Gambia

We’ve been gathering info on average paternal age in different societies: here’s some for some rural villages in Gambia, from an article by Ruth Mace.

This shows age-specific  fertility for males and females over the lifespan.  The average paternal age is 47, the oldest we’ve found so far.  It’s a consequence of polygyny, which both delays and extends male fertility.  Extrapolating from Decode’s results, this population would have a mutation rate 67% higher than one with an average paternal age of 28.

The only likely event that would cause genetic problems comparable to those expected from a long-term pattern of high paternal age would be a central nuclear war.  Maybe. We don’t really know the extent to which a  given amount of radiation increases the human mutation rate, although we could easily find out in the near future, by sequencing family triads with known exposure to medical radiation.  Judging from mice, the doubling dose is about a hundred rads, about one fifth of a fatal dose.   The existing background level of  radiation is a minor factor in the human mutation rate: it would have to increase a lot to become the most important factor.

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43 Responses to Gambia

  1. typal says:

    In poygyny there are going to be many young males trying to mate with the wives of old geezers. Cosmic rays are a major cause of mutations, and they don’t get through at the equatorial regions.
    A lot of bad mutations = genetic drift.

    • Greying Wanderer says:

      “In poygyny there are going to be many young males trying to mate with the wives of old geezers”

      Gene-culture coevolution. The old geezers would form a gang to prevent that and between them create a culture that pushs the young men in a different direction until they’re older e.g.
      - raiding for cattle / females
      - homosexuality / young boys
      - spending 20 years locked up in a zulu regiment
      etc

      (A possible tie-in there to the germ theory?)

  2. gcochran9 says:

    Cosmic rays are NOT a major cause of mutations, and a lot of bad mutations is NOT equivalent to genetic drift.

  3. Steve Setzer says:

    I wonder if there have been enough generations among the polygynous Mormon offshoots to make for an interesting comparison with their monogamous kinfolk among “regular” Mormons. Same environment and ancestry.

  4. ironrailsironweights says:

    Do Gambians have a high rate of genetic problems?

    • gcochran9 says:

      They must, if their paternal age is this high. But you’d need good records to see it. The simplest case would be a dominant lethal – there would be about 5/3 as many cases.

      • dave chamberlin says:

        Facinating and wide ranging implications follow from your hypothesis that there is a strong correlation between polygyny and higher mutational load. As an amatuer evolutionary theorist it has bugged me for a long time as to why societies that favor polygyny (a male with two or more wives, a sub category of polygamy) slump. Without any negative side effects one would think they would flourish, afterall the male that is fittest is now the father of more children. This is exactly the case in other species, deer for example, but it for some reason it doesn’t work for humans. The largest and most obvious example in human societies that domonstrate a slump because of the widespread practice of polygyny is the muslim world. Historians have long known that the muslim world lost its mojo (OK thats not scientic, its ability to lead in either economic industry or science) around 900 AD. Hunter gatherer societies are far more prone to practice polgyny than are agricultural ones, but this I fear is too general a statement to mean anything. But still societies follow the same laws of evolution that species do, and small advantages one holds over the other can mean the differences between dominance and extinction given enough generations. In short I believe you are on to something big Cochran.

      • gcochran9 says:

        “Hunter gatherer societies are far more prone to practice polgyny”

        Nope.

      • dave chamberlin says:

        Thanks for the correction. I was basing my assumption on a group of completely atypical hunter gatherers which I know the most about, the american indians at the time of first contact with europeans. A few other questions that may or may not be worth answering. Don’t herbivores typically favor polygyny when the males play little part in raising the young, are their any exceptions amoung the very long lived ones because of increased mutational load? Secondly am I right or wrong about the muslims.

      • pablo brandt says:

        If high age would cause so many mutations, how could the mutated offspring be breeding at a 47 year old average? The system must be strong for this, even more being this a cultural mark, done for generations and generations.

  5. That Guy says:

    Saw this elsewhere:

    “In 1754 an Act was passed called Lord Hardwicke’s Marriage Act which precluded anyone from under the age of 21 in England and Ireland from marrying without parental consent.

    In Scotland, anyone over the age of 14 (male) or 12 (female) could marry without parental consent and with only one day’s residence (in the 1850s this was changed to three weeks’ residence). In addition no clergyman was necessary and marriages could be conducted by simply making a declaration before two witnesses (a blacksmith was often a popular choice, hence the idea of ‘marriage over the anvil’).”

    So was a very young marriage age actually observed in Scotland??

  6. Steve Sailer says:

    How do we know the 50-year-olds really are the fathers? Do they have eunuch harem guards in Gambia?

    • gcochran9 says:

      IN a recent (PNAS 2012) study of the Dogon, a tribe in Mali, they found father-son Y-chromosome DNA mismatches 1.8% of the time. People talk about paternal uncertainty all of the time, but it seems that hardly anyone does anything about it.

      • H.O. says:

        I’m not convinced yet for the following reasons:

        First of all, the life expectancy of males in Gambia is low. It is currently 57 but was only 34 as recently as 1960 (around the mid-point of the period in which the data was collected). I know this could be consistent with high paternal age if most of the deaths are occuring in infancy but I doubt that explains it all. The low life expectancy suggests that the average paternal age is likely to be low in most of Gambia’s history.

        Secondly, I’d take the reported ages in Mace’s study with a grain of salt. Most adults in that region of that country are illiterate even today, much less in the 1950s. Gambian society reveres age, which gives incentives to individuals to inflate their age. So the numbers we see in the histogram are self-reported ages. We should also recall that Gambia got its independence only in 1965, and it took a few years to set-up basic administration. So there are no birth certificates to speak off during the period the data was collected.

        Thirdly, Gambia is very agricultural, especially in rural areas where women have high degree of freedom of movement. This is not conducive to a harem situation that would enable much older men to father all the kids that are reportedly theirs.

      • gcochran9 says:

        Those low life expectancies are almost always driven by infant and childhood mortality. I think that is true in this case as well – which is not to say that that different societies can’t differ some in midlife mortality, even in the absence of modern medical care.

        West Africa has had female farming for a long time, and it is also highly polygynous. The first fact makes the second possible – women support themselves.

        As for people not knowing how old they were, or lying about it, I guess it’s possible. And lots of paternal uncertainty is also possible, although I can’t think of any place where close investigation has shown it.

        And, while we’re at it, it’s entirely possible that those recent reports of higher levels of deleterious mutations in Africans came to me in a dream.

      • gcochran9 says:

        A bottleneck has no such effect, unless you get down to ~10 individuals. In that case, the bad recessives run into each other and are eliminated. Of course, usually the population goes extinct before this process gets far.

    • Greying Wanderer says:

      “Do they have eunuch harem guards in Gambia?”

      If they’re still alive the men’s mothers would act as harem guards imo.

      • harpend says:

        Mother harem guards are prominent where males own and control the resources and are thus able to coerce their wives to act right. The best descriptions are from the Indian subcontinent. In female farming societies men cannot and do not get away with that kind of thing.

        I have no idea what the subsistence system is in the Gambia.

  7. typal says:

    Black Africans just don’t look to me like they have a lot of mutations, they move well and are great dancers. Would a population with lots of nasty mutations be like that? If consanguineous marraige isn’t taking mutations out, then Waddington’s canalization must be the explaination for the apparent lack of effect from all these mutations.

  8. Greying Wanderer says:

    “Black Africans just don’t look to me like they have a lot of mutations, they move well and are great dancers.”

    It’s interesting that Olympic sprinters mostly come from the US or Jamaica and not West Africa despite both being descended from West Africa. I’m assuming the bottleneck of the slave trade meant the survivors had a below average level of genetic load?

    • That Guy says:

      @Greying,

      IMO the greater sprinting performance of Jamaican and to a lesser extent US Blacks is to be attributed to something in their partial White ancestry.

      Since most researchers see the White ancestry of Jamaicans and other Caribbean Blacks as coming from Irish Slaves and that of US Blacks from Irish/Scottish Indentured Servants and Irish Slaves to a lesser extent, it could be something in these populations.

      One such candidate comes to mind – Haemochromatosis or Iron Overload Disease in a heterozygous state, especially that of the HFE Gene. The Irish have the highest carrier percentages (10-30%) of Haemochromatosis in the world – in fact both my parents are carriers of different alleles.

      Sprinters need raw power to win, so need lots of fast twitch muscle + lots of oxygen. HFE especially and the 2 other minor alleles increase the amount of oxygen that the blood can carry – so lead to greater Sprinting performance.

      More Info:
      http://spittoon.23andme.com/news/announcements/updated-results-for-hereditary-hemochromatosis/#more-14618

      • Greying Wanderer says:

        “IMO the greater sprinting performance of Jamaican and to a lesser extent US Blacks is to be attributed to something in their partial White ancestry.”

        Maybe bu given the death rate on the slave ships i’d assume the survivors were notably more healthy on average than the non-survivors. Bottleneck may be the wrong word for that but i think that rather extreme selection process is a simpler explanation.

      • gcochran9 says:

        About 85% of slaves made it across alive. That is not an extreme selective event. I’ve seen a number of people suggest this or closely related ideas. They all had one thing in common.

  9. That Guy says:

    @Greg,

    In terms of Haemochromatosis and HFE especially, check out this article from 2009, where the authors find it positively selected for in endurance athletes, so it has been linked to athletic performance already – though not sprinting in particular.

    http://jp.physoc.org/content/587/7/1527.full

  10. hbd chick says:

    some of the USAID Demographic and Health Surveys include info on age at first marriage (if that’s of any use), like the 2005-06 report for india (see the chapter on “Other Proximate Determinants of Fertility”).

    you can request access to the raw data, too.

  11. Steve Sailer says:

    Speaking of paternal uncertainty, I saw this in a Daily Mail article on Marc Leder, Mitt Romney’s fundraiser host:

    “Mr Leder, 50, reportedly kicked up his partying lifestyle after his wife of 22 years cheated on him with her 23-year-old tennis instructor.”

    This rich-man’s-wife-and-her-tennis-pro stuff really does happen in real life. I know stories.

    • typal says:

      Do we know if Black Africans have germline mutations at the same rate as Europeans of the same age? I believe Blacks produce fewer damaged sperm, and have smaller testes

    • albatross says:

      She must have been quite an attractive lady if she was able to get an athletic 23 year old man in her mid-40s. (Assuming she wasn’t a child bride, after 22 years of marriage, she was almost certainly in her 40s.) I’m assuming a 23 year old tennis pro working with wealthy clients actually has some alternatives, and that he wasn’t being paid for the sex, just for the tennis lessons. (He may have hit her up for gifts or something, but probably not anything nearly as simple and straightforward as paying for sex.)

  12. Greying Wanderer says:

    “About 85% of slaves made it across alive. That is not an extreme selective event.”

    I was mistaken then. I think if you asked the average person who hadn’t personally studied it what percentage had died they’d all say a lot more than 15% because that is the impression you get from school / media.

    • ziel says:

      Right. But no one ever asks why any shipper would treat his cargo so poorly.

      • gcochran9 says:

        A lot of people were killed in the enslaving process, before they got on the boat. Most ended up on sugar plantations, which were unhealthy, being in the tropical disease zone. Moreover, sugar was so profitable that planters could make money by working slaves to death and buying new ones – so they did.

        Slaves had positive population growth in British North America, but mostly didn’t elsewhere until quite late. Brazil and the West Indies were population sinks.

      • Greying Wanderer says:

        I had the idea it was more like 85% died but as you say, when you stop and think about it, or actually go and check, you realise it makes no sense.

  13. Greying Wanderer says:

    “In Utah they send the young males away on a mission.”

    Just to add to the list of a possible older male vs younger male culture war over females (in certain environments)

    http://en.wikipedia.org/wiki/Cherokee

    “The Payne papers describe the account by Cherokee elders of a traditional two-part societal structure. A “white” organization of elders represented the seven clans. As Payne recounted, this group, which was hereditary and priestly, was responsible for religious activities, such as healing, purification, and prayer. A second group of younger men, the “red” organization, was responsible for warfare. The Cherokee considered warfare a polluting activity, and warriors required the purification by the priestly class before participants could reintegrate into normal village life.”

    “Before the 19th century, polygamy was common among the Cherokee, especially by elite men.[48] The matrilineal culture meant that women controlled property, such as their dwellings, and their children were considered born into their mother’s clan, where they gained hereditary status. Advancement to leadership positions were generally subject to approval by the women elders. In addition, the society was matrifocal; customarily, a married couple lived with or near the woman’s family, so she could be aided by her female relatives.”

    I’d suggest the environments where this could potentially happen would be ones where
    1) females can provision their children themselves or in conjunction with other female family members
    2) elite males can provision the children from more than one female

    (I’d suggest environments where the females couldn’t provision their children and where a single male couldn’t provision more than one female would tend to develop monogamy.)

    In the second case it seems to me the elite males are likely to have the material means to enforce the marriage system e.g. harem guards, but not so much in the second case so i think the first case, where females don’t need male provisioning, is actually the most likely to develop a system where the older males figure out a cultural way of excluding younger males from marriage.

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  15. typal says:

    The Jewish Tay sachs and Torsion Dystonia mutations affect IQ. More that one of the Quebec genetic neurological disorders hypothesized to affect IQ have an effect on movement and motor skills as well. (Leigh syndrome – “movement disorders”, Mucolipidosis type II- “motor skills” , Autosomal recessive spastic ataxia of Charlevoix-Saguenay, “motor nerve conduction”) The condition ‘Jumping Frenchmen of Maine’ speaks for itself.

    If so many mutations that have an effect on IQ also affect motor skills, the idea that a population loaded with mutations which decrease IQ could be totally unaffected in their movements is dubious. Africans move at least as well as Europeans.

  16. neilfutureboy says:

    There are parts of the world, primarily the Kerala in the Deccan area of India, where background radiation is as much as 100 times the world average. If radiation was such a major cause of mutation it should have been noticed there.

    Personally I am convinced the radiation hormesis theory is, if not absolutely proven, infinitely more evidence based than the official LNT one. A general hormetic effect would not be entirely incompatible with specific damage to genetic transmission but one would not expect to see them together.

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