Fight Aging!

Few mammalian species exhibit menopause. It is thought that humans evolved into this state of post-reproductive old age in part because older individuals can help to enhance the reproductive fitness of their direct offspring. This view is known as the "grandmother hypothesis". The same behavior is observed in orcas, one of the few other mammals to exhibit menopause. Researchers here provide evidence for chimpanzees to undergo menopause, which is a strike against the grandmother hypothesis, as chimpanzee elders do not assist their offspring in this way.

A team of researchers studying the Ngogo community of wild chimpanzees in western Uganda's Kibale National Park for two decades has published a report showing that females in this population can experience menopause and postreproductive survival. Prior to the study these traits had only been found among mammals in a few species of toothed whales, and among primates only in humans. These new demographic and physiological data can help researchers better understand why menopause and post-fertile survival occur in nature, and how it evolved in the human species.

The grandmother hypothesis has been used to explain the existence of human postmenopausal survival, proposes that females in their postreproductive years may be able to pass on more of their genes by helping to raise the birth rates of their own children or by caring directly for grandchildren, thereby increasing grandchildren's odds of survival. And indeed, several studies of human grandmothers have found these positive effects. But chimpanzees have very different living arrangements than humans. Older female chimpanzees typically do not live near their daughters or provide care for grandchildren, yet females at Ngogo often live past their childbearing years.

While substantial postreproductive life spans have not previously been observed in other long-term studies of wild chimpanzees, they have sometimes been seen in chimpanzees and other primates in captivity, who receive good nutrition and medical care. This raises the possibility that the postreproductive life spans of female Ngogo chimpanzees may be a temporary response to unusually favorable ecological conditions, as this population enjoys a stable and abundant food supply and low levels of predation. Another possibility, however, is that postreproductive life spans are actually an evolved, species-typical trait in chimpanzees but have not been observed in other chimpanzee populations because of the recent negative impacts of humans.

Link: https://newsroom.ucla.edu/releases/ucla-researcher-first-proof-menopause-wild-chimpanzees