血縁選択説
Within species cooperation occurs among members of the same species. Examples of intraspecific cooperation include cooperative breeding (such as in weeper capuchins) and cooperative foraging (such as in wolves). There are also forms of cooperative defense mechanisms, such as the "fighting swarm" behavior used by the stingless bee "Tetragonula carbonaria". Much of this behavior occurs due to kin selection. Kin selection allows cooperative behavior to evolve where the actor receives no direct benefits from the cooperation.