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Inbreeding in the Persian Gulf

Gene ExpressionBy Razib KhanAugust 26, 2010 2:01 AM


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On the heels of my post on cousin marriage, I thought readers might find this article on genetic screening in the United Arab Emirates of interest. One way to tackle the problem of genetic diseases which emerge out of consanguineous unions apparently isn't to discourage the unions themselves, but dodge the outcomes. So pre-implantation screening of eggs as well as selective abortion of fetuses both seem to be options being evaluated. Aside from the costs, especially in the former case (though abortions are not without risk, and the initial stages of pregnancy are an investment of time as well), I still think there are long term problems with this. But first, Alan Bittles (who produced the map in the previous post) points to a major shortfall of a simple do-not-marry-cousins heuristic in this case:

People from the same tribe can also be highly genetically similar, he said. “You can’t just compare the health of those children born of cousins but the comparison must be made within the tribes as well as between them, as some disorders are unique to particular tribes,” he said. “To stop consanguinity affecting health, you’d not only need to stop first cousin marriage but people in the same clan too, which is highly improbable and going against centuries of tradition.”

Another medical specialist opines:

Dr Anand Saggar, a clinical geneticist based in London, sees patients from the Gulf — who have been sponsored by their governments — at his clinic in Harley Street. Western prejudice and health economics have led to the negative attitude towards cousin marriages, which are legal and accepted in many parts of the world, he said, pointing to Amish communities in the US. “We’ll never get rid of any old genetic diseases because our genetic code keeps on mutating. You just have to accept that genetic disease is part of our evolution. It is a foolish and erroneous assumption that to stop marrying cousins would eradicate genetic disease.”

The National is paper based out of the United Arab Emirates, a former British colony. Therefore, I won't put it past them to quote mine or distort (rule: beware of British newspapers!)...but this is just kind of a dumb assertion. The problem with inbreeding isn't that one has deleterious alleles, it's that there are correlations of deleterious alleles at the same locus. So the Jewish community has sharply reduced the manifestation of Tay-Sachs disease through genetic screening. The Amish community is is also impacted by recessive genetic diseases. As I noted earlier, inbred communities should have lower aggregate genetic load, and yet the the fact that deleterious alleles are concentrated on specific loci mean that they have reduced physiological fitness. I'm skeptical of Alan Bittles assumption that there's something set in stone about current Arab practices. Apparently miniskirts and exposed hair were de rigueur among the Arab female smart set in the 1960s, but now veiling is all the rage. Times change. But, the logical conclusion of generations of genetic screening of particular Arab lineages is that the clans of the Persian Gulf will eventually transform themselves into clones with very low mutational load. Even if the power of screening shields these lineages from the ill effects of inbreeding (by literally yanking out all the deleterious alleles from the gene pool by discarding eggs with problematic genotypes every generation), biological uniformity is going to have problematic long term consequences when it comes to battling co-evolving pathogens. Monocultures aren't built to last. In any case, interesting idea for a science fiction short story. The formula would be to take a pre-modern custom (e.g., cousin marriage) and mix it with future technology, and iterate forward.

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