Humans adapt to very high levels of arsenic.

A new study has identified the gene involved in a mutation that allows humans to tolerate high levels of arsenic in Andean villagers exposed for thousands of years to very high arsenic levels.

http://www.the-scientist.com/?articles.view/articleNo/43019/title/Adapting-to-Arsenic/

By Ashley P. Taylor June 1, 2015

I[/size]n parts of Argentina, people have been drinking poison—arsenic, to be specific—for thousands of years. The river running through the Andean village of San Antonio de los Cobres (SAC) has arsenic levels up to 80 times the safe limit established by the World Health Organization (WHO); it seeps into the groundwater from volcanic bedrock. Arsenic levels in the region’s tap water were as high as 20 times the WHO’s limit before 2012, when a filtration system was installed. The villagers are descended from indigenous Atacameño people who have lived and drunk the water in northern Argentina for as long as 11,000 years. Since 1994, Swedish biologist Karin Broberg, of Stockholm’s Karolinska Institute, and colleagues at Uppsala and Lund Universities have been trying to figure out how generations of SAC’s now nearly 6,000 residents have been able to survive this chronic arsenic exposure.