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.
Until 2022 it had been going down since WWII.