I don't even know, to be honest.
I think it had something to do with evolution or some shit. Or like he traveled to some place where he saw himself in an alternate universe, as an old man, and then he became an embryo again or something? I DON'T KNOW.
Check out Google.
Or maybe this site, although I don't know if it's any good:
http://www.leaderu.com/science/2001.html