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Title: Desert people evolve to drink water poisoned with deadly arsenic Arsenic
Source: [None]
URL Source: https://www.newscientist.com/articl ... -poisoned-with-deadly-arsenic/
Published: Feb 25, 2017
Author: Ian Graber-Stiehl
Post Date: 2017-02-25 07:05:07 by Ada
Keywords: None
Views: 315
Comments: 18

PEOPLE in a south American desert have evolved to detoxify potentially deadly arsenic that laces their water supply.

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 microgram 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).

The variants that protect the Camarones people are called single nucleotide polymorphisms – changes in a single DNA letter of the genetic code. Anthropologist Lorena Madrigal of the University of South Florida in Tampa says these are such tiny mutations that they aren’t telling us exactly how the changes affect the enzyme molecule and its detoxifying effects.

Previous studies found similar mutations in the AS3MT gene that contribute to improved arsenic metabolisation in Vietnam and Argentina. Sequencing the entire chromosomal region around this gene could reveal more, but there’s still a long way to go before we fully understand the molecular mechanism for how arsenic resistance works.

Though it’s a fascinating example of what appears to be contemporary evolution in humans, it also underscores the water quality problems that many populations face, says Madrigal. And many may not be able to evolve to deal with it.

Another notable example of recent human evolution is lactose tolerance. A mutation which allowed adults to keep producing the enzyme lactase to digest milk emerged around 7000 years ago, alongside dairy farming, and now 35 per cent of adults carry it and can digest milk as a result.

“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,” says Aaron Miller at Northwestern University in Evanston, Illinois.

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Begin Trace Mode for Comment # 18.

#1. To: Ada (#0)

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.

And they didn't migrate to where the water was good because........?

The question has to be asked,"Wouldn't humanity be stronger if idiots like this had died out before they were able to breed?"

sneakypete  posted on  2017-02-25   8:50:43 ET  Reply   Untrace   Trace   Private Reply  


#3. To: sneakypete (#1)

And they didn't migrate to where the water was good because........?

Because they didn't need to? Because they didn't know what arsenic was? Because they didn't know their water supply was contaminated?

Pinguinite  posted on  2017-02-25   9:28:47 ET  Reply   Untrace   Trace   Private Reply  


#8. To: Pinguinite, randge, sneakypete, BTP (#3)

While less than those living in the Chilean desert (or Bangalesh), we get our share from apples and apple juice as well as rice grown outside the US.

Ada  posted on  2017-02-25   16:14:24 ET  Reply   Untrace   Trace   Private Reply  


#9. To: Ada (#8)

from Wikipedia: Arsenic->Applications->Agricultural

Arsenic was also used in various agricultural insecticides and poisons. For example, lead hydrogen arsenate was a common insecticide on fruit trees,[53] but contact with the compound sometimes resulted in brain damage among those working the sprayers. In the second half of the 20th century, monosodium methyl arsenate (MSMA) and disodium methyl arsenate (DSMA) – less toxic organic forms of arsenic – replaced lead arsenate in agriculture. These organic arsenicals were in turn phased out by 2013 in all agricultural activities except cotton farming.[54]

The biogeochemistry of arsenic is complex and includes various adsorption and desorption processes. The toxicity of arsenic is connected to its solubility and is affected by pH. Arsenite (AsO3− 3) is more soluble than arsenate (AsO3− 4) and is more toxic; however, at a lower pH, arsenate becomes more mobile and toxic. It was found that addition of sulfur, phosphorus, and iron oxides to high-arsenite soils greatly reduces arsenic phytotoxicity.[55]

Arsenic is used as a feed additive in poultry and swine production, in particular in the U.S. to increase weight gain, improve feed efficiency, and to prevent disease.[56][57] An example is roxarsone, which had been used as a broiler starter by about 70% of U.S. broiler growers.[58] The Poison-Free Poultry Act of 2009 proposed to ban the use of roxarsone in industrial swine and poultry production.[59] Alpharma, a subsidiary of Pfizer Inc., which produces roxarsone, voluntarily suspended sales of the drug in response to studies showing elevated levels of inorganic arsenic, a carcinogen, in treated chickens.[60] A successor to Alpharma, Zoetis, continues to sell nitarsone, primarily for use in turkeys

Dakmar  posted on  2017-02-25   18:39:01 ET  Reply   Untrace   Trace   Private Reply  


#18. To: Dakmar (#9)

If we Americans eat apples and non-US grown rice, we get a dose of arsenic. A little, I guess, won't harm. The article implied that the Chilean desert dwellers could tolerate a lot more than we can and maybe that toleration was inherited.

Ada  posted on  2017-02-26   10:26:54 ET  Reply   Untrace   Trace   Private Reply  


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