Mao was correct.
Normal human society is similar to Meerkats, where the tribe all shares and defends each other out of instincts of empathy and sympathy.
Due to Mideast desertification, people were forced to increase population density along river banks, and human nature was over ridden by greed and "might makes right". R5 #156
Perhaps.
Some anthropologist suggest a major step humans took diverging from nomadic hunter / gatherers was the invention of the agricultural plow.
Before that, apart from vying for access to scarce resources, potable water for example, they're likely to have taken the live-&-let-live approach to peripheral encounters with strangers.
The planetary population density was low enough, and inbreeding a problem serious enough, that creating mortal enemies between clans at that stage of human development risked catastrophe.
The theory is, the agricultural plow created for the first time, food surplus, and permanent settlements, which in turn provided need & opportunity for developing crafts, leather-working, simple architecture, food storage technology, etc.
BUT !
Once there was surplus, there was incentive for the slothful to wait until after the harvest, and then raid the settlement for plunder, the spark that has lead to military.