The Hunter-Gatherer Lifestyle Ran Into the Wall of Overpopulation
As populations grew, it became more difficult for hunter-gatherers to simply move over to the next valley when they depleted the resources in their own valley. The next valley now probably already had other hunter-gatherers. They were unlikely to welcome another band that wanted to encroach on their territory and use up the resources they needed for their own survival. One possible solution was to violently oust such bands in order to take their place, and many undoubtedly chose that option.
However, violence was not always practical. The neighboring hunter-gatherers might have been more numerous, and even more bloodthirsty in defense of their turf. Another option was to stay put, and resort to more intensive and efficient extraction of resources from the local environment. That often meant hunter gatherers were forced to take a second look at food items that their ancestors, who had lived in times of abundance and plenty, would not have bothered with. Things got hard enough that some communities, driven by hunger, began to experiment with eating grass – wild wheat and barley.