According to Cant and Johnstone, several lines of evidence, including mitochondrial DNA and Y chromosome analysis, as well as studies of modern hunter-gatherers, suggest that in our ancestors it was overwhelmingly the females who moved. So older women were competing for resources with young women who had come from elsewhere. Cant points out that when a young woman leaves her family group and joins another, she is unrelated to anyone in her new home and is thus insensitive to the costs she might inflict on the older females by having children. As females age, however, they are increasingly related to the group, and have less to lose and more to gain by helping with the care and provisioning of the younger generation.
Did menopause evolve because older women found it less costly in evolutionary terms to forgo reproduction than their daughters-in-law did? “A system in which females become more related to their group as they age has this predicted outcome,” says Cant. He calls menopause the “ghost of reproductive competitions past”.
Join the conversation as a VIP Member