Evolution may be to blame for that dreaded right of passage and emotional captor of womankind - menopause, according to a study co-authored by a University of Calgary researcher.
U of C Anthropology professor Linda M. Fedigan and her co-authors found that human females are the only ones of all closely-related primates to endure the dreaded process.
Fedigan and her colleagues studied baboons and blue monkeys in Kenya, chimpanzees in Tanzania, gorillas in Rwanda, sifakas in Madagascar and muriqui monkeys in Brazil, and compared their findings with hunter-gatherer research and found that menopause only seems to afflict human females.
While the ability of other primates to reproduce diminishes as they get older, they are capable of reproduction for the entire span of their adult lives, the study concludes.
But somewhere along the evolutionary line, women became able to live beyond their child-rearing years, something apes or monkeys seem unable to do, the study explains.
"It tells us that something happened in human evolution that caused us to live longer, while our ability to continue reproducing didn't keep pace," says Fedigan, who will speak about her findings at the university on Nov. 1.
"The age at which human females cease to have menstrual cycles corresponds to the age at which our ape relatives die."
One of the reasons for this marked difference, according to the study, may be due to the fact mammalian eggs have a limited shelf-life and women simply outlive their eggs.
But in an evolutionary environment where survival and reproduction are paramount, menopause seems to be running counter to the concepts.
The explanation may lie in "the grandmother hypothesis," says Fedigan.
"With a few exceptions, non-human primates don't share food with their offspring beyond lactation," she says.
"It's a human characteristic that we share food with our offspring. They're dependent on us for years.
"So a human female might be better off to stop reproducing at a certain point and start investing more time and energy into the survival of her offspring."
The report took into account Fedigan's research as well as data collected from researchers in Duke Univeristy, Princeton University, Columbia University, North Carolina-Charlotte University, as well as the Dian Fossey Gorilla Fund International.
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