Wisdom teeth are considered to be vestigial structures. Vestigial structures are those parts of the body that are considered ancestral leftovers and are not actually necessary anymore. Where they were once needed by ancient humans, structures like wisdom teeth aren't useful in modern humans and so are considered vestigial. Early humans likely needed a third set of molars to grind and chew rough plant matter such as leaves and roots. However, nowadays we have plenty of teeth as well as technology to cook our food, placing less demand on chewing. Because of this, wisdom teeth are typically removed as they often cause more harm than good.