>Animals and medieval people didn't get cavities because they didn't eat refined sugar.
Bullshit. Sugar in fruit and just regular carbs will also lead to cavities and every dentist will happily tell you this when they find some cavity despite you not eating that much sugar and brushing/flossing regularly.

So what gives? How come an animal can eat sugar heavy, acidic fruits all the time all day and not get cavities despite never brushing?