Wisdom teeth are vestigial third molars that used to help human ancestors in grinding down plant tissue. It is believed that wisdom teeth were the evolutionary answer to our ancestors early diet of coarse, rough food like leaves, roots, nuts and meats which required more chewing power and resulted in excessive wear of the teeth. The modern diet with its softer foods along with forks, spoons and knives, has made the need for wisdom teeth nonexistent. As a result, evolutionary biologists now classify wisdom teeth as vestigial organs, or body parts that have become functionless due to evolution.
Some other examples of vestigial organs are the coccyx or tailbone (remnant of a lost tail) and the plica semilunaris which is a small fold of tissue on the inside corner of the eye (vestigial remnant of the nictitating membrane)