Some clues :
Douglas P. Fry : Pacified Past
Azar Gat : Warfare as an Ancient Feature
Robert L. Carneiro : Complexity and State Formation
Was the 20th century one of the most violent in human history ? (with two world wars and numerous other conflicts) ?
i also like the documentary series : “The Ascent of man” from the BBC in 1973 by Jacob Bronowski.
As a species we have always made war on each other. Our ancestal species also most likely did. Our closest living genus also frequently raids other tribes.
It is a part of who we are. However, like xenophobia it is something we can work to minimise with the goal to eradicating one day.
Your answer here is the best one so far for me. Are chimpanzees some of those frequently raiding other groups (tribes) ?
Better education will always be a major part of the solution … but i don’t think education alone will be sufficient to make us good.
Like 99% of people you will (probably) disagree with me on the following, but eventually (in 50 years ?), i believe that many people will volunteer to have genetic therapy to decrease their aggressivity and that of their descendants.
We have to change in a fundamental way since we are still waging wars while climate change will likely kill a majority of us in the next few decades.