Ever wonder about the small vertical indentation just below your nose? Few people know its name or function, yet we all have one.
Well, its proper name is the philtrum, and it is common to virtually all mammals. Also known as the medial infra-nasal cleft, its main function in most mammals to help carry moisture from the mouth to the nose, since a small amount of moisture makes the olfactory sense more efficient.
In humans, and other primates, it seems now to be vestigial since we rely more heavily on sight than smell and no longer require such efficient noses.