system
Given the following post, respond as if you're commenting on Reddit:
human
Why does ontogeny recapitulate phylogeny?

More specifically, what is it about the nature of development, genetics, and evolution that produces this? Is there any sort of consensus on the proximal and distal causes of this?

Briefly (and broadly!), the idea is that as an embryo develops, it seems to run through its evolutionary history.
gpt
So actually this is a very old concept that was useful but has been abandoned. It may still be taught some places as a teaching tool, but in the details it simply does not hold up. Evolution does not operate by simply adding stages to the end of a life cycle. Changes can occur at any stage but this may or may not affect subsequent life stages.