Anthropologists believe the probable function of wisdom teeth is a response to the coarse diet that earlier humans had. Foods such as roots and nuts required more chewing before swallowing.
Another theory about the function of wisdom teeth is that poor dental hygiene led to earlier humans losing teeth more. By the time wisdom teeth developed, they were sorely needed.
Scientists now consider wisdom teeth to be functionless due to evolution. Earlier humans had larger jaws which meant that the teeth had more room. Since then, human jaws have become smaller which leads to the wisdom teeth becoming impacted by other teeth after eruption.