Humans and chimpanzees are intensely territorial, E.O. Wilson reminds us:
That is the apparent population control hardwired into their social systems. What the events were that occurred in the origin of the chimpanzee and human lines — before the chimpanzee-human split of 6 million years ago — can only be speculated. I believe that the evidence best fits the following sequence. The original limiting factor, which intensified with the introduction of group hunting for animal protein, was food. Territorial behavior evolved as a device to sequester the food supply. Expansive wars and annexation resulted in enlarged territories and favored genes that prescribe group cohesion, networking, and the formation of alliances.
For hundreds of millennia, the territorial imperative gave stability to the small, scattered communities of Homo sapiens, just as they do today in the small, scattered populations of surviving hunter-gatherers. During this long period, randomly spaced extremes in the environment alternately increased and decreased the population size so that it could be contained within territories. These demographic shocks led to forced emigration or aggressive expansion of territory size by conquest, or both together. They also raised the value of forming alliances outside of kin-based networks in order to subdue other neighboring groups.
Ten thousand years ago, at the dawn of the Neolithic era, the agricultural revolution began to yield vastly larger amounts of food from cultivated crops and livestock, allowing rapid growth in human populations. But that advance did not change human nature. People simply increased their numbers as fast as the rich new resources allowed. As food again inevitably became the limiting factor, they obeyed the territorial imperative. Their descendants have never changed. At the present time, we are still fundamentally the same as our hunter-gatherer ancestors, but with more food and larger territories. Region by region, recent studies show, the populations have approached a limit set by the supply of food and water. And so it has always been for every tribe, except for the brief periods after new lands were discovered and their indigenous inhabitants displaced or killed.
Actually Wilson is wrong. (He’s wrong on very many things, including extinction rates.) As Cochrane and Harpending argued in The 10,000 Year Explosion, agriculture introduced new and very strong selection pressures on human that have changed our character, at least for those with a few thousand years of agriculture.
P.S. Harpending has suffered a stroke and is hospitalized.
I agree, Bob. But farming would grow human territorial-ness.
Say these words before considering the reasons for an odd human behavior: “We are bred for farming.”
Wow, now that behavior makes sense!
Bob, when you view the original stock and the evolutionary pressure you see that we go from territorial, distrusting of outsiders but highly cooperative within the tribe (where the maximum size of the tribe is limited by food supply) hunter-gatherers to pastoralists and farmers, where the most important change was the increase in the possible maximum size of the tribe. The 10,000 Year Explosion describes the evolutionary pressure that increasing the size of the tribe exerted.
The “cooperative with tribe members, distrustful of outsiders” module is still going strong but has a few bolt-on pieces — a “don’t resort to violence easily” module, a “be willing to accept strangers as tribe members”, etc.