Andean Population Evolved Genetic Tolerance to Arsenic

For thousands of years, communities in the Argentinian Andes have relied on water sources contaminated with high levels of arsenic, a toxic metalloid that poses significant health risks to most populations. However, a unique genetic adaptation has allowed one group in northern Argentina to not only survive but thrive despite this exposure.

Arsenic Contamination in the Andes

Naturally occurring arsenic leaches into the groundwater from volcanic bedrock in the Andes region. In the town of San Antonio de los Cobres, Argentina, the water contained approximately 200 micrograms of arsenic per liter – about 20 times the level deemed safe by the World Health Organization WHO – until a filtration system was installed in 2012. Despite these dangerously high levels, the area has been inhabited for at least 7,000 years, and potentially as long as 11,000 years.

Genetic Adaptation to Arsenic Exposure

Scientists have long been puzzled by the ability of this population to withstand chronic arsenic exposure. Research indicates that individuals in San Antonio de los Cobres possess a genetic variant that enhances their ability to metabolize arsenic more safely. A 2015 study led by evolutionary biologists Carina Schlebusch and Lucie Gattepaille of Uppsala University highlighted this adaptation, noting it as the first evidence of human adaptation to a toxic chemical ScienceAlert.

How the Adaptation Works

When arsenic enters the body, it is converted into different chemical forms. One intermediate form, monomethylated arsenic (MMA), is particularly toxic. A later form, dimethylated arsenic (DMA), is more easily excreted. People in San Antonio de los Cobres tend to produce less of the toxic MMA and more of the readily excreted DMA, suggesting a more efficient arsenic processing system.

The AS3MT Gene and Genetic Variants

Researchers focused on the arsenic (+3 oxidation state) methyltransferase (AS3MT) gene, known to play a role in arsenic metabolism. Analysis of DNA from 124 women in San Antonio de los Cobres revealed a cluster of genetic variants near the AS3MT gene that were significantly more common in this population compared to genetically similar groups in Peru and Colombia RealClearScience. These variants appear to increase the body’s efficiency in converting arsenic into forms that can be safely eliminated.

Implications and Future Research

This research demonstrates the remarkable ability of humans to adapt to extreme environmental stressors over long periods. The genetic tolerance to arsenic observed in the Andean population likely provided a significant survival advantage in a high-arsenic environment. Further research suggests similar genetic signals may appear in other Andean populations with long-term arsenic exposure, indicating the adaptation may be more widespread. Understanding the mechanisms behind this adaptation could have implications for developing strategies to mitigate the health effects of arsenic exposure in other parts of the world Smithsonian Magazine.

Key Takeaways

• A population in the Argentinian Andes has developed a genetic tolerance to high levels of arsenic in their drinking water.
• This adaptation involves genetic variants near the AS3MT gene, which enhance the body’s ability to process and excrete arsenic.
• The adaptation likely arose due to thousands of years of exposure to arsenic-contaminated groundwater.
• This research provides valuable insights into human adaptation to toxic environmental stressors.