A few populations of Native Americans that live in the Andes of Peru have evolved an immunity to toxic levels of arsenic. This is the first known instance of humans evolving to overcome a toxic chemical. A Swedish research team led by Karolinska Institutet and Uppsala University professor Karin Broberg reported the discovery in the edition of the journal Molecular Biology and Evolution.
Some regions of Peru naturally produce high levels of arsenic due to the mineral content of the mountains. The arsenic eventually leeches into the water. The people that live in these areas are frequently isolated small populations and do not migrate. Between 7,000 years ago and 10,000 years ago these Peruvian natives evolved immunity to the toxic effects of arsenic. The researchers confirmed that the arsenic involved is the poisonous trivalent variant. The adaptation precedes the development of the Inca civilization.
The researchers compared the genome of 124 women that lived in high arsenic areas of Peru to control groups from Columbia and other parts of Peru that had never been exposed to high levels of arsenic. The arsenic immune women had evolved a set of nucleotide variants in a gene called AS3MT on chromosome 10 that allows the women to metabolize arsenic and remove the metal in urine. The development of an evolutionary adaptation that allows the isolated populations to metabolize a known poison was confirmed by hair samples from recently exhumed Andean mummies.
The researchers consider the driver for the adaptation to have been reproduction. Infants are more susceptible to small quantities of arsenic than adults. If the populations in the high Andes were to survive, they had to evolve a genetic mechanism that dealt with arsenic at toxic levels quickly. In terms of evolutionary time the adaptation occurred very quickly and could possibly have been established in 3,000 years.
