People living high in the Andes Mountains of Argentina may possess a genetic adaptation that allows them to consume water with dangerously high levels of arsenic without experiencing ill health effects, according to a recent study. The findings, published in March 2026, shed light on the remarkable ability of the human body to adapt to extreme environmental conditions.
For generations, communities in the Puna region of Argentina have relied on groundwater sources contaminated with naturally occurring arsenic leached from volcanic rocks. While the water supply in San Antonio de los Cobres tested at 200 micrograms of arsenic per liter in 2012 – 20 times the 10 microgram limit recommended by the World Health Organization (OMS) – residents have historically shown limited adverse health effects. This anomaly prompted researchers to investigate a possible genetic basis for their resilience.
Scientists analyzed the DNA and urine samples of 124 women from the region, comparing their genetic markers to those of populations in other areas with arsenic-contaminated water, such as Peru and Colombia. The research, originally published in the journal Molecular Biology and Evolution in 2015, revealed that the Andean women possessed genetic variations near the AS3MT gene. These variations appear to enhance the body’s ability to convert arsenic into forms that can be safely excreted through urine.
Arsenic, a naturally occurring element found in rocks, soil, and water, can become toxic to humans in certain concentrations, leading to cancer, skin lesions, birth defects, and premature death. The study suggests that long-term exposure to arsenic in the Andes region has driven natural selection, resulting in a unique genetic tolerance within the population.
Researchers first observed this unusual metabolic pattern in women from the area in 1995, noting their bodies transformed arsenic more efficiently, producing less of a particularly toxic intermediate compound and increasing the excretion of arsenic through urine. The recent genetic analysis confirmed the link to the AS3MT gene.
While the genetic variant is more prevalent in the Argentine Andes, it was found to be less common in similar populations in Peru and Colombia. Researchers believe this suggests the adaptation is specific to the long-term exposure experienced by the communities in San Antonio de los Cobres. The findings underscore the power of natural selection in shaping human resilience to environmental challenges.
