Menopause is an important topic in considerations of the evolution of aging, alongside the unusual longevity of humans in comparison to other primates. Any evolutionary theory worthy of the name has to explain why both of these features exist. The Grandmother hypothesis has been deployed to try to explain human longevity, that our intelligence and culture allows for the selection of increased lifespan through the influence of older individuals on the evolutionary fitness of their descendants. Lacking that intelligence and culture, other primates are not as long-lived as we are. What of menopause, however, and how to explain the observation that we share it with some toothed whales, but with none of our closest primate relatives?
Scientists have discovered that beluga whales and narwhals go through the menopause, taking the total number of species known to experience this to five. Aside from humans, the species now known to experience menopause are all toothed whales – belugas, narwhals, killer whales and short-finned pilot whales. Almost all animals continue reproducing throughout their lives, and scientists have long been puzzled about why some have evolved to stop.
The new study suggests menopause has evolved independently in