According to group selection theory, some genes have an effect at the level of the group. Genes that act at the group level affect survival and reproduction between groups in such a way that some groups leave descendants and other groups don't. Think about a gene for getting along nicely with other people, for example. If selection acts at the group level, a get-along-with-others gene may increase in frequency if groups of people who have this gene are more successful than groups of people who don't have this gene.
As you wrap your brain around group selection, keep these points in mind:
1 Group selection, when it occurs, acts in addition to selection at the level of the individual. Selection still occurs at the level of the individual.
i Selection at the level of the individual could act in the same direction as selection at the level of the group or in a different direction. For evolutionary biologists, the most intriguing cases are those where different levels of selection conflict and as a result are of considerable interest.
i Group selection can be important when the population structure of the species involves interacting groups.
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