Razib from Gene Expression describes a potentially fascinating study on a variant of the DRD4 gene, which was first shown to be associated with attention deficit hyperactivity disorder (ADHD) more than ten years ago. (It's worth emphasising, by the way, that DRD4 is just one of the many genes likely to be involved in this complex trait). Interestingly, the same variant has also been reported to show a signature of recent positive selection in some human populations, suggesting that the behavioural "problems" displayed by modern individuals with ADHD may actually result from a mis-match between the environment our hunter-gatherer ancestors were adapted to and the bizarre, restrictive environment of Homo suburbanensis.
The full article hasn't actually been released yet, so we're all forced to play the now-familiar game of "science by press release" based on an article in ScienceDaily. Apparently, researchers directly tested the mis-match hypothesis by looking at the effects of the ADHD version of the gene on body mass index, a crude measure of nutrition levels, in men from the Ariaal tribe in Kenya. Some of the members of this tribe are nomadic while others live in settled communities. In agreement with the predictions of the mis-match hypothesis, those with the ADHD version of DRD4 were fatter (i.e. healthier) in nomadic populations, but skinnier (unhealthier) in settled groups.
The explanation of the results by the study's lead author:
"The DRD4/7R allele [i.e. the ADHD version of the gene] has been linked to greater food and drug cravings, novelty-seeking, and ADHD symptoms. It is possible that in the nomadic setting, a boy with this allele might be able to more effectively defend livestock against raiders or locate food and water sources, but that the same tendencies might not be as beneficial in settled pursuits such as focusing in school, farming or selling goods".
In other words, behaviour that would result in a rapid trip to the headmaster (followed by the psychiatrist) in stable, industrialised society may actually have been extremely useful in the relatively uncertain world of the hunter-gatherer tribesman.
Of course, simply knowing that ADHD is "natural" doesn't necessarily make it any easier to solve the broader problem of how society should be dealing with individuals with ADHD. In an ideal world, education would be tailored to the unique learning demands of individual students, resulting in the maximisation of each child's potential skills. However, in a world with limited resources for education, is society's current approach (medicate them until they shut up and learn like the other kids) the only workable solution? Or can we figure out a way to restructure society such that "obsolete" ADHD tendencies become useful again?
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3 comments:
hm. what's up with the photo? is this part of the concerted societal effort to associate albinos with every ill?
surely it's axiomatic that if something is wrong with society, it's whitey's fault?
surely it's axiomatic that if something is wrong with society, it's whitey's fault?
in a place like iceland that would be tautological :0) (since aside from a few filipino guest workers everyone is white).
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