Why did our ancestors develop a prominent protruding nose?

A new study suggests that our unusual nose may have gained its shape simply as a by-product of other, more important changes in the structure of our face – although other researchers insist that some human noses have been directly shaped by natural selection. One of the many functions of the nose and nasal cavity is to act as an “air conditioner”. Together, they make sure that the air an animal breathes in is made warm and humid enough to avoid damaging the delicate lining of the lungs.
 But Takeshi Nishimura at Kyoto University, Japan, and his colleagues argue that the human nose performs this job poorly.