Genetic Disease and the Heterozygote Advantage of Intelligence in Ashkenazi Jews

The specific high intelligence pattern seen in the genetically distinct population of Ashkenazi Jews is attributed to a heterozygote advantage of genetic diseases that frequent this population. Mutations that cause increased fitness for a heterozygote while causing a great decrease in fitness for a homozygote occur as a response to a unique environment (Hammerstein 1996). A classic example of this is sickle cell anemia that involves hemoglobin and malaria resistance in the Old World tropics. It has been proposed that clusters of Ashkenazi genetic diseases, the DNA repair cluster and the sphingolipid cluster, cause an increase in intelligence of heterozygotes (Cochran et al. 2006). Heterozygotes for these mutations show increased levels of storage in brain cells, increased brain cell growth, and have significantly higher intelligences levels than other European populations (Cochran et al. 2006). It is believed that the genetic diseases are a by-product of selection for higher intelligence. It has been proposed that these clusters of genetic diseases arouse due to strong and recent selection pressures, as the disease clusters affect specific pathways and contain many alleles (Cochran et al. 2006). This shows that they were not produced by a bottleneck followed with genetic drift as previously believed. The selection experienced is that of a unique social niche during 18th century Europe, which selected for high cognitive ability (Ostrer 2001). This theory of selection for intelligence in Ashkenazi Jews is a great modern day example of the heterozygote advantage in a complex trait.

Literature Cited:

Cochran, G., J. Hardy, and H. Harpending. 2006. Natural history of Ashkenazi

intelligence. J. Biosoc. Sci. 38:659–693.

Hammerstein, P. 1996. Darwinian adaptation, population genetics, and the streetcar

theory of evolution. J. Math. Biol. 34:511–532.

Ostrer, H. 2001. A genetic profile of contemporary Jewish populations. Nat. Rev. Genet.

4:891–898.

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2 thoughts on “Genetic Disease and the Heterozygote Advantage of Intelligence in Ashkenazi Jews

  1. Thanks for posting. I have seen these studies: neurodegenerative diseases of an autosomal recessive inheritance pattern (Tay-Sachs, etc,), which leaves carriers with a higher IQ as a trade-off of sorts (akin to the sickle-cell phenomenon). It sounds plausible as it has been proven that Ashkenazi Jews do have a higher IQ than their European counterparts, thus creating more geniuses within the population. However, I received an article via e-mail–wish it were sourced–which offers other reasons for the increase in IQ. Some other theories are quite plausible in my mind, as well. Apparently, due to a fear of anti-Semitism, there is not a lot of research going into this at the moment from what I read. The article was moved from its original location, but thought I’d post it if interested (you have to scroll down a bit):
    http://immortallife.info/articles/entry/why-is-the-iq-of-ashkenazi-jews-so-high
    A (an Ashkenazi Jew not in the genius category!)

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