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Menopause Caused by Men?

A new hypothesis holds that women become infertile later in life because males prefer younger mates.

By | June 17, 2013

WIKIMEDIA, AZOREGWomen of a certain age undergo menopause not as an adaptation to allow older females to focus on helping out with rearing children—a prevailing notion known as the “grandmother theory”—but as an unintended consequence of males preferentially mating with younger females, according to a new study published in PLOS Computational Biology last week.

“How do you evolve infertility?” asked Rama Singh, the McMaster University biologist who led the study. “It is contrary to the whole notion of natural selection. Natural selection selects for fertility, for reproduction—not for stopping it.”

Singh and colleagues instead posit that menopause, a sudden drop in fertility that occurs in human females later in life, arose because competition for younger mates among men leaves older females with fewer chances to reproduce. As that selective force, which protects fertility in younger women, slackens, the genetic mutations that bring on menopause are allowed to accumulate, causing infertility. “This theory says that natural selection doesn’t have to do anything,” Singh said in a statement. “If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives.”

And conversely, Singh added, if women had been the ones to select younger mates throughout the evolutionary history of the species, human males would lose fertility in old age instead of remaining reproductively viable throughout their lives.

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Avatar of: Neurona

Neurona

Posts: 33

June 17, 2013

I know a middle aged woman who was celibate for nearly a decade. Around the time she had gone 11 months without ovulation ("menopause" = 12 months without ovulation), she hooked up with a man her own age group and resumed regular intercourse.  Her ovulation cycles resumed for a couple of years, but only in the spring of the year.   This leads me to suspect that female human fertility is responsive, in real time, to the immediate sex partner environment, even though humans are not considered to be "reflex ovulators".  

Avatar of: BobD

BobD

Posts: 20

June 17, 2013

Fertility with age drops among men as well as women, as you would expect if accumulated mutations were the cause.  Since women have a fertility cycle and men do not, is it not likely that there is a point at which the acumulated mutations cause the whole ovulation cycle to fail catastrophically, as opposed to a gradual decline?

Avatar of: Akasha

Akasha

Posts: 1

June 17, 2013

This study has quite a few holes in it. For instance, it doesn't even come close to addressing the new trend -- in the past ten years -- of men in their 20s chasing after women in their 40s and having children with them. It also doesn't address differences in when a woman goes through menopause: in the U.S. and other more developed countries, like Germany, women go through menopause in their mid to late 50s, sometimes later. In Latin America, where women (and many men) have children in their teenage years, the women often go through menopause in their mid 30s. Also, sperm count goes down for men as they age, so it's not like only one gender faces hormonal changes with aging and many men suffer fertility problems. This study further fails to address menopause among women who never have sex, such as nuns, and among women who never have children. But, wow, it certainly is going around the web like wildfire. False facts travel fast.

Avatar of: saxmaam

saxmaam

Posts: 1

June 18, 2013

"How do you select for infertility?"  One way is for the grandchildren of infertile women to survive better than the grandchildren of fertile women.

How did a programmed shutdown of reproduction happen _without_ selection?

Avatar of: Kevin Gitau

Kevin Gitau

Posts: 1

October 19, 2013

As Always a little embellishing of the findings of a scientific paper. The paper is not at all a historical expositions about menopause, but the findings of a simulation. Its not suppose to be a documentation of menopause in ancestral humans but rather it shows us the population components that are sufficient for causing menopause. So a bit of a fallacious title. 

Avatar of: krupesh

krupesh

Posts: 1

October 24, 2013

I would like to say that this paper has been reported on by several news agencies, and often times the headlines are similar to yours, stating that men 'cause' menopause. unfrotunately, others have not gone too much into the scinetific explanation of what exactly that means and have thus lead to the misconception, as seen by many of the comments in those articles, that men are actually the reason for this. So kudos on prividing a scientific background/explanation to your somewhat misleading headline.

I would also like to point out that the paper concluded several other things that are mentioned here in brief but it is good to take a looks at the article in full to properly understand what was tested and the results that were found, men causing menopause, being only one.

Avatar of: danielhsieh

danielhsieh

Posts: 1

October 25, 2013

I think that this news article accurately portrays the original scientific article which was based entirely on evolutionary computational models. However, opposing ideas should be based on peer reviewed factual statements, rather than unfounded anectotes about knowing celibate middle-aged women. 

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