Mexican genes, Mexican diseases, and the idea of race

The just-released paper addresses what a Science news story called Mexico’s “stunning amount of genetic diversity.”  Something important can be gleaned about people’s befuddled attitudes toward the idea of “race” from how headline writers responded to this paper.

The paper reported on genomic variation within Mexico, drawing on the genomes of more than 1,000 people from 20 indigenous and 11 mestizo populations. (Mestizos are a mixture of Native American, European, and sometimes African genes.) One of its major points is that the medical profession needs to be more aware of and informed about medically important genetic variation in populations that have often been lumped together as “Mexicans.”

A San Francisco TV station’s website said “UCSF-Stanford study provides unique look at race,” a piece that was picked up and widely circulated, headline and all, by Yahoo News.

Headlines are not usually written by the person who wrote the story, but in this case the headline reflected the article’s first paragraph: “A newly released study by researchers at UCSF and Stanford University could change the way we view race, at least as it applies to how doctors diagnose and treat many of their patients.”

It was news to me that Mexicans are seen (by some) as a “race,” although the study, which demonstrated Mexican genetic multifariousness and largely mixed ancestry, should certainly banish that illogical notion. Yet the TV article didn’t quite want to let “race” go, did it? It conceded that the study “could change the way we view race,” implying that believing Mexicans are a race is a universal (or at least common) idea that “we” hold.  And the article wanted to confine the changed perception to medical matters. Implying that it’s OK (in fact, conventional thinking) to see Mexicans as a race outside a doctor’s office.

The medical meaning of “race”

There’s no consensus on how to define that very slippery term “race,” as I wrote here at the GLP a few weeks ago, and in any case the idea of race is becoming increasingly meaningless because mixed ancestry may now be true of as many as 1 in 7 humans. Whatever your definition, though, “race” has no meaning applied across the board to Mexicans. “Genetically, There’s No Such Thing as a Mexican,” was the (accurate) headline at NBC News. But that does not mean that genetic subpopulations or genetic variation significant for human life and human health do not exist in particular populations.

“Race” is not, of course, a term that the researchers used. If there was ever any doubt, the study made clear also that terms like “Latino” and “Hispanic” are nearly as meaningless as “race.” At most they signify someone born in the Americas whose first language is Spanish. The “Latino” and “Hispanic” labels say nothing about their genes.

National Geographic saw Mexico’s genetic diversity from a different angle. The headline on its news story read “Mexico’s Natives Didn’t Mix Much, New Study Shows.” Not quite accurate, because the researchers found that was true mostly in small isolated populations.

The paper points this out as early as its Abstract, claiming, “Some [Mexican] groups were as differentiated as Europeans are from East Asians.” This refers to dramatic genetic differences between the Seri population (a group of only 1,000 people who live on the Gulf of California coast in northern Mexico) and the Lacandon (a Maya people who live in jungly Chiapas, the southern Mexican state near the Guatemala border.)

The blogger Maju argues that the researchers’ claim is misleading because it applies to tiny populations that have long been isolated from the rest of Mexico. However, despite their apparent genetic differences, both of these small Mexican isolates are descended from well-known Native American populations: the Seri from the peoples of the Uto-Aztecan language family widespread in the Western U.S. and Mexico and the Lacandon, who speak a Maya-derived language.

Latino gene variant for type 2 diabetes

If “race” is at best a sloppy and increasingly undescriptive concept, that doesn’t mean that genetic differences among groups of people don’t exist or don’t matter. Medically significant differences persist even in people of mixed ancestry. The medical profession now knows that East Asians can present different medical problems from Europeans. They are often vulnerable to particular diseases and respond differently to medications and other forms of treatment.

What medicine hasn’t known as clearly, until now, is that classifying people as “Mexican” speaks only to their nationality, not their genes. It explains almost nothing about their medical vulnerabilities nor how they will react to drugs.

Case in point is another new paper about the genes of Mexicans, this one about the genetics of diabetes and published in the Journal of the American Medical Association on June 11.

Some 70 genetic regions have now been associated with Type 2 diabetes, but nearly all have been discovered in studies of northwestern European populations.

Diabetes, however, is the leading cause of death in Mexico. The new research identified a single rare gene variant that quintuples the risk of Type 2 diabetes. The variant is present in about two percent of diabetic Mexicans. The significance of this discovery is potentially enormous, not least because it could have a major effect on the cost of treatment.

The usual diabetes treatment involves the expensive drug metformin, but some types of diabetes respond well to a class of drugs called sulfonylureas. If the new Latino variant turns out to be one of them, the impact on treatment expenses could be dramatic. That’s because sulfonylureas are cheap, according to Karol Estrada, who did the analysis for this paper. He is a research fellow within the Analytic and Translational Genetics Unit at Massachusetts General Hospital and at the Broad Institute, and he blogged about the research at Genomes Unzipped.

Estrada told me in an email, “We actually do not know if the variant is present only in Mexico as we also found carriers in U.S. Latinos (although these could be Mexican-Americans). This is something that we need to follow in much larger studies within and outside Mexico.”

Tabitha M. Powledge is a long-time science journalist and a contributing columnist for the Genetic Literacy Project. She also writes On Science Blogs  for the PLOS Blogs Network. Follow her @tamfecit.

 

3 thoughts on “Mexican genes, Mexican diseases, and the idea of race”

    • No, it does NOT prove what is scientifically invalid. “race” is an invented concept used by SOCIAL scientists. The article discusses the “admixture” (your word) of genetic material.

      Reply

Leave a Reply

glp menu logo outlined

Newsletter Subscription

* indicates required
Email Lists
glp menu logo outlined

Get news on human & agricultural genetics and biotechnology delivered to your inbox.