Evidence For
If the grandmother effect were true, post-menopausal women should continue to work after the cessation of fertility and use the proceeds to preferentially provision their kin. Studies of Hadza women have provided such evidence, but they have not shown that this behaviour actually increased the grandmother’s fitness by producing more grandchildren. Furthermore, some commentators felt that the role of Hadza men, who contribute 96% of the mean daily intake of protein, was ignored; though the authors have addressed this criticism in numerous publications. Other studies also demonstrated reservations about behavioural similarities between the Hadza and our ancestors.
One quantitative model, however, showed limited increases in fitness. One of the reasons given for low benefits is the inflexibility of the age at which menopause occurs. It could be that fertility behaviour is adjusted depending on long-term expected fitness. Such choice, however, is not available to an already infertile female – she cannot ‘choose’ to redirect investment.
Read more about this topic: Grandmother Hypothesis
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