AIBU to ask why you think women stop being able to reproduce...

[TokenGinger]

... And men do not?

There's been a discussion in the office today about why a woman's body stops being able to reproduce and a man's doesn't. There's been the typical comments of, men are meant to continue procreating with more than one woman, men should be with younger women, yada yada.

I'd be interested to hear people's views on this.

I heard a theory that the reason women go through the menopause is because in evolutionary terms it is an advantage for older women to be able to help look after their children's children. If women continued to give birth until they were really old this 'grandparent advantage' would be lost. Young humans need so much care until they are able to look after themselves that this theory makes sense to me particularly in pre contraception days where women could have many children (albeit not all surviving)

Well women need to be around to raise their young to maturity. Not much point in giving birth then dying of old age a couple of years later.

maggie - but that theory doesn't work so well when you consider the life expectancy which was very low until very, VERY recently!

Because without grandmothers human culture (language, craft, storytelling, clothing, healthcare) wouldn't exist, so it makes sense for women to stop bearing children in mid-life, whereas older men are an anomaly in a hunter-based society but there's no particular advantage to them being unable to breed, though actually sex-drive and fertility tend to decline.

Our bodies weren't designed to last beyond menopause anyway - neither male or female!

That's a good point about historical life expectancy. It makes sense that a woman's fertility would come to an end in time so that she could raise her youngest child to an age of self-sufficiency (early teens maybe?) before her death.

I'm not sure about the "helpful grandparent" theory. Yes, a woman would probably become a grandmother back in the days when women would bear children throughout their fertile years, but without birth control available she would still be having children of her own while her firstborns were starting to reproduce, so wouldn't necessarily be much help.

on an evolutionary scale, pregnancy is hard on the body, it takes nutrients from our bones, causes things like osteoporosis...etc.

knowing how we have evolved, and how arduous pregnancy, labour and birth is on the body, it made more evolutionary sense for us to have fewer children in the years our bodies are capable of carrying them and birthing them with minimal damage, and then to concentrate on raising them.. its about investing in the future.

If you look in the animal world, those animals who have complex family systems often have older, infertile females around to help teach/raise the young. Apes do it, elephants do it, there is even evidence that some types of Crow do it.

Life expectancy is tricky.
You often hear people say 'life expectancy used to be 40' (or similar) but that is average life expectancy. Lots of babies and children dying skew the numbers. If you made it to adulthood, you had a chance to live to a good age.

In summary, the female doesn't need to have fertility that lasts a lifetime. Males needs to stay fertile to give them as many years as possible to "win" a female. Females don't need to be able to fight to win a mate, but do need to be in top physical condition to give birth.

I'm not sure I agree with this entirely. Women might not need to fight but they do actually need to use their judgement to select a partner who will hang around long enough to be a proper father, especially during the early years.

If you're going to relate humans to wild animals then a woman would be looking for a male who would support mother and baby whilst both were at their most vulnerable i.e. directly after childbirth.

Obviously nowadays that's not quite so critical but then neither did I have to fight anyone to 'win' my wife's affection

Menopause is believed to kick in with women at an age where they are still able to do childcare, this freeing up the younger members of their community to hunt and gather.

If we still had Community this would work just great

if you think, originally we used to child bear mostly between 15 and 30, by the time we hit menopause, our children are in the prime child bearing years, its obviously not an evolutionary co-incidence and was meant to work out that way.

when was the last time ejaculating killed a man, or made any great physical demands on his body?

That is because women aren't generally holding hammers 9 months after ejeculation, or the physical demands on his body would be terrible.

As a woman ages, her chances of surviving pregnancy and childbirth decrease. As she ages, she also gains more knowledge. Quite simply, menopause exists in humans because the knowledge and life-experience of a matriarch become too important to the tribe's survival to risk losing in childbirth.

Evolution indicates the female human brain is important!

Just a point about life expectancy. Once you'd survived infancy and childhood (and childbirth), your odds of surviving to 50/60 years were not too different to today.
High mortality among babies and children greatly lowers life expectancy.
So the grandmother hypothesis.holds

Grandmothering. Having a decade or so free from our own reproductive drama frees us up to help caring for our children's offspring (particularly those of our daughters), hence maximising our chance of having many surviving descendants. I'm pretty sure there's a chapter about this in one of Richard Dawkins' books (The Selfish Gene?).

Apes do it, elephants do it, there is even evidence that some types of Crow do it.

Am I the only one whose brain put this sentence to the tune of "Birds do it, bees do it, even educated fleas do it."

the first

TheFirstOfHerName I thought the sentence was written with Cole Porter in mind.

honeydragon You ask when was the last time ejaculating killed a man and I am trying to remember the name of the President of France who died getting a blow-job from his mistress whom the wits of Paris nicknamed Pompe funèbre. Whart a way to go!

Let's do it, let's educate the GC!

What TheMoa said.

I'd also heard the 'Granny' theory - but that early females would go through the menopause earlier than now. There would be around 10 years of female life expectancy after menopause allowing 10 years to be 'helpful' to the younger mothers.

Also heard that men would need to compete for mates, so as in early humans, life expectancy would be around 45-50, that would pretty much mean male fertility stayed high throughout life, and men would have their whole adult life to 'compete'.

Evolutionary advantage. I think just about everything in nature is a result of evolutionary advantage.

As a woman gets older the chances of her pregnancy resulting in the birth of a child with disabilities increases. As a species it is better to have fewer but 'healthier' children.

(clumsy way to put it but it's so easy to get in to a eugenics debate)

A woman who can continue to 'work' whether that is work as we know it or hunter/gatherer/looking after grandchildren etc but is not able to become pregnant is useful, the species has someone to care for the children leaving the younger fitter adults to go hunting.

As for men continuing to be 'fertile', well does it give an evolutionary advantage? Yes it does, the younger woman makes a choice, if she has a child with a younger man then the child will probably be healthy and she can have more than one, but if we are talking cave dwellers then a man who has reached a certain age will have or should have the means to protect her and her offspring. So more healthy children or fewer children who are better protected.

If you rephrase 'why do women stop being able to reproduce?' to 'why don't they die after becoming unable to reproduce?', the evolutionary explanation becomes clearer. It's usually reasonable to start looking for evolutionary explanations with the question 'why don't they die?' . It's what it boils down to.

Humans have a long generation time and we produce few offspring. It takes massive effort to nurture a human being to become a sexually-reproducing organism. Therefore, the emerging biological ability to stay alive beyond childbearing years confers a very large selection advantage for ones children and grandchildren, who carry those same genes, which confer the same selection advantage, and so on.

Therefore, I agree with the posters above.

I understood that it was because so many women died in childbirth, so it's to make sure older women have time to look after their grandchildren if the mother died.

We are meant to last beyond the menopause - even in the days of zero decent medical care, people lived to decent ages - my husband has done lots of work on his family tree and plenty of his ancestors made it into their 70s and 80s in the 19th century. Life expectancy figures are usually based on your chances from birth - many children died before they were 5. Once you got beyond 5, your chances of making it beyond your 40s were much increased.

I think that generally (based on no particular evidence) in a lot of societies there are generally more women than men. Therefore as women can't go on bearing children all the time, it's useful that men can to ensure the fertile women can reproduce from the smaller pool of fertilisers available.
This is skewed by cultural interventions such as China's "one child" policy or societies which value male children and kill off females, where you end up with a glut of single men who have no wives as the women have been aborted, left to die etc.
I wonder if evolution will start to catch up with modern society and men will in coming years lose the ability to father children after a certain age? There's a thought for your colleagues