Well that just kicks the can down the road, and is also probably not accurate. People move today for better jobs, to escape warzones, because they like a country’s laws, and more reasons. Most of those reasons didn’t apply to hunter gatherers living thousands of years ago.
Really? What if the better hunting grounds were taken? What if a rival tribe kept harassing another and people just didn't want to fight? What if the ambitious youth didn't agree with the tribal leaders, so they moved to make their own fortune?
At our core, we really haven't changed all that much from our ancestors.
Could really be the same reasons for them too.
People moved for better hunting/grazing areas. To escape areas of warfare. They didn’t like the tribes rules, and more reasons.