[ELI5] Why do mammal embryos look the same when they are developing inside their mothers?

Question

[ELI5] Why do mammal embryos look the same when they are developing inside their mothers?

In: 27

Answer 1

This is known as the recapitulation theory by Ernst Haekel i believe, according to which, all animals metaphorically go through thousands of years of evolution in their few months of gestation