Why do we have wisdom teeth?

A: The wisdom teeth are the third molars that sit at the very back of the jaw. They usually start forming in the teens and try to erupt in the late teens to the mid-20s, hence the name ‘wisdom’.

We have wisdom teeth because of our ancestors, whose lives demanded more chewing to get through.

For most stretches of their evolution, humans’ diets were tougher and grittier, including uncooked plants, fibrous roots, meat unsoftened by modern tools, and nuts and seeds. So chewing them led to more cavities and cracks (relative to today) and wore teeth down faster. Having an ‘extra set’ of grinding teeth could help adult humans keep eating well into midlife before experiencing discomfort.

These human ancestors also tended to have larger jaws. Over thousands of years, however, human diets and technologies changed and cooking and other forms of processing foods reduced the daily chewing load.

At the same time, the average jaw size declined in many populations, leaving less room at the back for the third molars to erupt cleanly. This is an example of ‘evolutionary mismatch’, where our genes build teeth suited to older diets but our modern jaws and foods don’t match those conditions.

The wisdom teeth are the last adult teeth to erupt, so they compete for space after the jaw has already settled. Sometimes they emerge at awkward angles, if they emerge at all, and require dental care if they become a source of discomfort.