Expel the 7R?

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Dan at Genetic Future, a great guy, has another DRD4 post up. He has reproduced a chart from an article in The Economist which shows a trend where a higher frequency of the 7R (ADHD correlated variant) is found in groups which have migrated a greater distance. He asks whether “the “novelty-seeking” behavior associated with ADD may have extended into a desire to explore new territories.” My first thought was this: perhaps people with the 7R variant were more likely to be kicked out of the tribe or village because they couldn’t/wouldn’t conform. Certainly the chart seems to imply that stable populations hovering around the Malthusian limit probably aren’t too congenial for nonconformists. This is the argument at the heart of books such as The Moral Consequences of Economic Growth and Age of Abundance, though obviously there wasn’t a genetic perspective there.

In any case, I think there’s going to be some interesting stuff coming out of this area correlating lifestyle with personality profiles. You might recall that in Farewell to Alms Greg Clark repeated the old truism that farmers tended not to be more affluent than hunter-gatherers, and in fact the balance of the data implies most hunter-gatherer and nomadic groups have a median physiological fitness that is greater than that among farmers as measured by size and nutrition as evidenced by enamel growth. The genius of farming is that it obviously increased the productivity per unit area in terms of calories and so supported larger populations (physiological fitness obviously does not translate into reproductive fitness always), but it seems to me that the less violent and risky nature of this lifestyle (famines notwithstanding) meant that there was also less room for the nonconformists on the margins. I’ve argued in the past in some ways theat modern individualistic Westerners have more in common with hunter-gatherers than with peasants in “traditional” societies in regards to their mores. I wonder if the need and necessity for straight-jacket social control in village life induced a powerful bout of purifying selection against 7R across much of Eurasia, a pressure that is only now being relaxed.

Addendum: The expulsion of male misfits is one of the accounts given of the founding of Greek colonies. Of course, it could simply be that the annalists used the argument that these men were misfits to get rid of them and they were actually economical marginals who were a burden upon the citizenry.

Update: I want to be clear here to note that I don’t expect that all H & G societies would favor 7R more than farmers. Just that I think that the constraints of an agrarian lifestyle around the Malthusian limit would result in less tolerance of variance of behavior on the margins. The marginal slack for H & G groups I assume would be due to more frequent tribe-level extinctions, war and interpersonal violence, as well as localized ecological parameters which have a more direct impact on H & G peoples.

Related: DRD4 posts.



  1. The key factor for farmers (peasants) is that once all the good land is in production, they’re easy to exploit because they can’t migrate and are trapped on their plot of land. An undernourished farmer might be producing enough to feed his family very well if his taxes + rent weren’t 50% or more of the total.  
    Only a small part of the taxes + rent pays for any specific service concretely useful to the farmer; most of it goes to luxury products, idle elites, and the military (which supplies “protection”, though usually at an exorbitant cost).

  2. Responding to John Emerson – The point made by Greg Clark in Farewell to Alms is that – pre industrial revolution – all technological breakthroughs such as the invention of agriculture have only a temporary effect on raising standard of living – since over the next few generations population growth will erode any standard of living benefits.  
    So, if John Emerson’s ‘imaginary farmer’ did produce enough to feed his family very well, then more children would survive (etc) and the population would expand until the standard of living was again pushed down to subsistence.  
    Clark’s explanation for the high standard of living of many hunter gatherers is their higher mortality rates due to factors such as violence and accidents (there seems to have been an especially high childhood mortality – and probably – says Sarah Blaffer Hrdy – frequent infanticide). The fact that populations are kept in check by these kinds of factors means that HGs usually have more food per person.  
    In Western Europe Clark suggests that the main population constraint was infectious disease due to poor hygeinic practices – consequently Western Europeans had a higher standard of living (ie. more calories of food per day and greater variety of foods) than the more hygienic Chinese where the population was constrained mainly by starvation.  
    The message is that – pre industrial revolution – death rates and birth rates must be equal in the long term – and differences between societies standard of living are mainly related to the predominant causes of mortality.  
    Humankind only broke free from this Malthusian Trap, and the standard of living began to rise over the long(er) term, when the rate of breakthroughs in productivity exceeded the rate of population growth.

  3. DRD4 seems to be related mostly to novelty-seeking, reward-dependence, or something like that. In personality trait terms, high Extraversion and maybe high Neuroticism too. 
    Conformity, susceptibility to socialization, etc., are different personality traits — Psychoticism in Eysenck’s system, low Agreeablenss and low Conscientiousness in the Big Five system. Afaik, DRD4 hasn’t been strongly associated with these traits. 
    The population to study for non-conformity / low socialization is Gypsies. You could probably do the research in one of the Balkan countries: that’s where Gypsies are most numerous, and the locals don’t like them much and are not paralyzed by PC policies. The Rushton study showing that the average IQ in Gypsies is 70 was co-authored with a Balkan researcher. 
    They’re also good because they have lots of variation — some (mostly endogamous) communities are solid blue-collar skilled worker types, others are musicians, others are skilled criminals and parasites.

  4. But I agree that the larger ecological forces that would purge novelty-seeking alleles would likely also purge non-conformist alleles, even if these are different phenotypes affected by different loci.

  5. what’s a good personality book/text? don’t know about this.

  6. Razib:  
    “Personality” by my colleague Daniel Nettle (Oxford University Press, 2007) is short, sound, very interesting and takes an evolutionary perspective.

  7. Personality Traits, 2nd Ed., by Matthews, Deary (i.e. Ian Deary, who also writes a lot of good stuff on intelligence), & Whiteman (2005). It covers everything you’d want to know: the psychometric approach; how stable are traits across situations, cultures, and the lifespan; what traits have been identified / what they measure; behavior genetics; physiology of personality; and real-world consequences (though the best for this sub-topic may be a review article that Jason Malloy posted to backchannel some time ago).

  8. If you’re just interested in what traits measure what, here are two simple links: 
    The 2nd is a bit more thorough, but its labels are not standard, so make sure to read the 1st for that.

  9. Once were warriors.

  10. I have corresponded with Steve Sailor a bit about this. In part I said: 
    The 7R alelle is almost completely missing in the Han Chinese. That it was once present is suggested by the fact that the 5R alelle which almost universal among the Chinese (and found nowhere else) is a simple recombination of the 7R alelle with itself. The disappearance of 7R is probably a recent development in Chinese history. The early emergence of central state authority (which made looting and plundering a poor career choice) and the emergence of a very productive but labor intensive system of agriculture (paddy rice cultivation) caused it to be bred out of existence. 7R types are grasshoppers; the other variants are ants. Once the population of China expanded enough to require incessant toil as the price of survival, the grasshoppers were doomed. 
    Europeans never went through a Malthusian Trap that was as severe or prolonged as that endured by the Chinese. One could argue that as recently as 500 years ago, many parts of Europe were underpopulated with large tracts of fertile forest land which had not yet been cleared for agriculture. The discovery of the new world and the industrial revolution then further eased population pressures–leaving us with a gene pool more suitable for a pastoral, nomadic people.

  11. re: chinese, it is notable that the military was a low status profession for most of history. ergo, criminals and minority groups were often pushed into service as professional soldiers.

  12. I wonder what about the 7R allele in South Asians and West Asians? They did any study?

  13. I know they’ve found ADHD is comorbid with bipolar disorder around 30% of the time. I understand that not all ADHD is the result of the 7-repeat allele, and there are other genetic causes sometimes (though the 7-repeat allele is the one associated with higher IQ’s and better outcomes among children with ADHD); so this makes me wonder if the 7-repeat allele has a higher or lower comorbidity with bipolar than the other non-7-repeat kinds of ADHD. 
    If ADHD can be divided into two clasees– those in which the disorder is caused by the 7-repeat allele, and those in which there is some other cause– then which group is shouldering the burden of a higher than normal frequency of bipolar? 
    Also, has anyone worked out the load effect of the 7-repeat? How are homozygotes different than heterozygotes?  
    I had pretty severe ADHD as a kid, and still deal with it to some extent today. (Though I’ve managed to carve out a pretty good life as a lab researcher and fiction writer) I have a parent with bipolar, and I’m not sure if I’m likely to be a carrier of the 7-repeat, or if instead my ADHD is more a subclinical level of bipolar that I’m able to control.

  14. One thing that might also be interesting is to see whether the 7 repeat allele is associated more with the inattentive part of the disorder (ADD) or the hyperactive part of the disorder (ADHD). Those with the hyperactive component (ADHD) are much more likely to grow out of the disorder than are those with the inattentive component (ADD) alone, and those with both the hyperactive *and* inattentive component are more likely to grow out of the hyperactivity than the inattention. I’d be curious whether genetics reflect the disorder’s (albeit imperfect) symptomatic divide.  
    Regarding fitness, I can see ADHD having fitness benefits much more easily than I can see ADD having fitness benefits. Even people who grow out of ADD/ADHD retain some traits, as would be expected. If you’re hyperactive as a kid but grow out of it to the extent that you can focus as an adult when you need to, but have a somewhat shorter attention span or are more physically active, that could be a big boost. I can’t see just being inattentive adding anything to one’s fitness, in any circumstance. 
    Also, I think people sometimes misconstrue what it means to have inattentive ADD. It doesn’t mean you’re just really good at multitasking. It means you literally can’t focus on anything, so you’re no more effective doing a whole bunch of tasks at once than you would be doing one task at a time. Absent medication, you literally can’t form thoughts and your mind is a constant haze. I have inattentive ADD (never had the hyperactive component) so I know of what I speak.

  15. Marc, that was some interesting info. I certainly had the hyperactive component of ADHD when I was a kid. My teachers made me sit on my hands for most of third and fourth grade. I was suspended more times than any other student in 6th grade. But then it was like somone hit a switch between 8th and 9th grade, and I could suddenly sit still.  
    The hyperactive part is totally gone now, as are many aspects of the ADD. The remnants that I keep seeing in myself now are primarily in novelty seeking behaviors. I can’t force myself to watch a movie more than once. I’ve found I even play video games differently than a lot of people. I tend to zoom through the levels, skipping over tokens, or coins, or whatever bonus items are avail– and I am always moving forward as fast as I can. Other players get frustrated with me, and I get frustrated with them. Strange the way these things can manifest, and it is easy to see how a trait like that could be adaptive in one situation, and maladaptive in another.

  16. Kosmo, 
    Like I said I’m not hyperactive and never have been, but I certainly have the novelty seeking down pat. Come to think of it, I think that in itself might be a great deal of the evolutionary advantage. Once I sleep with someone, I literally have no interest in sleeping with that person ever again. God knows how many bastard children I’d have by now if I weren’t gay. 
    Speaking of which, I remembered after I posted my last post that there was also evidence that men with ADD/ADHD tend to have more of the hyperactive component, whereas women tend to have more of the inattentive component, which suggests, at least to me, that the difference between the two is less in the genes and more in their expression in the brain. It would be interesting to see if gay men followed the “female” ADD/ADHD pattern, and if lesbians followed the “male” pattern.

  17. Fascinating stuff, Marc. I?d been right on the cusp, in my last comments, of speculating on my suspicions about how ADHD might impact dating behavior. I?m a married guy myself, 2.5 kids, minivan, about as domestic and settled as you can get, but? this was not always the case. In high school and college, the novelty-seeking certainly played an important role in how I handled (and mishandled) relationships. You could very well be right that this aspect of the disorder is actually what is driving selection for it.