eli5: why do we grow teeth twice in our life?

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eli5: why do we grow teeth twice in our life?

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Because our ancestors who survived that would later passed on their genes didn’t have a selective pressure that made us retain the ability to regrow the teeth. Rodents front 2 teeth – Incisors never cease growing either, however that was because they used the teeth to cut trees so there was a selective pressure for continuous growth of teeth.

So we wouldn’t end with either teeth to big for a small jaw or teeth too small for an adult jaw.

Good thought. I think it’s a good idea to start by checking out the average life expectancy of people for most of human development. They didn’t live as long so their teeth didn’t need to last as long

This trait isnt unique to humans, common mammals often called nursing teeth or deciduous teeth https://en.m.wikipedia.org/wiki/Deciduous_teeth they act as placeholders in tiny jaw itself from an anatomical standpoint and while the primary teeth root nodes germinate

Adult teeth are too big to fit in the jaw of a growing child. Baby teeth are too small to be useful to adults. Teeth are not made of living tissue, so once they erupt from the gums they can’t be fixed or rebuilt or made bigger. Plus, building teeth takes time and children need to eat.

So, baby teeth grow big enough to allow children to eat to survive. During childhood, the adult teeth have lots of time to grow inside the jaw and inside the gums. By the time they’re ready, the jaw should be more or less big enough to accommodate them. And adult teeth should be capable of lasting throughout our lifetime, as long as our diets aren’t garbage.