What is the evolutionary reason we live, on average, 40 years longer than our reproductive ability?

[justanotherneighinparadise]

I was pondering this whilst putting in my make up 🤣

If the sole reason for existence is to reproduce, why do we generally live forty years or so later than our eggs viability?

The only thing I’ve come up with is to be old enough to raise our own children to adulthood and then perhaps be the matriarch of a troop and help raise grandchildren etc?

@MrsDeadlock

Also a long time ago, we didn't live 40 years past our reproductive age. Advances in medicine, living conditions, public health mean that average life expectancy has increased massively. Previously we would have been a lucky to live past infancy, and exceptionally lucky to live to around 40

Yes agree We were playing HH top trumps the other day and a female Chinese emperor who lived to 81. On google Wu Zetian (624-705) In those days remarkable!

Women have always lived a long time if they survived to menopause.
Eleanor of Aquitaine had 10 children and lived to be over 80 in the 12th century.

Other primates don't have infants that need as long to raise to independence as humans

^ Older women were crucial in child rearing as younger women were out hunting and gathering

I think some people don't have much of a grasp of history either!^

And some don't keep abreast of recent discoveries.(archaeological evidence)

@justanotherneighinparadise Primates don't appear to experience the menopause - at least in chimpanzees, a female can become pregnant from her early teens, and remain fertile through her 40's; the average lifespan of a chimp in the wild is mid-40's. Chimps usually only have one baby at a time, and bigger gaps between their pregnancies, so at any one time there are likely to be several female chimps in a pack who don't have any young offspring of their own to look after.

Scientists think it may be that as a cooperative species, there's an evolutionary advantage in grandmothers, aunts and siblings sharing the child rearing as it increases the number of infants from the same genetic lineage that survive to adulthood, and also that older females staying fertile for longer may be a way to pass down longevity.

FWIW I'm not a primatologist, just an armchair enthusiast

@MrsDeadlock

Also a long time ago, we didn't live 40 years past our reproductive age. Advances in medicine, living conditions, public health mean that average life expectancy has increased massively. Previously we would have been a lucky to live past infancy, and exceptionally lucky to live to around 40

They did though, it's just that infant deaths were so common they brought the average down. Look at famous historical people and their ages, many were very old when they died. The biggest obstacle was making it through childhood and for women, life expectancy rose after the fertile years as childbirth was also a major killer.

@NotDavidTennant

It's generally thought that it was evolutionary advantageous for women to invest their time and resources on their grandchildren rather than keep on having children of their own. Hence female fertility drops off at the age that when women would have started to become grandparents.

This has always been my understanding too

@ErrolTheDragon

^ Older women were crucial in child rearing as younger women were out hunting and gathering

I think some people don't have much of a grasp of history either!^

And some don't keep abreast of recent discoveries.(archaeological evidence)

@ErrolTheDragon, I think @Changi was only mocking the fact that a pp appeared to be conflating hunter-gatherer societies with the medieval period, not casting doubt on the existence of female hunter-gatherers.

Hunter gatherers are far more interesting that medieval times

Reproduction is not why we are here. That is merely how we get here.

There is no reason why we are here at all. Zilch. We and the universe just are.

@Roystonv

Off topic we are keeping sad, ill, mad people alive. Resources should go to those who still have a life to enjoy. I want to choose when I go and not be a burden to family or society.

Wow. Really? Do you have a link to the criteria that tells us how sad, mad or ill someone should be before we just let them die?

120 years ago the average lifespan for a woman was 57. The average age to start menopause then was 55 so people thought that when you hit menopause it was the end of your life. The average lifespan for a woman is now something like 84 and menopause hits about 48. It is down to better quality of life, modern medicine and knowledge. Not evolution.

I would imagine to support the next generation having children. Thinking about how we lived and to an extent how we live now. It's much easier to have lots of children who remain healthy if you have community and family support.

When people lived in tribes or communities child rearing was much more communal. So I imagine the more successful communities were those with longer lived people.

Also there's a big difference between potential life span and actually life span. So in the past, for example early humans poss had potential to live long but didn't. Due to injury, lack of medical care etc. So it makes me wonder what our natural life span actually is in a way.

@ramblingsonthego

120 years ago the average lifespan for a woman was 57. The average age to start menopause then was 55 so people thought that when you hit menopause it was the end of your life. The average lifespan for a woman is now something like 84 and menopause hits about 48. It is down to better quality of life, modern medicine and knowledge. Not evolution.

Another person who doesn't understand the math....

@ramblingsonthego

120 years ago the average lifespan for a woman was 57. The average age to start menopause then was 55 so people thought that when you hit menopause it was the end of your life. The average lifespan for a woman is now something like 84 and menopause hits about 48. It is down to better quality of life, modern medicine and knowledge. Not evolution.

I suspect that we’re going to have to keep repeating this point throughout the thread. Average life expectancy was 57 because the babies who died of diphtheria or whatever brought the averages down. Not because people routinely dropped off the perch in their fifties. Women who made it through infancy and childbirth were highly likely to make it to seventy.

I suspect that it’s related to the sheer uselessness of human infants, which as a pp said is probably linked to our upright stance which means that human reproduction is a godawful bodge job compromising on the size of head you can get through our pelvises without quite killing either mother or baby. Trust me, I have the scars to prove it.

I'm just looking at the obituary of a woman who died in 1933 aged 91. And a man of 78 who died in 1935. They were both organists in their local church. My children's piano teacher, who died aged 98, was also an organist.

I think I'm going to start learning to play the organ.

Women who made it through infancy and childbirth were highly likely to make it to seventy.

There was programme on the TV recently (The truth about fat) that examined the lifestyle of one of the last remaining hunter gatherer societies. The average lifespan was just over 40. However, if they lived past 15, they stood a good chance as living as long as anybody in the Western world.

Yes, life expectancy has increased but people have always lived to old age (just fewer of them) and those dying what we would term early did not die of old age but disease, accidents and famine.

So yes, we are biologically "supposed" to live until our body gives up which is, as the OP says, a long time after our natural reproductive years. This is also true for other large mammals like gorillas and elephants.

I don't know the evolutionary reason for women living long beyond the age when they can become a parent. It's not the same for men though, which when you consider the age that Mick Jagger has become a father (again) and Boris Johnson, you wish sometimes was not the case.

@justanotherneighinparadise a quick Google gives me Walker and Herndon 2008 (important disclaimer, am physical scientist not biologist and have only scanned the abstract and conclusions) but it looks like other great apes do have something like a menopause, albeit later (relatively speaking) and not quite such an abrupt cliff edge. Below is the conclusions section:

We draw the following conclusions:

The multitude of definitions for menopause has contributed to a general confusion about its occurrence among nonhuman primate species. A uniform definition would facilitate our understanding of the way in which menopause reflects species-specific patterns of reproductive senescence.

We define menopause in primates as the permanent, nonpathlogic, age-associated cessation of ovulation. Menopause is associated with concomitant structural and functional changes, including (in species that exhibit menstrual bleeding) the termination of menstruation.

Whereas humans have a uniquely extended postmenopausal life expectancy, other primate species do experience a postreproductive period. The length of this period is not necessarily related to the existence of menopause per se.

Many of the apparent discrepancies in reports regarding the occurrence of menopause in nonhuman primates may be accounted for by environmental and social factors that distinguish captive versus wild animals, and by a paucity of data from sufficiently powered studies.

By almost any generally accepted definition, several species of nonhuman primates experience menopause.

I’ve always thought it’s typical of male scientists that they ask “why would women keep living after they stop being able to reproduce” and not “why do women stop reproducing such a long time before the end of their lives?” The fact that men and women have similar (potential) life spans but women knock off the old baby-having clearly shows that it’s advantageous. Amazingly in years of reading about this, I’ve never seen anyone make the excellent point a PP made - that if you have your last kid in your mid 40s you’ll be 60 at least before they’re ready to look after themselves. So much of evolutionary biology seems to be run by blokes who don’t understand the point of women beyond the actual shag-and-baby-having stage. Makes total sense though that experienced mums being about for longer generally helps their descendants survive.

I also think it’s worth saying that in small social groups, the best way to increase the group’s size is by having people around longer. What I mean is, if you have a single family group of maybe 3 generations where life ends at 40 (forty year olds, their kids, a couple of grandchildren) you’re talking maybe 20 people. If you kept that same group alive into their 70s or 80s the “tribe” has really grown into a group of 50 or 100. A much more powerful social group with plenty of working adults to keep things together, older people who can babysit and have learnt survival skills (eg medicine, which foods to avoid, getting through tough weather years). So surviving longer - even if the older adults stop reproducing - means your family group has more power and efficiency because there are just more of you.

Good points, WitchWife

Do these chaps ever question why they're still alive when past the age to hunt and their fertility is, if not extinct, liable to be waning sans viagra?

@nosswith

I don't know the evolutionary reason for women living long beyond the age when they can become a parent. It's not the same for men though, which when you consider the age that Mick Jagger has become a father (again) and Boris Johnson, you wish sometimes was not the case.

Men can still father offspring but old man's sperm is not as good as young man sperm

The Grandmother Hypothesis explains it. By helping rear the offspring of kin they are increasing their reproductive fitness by contributing to the survival of their genes. Genes that contribute to this behavior would experience positive selective pressure as more of the offspring would survive.
Maximal lifespan has always been ~120 years. Average lifespan has increased largely due to changes in nutrition and public health (access to clean water, washing hands etc...). There were some decreases in average lifespan around 1918 (Spanish flu, WWI) and increases in the 1950s (antibiotics).

Large numbers of my ancestors/relatives, died in infancy/young (under 25) in the 17th, 18th, 19th , 20th centuries ( of various ghastly diseases - TB, diphtheria, heart problems , accidents at work etc.) One poor chap in 18th Century had 16 of his 18 children die in infancy. Both wives dead by 40.
Several women died in childbirth.
In these circumstances the children were raised variously by aunts, grandmothers/fathers (even sometimes helped by their great grand parents!)
I have a female ancestor born 1830 died 1927, male one born 1860 died 1957 - both helped with child care. These long lived ancestors were crucial in the survival of their descendants. Women and men working long hours hunter/gathering, on the land or at cottage industries ( well before the arrival of the factory system) needed some one to care for toddlers, the sick , injured etc etc.