I want to ask 2 questions.....?!

I want to ask 2 questions.....?

Ok why do humans have two sets of teeth??Explain why please. And why do people need to get there wisdom teeth pull out, what happens if you keep them in??

I'd like to think of the first set as our "practice run set" :)Can you imagine what a 3 yr old would look like with adult-sized teeth? as we all know baby teeth don't get cleaned well unless the parent is very deligent in cleaning them theirselves.baby teeth are in direct correlation to the size of the jaw bones -as the bone grows bigger and denser new teeth are introduced to accomodate the spaces. wisdom teeth only need extracted if they hurt, are erupted and can't be cleaned well,or patient is getting braces in most cases.