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First-ever human population adaptation to arsenic identified

Scientists have identified the first-ever evidence of a human population uniquely adapted to tolerate the toxic chemical arsenic in the Andes Mountains of Argentina. A Swedish research team led by Karolinska Institutet and Uppsala University professor Karin Broberg, performed a genome wide survey from a group of 124 Andean women screened for the ability to metabolise arsenic (measured by levels in the urine).

The study pinpointed a key set of nucleotide variants in a gene, AS3MT, which were at much lower frequencies in control populations from Columbia and Peru. The researchers estimated that the increase in frequency of these variants occurred recently, between 10,000-7,000 years ago, based on the age of a recently excavated mummy that was found to have high arsenic levels in its hair.

Thus, this Andean population has adapted to their environment through increased frequencies in protective variants against a toxicant, researchers said. The set of AS3MT nucleotide variants, harboured on chromosome 10, were distributed worldwide, with the highest frequencies in Peruvians, Native Americans, Eastern Asia and Vietnam, researchers said. The authors speculated that the forces driving the local adaptation may have occurred as a result of the severe health effects of arsenic, which is most toxic to young children and those in their reproductive prime, and the need for faster metabolisers of arsenic, which may have been a matter of life or death in ancient times.

Long-term exposure to high levels of arsenic in drinking water can cause thickening and pigment spots in the skin, and cancer of the skin, lungs, bladder or kidney. A large amount of arsenic swallowed by humans, in a form that is readily absorbed, can cause rapid poisoning and death. The study was published in the journal Molecular Biology and Evolution. PTI


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