2 . Wisdom teeth removal is common for many people in their late teens and early 20s. But why don’t they come in during childhood with the rest of our permanent teeth?

The answer comes down to child development. There’s not enough room in a child’s jaw for wisdom teeth.     1     So there’s more room for wisdom teeth to emerge.

However, many modern human jaws don’t grow long enough for wisdom teeth to come in. Ancient humans ate diets full of hard nuts, uncooked vegetables, and other tough foods.     2     But nowadays we have shifted to eating softer foods, meaning humans have shorter jaws than ancient humans do.

There is another reason wisdom teeth grow in later.     3     When ancient people would lose their molars (臼齿) from chewing tough food, wisdom teeth — the third set of molars — would take their place. But because most people don’t lose their molars as young children, wisdom teeth wait until adulthood to arrive.     4    

Nowadays, dentists often remove wisdom teeth because their emergence can cause pain in crowded mouths. Or it can cause problems and tooth damage later on.     5     But as a person gets older and their gums (牙龈) become weaker, their wisdom teeth may stick through. In this case, they tend to cause pain and needs removing.