The Origin of War: The Evolution of a Male-coalitional Reproductive Strategy, Volume 1

according activity adaptive aggression animals appears attack battle become behavior benefits biological called cannibalism causes chimpanzees civilization coalitions competition complex concept considered cooperation costs cultural Darwin death defense early economic effect enemy evidence evolution evolutionary evolved example existence expected explain fact factors females feuding fighting fitness force function hostility human hunting idea important increase individual instinct interests intergroup involved killing kind lead least less living males material means military motives natural natural selection observed occur organization origin participants patterns peace political population possible practice present primitive probably produce races raiding reason regarded relatively reproductive result revenge seems selection sexual similar social societies sometimes species strategy struggle success suggests territorial theory tribes types violence warfare warriors wars weapons women