Consider this.

http://www.embl.de/aboutus/communication_outreach/media_relations/2014/140911_Heidelberg/

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