Monday, May 16, 2011

Double-Edged

If there is anything evolution ought to be good at, it’s eliminating harmful genes. There at least a few genes in our pool, though, which are surprisingly common despite being very harmful. The classic example is sickle cell anemia. At least before modern medicine, if you got two copies of the sickle cell gene, you were very likely to die early from sickle cell anemia. Having one copy, however, tended to make the symptoms of malaria milder and make surviving it more likely. This double edged quality helped this otherwise purely harmful gene survive and prosper. You might ask your intelligent designer friends to explain that, though no doubt they have some BS answer.

I want to consider the surprising results of a recent South Korean study in the light of the above.

In the first study to take a broad-population look at the prevalence of autism spectrum disorders — types of autism ranging from severe symptoms to the milder Asperger's syndrome — researchers found a rate of 2.64% among South Korean children. That's 1 in 38 children, a rate far higher than the estimate of 1 in 110 children for the U.S. by the Centers for Disease Control and Prevention.

The study, being published Monday in the American Journal of Psychiatry, suggests that, under rigorous examination, many more children may be affected than previously suspected.

Even the more conventional 1% value seems to show that incidence of autism is far higher than one would expect from random genetic mutation. Autism is known to be at least partially genetic, but its genetic basis is complex and nonstandard, with at least some indication that the genetic changes involved are not always present in the parents but occur before conception, during formation of egg and /or sperm.


Of course it’s still possible that this is purely accidental damage to a particularly delicate or susceptible part of the genome, but I remain curious about the possibility that this is another example of a double-edged genetic effect of the sort that leads to all our aphorisms about the fine line between genius and madness. The strongest evidence of that is the large number of the exceptionally accomplished who show some traits.


I have previously annoyed my readers with my speculations about acknowledged geniuses who appeared to display a lot of autistic spectrum traits. Real life diagnoses are available only for the very recent of course, but the list includes a lot of the very accomplished. I don’t think that I have learned anything to date that make it less likely that some autistic traits can facilitate genius. For the worst afflicted though, it’s a devastating disease, and even for the geniuses it often seems a painful burden.