Dirty Old Men

An interesting PLOS ONE paper from a few years back has been brought to my attention Why Men Matter: Mating Patterns Drive Evolution of Human Lifespan, by Shripad D. Tuljapurkar, Cedric O. Puleston, and Michael D. Gurven.

They begin with a brief explanation of the evolutionary theory of senescence, a subject with which I am intimately familiar. Hamilton (considering only female demography) showed that selection against a rare autosomal mutation that reduces survival at some age is proportional to that female’s survival-weighted reproductive output past that age. A mutation that caused trouble after the end of reproduction will not be purged by selection – at all. By this argument, since menopause happens, everyone should be dead by 55. Hey, it works for salmon and marsupial mice.

But we aren’t. There have been several attempts to explain this: Kristen Hawkes’ grandmother hypothesis, and various arguments involving codgers transferring resources or information. It’s hard to make the numbers work out. Tuljapurkar et al argue that dirty old men are the answer: as long as they keep reproducing at a significant level when past the age of female menopause, there is some selection against those late-onset deleterious mutations.

I doubt if they’re right, because I think the societies with lots of old goats reproducing are somewhat atypical, not too likely to have been the pattern before agriculture. Although the Australian Aborigines manage it. I could be wrong. There was an illuminating graph in this article, better than a Bo Tree:

Male Fertility

The black line is male fertility as a function of age in France in 1980: blue dots are Pakistan 1984: red dashes are Cameroon 1964. Tuljapurkar et al mention that Cameroon’s distribution is typical of high-fertility polygynous societies. Like I said before.

Even if dirty old men are not the main or only factor selecting for longer human lifespans, they must push in that direction. This may well explain the black-white mortality crossover. Unfortunately, this kind of reproductive pattern decreases the strength of selection in early life, which ought to increase child mortality, all else equal. It also increases the mutation rate by up to 50%, which must really interfere with the most complex adaptations. Tuljapurkar and company weren’t thinking about the long-term effects of the increased mutation rate, but as far as we can tell, nobody ever has.

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31 Responses to Dirty Old Men

  1. Anonymous says:

    So how come women live longer than men?

    • ziel says:

      Just based on numerous in situ observations of this odd cohort over the years, it seems to me that old women are just plain more useful than old men.

      • Greying Wanderer says:

        More to the point imo they seem to be more driven to make themselves more useful – which i think points towards the grandmother idea.

  2. Je Thoker says:

    “It’s hard to make the numbers work out.”
    Unless you’re EO Wilson or Corina E. Tarnita. Maybe you should stop worshiping Hamilton’s sacred spherical cow.

    • gcochran9 says:

      E. O. Wilson is of course innumerate, and I’ve never thought that he was particularly smart. . Tarniţă is certainly numerate and ought to be smart.. Neither have worked on the evolutionary theory of senescence.

  3. dearieme says:

    I happened to be thinking the other day about the lifespans of the leading musicians of the era of classic jazz. It seemed to me that more of the whites died early (Bix Beiderbecke, for example) and more of the blacks lasted longer (Louis Armstrong, for instance). Eubie Blake lasted so long that he famously said “If I’d known I was going to live this long, I would have taken better care of myself”.

  4. Sid says:

    “This may well explain the black-white mortality crossover.”

    Can you explicate on this?

    • Sideways says:

      Blacks die earlier, on average, than whites, but for given whites and blacks who have already reached a certain old age, the blacks will tend to outlive the whites.

      While a random white kid is more likely to live to 70 than a random black kid, a random 70 year old black person is more likely to see 80 than a random 70 year old white (I pulled those ages out of my ass, but they’re in the ballpark).

      • Greying Wanderer says:

        Could that be the result of mixing two base populations – a majority shorter-lived one and a minority longer-lived one where the minority part was longer-lived than the white average?

      • Sid says:

        Got it, thank you.

      • Greying Wanderer says:

        “the black-white mortality crossover”

        Does the same pattern exist in places like Brazil but with different numbers?
        Do the numbers in the US correlate with the white admixture?
        Do the ancestors of the people from whom the white admixture came have greater longevity than the white average?

  5. bruce says:

    Dirty Old Men have time to accumulate Das Kapital; K strategy. Where Men with Capital are seen, Beer must be presumed: Early ‘spears’ are more properly pointy walking sticks for Dirty Old Men to at once maintain balance when Beered up and, at need, defend their Beer. 200,000 years ago (Rushton, 1995) African man evolved; being a man, he needed beer. Anything organic will ferment some kind of kick in a dugout log (though according to some authorities a secondary transport use may be acknowledged).

    We see Man (Toperpithecus) and His Beer. 110,000 years ago (Rushton, 1995) Man’s Beer Belly and manboobs developed: Now men falling into the water during the secondary, transport use of the dugout log were less likely to drown, even well-beered up. The surfacing of R’lyeh off Addis Abbaba provided hot Deep One chicks (Charles Strauss, 2008; previously Mr Derleth and Lovecraft) for Toperpithecus to beer up and breed with. Their children had a more durable, chunky, fish-man build, proper to improved riverine and coastal survival. With a more stoutly evolved Fat/Muscle ratio, we see improved fat in all fatty organs, including a Fatter Brain. With all the increased intelligence that implies.

    Homo Fathead, with his evolved bodyfat level and Deep One tendency to Aggregate That Which Should Not Be Aggregated, conducted the first White Flight from Africa, heading north. 40,000 years ago, orbiting the event horizon of the black hole of Calcutta (Coon, 1960) , Kurunaga Jeevesdotter, first Hot Asian Chick, gave Batou Woosterson his conge’ and went East for purposes of Being Sensitive to plinky-plonky pop music, becoming awfully brainy on the trip since she practically LIVED on fish. Batou by drowning his sorrows in kumis, evolved lactose-tolerance. Though his nasal passages narrowed some.

    Just So.

  6. teageegeepea says:

    The article is linked from here.

  7. Greying Wanderer says:

    “I doubt if they’re right, because I think the societies with lots of old goats reproducing are somewhat atypical”

    If you assume the main engine is “how do the kids get fed” then i think there is a logical pattern to the potential solutions.

    Say your premises are (pre-farming)
    – food-getting is divided into hunting or gathering
    – hunting is young and male
    – simplicity dominates

    then environments separate into logical categories like

    Type 1, where a female can gather enough to feed her offspring herself
    Type 2, where a female can’t gather enough and the extra can be gathered or hunted
    Type 3, where a female can’t gather enough and the extra has to be hunted

    where for this purpose it doesn’t matter if the type 3 environment is a desert or the antarctic.

    Assuming the environment where you might expect humans (or primates) to start off would be the simplest survivable environment which would be environment (1) then you ought to be able to construct a logical tree comprising the possible paths through the environment categories and from that how those populations might have had to adapt to those different environments as they moved along the path and from that a set of recurring patterns of human social forms.

    For example taking the three categories above you might get:
    1) Type 1 default, stayed put.
    2) Type 1 default, moved to type 2, changed, stayed put.
    3) Type 1 default, moved to type 2, changed, moved to type 3, changed again, stayed put.
    4) Type 1 default, moved directly to type 3, changed, stayed put.

    For each of these path types there should be recurring patterns of behaviour imo.

    If you imagine a population adapted to a type 1 environment moving into a type 2 environment on the edge of their range where the females can’t quite feed their kids on their own – including with irregular male hunting treats – and where the shortfall in calories could come from either extra gathering or extra hunting then one branch on the solution tree might be where those females whose mothers already had better longevity genes from random mutation get more help and their children survive better leading to increased female longevity (with increased male longevity as a side-effect).

    (A second option would be the males helping more which could have happened as well or instead but i’m going to assume the simplicity of the grandmother solution made it the most common.)

    (The grandmother solution wouldn’t work if a population moved directly from a type 1 environment to a type 3 environment however so if a population made that move directly there would have to be a different solution.)

    However is the grandmother solution actually a stable solution? If the default state is violent, promiscuous and short-lived and the grandmother solution to a move from a type 1 environment to a type 2 environemnt simply shifts it one step to violent, promiscuous and longer-lived then what happens to the older males who survive the culling process and who can still father children? There seems to be an over-hanging incentive here for them to try and use cultural manipulation to rig the game in their favour such that the younger males still do all the hunting and killing while the older males (who survive the cull) get to make all the babies. The mothers and grandmothers still do all the feeding – this is just a variant on the grandmother solution related to male competition over who gets to be the daddy.

    Achieving this might be easier said than done as it might require things like the older males ganging up somewhat and inventing religion and such but the incentive is there so it seems plausible at least that one quite common branch of the (pre-farming) logical solution tree to the kid-feeding problem could go
    – default
    — grandmother solution
    — grandaddy solution

    In terms of numbers working out



    1) In this context doesn’t longevity select itself? If grandchildren survive better if the grandmother lives past 55 then isn’t the selection mechanism against hereditary deleterious alleles in the grandmother the survival or otherwise of her grandchildren i.e. if 50 out of 100 grandmothers have a deleterious gene related to longevity and their dying younger means their grandchildren are less likely to survive then the grandchildren will take that inherited allele with them when they don’t survive and vice versa for the grandchildren of women with good longevity genes?

    2) If the above isn’t enough and the grandmother solution did have a tendency to morph into the grandaddy solution then couldn’t the culling effect make a difference? If you have a population where the men are culling each other then if most of the fathering is done by 20-somethings then although the amount of mutational load would be lower the survivors might also only be the survivors of a 20% cull. The survivors at age 50 might be the survivors of an 80% cull so although their mutational load is higher it’s higher on top of genes that survived an 80% cull as well as age, disease and accident – so depending on the extremity of the violent death rate it might even be better on balance?

    If correct then the real problem for a population like that might come if they retained the older daddy part of their culture but *stopped* being as violent as they needed to be so they got the older mutational load without the counter-balancing effect of surviving an 80% cull.

    • misdreavus says:

      Do you have aspergers, by any chance?

      • Greying Wanderer says:

        Take 100 men at age 18 and have them live in a forest and try and kill each other then take two test points at 80 survivors and 20 survivors.

        What age are they at 80 survivors?
        What age are they at 20 survivors?

        What is the balance between the level of mutational load of paternity at those ages and the base genetic load of the survivors themselves?

        If the survivors of the culling process have the *least* genetic load of the original 100 then the benefit of that may outweigh the additional load from paternal age – depending on how the numbers work out.

      • misdreavus says:

        Yep, you have aspergers.

      • misdreavus says:

        And presumably not the kind that gives you special cognitive abilities, either. Because I see no proof for such a thing in any of your posts.

  8. bob says:

    A late-in-life ‘reproductive pattern decreases the strength of selection in early life.’ Could you explain this for the idiots. (I being one of them).

  9. Greying Wanderer says:

    So basically you’re saying no – selecting very harshly for the 20% of males with the least genetic load to father most of the children wouldn’t compensate for their later average paternal age?

    It may not be true for some other reason but logically it must be true or at least possible depending on how the numbers work out.

  10. whatever says:

    Could be the hunter-gatherer thing, that old, millennial long division of labor. Men hunt and women gather, gathering is as safe and productive on those of the age of 70 as it is on those of the age of 20. Hunting is not. Hence, women are more useful for the fitness of the offspring than men beyond their fertility age.

  11. Jack says:

    Regarding the black-white crossover: in the 2000 census, blacks (including those who checked both black and another race) made up 12.9% of the total U.S. population and 8.23% of the population 65 and over. Within the 65+ population, blacks made up the following percentages of each age group:

    65-69 9.45%
    70-74 8.43%
    75-79 7.57%
    80-84 7.14%
    85-89 7.24%
    90-94 7.46%
    95-99 9.41%
    100+ 14%

    http://www.census.gov/prod/2006pubs/p23-209.pdf (percentages converted from raw figures on p.18).

    • Steve Sailer says:

      Henry has been pointing out this mortality crossover for years. It seems real, but I don’t recall how we proved that it wasn’t just old black people embellishing their ages for whatever reason. When I was a kid, there was an old black guy named Charlie Smith who claimed to be 130 years old. He popped up a lot on TV, like at the Apollo 17 launch.


      Later on, it was said that his story was debunked, since nobody appears to be that old.

  12. Steve Sailer says:

    How did the researchers know for sure the ages of fathers in Cameroon in 1964? There would seem to be a couple of issues:

    – Are we sure that the elderly nominal fathers were the real fathers?

    – In a culture that celebrates fatherhood at an old age, wouldn’t that encourage men to add some years to their ages, just as in a culture that celebrates youth, actress Jessica Chastain isn’t as young as she implied?

    • Anthony says:

      In 1964, Cameroon was only three years independent from France (and previously Germany). French colonial administration left bureaucracies which kept records of *everything*. The genocide in Rwanda was more efficient because the successors of the Belgian bureaucracy kept good enough records to know who was who, even 30-odd years after independence.

  13. JayMan says:

    Dr. Cochran:

    So here’s a paper you might be interested in:

    Host Demise as a Beneficial Function of Indigenous Microbiota in Human Hosts

    It basically claims that certain organisms have the purportedly beneficial effect of killing off seniors. This seems predicated on the idea that having old folks around eventually becomes a fitness cost to their progeny, but I’m not sure that’s that clear at the moment. Even so, would the (tiny, I’d imagine) purported benefit be enough to exert positive selection on said organisms?

    • gcochran9 says:

      That’s Martin Blaser talking. I’ve corresponded with him. He’s a compete loon: I tremble for my country, knowing that he has a job. Any job. I wouldn’t trust him with garbage.

    • harpend says:

      We speculated about selection against senescent lifespan in

      Pennington, Renee & Harpending, Henry, Published by O.U.P. 1993 1st (1993)

      but without the microbiota angle. Not completely crazy I think given human empathy.

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