This study suggests that our earlier ancestors, pre fish I assume, may have been from the worm family. So many relevant details in the article, I’d have to darn near copy/paste them all. More efficient to just click the link, I think. If you are inclined that is.
There is a video there, but if there was a narration it was not present for me.
In a nutshell:
- Notochord (1st vertebrate skeleton) probably evolved from muscle
- Evolutionary origin of notochord likely older than assumed
- Marine worm has muscle with same genetic signature, in same place