Revealing mistake: After Evolet got hit by the arrow and presumably dies, D'leh is staring at a mammoth. Behind the mammoth, you can see that the background is a picture.
Revealing mistake: In the scene where D'Leh is chasing deer across an open plain, there is a row of 4 to 6 cars with headlights on in the distance coming down a gentle slope.
Answer: When the mammoth numbers diminished, D'leh's father (the chieftain) left on a quest to find new hunting grounds in order to feed the tribe. Not knowing the true nature of his quest, many tribesmen thought the chieftain left because he was a coward, which was a source of anxiety and guilt for D'leh. Later in the movie, it is learned that D'leh's father was captured by slavers and died as a slave.
Charles Austin Miller