Humans

Anatomy and physiology

Humans share with chimpanzees a vestigial tail, appendix, flexible shoulder joints, grasping fingers and opposable thumbs. Humans also have a more barrel-shaped chest in contrast to the funnel shape of other apes, an adaptation for bipedal respiration. Apart from bipedalism and brain size, humans differ from chimpanzees mostly in smelling, hearing, and digesting proteins. While humans have a density of hair follicles comparable to other apes, it is predominantly vellus hair, most of which is so short and wispy as to be practically invisible. Humans have about 2 million sweat glands spread over their entire bodies, many more than chimpanzees, whose sweat glands are scarce and are mainly located on the palm of the hand and on the soles of the feet.