Older father = duller child?

Posted by on March 10, 2009; This entry is filed under Uncategorized.
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Advanced Paternal Age Is Associated with Impaired Neurocognitive Outcomes during Infancy and Childhood. I blogged it at ScienceBlogs.

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20 Comments

  1. Orion March 10th, 2009 at 12:37 pm

    I find these findings to be weak. They split the two groups of fathers 30 years apart (age 20 vs. age 50) and still the difference in IQ of the two children was almost negated by the 95% confidence interval. 
     
    My interpretation: fathers who wait until they’re 50 to have kids are slightly dumber than those who don’t. Big deal. I don’t buy the genetic explanation really, how significant are these de novo mutations? We have no way of knowing at this time…

  2. razib March 10th, 2009 at 2:54 pm

    My interpretation: fathers who wait until they’re 50 to have kids are slightly dumber than those who don’t.  
     
    that doesn’t seem very plausible to me.

  3. bioIgnoramus March 10th, 2009 at 5:23 pm

    This topic begs for one of those Galton-type studies of the ages of the fathers of outstanding intellectuals – how old was Newton’s dad, that sort of thing.

  4. time’s out March 10th, 2009 at 6:18 pm

    It’s not just IQ. The article I read was by a 40 something man who remarked that had he known the stats (as striking as those for women and motherhood over 40) he’s not sure he’d have taken the risk. It’s not just “duller.” It’s other forms of mental illness and birth defects. http://autism-prevention.blogspot.com/2008/05/cause-of-autism-unvieled-older-fathers.html 
    Fact is, common sense and common practice tell us that parenthood is best undertaken in the 20-30s, maybe 40s, for both genders. There’s nothing creepier than a 50 something man, or 45 year old woman, who suddenly decides s/he’s now grown up enough parenthood. If that’s really case, it’s just as well they will probably never get to reproduce.

  5. time’s out March 10th, 2009 at 6:20 pm

    Sperm banks cut off, so to speak, donors at age 45. Or they used to…I think it’s been 35 for some time. Paying customers want to be as sure of the goods as they can.

  6. AJ March 11th, 2009 at 12:47 am

    Did this study control for the IQ of each age group of the father?

  7. razib March 11th, 2009 at 1:10 am

    nope. education.

  8. EW March 11th, 2009 at 12:59 pm

    Oh, woe me, I could have been a genius, had my father not be 62…or maybe my mother aged 38 acted as counterbalance?

  9. Orion March 11th, 2009 at 3:15 pm

    Yeah that’s one of main problem with a lot of these studies the look at the child’s IQ. In such cases, the researchers should ALWAYS control for the father’s and mother’s IQ (both because of assortative mating). 
     
    Razib, I know you weren’t convinced by my first statement but I didn’t give you my reasoning. Say that for some percentage of the men who had kids after they were 50, the main reason they delayed was not choice, but because they weren’t competent enough to attract a partner and have kids before the customary age of 25-45. I’m not exactly sure the ability to find a mate and settle down at an appropriate time is highly correlated with IQ, but it only has to be slightly, because IQ is highly heritable and a slight mean change in the father’s could produce the effect they observed. 
     
    I think they should have asked the father’s what the main reason was for having their kids at an older age, with options like: a) lack of a committed partner, b) lack of money, c) free choice, d) other, and compared their answers to the younger men on a similar question.

  10. time’s out March 11th, 2009 at 6:02 pm

    good god. If the studies said old guys produce smarter kids you’d be rationalizing about higher iq people waiting longer to reproduce.  
     
    Why is it so hard to accept that the human body deteriorates pretty much on cue and this would include the production of genetic material. The article I read (can’t find it now) mentioned some well known examples of older father/offspring and again, the statistics were not indicative of rare exceptions, but very probable problems. It would put me off if i were considering it, but some of us like risks.

  11. Orion March 12th, 2009 at 12:00 pm

    “Why is it so hard to accept that the human body deteriorates pretty much on cue and this would include the production of genetic material.” 
     
    I’m no geneticist, but it seems to me DNA copying errors, if they are random, shouldn’t have this magnitude of an effect on IQ. For example, the QTL’s that have been found for IQ are very numerous but even the strongest ones have effect sizes that are quite small (0.5 IQ points max). Every person has around 20 new mutations that they receive from their parents, but what are the chances that these will fall onto the few genes that significantly affect IQ? Very small, I would say. So if a person was born to a father of 50 years or older they would have more of the these mutations, maybe 30-40, but that still wouldn’t make a difference compared to small number of significant IQ genes spread throughout the 25,000 coding regions of the genome. This may be different for non-additive traits like autism or Down’s syndrome (because they are controlled by other genetic processes), but I don’t buy it for IQ.  
     
    Another plausible cause for the IQ difference they observed is environmental: that fathers over 50 don’t spend as much time running around and playing with their kids, hence their lower IQ. Myself, I would favor the idea that there is something different about the non-mutated genetic profile of individuals who father children over 50 versus those at age 20.

  12. Hush the Silent March 12th, 2009 at 12:04 pm

    Orion might be on the right track. Darlington introduced the concepts of hyper- and hypogamy in the frame of hinduism. The outcome from an extrapolated interpretation of these principles would give a similar result on IQ without any genetic influence of age. Men who have to postpone the realisation of offspring have a lower value on a market of partners when a certain fitness, corresponding more or less to IQ, is lower. They will have to wait longer to find a partner (maybe slightly more in the years ’59-’65 than nowadays). For women the inverse can be expected. If the study would have been introduced as a verification of the confirmation of the hypothesis of a larger applicability of the rules of hyper- and hypogamy, the results would have a completely different interpretation. The concepts could fit in a very general way in human evolutionary psychology as consequences of the r- and K procreation strategies of men and woman respectively, in the approach (exploration)of a market of partners.

  13. pconroy March 13th, 2009 at 12:19 pm

    AJ, EW, Razib, 
     
    I agree not controlling for IQ of the father is a huge mistake, controlling for education is not a substitute. 
     
    As an example my grandfather was born in a time in Ireland when it was illegal to be educated past primary school if you were Catholic. He was the youngest of 3 brothers, born on a medium sized farm, so he left a got a job with the police, rising to a very senior position in Dublin Castle. Probably due to the dangers inherent in his job – civil war in Ireland, multiple assassination attempts on him – he married only after he retired at 55 yo, to a 30 yo bride, who hadn’t finished primary school. He had 7 children, born to him between the ages of 57 and 70 yo, and I’d say 3 of them were Gifted intellectually. My grandfather had taught himself Latin, Greek, Math and – in his 60′s – Irish Gaelic, and would spend every school evening helping his kids with their homework. He learned Calculus so that he could teach my aunt Calculus when she was 11 or 12 in primary school – she later went on to be the Irish equivalent of the surgeon general, and was one of the very first women from the county to graduate college. 
     
    So my point is that if you are an older male, with high IQ, your children will probably also have high IQ, regardless of your age at their birth. I don’t know if the fact that my grandfather was also very physically fit – could swim 3 miles in the open ocean, from one headland to another, at about 65 yo also played a part.

  14. Hyperbole March 14th, 2009 at 2:08 am

    I just want to point something out… if you control for education between a people in their 20s and people in their 50s, then you will probably have a dumber 50 y.o. sample than 20 year old. Not having been to college by age 20 is less indicative of the inability to go than not having been by age 50. You also have to account for general standards of education. Fewer people received a university education 50 years ago… so there are a lot of confounding factors. 
     
    On the other hand, I think controlling for IQ might also be problematic due to the flynn effect. If there are consistent increases in average IQ unrelated to genes, then this study would also be flawed even controlling for IQ.  
     
    I find it plausible that degradation in sperm quality from aging would have these effects, but we need to come up with some better / more refined tests.

  15. dougjnn March 14th, 2009 at 7:39 pm

    My interpretation is feminists, male and female, searching far and wide for any shred of scientific evidence they can find or concoct to eliminate a double standard. I.e. sexual differences privileging males to being worth worthy mates of younger and sometimes much younger females, which happens all the time including in hyper feminist countries like the US and Britain. While at the same time the evidence has strongly and unambiguously shown that older females, esp. past 35, rapidly become far less likely to be fertile and if they are, far more likely to produce genetically impaired offspring. 
     
    Yes I’m suggesting there’s huge PC political motive here, and so the results should be viewed with great skepticism.

  16. Curve March 14th, 2009 at 8:07 pm

    It’s two to three points…with unknown effect of the deviation. The effect is small… 
     
    138 vs 140…158 vs 160….

  17. Anonymouse March 15th, 2009 at 10:25 am

    If the effect is due to mutation then it is permanent: A man who waits until 50 before having children passes on to all his descendants a genetic heritage that includes an IQ diminished by maybe two points over what they would have received had he had children at 25. If his male children also wait until 50 then his line has lost 4 IQ points in 2 generations, due to genetic deterioration. The rate of IQ loss, I’ll note, is considerably faster than the hypothesized rate of enhancement for medieval Ashkenazi Jews. 
     
    But mutations are random; they don’t start at 25! Maybe there are big differences in the effectiveness of DNA repair or something, but if the passage of time from age 25 to 50 resulted in a significant additional burden of deleterious mutations, then wouldn’t something comparable happen between 0 and 25? If the rate of deleterious mutation is that high, then don’t we have a Red Queen situation, where strong positive select needs to be applied to each generation just to maintain the status quo? This just doesn’t seem reasonable to me. (For one thing, wouldn’t we see rapid genetic deterioration in traits not being actively maintained in lab animals)? 
     
    (I’ll note that this question is related to some questions I asked in an earlier post, concerning the number of alleles that natural selection can act on simultaneously, and how strong natural selection needs to be to keep the load of deleterious mutations from increasing, given that bad mutations occur much more frequently than good ones).

  18. time’s out March 15th, 2009 at 12:16 pm

    Actually IQ is not the major problem. Genetic disorders are. 
     
    http://www.iht.com/articles/2007/02/28/healthscience/snfert.php 
     
    Of course noticing such things make them “male and female feminists.”  
     
    Of course. Of course they are.

  19. Orion March 15th, 2009 at 12:46 pm

    Here’s a related article for those interested. It shows that achrondroplasia (the common form of Dwarfism), the risk for which increases exponentially with paternal age, is not accounted for by mutation: 
     
    Title: The observed human sperm mutation frequency cannot explain the achondroplasia paternal age effect. 
     
    http://www.pnas.org/content/99/23/14952.abstract

  20. Eric J. Johnson March 15th, 2009 at 8:32 pm

    Mouse - 
    But the B. subtilis laboratory strains of today are a shadow of their former selves. Years and years of manipulation in the laboratory has robbed B. subtilis of much of its biology. On the one hand, laboratory strains can be transformed with DNA much more efficiently than undomesticated strains. On the other hand, laboratory strains are generally deficient in a variety of behaviors manifest in wild strains. 
    http://schaechter.asmblog.org/schaechter/2008/09/the-view-from-1.html#more 
     
    (That’s a top-quality microbio blog, by the way.) 
     
    I think there is a rationale for not expecting much “constitutional” degradation in lab mice or roundworms. I haven’t been involved with any mouse colonies myself, but I would imagine selection still exists. Unless you make sure that almost 100% of every generation breeds almost equally, then fairly substantial selection exists. (Even if you did that, there could be selection against embryos with high mutation burdens, via miscarriage.) Individuals with worse energy efficiency, lower resistance to autoimmunity, etc, should have retarded adolescence and smaller litters. I agree, though, that it seems like traits of near-zero use to cage life should indeed degrade, just as is claimed for Bacillus subtilis. 
     
    If the rate of deleterious mutation is that high, then don’t we have a Red Queen situation, where strong positive select needs to be applied to each generation just to maintain the status quo? This just doesn’t seem reasonable to me. (For one thing, wouldn’t we see rapid genetic deterioration in traits not being actively maintained in lab animals)? 
     
    I think it’s undeniable that there is robust selection against individuals with above-mean mutation burden (this does not alter the species, though, because it is negative/purifying selection). There would seem to be no other way that the species’ burden could be at equilibrium. I think what’s controversial is the Kondrashov hypothesis that the primary function of sex is to keep the species’ burden at a lower equilibrium. 
     
    I think I agree with your suggestion that if all men started introducing quite a bit more mutations into the germline, the species should begin to move off of the existing mutational burden equilibrium, toward a worse one. I am not certain though.

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