The grandmother effect

Two classes of explanation have been advanced to explain women's long post-menopausal life span - that it is an epiphenomenon of increased longevity or an evolved adaptation. While there is no decisive evidence to choose between them, the latter appears more likely. Two mechanisms for the evolved adaptation have been proposed, the 'mother effect' and the 'grandmother effect'. It is argued that both these effects, insofar as they have been shown to occur, are likely to be culturally rather than genetically evolved.