system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: why do teeth have to fall off once and grow back? like whats the point?
gpt
Adult teeth won't fit inside a kid's mouth. Conversely, kid's teeth are going to be horribly inefficient when you're an adult. So it's better for people to have small teeth when they are children and then get adult teeth when they're growing up.