That idea that conflicts were the result of agricultural hierarchical societies is the old Marxist paradigm raising it's ugly head. Marxists believe primitive man lived in harmony with nature despite the voluminous evidence that they didn't.
You have to remember that the neo-Marxist progressives are interspersed with Rousseauians, in that they believe that mankind is naturally good and that it is society that has corrupted it.
This “noble savage” theory has been disproven time and time again, but the social “scientists” keep returning to it like dogs return to vomit.