And yet, sharks do it. Also, the skeleton is similarly long lasting and that gets renewed.
So why not? Say a finger, which isn't too "expensive in terms of biochemical resources", why not regrow that? Take the acorn worm mentioned, in proportion to the worm regrowing itself must be really expensive.
I don't think this too expensive argument explains it.
It turns out that while sharks' teeth are functionally analogous to mammal teeth, they have an independent evolutionary origin - they are actually a specialized type of skin scale.
So why not? Say a finger, which isn't too "expensive in terms of biochemical resources", why not regrow that? Take the acorn worm mentioned, in proportion to the worm regrowing itself must be really expensive.
I don't think this too expensive argument explains it.