Almost all of this is... Not accurate. It pains me to say it, but this reads like Hollywood fiction. Most groups of people weren't living under constant threat of starvation or violence. Groups that badly located, or that badly divided, didn't tend to last. Additionally, if you're living in high stress, births become less successful.
Things took more effort, and had slightly lower skill caps, but only slightly. Humans are still human - if things are too hard, they went elsewhere.
