Residents of the Argentine Andes possess a unique genetic ability to neutralize arsenic found in local drinking water at concentrations that would be lethal to most people. That is the conclusion of evolutionary biologists Karin Schlebush and Lucy Gattepay of Uppsala University in Sweden, infohub.kz reports.
Their study, published in the journal "Molecular Biology and Evolution," provides the first rigorous proof of human adaptation to a toxic chemical through natural selection. Natural selection gave the highland indigenous population of Argentina a rare mutation in the AS3MT gene that helps the body safely and quickly excrete the highly toxic metalloid in urine, ScienceAlert writes.
For millennia, groundwater on the high-altitude Puna de Atacama plateau leached arsenic from volcanic rock. In the remote town of San Antonio de los Cobres, located at an altitude of about 3,775 meters, toxin levels in water sources reached 200 micrograms per liter. That was 20 times the World Health Organization's limit of 10 micrograms. Local residents regularly drank the dangerous water until modern filtration systems were installed in 2012.
Once inside the body, the toxic element is converted by enzymes into highly poisonous monomethylated arsenic (MMA) and then into dimethylated arsenic (DMA), which is easily excreted by the kidneys. An analysis of the DNA of 124 local women and a comparison of their genomes with databases of residents of Colombia and Peru showed the presence of protective variants of the AS3MT gene. This mutation causes the body to skip the dangerous intermediate phase, protecting tissues from the poison and from cancer.