I think that people are people, and they can become more aggressive or more docile under circumstances not having much to do with evolution. The Lakota (Sioux) were corn farmers, but when they acquired the horse they aggressively expanded their territory, battling other Plains Indians, even successfully (for a time) defending it from white invaders. The transformation of the Comanches was even more dramatic (Read “Empire of the Summer Moon: Quanah Parker and the Rise and Fall of the Comanches, the Most Powerful Indian Tribe in American History” by S.G. Gwynne)
And it’s hard to believe, but there have been times in the history of Jerusalem when Christian, Jew, and Muslim lived together in peace. (Read “Jerusalem: the Biography” by Simon Montefiore)
So, blessed be the peacemakers, and [content removed by moderator] the politicians who fan the flames of hate, demonizing people groups, and inciting violence.
There is a genetic component to aggression, especially in animals. In the famous experiments involving domesticating foxes, Dmitry Belyayev was able to create a more docile variety, but he also created a more aggressive line.
Some species of animals are very close genetically, but in terms of aggression they could not be more different. Chimps are very aggressive, but their close relatives, the bonobos, want to “make love, not war.”
Horses and zebras are another example. They look similar, but are so very different in nature. The aggressive nature of the zebra has made it impossible to domesticate them. They might look docile in the zoo, but zoo keepers have to stay vigilant when working with them.