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Explainer: why do women go through menopause?

Menstruation is a reproductive quirk that humans share with only a few other mammals. But even stranger is the fact that women stop menstruating when they have a whole third of their lives left to live…

One suggestion is that menopause enables women to provide for their grandchildren. Image from shutterstock.com

Menstruation is a reproductive quirk that humans share with only a few other mammals. But even stranger is the fact that women stop menstruating when they have a whole third of their lives left to live.

All animals have a finite reproductive life. But more often than not, their reproductive system winds down at roughly the same time as every other system in the body – the menopausal killer whale is a notable exception.

The ability to bear children gradually declines throughout a woman’s reproductive life. The average age at which a woman’s ability to natural conceive ceases is 38.

But when the fertility free-fall of menopause kicks in between the ages of 45 and 55, complete sterility is the inevitable result. No more ovulation, no more menstruation, and no more opportunities to procreate.

In contrast, males experience only a slight decrease in fertility in their senior years.

Giving kids a head start

Evolutionary theory predicts that life span and reproductive span should synchronise – why go on living if you are unable to go on breeding, bolstering the contribution of your genes to the next generation?

One reason for dialling back reproduction could be to maximise the level of nurturing available for children that already exist. Human infancy is marked for its length and also for the degree of dependence that infants have on their parents. Perhaps menopause is a reproductive compromise to ensure that a woman’s last born makes it out of the nest safely.

But this would only account for a ten or 15 year difference between menopause and death – much less than usually occurs.

Grandmothers and daughters-in-law

Another suggestion – dubbed the grandmother hypothesis – is that menopause enables women to provide for their grandchildren.

In evolutionary terms, a person is said to be “fit” if they are able to pass on their genes to future generations by reproducing. Given that our children bare 50% of our genes - the other 50% from our partner - and our grandchildren share 25% of our genes, a grandmother providing for her grandchildren still results in evolutionary fitness.

A more recent hypothesis centres on the age-old conflict between women and their mothers-in-law. Image from shutterstock.com

The numbers don’t add up, though. The fitness benefit of caring for grandchildren is less direct and, in the end, less potent than if the grandmother were simply able to have more children of her own.

A more recent hypothesis centres on the age-old conflict between women and their mothers-in-law. This intergenerational reproductive argy-bargy is apparently the result of ancestral daughters-in-law joining a partner’s family. The daughter-in-law gains nothing by helping her partner’s mother to reproduce, but the mother-in-law does benefit in an evolutionary sense by helping her own grandchildren to be raised.

Instead of having two competing females in the one clan reproducing, the older female relinquishes her own reproduction in favour of helping her daughter-in-law raise her grandkids.

Similarly to the grandmother hypothesis, the reproductive conflict hypothesis could explain why reproduction ceases at around the same time as a woman reaches the age at which she is likely to become a grandmother.

But a recent study of pre-industrial Norwegian women casts doubt on this reckoning of evolutionary events. The study found that grandmothers who had a reproductive overlap with their daughters-in-law had more grandchildren, not less.

A fluke of nature

So, perhaps it is to happenstance that we must turn for an explanation for menopause. Could it be that menopause is simply an evolutionary hitchhiker; a trait that has come along for the ride without providing any adaptive benefit?

It’s possible, for example, that menopause could be the result of a physiological trade-off that favours efficient reproduction early on.

In searching for an answer to why women live for so long post-fertility, palaeontology has reminded us of a very important fact: old age is actually relatively new age. Early human fossils are invariably young, and it wasn’t until a few thousand years ago that anyone lived into the senior years we have now grown to expect.

It is highly likely, therefore, that our long-lost great-great grannies didn’t live long enough to experience the hot flushes, night swears and yo-yo-ing hormones of the modern-day menopause. They never lived long enough to be denied the children that menopause robbed them of, because they may not have reached menopausal age at all.

We can be thankful for our longer lives, but menopause may be the cost women endure for it.

Join the conversation

38 Comments sorted by

  1. Julia Abbott

    logged in via email @gmail.com

    You say:
    "Perhaps menopause is a reproductive compromise to ensure that a woman’s last born makes it out of the nest safely. But this would only account for a ten or 15 year difference between menopause and death – much less than usually occurs."

    As you go on to note, this is a new phenomenon historically. Women live longer now - but only in developed nations. The life expectancy of women in poor countries is often 50 years or younger.

    So menopause may really be an authentic 'first world problem'.

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  2. Dale Bloom

    Analyst

    I would offer a hypothesis, which is to protect the human gene pool.

    Women are born with their supply of eggs, and that supply of female eggs is not replenished.

    The eggs gradually deteriorate throughout the life of the woman, and if an elderly woman has a baby, it is more than likely the baby will be deformed, which can then affect the gene pool.

    So nature does not allow ovulation after a certain age, to protect babies from being born deformed, and to protect the gene pool.

    The natural age women should have children may be around 15 to 20 years of age, and the situation of women having their first baby around 30 is not a natural occurrence.

    Similarly the situation of women having babies through IVF, or having babies without a father is not a natural occurrence.

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    1. Hugh McColl

      Geographer

      In reply to Dale Bloom

      Dale, I'm interested in your somewhat ambiguous view that women having babies "without a father" is not a natural occurrence. I presume you mean without the father being around (ie. the single mum) rather than without a male component in the conception? So is this a moralistic stance or a biological observation?

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    2. Dale Bloom

      Analyst

      In reply to Hugh McColl

      Both.

      The word "father" actually means "father" and not "partner", which is an artificial term recently introduced into our language mainly by feminists that implies that the father is superflous and non-essential.

      Back to the topic, and ovulation naturally ceases at a certain age, as beyond that age conception is more than likely to introduce deformities into the gene pool.

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    3. Hugh McColl

      Geographer

      In reply to Dale Bloom

      If you really mean "both" then you are saying that the 'single mother' arrangement, where a child is born without the biological father being around, is not a natural occurrence. Clearly, this is not a 'biological' observation, it is a moralistic position. Because each year (if not each day), hundreds of children are born without a father in evidence. You really don't intend that those children should bear the stigma of being described as 'unnatural' do you? That would be bigotry wouldn't it?

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    4. Dale Bloom

      Analyst

      In reply to Hugh McColl

      Introduction of the word “partner” into the English language by feminists instead of the word “father” is similar to introducing deformities into a gene pool.

      Nature does not like deformities, and eventually “partner” will be replaced again by “father”.

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    5. Dyani Lewis

      Sexual health researcher at University of Melbourne

      In reply to Dale Bloom

      I used the term 'partner' because we do not know when the features that lead to menopause, or menopause itself, evolved. It may have been that Homo erectus went through menopause. Did they marry? Probably not. I could have used the term father, but then I'd need to say "their child's father's family" - just too wordy for my liking.

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    6. Dale Bloom

      Analyst

      In reply to Dyani Lewis

      The term “partner” is a recent construct, but I have noticed the word “mother” still widely used within feminist circles.

      So obviously introduction of the word “partner” into the English language is meant to devalue fathers as much as possible.

      Menopause is possibly of less relevance that child bearing age for women, and attempts to extend the child bearing age through such things as IVF are basically at odds with nature.

      Nature always wins.

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    7. In reply to Dale Bloom

      Comment removed by moderator.

    8. In reply to Liam Hanlon

      Comment removed by moderator.

    9. Dale Bloom

      Analyst

      In reply to Liam Hanlon

      You are very abusive.

      I have heard the word "mother" throughout my life, but only in recent decades has the word "partner" been applied to the father.

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    10. Hugh McColl

      Geographer

      In reply to Dale Bloom

      Dale, I question your assertion that "partner" came from feminists. I'd say it came with modern feminism, that is, coincidentally, at about the same time. You say it's a feminist term for father but I'd suggest it's an artifact of the modernisation of marriage and divorce laws around the western world over the past 40 years and the rise, to very substantial proportions, of defacto or marriage-like relationships. Some (legally) married people actually frown upon unmarried couples referring to their partner as their 'husband' or 'wife' since they believe you can't call them that unless you are actually married. For a divorced person who has re-partnered without getting re-married, it's totally effective and meaningful terminology. And therefore not a deformity and so likely to stay.

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    11. Dale Bloom

      Analyst

      In reply to Hugh McColl

      This is actually a side issue, although important in other circumstances.

      Our way of life of hunting and gathering in the shopping mall is very different to that in the past in more tribal or village based societies.

      Because of the often short life expectancy, a woman of childbearing age had to be almost constantly pregnant or lactating to get enough children to continue the tribe.

      But still, there is no record of widespread de facto relationships and children being born to whatever father in past societies as there is in ours.

      Perhaps other societies in the past were more civilised.

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    12. Liam Hanlon

      Student

      In reply to Dale Bloom

      Telling you that your argument is full of crap is hardly abusive. Hugh below has shown that to be the case...its actually about modern relationships.

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    13. Hugh McColl

      Geographer

      In reply to Dale Bloom

      Not sure what tribal or village-based societies you might be referring to but then it doesn't really matter because as you say there was no record of de facto relationships. Dale, there is no record of de facto relationships in modern western societies now. Neither government or churches keep such records. No one does - although occasionally Centrelink thinks it might have uncovered the odd 'marriage-like relationship' and will sic it's snoopers onto those co-habiting dole bludgers. I don't think…

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    14. Dale Bloom

      Analyst

      In reply to Hugh McColl

      Women’s reproduction may become important in the future as health care costs seem to be forever increasing, and may be too high to be sustainable.

      So humans will begin to return back to how they lived for many 1,000's of years, with increased infant mortality rates and decreased life expectancy, as we can no longer afford the health care costs.

      As I wrote in another comment, nature always wins, and feminism (which is the attempt to raise children without a father) will be just a mere aberration in the timeline of human history.

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    15. Hugh McColl

      Geographer

      In reply to Dale Bloom

      Dale, you say feminism = the attempt to raise children without a father. My dictionary says feminism is the advocacy of women's rights on ground of the equality of the sexes, whence feminist. I think we might be at cross purposes.

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    16. Sue Ieraci

      Public hospital clinician

      In reply to Dale Bloom

      Dale Bloom must have a different dictionary to the rest of us. In most dictionaries, fatherhood requires offspring. Partnership does not.

      The term "partner" is more useful than "boy/girlfriend" or "de-facto husband/wife" - no need to invoke the "f" word, Mr Bloom.

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  3. Henry Franceschi

    Director, NCD Treatment Centers

    Thank you for a very interesting topic, but I think you ask the wrong question. The evolutionary question should be, What conditions led the human species to go through menopause?

    Viewed this way, statistics enters the picture and menopause then appears more to have to with the odds of our species surviving by how we reproduce. That is, by combining the inheritable traits of a man and a woman in a unique environment and unique reinforcement histories to optimize the odds of successful survival…

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    1. Dyani Lewis

      Sexual health researcher at University of Melbourne

      In reply to Henry Franceschi

      Yes, the evolutionary basis for menopause is exactly the question that I was trying to address. And the way I view menopause is as a human phenomenon, not a female phenomenon.

      The fact that eggs deteriorate over life is a good one, and indeed there is increasing evidence that sperm produced after the age of 40 for men aren't as high quality as those produced before.

      Two things that I would note, though. First is that women don't reach an egg count of zero when menopause starts - there are still eggs, but it is mostly hormonal cues that end a woman's reproductive life.

      Secondly, chimpanzees are also endowed with all the eggs they will ever produce before birth, as we are, yet female chimpanzees reproduce until they die. Elderly female chimpanzees are often highly sought after.

      So the mystery of what has lead to humans in particular evolving a mechanism such as menopause still remains.

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    2. Judith Olney

      Ms

      In reply to Dyani Lewis

      Hi Dyani, menopause is not only a biological fact in human beings, but in many other species as well, although I'm not sure the cessation of menstrual cycle is called menopause in other species.

      Females of other species do not drop dead when they no longer are able to produce offspring, some live quite a long time after they are no longer able to reproduce. I've had chickens that have lived 50% of their lives after laying their last eggs.

      What is attributable to only humans is the way that female biology is politicised.

      I look at menopause as a gift from nature, and know many postmenopausal women who feel the same way. A freedom from the monthly cycle is most welcome to many women, and many women do not suffer the worst symptoms associated with menopause. For a great many women menopause is seen as just another stage of life, and many look forward to it.

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  4. Meg Thornton

    Dilletante

    Can I just comment on one aspect of this article I found somewhat bothersome? Namely the way the various theories for the evolutionary justification for menopause are phrased in such a way as to imply menopause is a conscious choice on the part of the women who undergo it. In particular, I'd point to this paragraph:

    "Instead of having two competing females in the one clan reproducing, the older female relinquishes her own reproduction in favour of helping her daughter-in-law raise her grandkids…

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    1. Dyani Lewis

      Sexual health researcher at University of Melbourne

      In reply to Meg Thornton

      I'm sorry you see this as increasing stigma in any way. Menopause is part of the human condition, and has implications for both males and females.

      In evolutionary terms, choice doesn't factor into the equation, so I used the term relinquish not to denote choice, but to highlight the cost-benefit nature of evolution. Females give something up (cost) for some kind of benefit (no conflict). Evolution doesn't always work this way, of course.

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  5. Peter Hindrup

    consultant

    ‘But even stranger is the fact that women stop menstruating when they have a whole third of their lives left to live.’

    Walk through any really old cemeteries and take note of the ages of death, overwhelmingly the women are under, ‘or around’ thirty. Assuming that my observation are correct, these women where still within the age that they could reproduce.

    However, being old enough to have grown up while poor families had innumerable kids, and remembering the ‘old’ women, old, often having…

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    1. Peter Hindrup

      consultant

      In reply to Peter Hindrup

      precious births --- previous births, of course.

      Bloody too clever spelling corrector s!

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    2. Dale Bloom

      Analyst

      In reply to Peter Hindrup

      The infant mortality rate in earlier times was about 50%, and chances for survival to adulthood not much better.

      Records of children born to kings and queens often show that the majority of their children usually died before the age of 20 (even though they would have had the best food and attention etc).

      It made it even more imperative that women began having children at a younger age, and the female form is basically designed for that.

      It also made it more imperative that babies were born healthy, and any potential for deformities had to be eliminated from the gene pool.

      Feminists of course understand all this.

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  6. Raine S Ferdinands

    Education at Education

    On a different note: who coined the word "menopause"? It seem to suggest "men o pause" for she is past it, mate!! Bet it was coined by some male medical or research person as a joke that got mainstreamed. I find this funny!! I know of several women who actually say that life gets better after men-o-pause, as long as they don't fall victim to commercial hype about "looking younger". In my view, women who embrace their maturity with wisdom, grace, feminine beauty exude confidence. Perhaps, finally, women come to realise the beauty of just being. What a freeing feeling that can be.

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    1. Dale Bloom

      Analyst

      In reply to Raine S Ferdinands

      A little bit of male denigration it would seem.

      The word menopause is derived from the Greek words pausis (meaning cessation) and men (meaning monthly).

      But of course you never meant that the word be corrupted so as to carry out the male denigration.

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    2. Raine S Ferdinands

      Education at Education

      In reply to Dale Bloom

      Oooops ... you are way too sensitive 'bout the male/female stuff. Learn to laugh, Dale, no "denigration"of any kind was meant. As a scientist, I am aware of the origin of the word "menopause" just trying to have some fun at the Anglo version of literal meaning. Phew!!

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    3. Dale Bloom

      Analyst

      In reply to Raine S Ferdinands

      Wasn't funny, but I have noticed the routine denigration of the male gender by so many people.

      My guess it comes from a lifetime of being trained and educated to denigrate the male gender.

      "In my view, women who embrace their maturity with wisdom, grace, feminine beauty exude confidence."

      Frankly, I have found some, but not that many.

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  7. Chris Saunders

    retired

    The article claims as a beginning that evolutionary biology assumes that reproduction is the essential biological role of each one of us. To allow women to live many years post reproduction ability does not fit into this hypothesis. If the present concentration of potential child bearing years were for the benefit of the better nurture of existing children then Peter Hindrup’s description of how it really was hardly supports this. If menopause itself were anything to do with a “dialling back of…

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  8. Andrea Shoebridge

    logged in via Facebook

    Several thoughts... Evidence from the earliest artefacts shows the Goddess has three facets matching women's pre- and post-fertile life stages as well as the middle generative stage, indicating that menopause has always been a human condition. There is also evidence that men went to live with their wives' families rather than the patriarchal model of women moving to their husband's family so that mother/daughter-in-law antagonism is more likely to be cultural than inevitable. Questions about the purpose of menopause are predicated on the primacy of species reproduction but it is likely that reproduction is only part of what humans do. Women and men both parent but do many other things as well. Questions of women's longevity might best be understood as the collateral damage of their generative role. I was much struck, many years ago at an exhibition of Australian women artists, by the venerable ages most of them lived to, without marriage and maternity.

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  9. Paul Prociv

    ex medical academic; botanical engineer at University of Queensland

    This question has fascinated many for yonks. Looking at menopause in modern or recent society doesn't help much, as this is far from our "natural" state. If we accept that Homo sapiens is an intensely social species, and that we evolved as nomadic hunter-foragers on the savannahs of Africa, then the essential unit of our biological and socio-cultural evolution is not the individual, but the extended family-clan. Having lots of young children would impose a huge burden on women in their reproductive…

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  10. Peter Hindrup

    consultant

    Many of the assumptions here seem to be based on the notion that ‘tribes’ were made up of parents and their kids.
    I am a long time from this, and rusty, but amongst the Polynesians (some?) The young people slept in the long house. The only sex related ‘rule’ was that a couple could not sleep together for more than two nights. I don’t know how many partners they had to have before they could get back together, if they so desired. Nor am I certain of how the pairing off was eventually achieved…

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  11. ernest malley

    farmer

    I'm fascinated by the mind set of the author that assumes mother/daughter-in-law as a possible explanation for post menopause longevity.
    The move of a woman to her husband's home is a very recent habit, far too recent to have the slightest evolutionary effect.
    Until the aberration of male gods infected religion, the norm was mothers looking after their daughters' children, as is normal in most higher mammals.
    It is an indication of how deracinated we have become that a woman could assume that the patriarchal nuclear family was ever the norm until recently.
    Reminds me of the question, which even women get wrong - "which society would have the higher birth rate, polygynous or monogynous?"
    Hint: think typing pools, nurses residences, nunneries...

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  12. Lynette Hobcroft

    Student

    Has anyone noticed the article (June 14th) on the Science Daily site titled 'Menopause May Be an Unintended Outcome of Men's Preference for Younger Mates'. I'll post a very long link at the end here. One excerpt - "Over time, human males have shown a preference for younger women in selecting mates, stacking the Darwinian deck against continued fertility in older women, the researchers have found." They also claim, that with lots of time, the effect could be reversed. That if the predominant social behaviour was for women to always choose younger men, that menopause could be gender reversed. Food for thought! http://www.sciencedaily.com/releases/2013/06/130614082653.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Ffossils_ruins+%28ScienceDaily%3A+Fossils+%26+Ruins+News%29

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  13. Sarah Jenkins

    Sales

    This article well-illustrates that humans as a species just didn't use to live anywhere near as long as they do now.

    Along these lines, it's untrue to say "In contrast, males experience only a slight decrease in fertility in their senior years."

    Men's fertility drops each year and the risk of abnormalities in their offspring increases. The quality and motility of their sperm decreases. Besides that, by the age of 75, over half of men will have erectile dysfunction, with many men beginning to experience issues in their 40s and 50s.

    Also, 50% of men in their fifties have enlarged prostrate. This enlarged prostrate can prevent sperm from mixing in seminal fluid. The right PH balance for sperm may also not be able to be achieved, causing the sperm to die.

    http://www.webmd.com/infertility-and-reproduction/features/age-raises-infertility-risk-in-men-too

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