The Family That Walks On All Fours (2012). An amazing and controversial doco that talks about science, evolution, and religion. The family of 5 quadrupedal adults were studied to determine how this happened.

https://www.reddit.com/r/Documentaries/comments/gdxqwd/the_family_that_walks_on_all_fours_2012_an/

https://youtu.be/Jwiz-yhLpT0