Is this true? I read that humans are the only animals with proper buttcheeks due to walking upright all the time
have you never seen a baboon? as for the actual muscles, i think all primates have them to some degree, as they do walk bipedally to a degree
Many unique characteristics of the human body are indeed the result of the shift to full-time bipedality, such as the length of the hind leg relative to body size, the formation of the heel, and the reshaping of the knee. Other consequences of bipedality were more circuitous and are less obvious. With our hands freed from the tasks of support and locomotion, we were able to develop the dexterity to make and use tools, which accompanied an increase in intelligence. Giving birth to babies with larger brains required a wider pelvic cavity, despite newborn humans having severely underdeveloped brains and remaining in a helpless state much longer than other mammals. (Newborn giraffes can not merely stand up but run!) The wider pelvic cavity put the hip joints farther apart, which then had to become much stronger to handle an increase in the already enormous forces of bipedal walking: The muscles crossing the hip were rearranged to permit the necessary rotation. Two muscles that a chimpanzee uses for climbing, the gluteus minimus and gluteus medius, were moved into a different relation with the hip joint, in order to balance the trunk on the weight-bearing leg during walking. A third primate climbing muscle, the gluteus maximus, was modified to assist in this abduction and in keeping the weight-bearing knee straight. It is our two massive, powerful and uniquely human gluteus maximus muscles that form the familiar dual-hemisphere shape of the human buttocks.
