Why do we , and nearly all animals and birds have two nostrils ?

Question

Why do we , and nearly all animals and birds have two nostrils ?

In: 56

Answer 1

Because all the animals you’re thinking of are descended from a common ancestor which had two nostrils—early fish that had one on each side of their head (incidentally, the same reason we all have two eyes). It’s stuck around because there’s no significant evolutionary advantage to having one nostril instead of two.