Mexican Genetics Study Reveals Huge Variation in Ancestry

Medical Xpress, June 12, 2014

In the most comprehensive genetic study of the Mexican population to date, researchers from UC San Francisco and Stanford University, along with Mexico’s National Institute of Genomic Medicine (INMEGEN), have identified tremendous genetic diversity, reflecting thousands of years of separation among local populations and shedding light on a range of confounding aspects of Latino health.

The study, which documented nearly 1 million genetic variants among more than 1,000 individuals, unveiled genetic differences as extensive as the variations between some Europeans and Asians, indicating populations that have been isolated for hundreds to thousands of years.

These differences offer an explanation for the wide variety of health factors among Latinos of Mexican descent, including differing rates of breast cancer and asthma, as well as therapeutic response. Results of the study, on which UCSF and Stanford shared both first and senior authors, appear in the June 13, 2014 online edition of the journal Science.

“Over thousands of years, there’s been a tremendous language and cultural diversity across Mexico, with large empires like the Aztec and Maya, as well as small, isolated populations,” said Christopher Gignoux, PhD, who was first author on the study with Andres Moreno-Estrada, first as a graduate student at UCSF and now as a postdoctoral fellow at Stanford. “Not only were we able to measure this diversity across the country, but we identified tremendous genetic diversity, with real disease implications based on where, precisely, your ancestors are from in Mexico.”

For decades, physicians have based a range of diagnoses on patients’ stated or perceived ethnic heritage, including baseline measurements for lung capacity, which are used to assess whether a patients’ lungs are damaged by disease or environmental factors. In that context, categories such as Latino or African-American, both of which reflect people of diverse combinations of genetic ancestry, can be dangerously misleading and cause both misdiagnoses and incorrect treatment.

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“In lung disease such as asthma or emphysema, we know that it matters what ancestry you have at specific locations on your genes,” said Esteban González Burchard, M.D., M.P.H., professor of Bioengineering and Therapeutic Sciences, and of Medicine, in the UCSF schools of Pharmacy and Medicine. Burchard is co-senior author of the paper with Carlos Bustamante, PhD, a professor of genetics at Stanford. “In this study, we realized that for disease classification it also matters what type of Native American ancestry you have. In terms of genetics, it’s the difference between a neighborhood and a precise street address.”

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The study covered most geographic regions in Mexico and represented 511 people from 20 indigenous and 11 mestizo (ethnically mixed) populations. Their information was compared to genetic and lung-measurement data from two previous studies, including roughly 250 Mexican and Mexican-American children in the Genetics of Asthma in Latino Americans (GALA) study, the largest genetic study of Latino children in the United States, which Burchard leads.

Among the results was the discovery of three distinct genetic clusters in different areas of Mexico, as well as clear remnants of ancient empires that cross seemingly remote geographical zones. In particular, the Seri people along the northern mainland coast of the Gulf of California and a Mayan people known as the Lacandon, near the Guatemalan border, are as genetically different from one another as Europeans are from Chinese.

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The study also revealed a dramatic difference in lung capacity between mestizo individuals with western indigenous Mexican ancestry and those with eastern ancestry, to the degree that in a lung test of two equally healthy people of the same age, someone from the west could appear to be a decade younger than a Yucatan counterpart. Burchard said this was clinically significant and could have important implications in diagnosing lung disease.

Significantly, the study found that these genetic origins correlated directly to lung function in modern Mexican-Americans. As a result, the research lays the groundwork for both further research and for developing precise diagnostics and possibly even therapeutics, based on these genetic variations. {snip}

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Over the past few years, researchers have begun to understand that genetic variationhas a very peculiar structure, Bustamante said. Some common genetic variants reach appreciable frequencies (e.g., 30-50 percent) in many of the world’s populations. Most of these appear to have existed in the human gene pool at the time of the great human diasporas, including the migrations out of Africa. However, Bustamante said a “huge flurry” of other mutations have arisen since then, as human populations grew due to the advent and adoption of agriculture. These are much rarer, occurring in about 1- to 2 percent of the population, and are thought to be both more recent and relevant to health and disease. These rare variants make up the bulk of genetic alterations we see in human populations.

Many of these genetic differences already are known to have a direct impact on our risk for certain diseases, such as the BRCA gene in breast cancer, or our ability to metabolize medications. But before we can develop more precise therapies or prescribe them to the right patients, we need far more knowledge of what those variants are across diverse populations, and how they affect health.

“This is driving the ball down the field toward precision medicine,” Burchard said. “We can’t just clump everyone together and call them European Americans or Mexican Americans. There’s been a lot of resistance to studying racially mixed populations, because they’ve been considered too complex. We think that offers a real scientific advantage.”

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  • Samuel_Morton

    This is a fascinating study. Basically it shows that before the Spaniards mixed everyone (and themselves) together, the populations in central America were largely isolated. Who knows what kinds of crazy admixture has been going on in the past 500 years, and what the implications are for the larger Latino population.

    • Zimriel

      The process had started with the Triple Alliance’s conquest of central Mexico, not very long before.

    • John R

      “Latino” population?

  • Samuel_Morton

    This is a fascinating study. Basically it shows that before the Spaniards mixed everyone (and themselves) together, the populations in central America were largely isolated. Who knows what kinds of crazy admixture has been going on in the past 500 years, and what the implications are for the larger Latino population.

  • Shadow

    Regardless of the discoveries revealed in this study,I still don’t want any more Mexicans living in our country;we have way too many of them the way it is.

  • Shadow

    Regardless of the discoveries revealed in this study,I still don’t want any more Mexicans living in our country;we have way too many of them the way it is.

    • baldowl

      It’s all the wrong ones coming here anyway, the ones wanting good pay for menial labor or, worse, something for nothing.

      • Zimriel

        It’s not even Mexicans these days so much. It’s Guatemalans.

        • John R

          Yeah, who probably don’t even have a trace of White ancestry. Even the Mexicans don’t want them! What does THAT tell you?

        • Sick of it

          El Salvadoran savages…

  • APaige

    So there are “genetic differences” with ‘extensive’ ‘variations’ between “populations that have been isolated for hundreds to thousands of years”? If that is true between groups in close proximity and appearance what about groups that were isolated for thousands of years, separated by great distance and look completely different? I am going to guess it is not a ‘social construct.’

    • John R

      Didn’t you hear? We are all Africans.

  • Tarczan

    So if populations are isolated from one another they end up different by adapting to their environments? Racist.

    • baldowl

      Except black people are just the same as everybody else, except better and more oppressed.

  • Oh great! More money being spent on how to prolong the lives of Mexicans living in the USA. I think I read somewhere (amren?) that Mex-ams live 2 years longer than whites on average anyway. How about spending some money on whites so we can catch up to the Mex-am longevity.

  • Truth Teller

    Mexico has both private, and employment health insurance, free social service medical care for the uninsured and public health service and numerous medical schools. Why doesn’t Mexico do this kind of research for its own people?

  • IKUredux

    The fact that these researchers felt compelled to even engage in this research says volumes about where they see the future of so called “Americans”. Do any of us even care about the genetics of mexicans? Here, let me save you guys some money:They’re short, stupid, and the ones who were able to hold their breath the longest to cross the Rio Grande survived. Meanwhile, how about our veterans? Why don’t you guys do a study and figure out why Whites still feel compelled to sacrifice themselves in the armed services for a country that HATES them, and then treats them worse than illegal pos who don’t even SNEAK across the border, but who apparently are ushered in with open arms and welfare benefits provided by those same White taxpayers whose sons and daughters and Fathers and Mothers in the miliitary are denied even the most rudimentary of benefits and necessary medical care. DO NOT allow anyone in your family to join the military. Unless, a decision has been made that the training could become invaluable.

    • John R

      Yeah, the ones with straight hair and faces wider than they are long are Indians. There, I solved the problem.

  • John R

    Another study that just goes to show what most of we race realists have already known: That this ridiculous classification of people south of the border as “Latino” or “Hispanic” is meaningless. These sub-US countries are racially the most diverse places in the world, and most Mexicans could be more accurately called “American Indian” racially than the people living on our reservations. In these countries it is considered a mark of social advancement to call yourself “White” even if you are not from a purely racial standpoint. Just as people who are really American Indian like to consider themselves “mestizo” instead. To be considered “Indian” in Mexico, you must be of pure Indian blood, live in an Indian community, and speak an Indian language! That is pretty pure injun to me! Yeah, so much for all the “Hispanic” people coming into the US.

  • Sick of it

    All one has to do is look at the old charts and portraits of the many racial castes described by the Spanish to see how much genetic variation exists within Mexico.

  • JDInSanD

    The Mexican government and elites have known this for centuries and they didn’t need DNA studies to figure it out. They’ve been purposely sending us their worst for decades to get rid of them.

  • SlizzardAjeosshi

    Not surprised, considering the pre-Columbian history of North and Meso America.

    Even “progressive scientists” that don’t go for the Solutrean hypothesis now recognise the Continent was not populated through a single migration event by highly homogeneous Central Siberian cluster.

    On top of that millennia of hunter gathering in a naturally rich but demanding environment have contributed to a very high level of genetic drift through population bottlenecks/founder effect which resulted in very identifiable and isolated clusters alll over the territory

  • Different groups of Amerindians are not always closely related. The Navajo and Apache speak an Inuit dialect, so must have been more recent arrivals to the southwest from Alaska and Canada. The Carolina and Oklahoma Cherokee speak a version of Delaware-to-New York Iroquois, which makes them relatives in spite of even their original geographic separation.

    • Carlos Geary

      Michael: I am glad to read your intelligent comment

  • ElComadreja

    But…but….but…..We’re all the same, aren’t we? *sarc*

  • David Ashton

    Multi-ethnicity and/or miscegenation sadly result(s) in health problems. Humanitarian eugenics rather than emigration and unconstrained mating deserves reconsideration. Google “Eugenics in Mexico”.

  • Who Me?

    This lovely “diversity” proves why Mexico is such a cesspool of degeneracy, and is a stark case in point the diversity never works. Now the researchers need to take it just one step further and use this study to point out exactly why we most emphatically DON’T need these people here.

  • Melvin Bonzarelli

    Mexican females are short, squat, fat, hairy, and have enormous, ugly heads. That’s why there is very little interbreeding here in the states between humans and Mexicans. The Mexicans do not like blacks because they are afraid that the blacks will cook and eat them.
    That explains why they remain so genetically isolated once they swim across the Rio Grande and sign up for their welfare checks and food stamps.

    • Gabe

      “That’s why there is very little interbreeding here in the states between humans and Mexicans”

      Have you ever been in California, Arizona, Washington, Texas or New Mexico?

  • Melvin Bonzarelli

    Is there a lawnmower gene? If there is, and it is dominant among the Mexican population, that would explain why they are so good at mowing lawns.

  • Truth Teller

    Whats the messican word for n****r? Guatemalans.

    • Einsatzgrenadier

      Really? I always thought it was pinche mayate.

  • Truth Teller

    John R those faces with a potato shaped nose, wide nostrils, cheeks that look as though a grapefruit were stuffed in each one, low foreheads and misshapen jaws are one indication. The other indication is the body, short stumpy arms and legs, huge out of proportion to the limbs torsos, wide shoulders and pelvises but the women flat chested and flat hipped and enormous bellies on both men and women. Brown bowling balls is what they are. And the indio IQ is more like 82 IQ than the “advanced” mixed IQ of 87

    Bowling ball face and bowling ball body.

  • Truth Teller

    fed up
    The Spanish did not enslave the native people. Isabella of Castile outlawed slavery in the new world in 1498 or97. That was why she sent a Judge and prosecutor to arrest Columbus and bring him back in chains. He had enslaved not only indians but Spainish on his island dominion. Later, in 1540 something the Spanish crown again outlawed slavery
    in all its dominions. Brazil, being Portuguese brought africans to spread the black plague. But slavery was illegal in all Spanish dominions from Isabella’s law cerca 1497 98? on.
    Indentured servitude, serf dom etc are not slavery. A couple centuries later Scots working in coal mines were actual slaves. When baptized in the local protestant church the parents were obliged to “give” their children to the local mine owner who also owned their houses and lands. Those scots were considered slaves under the law. Oliver Cromwell deported about one hundred thousand Irish rebels who were sold as slaves, not indentured servants in the sugar islands of the West Indies. Numerous British were kidnapped and sold as slaves in the West Indies and American colonies. Not indentured servants but slaves.
    Claiming that Spanish colonies enslaved the indians means you believe the propaganda. One reason for the texas mexican war was that the Mexican goverment again outlawed slavery in 1827 which p***ed off the American slave owners the mexicans invited to colonize Texas.

  • Carlos Geary

    Latino is not a race. In Mexico, there is great genetic diversity in the indigenous population; but also in the Mexican population of Spanish ancestry. Spain is not a homogeneous country; the mountain areas of the northeast are populated by Celts (Gallegos), the northwest by the Catalans (Germanic stock), there also Basque territory which has been continually populated for 30,000 years. All of those mountain areas have a very different population from the genetic point of view compared to the low lands which were under the Roman and Moor rule. The Romans and, later, the Moors never really got much of a foothold in the Basque, Celt or Catalan Country due to its intricate landscape of forest covered mountains and hills and to fierce opposition. There are also Mexicans of French and Asian descend. No every body is mixed, there are full blood Europeans and full blood Indigenous or Amerindian people, as well as mestizos. Same thing in Central America.
    In South America, there is even more diversity, because, there are, also, people of German, Italian, Slavic descend.

    • Gilbert Jacobi

      Carlos,
      Do you know what areas of Mexico had the most contact with the French? Also, how about the Irish; wasn’t there some mixing with the San Patricios?

  • Carlos Geary

    Hispanic is not a race. An skeleton remain can tell you if a person is Caucasian, Back or Asian. Amerindians and Asians share physical characteristics. If you visit any Latin American country you will find people of different races and colors

  • Carlos Geary

    ed Up: Only the very first wave of Spanish conquerors were single men and marry Amerindians. Starting in the middle 1600’s, families from all part of Europe immigrated to Latin America. Mainstream society ignores that Latin America in general, but South America in particular, received great waves of immigration from Italy, France, Germany, Spain, Ireland, Eastern Europeans countries.

    • Gabe

      Argentina has a huge population of Italian and German descendants.