Yes, Sparta was a great asset, to the Greeks. It was never an independent state. The movie makes it seem like they were all bred from a combination of Thor and Wonder-Woman. The reality is that there was never a second guess that they had to fight off the Persians. They had to allow Greece to be "free". Sparta was basically a training camp for the best of the Greek soldiers, not a country that only bred soldiers. The fact that there were only 300 spartans, but as many as 7,000 other soldiers from neighboring states has nothing to do with it though, right?
Sure, cavemen existed, and woolly mammoths, and saber-toothed tigers... We can still see the pyramids, but all at once? In the movie, they depicted cavemen as being sort of suave and clean cut, you try shaving with a rock, won't get you too far. The writers of the movie decided that using wooly mammoths to build giant pyramids in the desert would be the best way to go, considering wooly mammoths love blazing sun and no water to speak of.