Evolution fends off HIV?
Posted on July 11th, 2007 in glbt, health, links | 3 Comments »
HIV immune prostitutes in Africa. Sound like an oxymoron? It could just be the amazing work of evolution. According to this article by TIME, scientists have been tracking a number of sex workers in Africa for several years now, and while the women caught many other STDs, they appear to be naturally immune to HIV, and thus, to AIDS as well. There are theories bouncing around about how exactly the women are fending off the deadly virus, but so far nothing concrete has been found. The story notes that this is similar to how the smallpox vaccine was developed - by studying the “milkmaids who had gone through bouts of cowpox [that] enjoyed natural protection against the much deadlier smallpox.”
But it doesn’t stop there however. Another article, this one by the New York Times, explains how humans may have spread globally, but evolved locally. The story here notes how separate colonies, studying humans in separate areas such as Europe, Asia, and Africa, all developed similar, but different natural immunities over time, due to differences in environment causing the evolution. For example, it explains the local development of different cases of lactose tolerance:
A notable instance of recent natural selection is the emergence of lactose tolerance — the ability to digest lactose in adulthood — among the cattle-herding people of northern Europe some 5,000 years ago. Lactase, the enzyme that digests the principal sugar of milk, is usually switched off after weaning. But because of the great nutritional benefit for cattle herders of being able to digest lactose in adulthood, a genetic change that keeps the lactase gene switched on spread through the population.
That lactose tolerance has evolved independently four times is an instance of convergent evolution. Natural selection has used the different mutations available in European and East African populations to make each develop lactose tolerance. In Africa, those who carried the mutation were able to leave 10 times more progeny, creating a strong selective advantage.
Researchers studying other single genes have found evidence for recent evolutionary change in the genes that mediate conditions like skin color, resistance to malaria and salt retention.
Now, I may be off here, but I find it particularly intriguing how, rather miraculously, prostitutes (!), in Africa (!), have become somehow immune to HIV. Again, correct me if I am wrong, but isn’t this blatantly some form of evolution? Not necessarily the development of a whole new mechanism of fighting the virus, but perhaps a tiny tweak somewhere in the genes that stops HIV in it’s tracks.
Now, taking into account the study that suggests evolution occurred locally, wouldn’t it simply make sense that the immunity would occur in the area that is suffering the most from the disease? Furthermore, it actually makes sense that the immunity would develop in the gene pool, as Africans pass along the virus through birth, unlike many in the Western World who catch it unexpectedly through unprotected sex or the sharing of needles. For example, it would presumably take evolution longer to produce an immunity for gay men, as the virus wouldn’t necessarily continue through a gene pool, generation after generation, like in Africa.
It’s hope for the future though. Especially in Africa, the one place that needs it most. Wouldn’t it be fantastic if, in 30 years time, the virus is nearly eradicated in Africa and a whole new generation of human beings are completely immune to such a tremendous killer in that continent?
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