Yesterday I realized why we have noses. I may very well be the first person to have realized this, although once you see it, it’s as plain as the nose on your face (ok, sorry about that).
When I was implementing that gaze tracking program I talked about a few days ago, I ran into the following issue: In order to correctly figure out where a person is looking, it’s not good enough merely to track their pupils. You also need to track how their face is turning (left, right, up or down). Once you know in which direction the face itself is pointing, then you can look at the eyes to figure out where the pupils are looking.
But what if the person is facing just slightly left or right — or just slightly up or down? Left or right look pretty similar, when the angles are small.
But not if you’ve got a big proboscis sticking out of your face. The tip of your nose looks really different, depending on you’re turning to the right or turning to the left. Which leads to my theory, which arises from a great evolutionary adaptation of humans — our extraordinary ability to communicate with each other.
Yes, other primates have highly developed communication abilities. But there are things they just can’t do. For example, humans have quite visible white regions in our eyes. Chimpanzees don’t. A study a number of years ago showed that if a human baby and a chimp baby are shown an adult using their head direction to look at something, both will follow. But if the adult moves only their eye gaze, not their head, the human baby will follow the gaze while the chimp will ignore it
I think something similar is at work with the nose. Social cues are so important to us, that I think our species evolved the nose to grow forward from the face, so that it could serve as a directional pointer for our vision system. The genetic benefits of being able to pick up even subtle cues about head movement were so important to our survival, that they trumped smell itself. We have only a fraction of the olfactory ability of our nearest cousins, the gorillas, chimps and bonobos — in fact our sense of smell is actually rather bad.
Which suggests that the human nose is satisfying a different purpose entirely — it allows us to see subtle head movements of the people we are talking to, quickly and accurately. If the eyes are the windows of the soul, perhaps the nose is the soul’s early warning system.