Well, we can actually explain this

Humanity would fare just as well without its elders as it does with them, according to scientists.
The claims come as part of a study which found no obvious evolutionary need to live beyond the age of 50 in humans.
The discovery disputes the ‘grandmother hypothesis’, which suggests humans live long beyond their reproductive age because they care for grandchildren.
The theory also suggests that older members of our communities pass down important cultural knowledge that helps us survive.

They’re studying communities which have much longer lifespans than those which applied over our evolutionary history.

In their study, the researchers analysed detailed family records of people born in Utah from 1860-1899.

That’s well past the first bit of the demographic transition. For example, someone born at the end of that period would have been into the antibiotic age by the time they were 50. Actually, 1950 is probably just about when medical care could do something more than just be a palliative for the first time (yeah, OK, extreme argument but I’m an extremist, me).

Rather, to test the idea we need to look at lifespans over a more representative period of our development. Also, at ages of menarche, primagravida and so on. Married off and probably pregnant by 16 or 17 sounds about right. Maybe a little later in places and times. Granny at 35 or 40, looking at people past 50 doesn’t really illuminate this, does it?

Yes, I know the English had later marriage historically and so on but that’s not over evolutionary periods and it’s also something noted because it was notable.

Yes, I also know about lifespans being shorter back then because of the skew of child deaths but again over evolutionary periods we’re also talking about much shorter at age 16 or 20 as well.

My own theory, with zero evidence of course, is that in order to survive life in earlier times one had to be pretty robust. As life became easier with better nutrition, shelter, clothing, then finally medicine, that robustness leads to these longer lifespans. Around and about and given the environment in which we found ourselves, we were good enough to get to menopause/soon after it and not much more just given the plethora of things which would and could kill us. Some beat the odds and lived to great ages. Very few though, what has changed now is the odds.

23 thoughts on “Well, we can actually explain this”

  1. The granny hypothesis is an evolutionary fable*, in this case to explain the massive difference in life expectancy between men and women, supposedly driven by the provision of care beyond 1 generation.

    *: It might be right but you can come up with a plausible evolutionary hypothesis to explain almost anything. My rule of thumb is that if you can also explain the exact opposite with an equally plausible fable (men live longer because in days of yore they could teach their grandchildren how to hunt better) the hypothesis is probably bullshit.

    The actual reason is probably vastly older than human grannies looking after the little ones – XX animals live longer than XY animals, not just for mammals but works for birds and insects too.

  2. I’m not sure at all about the granny hypothesis itself anyway. Because I’m not sure whether, once you take in the death rate in childbirth, women did have longer average lifespans. Those who survived it, yes, OK, but what’s the average across all? Which rather speaks to my robustness theory too. You’ve got to be tough to survive childbirth in a zero medicine world. Manage that and the robustness is likely to carry on, even if the average over the entire population is equal.

  3. Evolutionary pop fables are fun because anyone can come up with them as a plausible explanation for almost anything. Proving them is a lot harder.

    Evolution is little more than the consequences of selection in favour of heritable traits that contributed to the successful production of (themselves productive) offspring over a period of 4bn-odd years. If it had had much time to work specifically on human lifespan (it hasn’t), and there was any human-specific granny (or robustness) effect, why do we see the same effect in many species? There’s a clear lifespan benefit from being female, in animals with vastly different reproductive strategies from humans. For humans, the raising of one brood is an entire lifespan’s job. That’s not the case for cranes or sticklebacks, or pretty much any other animal. Most other animals that tend to die after one reproductive cycle produce thousands to millions of offspring.

    Incidentally, for another pop evo hypothesis, the high childbirth death rate would contribute to a granny effect (replacement carer in event of death, propensity to survive childbirth goes with other robustness, as you way), but we’re still making too many assumptions. It works if you have a Victorian world of monogamous-nuclear/extended families, but that’s a recent cultural invention which survived barely 2500 years in the civilised world (Europe/Middle-east)

    The selective pressure is going to be far lower when fathering and childrearing is the tribe’s job rather than a smaller unit. Surviving childbirth (being more robust, thus getting to a riper age) is going to be a much bigger selective factor.

  4. …but why it should select for female and not male lifespan is a puzzler, if we accept the granny fable.

  5. “It works if you have a Victorian world of monogamous-nuclear/extended families, but that’s a recent cultural invention which survived barely 2500 years in the civilised world (Europe/Middle-east)”……….”when fathering and childrearing is the tribe’s job rather than a smaller unit.”

    But where is the evidence for that? In those ‘Stone Age’ tribes we have been able to study in the modern era, child rearing was the primary responsibility of the parents. Yes, sure, the rest of the tribe gets involved, but then do/did we in the West; what are schools if not a form of that involvement?

  6. I’m with DocBud on that one.

    I’m not topping myself just because I am a little (cough, cough) over 50.

  7. Judging by the grandmothers I know, their evolutionary purpose seems to have become on-call childminder, taxi service and bank (often for their for their single-parent daughters).
    These duties have extended to later in life as they and then their daughters have had children later.

  8. So Much For Subtlety

    In their study, the researchers analysed detailed family records of people born in Utah from 1860-1899.

    Which is to say, they looked at families that would be middle class by modern standards. Intact two parent households.

    If you want to know whether grandparents are useful you have to look at families closer to the historic norm. I suggest inner city Chicago. For Black single mothers I would politely suggest that the presence of a grandmother – or even in those rare cases, a grandfather – would be literally life saving.

    Not even Obama could have done as well without the love and support of his White grandmother. A grandmother he was happy to throw under the bus as soon as it was politically convenient.

  9. @Recusant,

    I think I was commenting more on this era’s cultural regression than knowledge of stone age tribes. I’m skeptical we can know that much about the mating habits of groups that died out without discovering writing, and pre-writing covers most of human history, ergo the most cumulative selection pressure.

  10. BiG

    Accepted, though I think we Northern Europeans/Americans can see our “cultural regression” and assume it applies globally: like so many of our other cultural trends, it doesn’t.

  11. “when fathering and childrearing is the tribe’s job rather than a smaller unit.”

    But where is the evidence for that? In those ‘Stone Age’ tribes we have been able to study in the modern era, child rearing was the primary responsibility of the parents. ”

    The persistence of the “Primitive Communism” hypothesis which was based on exactly…. zero evidence.

  12. Tim, your “robustness plus good times leads to longevity” notion should apply to other species (the wild is tough on all). But evidence from animals in captivity doesn’t seem to indicate a pattern. Some animals do well with easy food, zero predation and medical care, others quite badly.

  13. This research is the thin edge of the wedge. There will be more evidence that old people are of no value. That they suffer in old age.
    this will meet the push for euthanasia. And , amidst talks of fairness and equality , discrete gas chamber will pop up to fashion a ‘just life span’ for everyone.
    Voila pension problems solved.

  14. John Malpas: Let the fuckers try their luck.

    Most of these millennial whine-wanks couldn’t euthanase themselves never mind anyone with even a bit of fight in them. And if you are too feeble to beat the punks you likely have to extremely old and knackered anyway. Which renders the entire exercise pointless.

  15. In primitive cultures it was probably useful to keep a granny or two around for the odd emergency such as the family being stalked across the tundra by a pack of wolves.

    Just chuck one of the old biddies off the back of the sled to keep the beasts occupied while you make your escape.

  16. The article has no mention of the menopause, which i think is only a trait found in orca and humans. That’s pretty interesting from an evolutionary point of view and the reason why its called the “grandmother hypothesis” rather than the grandparents one.
    Yeah– long livedness could be selected for by proxy for just survival, but the menopause is very likely to be selected for, in order for it to be a distinct characteristic of the species.

  17. We’ll never know, of course (lost in time, like [slight head movement] tears in rain) but it’s possible that human characteristics like big boobs, big dicks and long life were selected for by cultural preference in our prehistoric past.

  18. “In their study, the researchers analysed detailed family records of people born in Utah from 1860-1899.
    Which is to say, they looked at families that would be middle class by modern standards. Intact two parent households.
    The ‘standard family’ in Utah then was likely to have multiple wives.

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