are also inhabited by humans, are they not? So we can say that peacefulness is also an intrinsic part of human nature.
It seems that there are a lot of "studies" lately claiming that both tribalism and violence are the true biological natures of human beings, based on comparisons to our animal relatives and pre-historic ancestors. This study includes historical periods, too.
The last 100 years includes WW2, with its genocides, combat deaths around the entire globe, bombings of civilians in Berlin, London, Nagasaki, and Hiroshima. Also, independence wars of former colonies, and numerous acts if terrorism (Turkey, Israel, Africa). So pardon my skepticism about them as peaceful years.
Archaeological evidence indicates widespread trade in prehistoric as well as historic time, all around the globe. It showd raw materials and finished products far from their places of origin, e.g. food items, rocks and minerals, carved objects, jewelry, etc. Intermarriage cemented ties between different tribes and nations. This means cooperation and trade as well as war and killing. Trade with "the other" promotes peace and vice versa.
Animal comparisons with our closest relatives, chimps and bonobos, indicate that the cooperative, peaceful side of human nature is just as biologically intrinsic to us as war and killing. All 3 of us descend from an older common ancestor, but branched off from it to become separate species.
Chimps fight wars of extinction against other troops of chimps. They kill infants in their own troop and sometimes eat them. But they also cooperate among each other in common interests. Even among chimps, though, the degree and frequency of violence varies between troops.
Bonobos look like small chimps, but are a separate species from them. They are not inclined to genocidal wars like chimps. They resolve disputes more often by negotiations, often mediated by females. They are not prone to infanticide. They have been known to shun and exclude members that are too violent or domineering. But they are capable of killing, just less often, less inclined to it than chimps.
Humans, as close relatives to chimps and bonobos, sharing a common ancestor, also share traits in common, toward peaceful negotiations AND toward belligerent violence.
Cooperation, negotiation, peace, and acceptance/tolerance of differences are not artificially imposed behaviors on our intrinsic natures by civilization. They are intrinsic traits themselves that make the development of civilization possible in the first place.
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