There seems to be lots of confusion on the history of war, so let me try to clarify. Most confusion comes from seeking a one-way trend, as in “is there more or less war than in ancient times?” Problem is: overall, warfare increased, then decreased.
Since WWII, at least, we’ve seen a dramatic decrease in casualties from wars between states, from civil wars, and from crime. While these are lowest in richer nations, the strongest correlate seems to be the fraction of men aged 15-30. The fewer young men, the less war/crime. Rich societies today likely have the lowest war/murder rates ever. Rich industry does seem to have greatly discouraged war.
Yes, most of the “tribal” societies that anthropologists study have high rates of war. But most of these are intermediate forms between very distant ancestors and very modern societies, with many relatively modern features. So high rates of war in such tribes does not imply that our very distant ancestors had such high rates.
The rise in density before, during, and after farming seems to have been associated with a huge increase in war. Long ago, strong social norms limited violence within nomadic forager bands, and the fact that one gender typically moved to neighboring bands to find mates greatly discouraged attacking such bands. War was hard for foragers, as hostile victims were far away, at unpredictable locations, and with few physical goods worth taking; women taken in war could easily escape. Trading places, with predictable locations and trade worth taxing, made the first good war targets. Increasing density made targets easier to reach and find, and marriage as property made wars to grab women more tempting. Herding helped attacking armies to travel further and faster, while farming created more tempting and harder-to-defend targets to attack.
War is hell, not an especially modern hell, but also not an especially ancient hell. War is most distinctly, a farmer’s hell.
Chimpanzees murder for land
Between 1998 and 2009, John Mitani witnessed 18 murders firsthand, and found circumstantial evidence for three more. But no police were ever called, for these killers were all chimpanzees, from the Ngogo community in Uganda’s Kibale National Park.Groups of chimps, mostly male, will mount lengthy aggressive campaigns against individuals from other groups, attacking them en masse and beating them to death. After the chimps picked off their neighbours, they eventually took over their territory. It seems that chimps kill for land.The vast majority of these murders were carried out by groups of Ngogo males on patrol. These patrols are stern, single-file affairs. Males march along the borders of their territories, scanning for other chimps and neither feeding nor socialising. They monitor the northeastern part of their territory with particular fervour and indeed, 13 of their 21 kills took place here.Of these victims, 4 were adult males and 9 were youngsters. That may seem like a small number, but for chimps, these are severe losses. They were even higher (by around 5 to 17 times) than the death rates due to violence between groups of human hunter-gatherers.And because of their aggressive tactics, they have increased the size of their territory by some 22%, expanding into the northeast area that their neighbours once called home. With murder came new real estate to colonise.
Two drunken Indian fishermen washed up on North Sentinel Island a few years ago, which is inhabited by an Andamanese tribe that has resisted all contact. They were immediately killed by the natives.