For centuries, people in the Argentinian Andes have lived with water that would make most others sick. The ground here is rich in volcanic minerals that leach arsenic into the water. While high arsenic levels can be deadly, one group in northern Argentina seems to have a unique genetic edge—they may be better at handling this toxin.
A recent DNA study revealed that a population in the Andes carries a gene variant that helps metabolize arsenic more safely. Researchers Carina Schlebusch and Lucie Gattepaille from Uppsala University pointed out that this provides “the first evidence of human adaptation to a toxic chemical.”
Humans have shown a remarkable ability to adapt to extreme conditions, from high heat to radiation. Yet, we don’t know much about how we adapt to toxic substances like arsenic. According to the World Health Organization, arsenic is linked to serious health issues, including cancer and birth defects. It’s found in groundwater in many places around the world.
The WHO’s recommended limit for arsenic in drinking water is just 10 micrograms per liter. However, until 2012, the town of San Antonio de los Cobres had a staggering 200 micrograms per liter. Despite this, the area has been inhabited for over 7,000 years.
In 1995, scientists noted that women in the region could metabolize arsenic differently, as seen in their urine samples. When arsenic enters the body, it is converted into different forms. One harmful byproduct, monomethylated arsenic (MMA), is particularly toxic. People in this town seem to produce less of this toxic form and more of the safer dimethylated arsenic (DMA), which is easier to excrete.
Curious about the genetic basis for this adaptation, researchers collected cheek swab DNA from 124 women in the town. They found a cluster of genetic variants near the AS3MT gene that influence arsenic metabolism. These variants help the body convert arsenic into harmless forms that can be easily expelled.
This adaptation isn’t unique to this one town. Similar genetic traits may exist among other Andean populations exposed to high arsenic levels for generations, suggesting that over time, natural selection has favored those who can better handle arsenic. According to research published in Molecular Biology and Evolution, people with these genetic traits could have a significant advantage in arsenic-rich environments.
In a world where many communities struggle with arsenic exposure, the case of San Antonio de los Cobres offers a glimpse into human resilience and adaptability. As they navigate their environment, these people highlight the intricate dance between nature, genetics, and survival.
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