family selection

Kin selection is a biological theory that explains altruistic behavior by considering the role relatives play in an individual's genetic fitness. It's based on the concept of inclusive fitness, which combines an individual's direct survival and reproduction with the impact they have on the survival and reproduction of their relatives (indirect fitness).123

This theory suggests that behaviors benefiting relatives can evolve because they help pass on shared genes to future generations. For example, parental care is a form of altruism readily explained by kin selection, as a parent's investment increases the reproductive success of its own genes carried by its offspring. Kin selection also explains altruism among non-parental relatives when the benefits to kin outweigh the costs to the altruist. This concept is foundational to understanding social behavior in many species.134