An animal's instinct is to leave descendants that share its genes. Most animals continue reproducing throughout their lives. But there is no rule without exceptions. As of 2023, the life expectancy of Korean women is 86.4 years, but most face menopause, stopping reproduction around age 50. Arithmetically, more than 40% of their lifespan is unrelated to childbirth.
Scientists have newly found an animal that, like humans, undergoes menopause and lives long: the mountain gorilla in Africa. Menopause has so far been observed only in humans and chimpanzees, and among marine mammals in the long-finned pilot whale and short-finned pilot whale, killer whale, narwhal, and beluga—seven species in total. Menopause was previously observed in zoo gorillas, but not confirmed in the wild.
◇ One-third of females survive more than 10 years after menopause
A team led by Martha Robbins of the Max Planck Institute for Evolutionary Anthropology said, "In a mountain gorilla group living in Bwindi National Park in Uganda, Africa, we confirmed that one-third of females stop reproducing and live at least 10 more years," in a paper published on 13th in the Proceedings of the National Academy of Sciences (PNAS).
Mountain gorillas live 30 to 40 years in the wild. If so, gorillas, like humans, enjoy a long life after menopause. The Max Planck team said, "Of the seven individuals in which menopause was observed, six were 35 or older," adding, "Given that it is rare for wild females to survive to 50, this means the postmenopausal period accounts for 25% of their lifespan."
Menopause was first identified in gorillas living in U.S. zoos 20 years ago, but it was difficult to confirm in wild gorillas. The researchers observed four gorilla groups in Bwindi National Park over 30 years. Robbins, who led the study, said, "Two females that were mature when we began the study in 1998 had their last infants in 2010 and are still alive."
◇ Grandmothers who chose care over childbirth
Why do humans, chimpanzees, gorillas, and whales, unlike other animals, give up childbirth early? Scientists interpret early menopause in primates and whales as the result of evolution to spread more descendants sharing one's genes through offspring, rather than bearing the risks of late-age childbirth. In 2004, Virpi Lummaa of the University of Sheffield proposed the so-called "grandmother hypothesis" in Nature.
Lummaa's team analyzed pre-industrial birth, marriage, and death records from Finland's Lutheran Church. They found that, on average, women had two more grandchildren for every 10 years after menopause. Rather than giving birth themselves, grandmothers help raise grandchildren, allowing descendants who share their genes to thrive.
The same goes for killer whales. Female killer whales can live to 90 and spend 20 years after menopause. Postmenopausal mothers, like grandmothers in human society, tell the pod where prey can be found and share more than half of the fish they catch. This is why pods are led by postmenopausal grandmothers.
Darren Croft of the University of Exeter analyzed decades of footage of killer whale pods to support the grandmother hypothesis. According to a 2015 paper in Current Biology, cases where postmenopausal females led at the front of the pod were 32% more frequent than cases of females still capable of giving birth. They were 57% more frequent than fully grown males.
◇ Menopause originates in a common primate ancestor
For a time, menopause was thought to occur in only six mammalian species: humans and five toothed whale species such as killer whales. Recently, primates have been added in succession to the menopause list. In 2023, a team led by Kevin Langergraber of Arizona State University reported in Science that females in a chimpanzee group living in Uganda's Kibale National Park lived long after their last birth.
Until then, chimpanzee females were believed to be a species that gave birth until death. The researchers observed one chimpanzee group starting in 1995. Remarkably, a female chimpanzee named Malindi was 69 years old, and her last birth had been 23 years earlier.
To prove that the chimpanzees were menopausal, the team collected urine and measured four reproductive hormone levels. In humans after menopause, two of these hormones decrease and the other two surge. Chimpanzees showed the same pattern. The researchers said the postmenopausal survival period in chimpanzees corresponds to 20% of their average lifespan.
The Max Planck team said, "With gorillas now confirmed to undergo menopause after humans and chimpanzees, this will help us understand primate evolution," adding, "It suggests the origin of menopause traces back to the common ancestor of large African primates." However, they noted that confirming menopause in gorillas will require hormone analyses like those done in chimpanzees.
References
PNAS (2025), DOI: https://doi.org/10.1073/pnas.2510998122
Science (2023), DOI: https://doi.org/10.1126/science.add5473
Current Biology (2015), DOI: https://doi.org/10.1016/j.cub.2015.01.037
Nature (2004), DOI: https://doi.org/10.1038/nature02367