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posted by cmn32480 on Thursday June 04 2015, @04:14PM   Printer-friendly
from the Darwin-would-be-proud dept.

The Scientist reports on a study of a villages in Argentina, where the people have been drinking poison—arsenic, to be specific—for thousands of years. The levels in the principal water source is up to 80 times the level considered to be safe by the World Health Organization (WHO). Even the best wells exhibit over 20 times the arsenic allowed in the WHO limit.

And it doesn't seem to bother them at all. There is every indication that these Andean communities may have evolved the ability to metabolize arsenic.

Swedish biologist Karin Broberg, of Stockholm’s Karolinska Institute, and colleagues at Uppsala and Lund Universities have been trying to figure out how generations of villagers in the Andean village of San Antonio de los Cobres (SAC), an area of nearly 6,000 residents, have been able to survive this chronic exposure to toxic levels of arsenic.

The researchers knew that a particular allele, AS3MT, located on chromosome 10, was suspected as the main gene involved in arsenic metabolism in humans. But the metabolism rate in these Andean villagers was sky high compared to people elsewhere.

Broberg and her colleagues hypothesized that the remarkable arsenic tolerance of SAC residents might be due to particular variants of AS3MT that confer better arsenic metabolism. They wondered, further, if thousands of years of arsenic exposure had given a survival advantage to individuals with these metabolism-driving alleles and had increased the frequencies of these genetic variants.

By comparing genetic samples and urine from a wide selection of South American populations in Peru, Argentina, and Columbia, they hoped to determine if the arsenic tolerance was simply due to genetic accident, (population drift) or if it was a byproduct of natural selection. Natural selection tends to exhibit itself via higher levels of homozygosity, where particular alleles come from one lineage. (See here for a primer on Drift vs Selection.

In the area around AS3MT, the SAC population differed dramatically from the comparison populations. Not only did the SAC women have higher levels of protective AS3MT alleles, but these alleles also had longer stretches of homozygosity—a telltale sign of selection.

The extremely strong difference in allele frequency is considered a clear result of selective pressure on a population.


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  • (Score: 2) by sjames on Thursday June 04 2015, @05:50PM

    by sjames (2882) on Thursday June 04 2015, @05:50PM (#192192) Journal

    Unless the problem is new, it may already be taken care of and nobody knew.

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  • (Score: 2) by HiThere on Thursday June 04 2015, @06:08PM

    by HiThere (866) Subscriber Badge on Thursday June 04 2015, @06:08PM (#192203) Journal

    The problem *is* relatively new. The problem didn't exist until a "public service" set of pipe wells started to tap into a new aquifer that was further down, and derived from a different source. (I can't remember exactly why they needed the new wells, I think it was a drought, though.) So an international charity donated the wells and had them installed...but didn't think to test the water for arsenic.

    OTOH, gene therapy is not only new, it's expensive, and intentionally doesn't affect the gene line. So it's not a solution to this problem. A bunch of solar powered desalinization plants with the engineers to keep them running would be a much cheaper solution.

    --
    Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
    • (Score: 0) by Anonymous Coward on Thursday June 04 2015, @06:36PM

      by Anonymous Coward on Thursday June 04 2015, @06:36PM (#192221)

      Rather than gene therapy they could deploy a team nanoputian chelators.

    • (Score: 2) by Gravis on Thursday June 04 2015, @11:12PM

      by Gravis (4596) on Thursday June 04 2015, @11:12PM (#192298)

      So an international charity donated the wells and had them installed...but didn't think to test the water for arsenic.

      would the be the International Population Reduction charity? oh jimmy is such a prankster, he also puts out bear traps in the woods in places that dont have bears... you know, to keep bears away. ;)

      • (Score: 0) by Anonymous Coward on Friday June 05 2015, @06:05AM

        by Anonymous Coward on Friday June 05 2015, @06:05AM (#192386)

        Well, if there are no bears at those places where the bear traps are, the bear traps keeping them away obviously works, right? :-)