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Scientists claim to have discovered the initial evidence of menopause in chimpanzees living in the wild.
During a 20-year study, the team observed the Ngogo community of wild chimpanzees in Kibale National Park, Uganda and discovered that female fertility starts to decrease after the age of 30. Additionally, no births were documented after the age of 50.
The results can aid researchers in gaining a deeper understanding of the reasons behind menopause in nature and how it has evolved within the human species.
According to Brian Wood, an associate professor of anthropology at the University of California – Los Angeles in the United States, women who have reached menopause have valuable contributions in societies globally. They serve as key players in economic matters and offer guidance and support as experienced caregivers.
The development of this life story in humans is a captivating but difficult mystery.
Before this new study, the characteristics described had only been observed in a limited number of species of toothed whales and in humans among primates.
Researchers suggest that the post-reproductive life spans of female Ngogo chimpanzees may be a short-term adaptation to particularly favorable environmental circumstances.
This is due to the fact that the group they studied had a dependable and plentiful source of food and minimal instances of being hunted.
One potential explanation is that chimpanzees have naturally evolved to have post-reproductive life spans, but this trait has not been observed in other populations due to the harmful effects of human activity.
According to Kevin Langergraber, a professor at Arizona State University, chimpanzees are highly vulnerable to diseases that come from humans and to which they have limited natural resistance.
“We, the researchers at Ngogo, have discovered through our studies the severe impact that disease outbreaks can have on chimpanzee communities. We have also developed methods to minimize the likelihood of these occurrences.”
The study, which was published in Science, analyzed the mortality and reproduction rates of 185 female chimpanzees.
The researchers determined the proportion of time that adult females spent in a non-reproductive stage by studying a group of 66 females with different reproductive statuses and ages between 14 and 67 years. They also analyzed hormone levels in urine samples from these females.
The research discovered that female chimpanzees, much like humans, commonly live beyond the age of 50.
A woman who became an adult at 14 years old was no longer able to reproduce for approximately one fifth of her adult lifespan, which is about half the duration of a human hunter-gatherer.
According to Jacob Negrey from the University of Arizona, our team’s extensive observation of chimpanzees over the course of many years has allowed us to determine that some females continue to live for a significant amount of time after they have ceased reproducing.
“We have also dedicated numerous hours in the forest to gather urine samples from chimpanzees in order to analyze hormonal changes during menopause.”
The scientists suggest that monitoring the actions of elderly chimpanzees and studying their interactions with other members of the group will be crucial.