Group selection refers to the idea that natural selection sometimes acts on whole groups of organisms, favoring some groups over others, leading to the evolution of traits that are group-advantageous. This contrasts with the traditional ‘individualist’ view which holds that Darwinian selection usually occurs at the individual level, favoring some individual organisms over others, and leading to the evolution of traits that benefit individuals themselves. Thus, for example, the polar bear’s white coat is an adaptation that evolved to benefit individual polar bears, not the groups to which they belong.
The debate over group selection has raged for a long time in biology. Darwin himself primarily invoked selection at the individual level, for he was convinced that most features of the plants and animals he studied had evolved to benefit the individual plant or animal. But he did briefly toy with group selection in his discussion of social insect colonies, which often function as highly cohesive units, and also in his discussion of how self-sacrificial (‘altruistic’) behaviours might have evolved in early hominids.
Although Dr. Sapolsky’s religious views are distressingly poor, he is adapt at elucidating evo-psych concepts that are necessary for understanding Christian history.
Kin selection is a method of passing on genes by favoring those who are genetically-related to you. For example, if cousin marriage is legalized for a certain group, that group will be inclined to favor each other over outsiders much more often since inbreeding increased the level of genetic similarity. Kin selection is myopically focused on the individual’s genetic legacy rather than that of the entire species. Altruism only makes sense towards those one is genetically similar to.
Group selection is a way of favoring the entire species’ genetic legacy by making personal sacrifices that are reproductively unfavorable on the personal level. For example, if a group bans cousin marriage, the rate of inbreeding becomes extremely low and genetic similarities between members are weakened.