While the ability to drink poisonous water might not top the list of many people's most desired superpowers, it's a different story for those who live in South America's Atacama Desert, where scant water sources are often tainted with high levels of dangerous arsenic.

It turns out, though, that the native people that call this parched place home might have been born with the very superpower they most need, thanks to evolution.

Researchers at the University of Chile in Santiago have discovered that people from the Quebrada Camarones region of Atacama have a remarkable resistance to arsenic, and they have identified the genetic underpinnings of how this trait may have evolved, reports New Scientist.

It all comes down to an enzyme called AS3MT, which has the ability to incorporate arsenic into one of two compounds, monomethylarsonic (MMA) acid or dimethylarsinic (DMA) acid. The less toxic of the two is the DMA, so people who possess AS3MT variants that convert more arsenic into this good stuff ought to be able to metabolize the poison better. Sure enough, the researchers found that the population that lives in the desert had a significantly higher percentage of DMA-producing variants of AS3MT than other populations.

“Our data suggest that a high arsenic metabolization capacity has been selected as an adaptive mechanism in these populations in order to survive in an arsenic-laden environment,” the researchers concluded.

Evolution ... it's still happening

It's a fascinating example of evolution in progress among modern human populations. We're still evolving, and in some truly astonishing ways.

The Atacama desert is the driest non-polar desert in the world, so beggars can't be choosers when it comes to water quality. Arsenic contamination there often exceeds 1 microgram per liter, which is more than 100 times the World Health Organization’s safe limits. So the only way for people to have survived in this arid landscape was to develop some kind of resistance.

Researchers compared the evolution of arsenic resistance to another notable and well-studied example of recent human evolution: the development of lactose tolerance, which allows some people to digest dairy throughout their lives.

“I would say [the rise in arsenic tolerance] is comparable to the rapid spread of lactose tolerance. Certainly the timescales we are looking at for both cases are comparable,” explained Aaron Miller at Northwestern University in Evanston, Illinois.

The research was published in the American Journal of Physical Anthropology.