Evolution continues on despite the opinions of humanity – especially when it comes to poisons. NewScientist (25 February 2017) reports on the growing ability to tolerate arsenic:
For settlers in the Quebrada Camarones region of Chile’s Atacama desert some 7000 years ago, water posed more than a bit of a problem. They were living in the world’s driest non-polar desert, and several of their most readily available water sources, such as rivers and wells, had high levels of arsenic, which can cause a variety of health problems.
The arsenic contamination here exceeds 1 milligram per litre: the highest levels in the Americas, and over 100 times the World Health Organization’s safe limits. There are virtually no alternative water sources, and yet, somehow, people have survived in the area. Could it be that arsenic’s negative effects on human health, such as inducing miscarriages, acted as a natural selection pressure that made this population evolve adaptations to it? A new study suggests this is indeed so.
The body uses an enzyme called AS3MT to incorporate arsenic in two compounds, monomethylarsonic (MMA) acid and dimethylarsinic (DMA) acid. People who metabolise arsenic more efficiently convert more of it into the less toxic, more easily expelled DMA.
Mario Apata of the University of Chile in Santiago and his colleagues looked at variations in the gene coding for AS3MT in nearly 150 people from three regions of the country. They found higher frequencies of the protective variants in people from Camarones: 68 per cent there had them, as opposed to just 48 and 8 per cent of people in the other two. “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 conclude (American Journal of Physical Anthropology, doi.org/bz4s).
Too bad about the murder mysteries, though.
