Initially, It Was Assumed That War Was Somehow Unique to Humans

Initially, it was assumed that war was somehow unique to humans and resulted from the development of weapons or the denseness of population; however, the observation that _____ changed that view.

A) chimpanzees also engage in lethal attacks on one another
B) even primitive societies with no weapons engage in warfare
C) many species, from rats to rabbits, engage in organized violence
D) wars occur more frequently in less densely populated areas