Which step of mitosis involves the nucleus splitting and nuclear membranes forming around each new nucleus

Nucleus splitting or DNA splitting is in Anaphase !!

and The new nuclear memb is formed during the Telophase of Mitosis

so answers are Anaphase and Telophase !!

Idont know but good luck; )

It might. it might because if you think about if they discovered if we came from (lets say something funny like aliens) and thy found cells that matched and they would have t do more research about it but would most probably change their theory.