Researchers have found no evidence that chimpanzees in the wild undergo menopause in the way that women do, according to a new report published online on December 13th in Current Biology, a Cell Press publication.
That's despite the fact that reproduction tends to peter out at a similar age in both species.
“It is important to distinguish reproductive senescence, which is something animals are expected to experience if they live long enough, from menopause, which is a very unique trait that occurs because reproductive function declines much more rapidly than declines in other bodily systems,” said Melissa Emery Thompson of Harvard University. “This study of reproductive senescence indicates that chimpanzees do not routinely experience menopause.”
Therefore, she continued, scientists will have to “look to other unique features of human biology and socioecology to help explain why humans have menopause.”
Human menopause is remarkable in that reproductive deterioration is markedly accelerated relative to the aging of the rest of the body, leaving an extended post-reproductive period for many women, the researchers said. The explanation for that pattern has remained unclear, in part because comparative data from closely related species had been inadequate. Earlier studies of chimpanzees are based on very small samples and have not provided clear conclusions about the fertility of aging females, she said. And those studies have not examined whether reproductive declines in chimpanzees exceed the pace of general aging, as in humans, or occur in parallel with declines in overall health, as in many other animals.
To remedy those problems, Emery Thompson teamed up with researchers from six long-term chimpanzee research sites across Africa. “By combining our data, we were able to examine the effects of age on fertility rates in chimpanzees,” she said.