血縁選択説
Kin selection has played a large role in the evolution of social and adaptive behaviors in chimpanzees. Closely related chimpanzees will form a kin group that cooperates to protect a territory, thereby increasing their access to females and resources. By working together with close relatives, they can ensure that their genes will persist in the next generation, even if circumstances make them unable to reproduce themselves. This behavioral adaptation coincides with the chimpanzee's ability to distinguish kin from non-kin (referred to as visual kin selection) allowing chimps to formulate large, complex societies, where they use altruistic methods to ensure their genes persist in future generations. A wide variety of species, including lions, honeybees, and other insects have displayed kin selection as an adaptive behavior.