Plot hole: The "video history" of the crashed USAF ship makes it very clear that the planet is uninhabited when they "landed". I can understand how a race of apes develops - they had a bunch of them on board. I can understand how a race of humans develops - they are descendants of the original crew. What I don't understand is... where the heck did all the horses come from?

Continuity: When Thade takes the weapon from Leo the weapon is a futuristic laser type gun. When Thade is firing the weapon after being locked in the command centre, the gun is a stainless steel Beretta brigadier model. (Time)