血縁選択説
Kin selection is the evolutionary strategy of aiding the reproductive success of related organisms, even at a cost to the own individual's direct fitness. Hamilton's rule (rB−C&gt;0) explains that kin selection will exist if the genetic relatedness (r) of the aided recipient to the aiding individual, times the benefit to the aid recipient (B) is greater than the cost to the aiding individual (C). For example, the chestnut-crowned babbler ("Pomatostomus ruficeps") has been found to have high rates of kin selection. Helpers are predominantly found aiding closely related broods over nonrelated broods. Additional species such as "Neolamprologus pulcher" have shown that kin selection is a dominant driving force for cooperative breeding.