No he definitely returns to Earth in the final scene, Thade just got there first, WAY first and corrupted it.

The planet with two moons (or was it suns?) is the one he crashes on in the beginning.

If you go to the official website it sort of explains it all. The storm he flies through is a portal through BOTH space and time. It shoots you back and forth between the two planets but you come out in a random time each time.

vhelp, the way the official website explains it is that Thade repairs the ship that crashed into the lake. Since flying it requires nothing more than hitting a few buttons, he jets himself through the storm and winds up on Earth. It apparantly sent him way back into our timeline. Then he somehow populated the planet with apes.

I've heard the argument about horses before but I don't undestand why they couldn't just be indiginous to that planet. There were surely all kinds of insects and birds and such that were necessary to support the planet's ecosystem that they didn't bring on the initial ship with them.

The planet is enough like Earth that it supports human life, so it seems logical it might already have Earth-like species.