Menopause may be widespread among mammals, challenging famed hypothesis

By age 69, Marlene was gaunt, with rundown teeth, grizzled fur, and a receding hairline. The elderly chimpanzee living in Kibale National Park posed a puzzle for scientists. Multiple studies have shown female chimps can reproduce until the end of their lives, but Marlene had last given birth 23 years before. The great ape, it appeared, had undergone menopause—a reproductive shutdown that researchers have only documented in humans and a handful of whale species. A pair of studies published today suggests Marlene isn’t as rare as scientists thought. Chimps can undergo menopause, researchers have found, and females in dozens of other mammal species may also outlive their ability to reproduce. The results are provocative, researchers say, because they don’t jibe with the leading hypotheses for evolution of menopause in humans. All people who menstruate  who live long enough go through menopause. As their stockpile of eggs dwindles, the levels of hormones necessary for pregnancy fall, and eventually their menstrual cycles stop. As far as researchers could determine, females in only a small number of other species, including killer whales , curtail reproduction long before they die. Chimpanzees were one of the species that appeared to bear young until the bitter end, according to long-term studies, including some in Kibale. However, researchers with a project that has been tracking Marlene’s chimp community, the Ngogo group, since 1995 noticed s...
Source: ScienceNOW - Category: Science Source Type: news