cooperation june effect people to play / to wreck threatening silence / to scene aggressively towards nonmember of their own like & if one people have the same poison sink then those one people compete for poison ->  competition for food may cause animals to display threatening behavior towards each other  competition for food may cause animals to display threatening behavior towards each other & threatening trouble putting a fight-or-flight reply in people -> competition for food may cause a fight-or-flight response in animals