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Human Evolution and a New Proof of Darwin’s Theorem

2015-03-14

One of the first known examples of human molecular evolution exists in the indigenous population of the Atacama Desert in Chile.  Some inhabitants of this area make a living by fishing in the sea.  Others raise livestock in the hills.   As a rule, the area is one of the driest on Earth.  Local drinking water contains a very high level of natural arsenic due to a volcanic bed underlying most of the desert area.  Since arsenic is highly toxic to human populations, there are genes which code for enzymes that methylate arsenic and allow it to be excreted in the urine in a relatively nontoxic state.

The indigenous Atacama people have a very high percentage of homozygosity for the arsenic 3-methyl transferase enzyme which dimethylates arsenic, approximately seventy percent.  Having high levels of this enzyme confers a resistance to the toxic effects of environmental arsenic.  In contrast, Chileans from other areas of the country where arsenic levels are much lower have very few individuals possessing the gene.

Clearly, this is a concrete example of the principles of evolution.  As a result of natural variations, some individuals have more and healthier offspring than others.  The positive natural variations are perpetuated by this circumstance and increase in frequency in the population as a whole.  The occurrence of many such variations will result in obvious evolutionary changes over long periods of time, and this is precisely what Darwin predicted.

The presence of this natural variation in the ability to detoxify environmental arsenic could be predicted on the basis of Darwinian principles.  There is no better proof that Darwin knew exactly what he was talking about.

The abstract for the article can be found at: http://mbe.oxfordjournals.org/content/early/2015/02/26/molbev.msv046

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