Low hanging fruit for genetic engineering

Ashkenazi jews have both an unusally high average IQ, and a high incidence of genetic diseases like Tay-Sachs. A new paper [PDF] suggest that these may be related. The author argues that due to the particular economic niche of this group, intelligence was selected for even more strongly than usual. The result is that genes which confer increased IQ when heterozygic, but cause genetic diseases when homozgygic are more common. This is analogous to sickle-cell anemia in Africa, where a single copy of the gene confers resistance to malaria, but a double copy causes the condition. Here is coverage from the Economist and the NYT (reg required).

Given that modern genetic technology will soon make it easy to ensure that a child has exactly one copy of such a gene, it seems like this sort of thing is a "low-hanging fruit" for genetic engineering. If such a gene is common, then having one copy is probably an evolutionary advantage - otherwise it would be (mildly) selected against. The main disadvantage is the chance that your kids might end up with two copies of the recessive, so if technology can prevent that, now you just have upside. I wouldn't be suprised if it soon becomes common to give your offspring many such genes - which would have the side effect of making it impossible for them to reproduce with similarly endowed partners without using genetic engineering. My fiancee makes the interesting point that you could enhance women more than men this way - because only they can be given such genes which go on the X chromosome. (Although, could it be put somewhere else?)

A side-effect of the paper, of course, is to provide yet more evidence that IQ has a strong genetic component. Although I suppose I shouldn't worry that much about disbelievers - once the rest of us get to enhance our children, selection and markets will send them to join the Mennonites.

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If you want to talk about

If you want to talk about socially acceptable forms of what might be considered a prelude to genetic engineering or single generation eugenics, my best friend's sister is a genetic counselor and a devout Christian. I think in terms of business the main service is screening people for genetic and advising about whether or not to abort potentially diseased fetuses.

because like you said it

because like you said it means it’s dangerous for carriers to have children without the help of high-tech medical intervention.

only dangerous if you marry another carrier. 3% of ashkenazi jews are carriers. some quebecois are carriers. that's about it. the genes are at such a low frequency that the risk of having homozygous children is trivally low. of course, make sure and get genetic testing to prevent odd couplings, or engage in selective abortion or prezygotic screening if you do marry another carrier, but even if civilization collapses you only have a 1/4 changes of having a messed up child, 1/4 of having a normal child, and 1/2 chance of having a brighter-than-average child if you marry someone else who is also a carrier.

I’m sure there are plenty of genes corresponding with high intelligence that are benign when two copies are inherited.

yes, but probably of very small effect, on the order of 1% of the variation of the phenotype. these genes are much more powerful in the bang-for-the-buck, but so are their downsides.

I'm not sure we really want

I'm not sure we really want anyone to have even a single copy of the Tay-Sach's gene, because like you said it means it's dangerous for carriers to have children without the help of high-tech medical intervention.

I'm sure there are plenty of genes corresponding with high intelligence that are benign when two copies are inherited. It would be those genes which we'd want to endow to "genetically perfect" humans: assuming it's a good idea at all to mess with humanity in this manner.

Similar to the Tay-Sach's gene, I've explained in my blog that genes for gayness might have the same beneficial effect in moderation.

On The Evolution Of

On The Evolution Of Ashkenazi Jewish Intelligence
Ashkenazi Jews pose two mysteries for biological science. First, why do they have so many genetic diseases that fall into just a...