When you're smiling

Smiling is deeply etched into our DNA, probably beginning 30 million years ago among our primate ancestors. While there are many variations of the smile, not all of them pleasant, you can use a smile to your own benefit.

- Terry Robson

Picture this scenario if you will: I am walking towards you and when I see you my eyes crinkle a little at the sides, the corners of my mouth expose my teeth to you. How do you interpret this? Do you cross the road to avoid me because I am clearly contemplating eating you? Of course, you don't, because you have recognised my facial contortions as a "smile", and smiles are good. At least, we have come to accept that a smile connotes amiable feelings, but how did we come to be smilers and are we the only species to do it? An examination of the human smile reveals just how much we are creatures not only of our evolution but also our society, and it might encourage you to do a little more smiling yourself.

Smile origins

We can't know exactly when the smile originated, but we can make a guess, and our best guess is that smiling began about 30 million years ago. Those in the know will realise that this predates humans by at least 20 million years, depending on where you want to draw the line in the evolutionary sand. It means therefore that species other than humans must also smile.

The 30 million years figure comes from researchers who found that both human and chimpanzee infants will show facial movements that resemble smiles when they are asleep. These facial expressions are known as "spontaneous smiles" and are considered the evolutionary origin of real smiles and laughter. It might not be too surprising that chimps smile, because we know they are relatively close to us on the evolutionary tree. However, these researchers also found that these spontaneous smiles also exist in Japanese macaques, a much more distant relative.

These spontaneous smiles in infants are probably designed to enhance their appeal to their parents, but in our world the types and meaning behind smiles is much more nuanced.

Smile types