The evolution of menopause, causing women to stop reproducing relatively early in life, is a puzzle for evolutionary biologists. Although rare in the animal kingdom, menopause also affects killer whales (pictured), and research on this species is shedding new light on the problem. Part of the solution is that older, experienced females can help younger relatives, who share some of their genes, to breed more successfully. In addition, when killer whales breed in a group, calves born to older mothers are less likely to survive, losing out in competition. Combining the benefits of helping and increased costs of reproducing themselves makes menopause advantageous, but only because females are closely related to their social group, and increasingly so as more of their descendants join the pod. Early human societies are thought to have displayed similar patterns of relatedness, making menopause a prime example of how social structures can shape biology.
Written by Emmanuelle Briolat
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