gibbons, though otherwise fur-covered, have characteristic naked callosities on their buttocks. While human children generally have smooth, buttocks mature males and females have varying degrees of hair growth, as on other parts of their body. Females generally have hair growth in the gluteal cleft (particularly around the anus), often extending laterally onto the lower aspect of the cheeks. In addition to such areas, males often have hair growth over the most of (or the entire) the buttocks.