Sam, who is 11 asked us....

I have what might be a silly question. I've always wondered why humans have a large, pointy nose and great apes like chimps, orangutans and gorillas have hardly any nose at all? When did the nose evolve?

Well Sam, that is not a silly question at all, although it is a tricky one to answer. The first problem is looking at noses in the past. As you probably know, only the top of your nose has any bone in it, further down (where it is squishy) your nose is shaped by cartilidge, not bone, and as a result this is not usually preserved.

Currently the best supported idea is that a large nose helps you to keep warm. A large nose allows the air you breathe in to warm up a little and so it will not chill your lungs too much when you breathe in. Similarly, this change in tempreature combined with a large nose (and nasal cavity) helps you keep water in your body when you breathe out. You can see it when you breathe out on a cold day - there is always much more 'steam' when you breathe out through your mouth than your nose because you are losing more water vapour. But how does the evidence match up to this?

Well, first of all modern apes (chimps, gorillas, orangs and gibbons) all live in tropical climates, and as you correctly said, they tend to have small, flat noses. As early man / apes left the rainforests they would have encountered colder, dryer air on the plains and so the nose would have begun to evolve around then. This also explains when Neanderthal man (many of whom lived in high mountains) had a large nose, as do modern eskimos (innuits) who live in cold climates. So noses evolved to keep you warm and wet, but exactly when this happened is very difficult to say.

However, the nose also probably sticks out beasue we as humans have smaller jaws than other apes. As the muzzle moved back in early human, it left the nose sticking out in front of the face, rather than incorporated into it, as with things like gorillas.