War is not human nature. Small communities are.
“Simple hunting and gathering characterized human societies during most of humanity’s existence dating back more than 200,000 years. Broadly, these groups cooperate with one another and live in small, mobile, egalitarian bands… and few possessions.
In contrast, complex hunter-gatherers, live in fixed settlements with populations in the hundreds. They maintain social rankings of kin groups and individuals, restrict access to food resources by lines of descent and have more developed political leadership….These groups, moreover, often waged war.”
Link: War Is Not Part of Human Nature