Horses (Score 1)

As to the question of horses... It's obvious that space is inconsequential in the movie. It starts near Saturn or a look-alike, takes our hero to some Earth-like planet except it having an extra two moons, and then ends back up on a Parallel Earth. That is of course, unless you consider the alternative: Not wanting to risk human life, the crew turns the Oberon over to an ape (not until later realizing how silly that is - but this IS a movie - and humans apparently are rather stupid and can't pilot anyway). The ape bravely pilots Oberon into the storm. This transports the Oberon thousands of years into the past. Unfortunately, since humans seem only to make ships that crash into planets rather stay in space, the Oberon smashes into the moon breaking it into three pieces. The collision disables the magic "keep us from crashing stuff" that always fails in space ships. Oberon then crashes to Earth where there are already horses, but few if any evolved humans. Bingo! The Apes have several thousand years to evolve, and we have lesser humans. This allows the Earth to have little or no human artifacts as the landing of Oberon prevented human evolution. This also explains how you have so many humans even though the Oberon crew was supposedly slaughtered by the original apes. Movie Magic!