Patterns of admixture in Latin American mestizos

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New PLOS paper, Geographic Patterns of Genome Admixture in Latin American Mestizos. Nothing new, but pushing the ball forward….

A = autosomal
X = X chromosomal

24 Comments

  1. Interesting. The European fractions in Mexicans are really quite a bit higher than I would have guessed—looks like they could be close to 50-50 on the autosomal side, at least in the more urbanized areas if gigantic Mexico City isn’t a total outlier.

  2. Interesting. The European fractions in Mexicans are really quite a bit higher than I would have guessed 
     
    two points 
     
    1) the immigrant stream to the USA might not be representative 
     
    2) i think a bigger issue, many americans see more native mestizos on the street, but might not recognize whiter looking american mestizos as latino at all. so there’s a strong bias in visual perception i think in terms of the image of what american latinos look like…..

  3. Catamarca is intereting, as it is the most skewed in terms of % NA mtDNA, but % Euro autosomal. 
     
    Could this be that they was selection for NA mtDNA in these people, or was in selection for Euro autosomal?

  4. Could this be that they was selection for NA mtDNA in these people, or was in selection for Euro autosomal? 
     
    not mtDNA, it’s X chromosome. remember, 2/3 of X’s are in females in any given generation. mtDNA would be even more skewed.

  5. i think a bigger issue, many americans see more native mestizos on the street, but might not recognize whiter looking american mestizos as latino at all. so there’s a strong bias in visual perception i think in terms of the image of what american latinos look like….. 
     
    Yes, I’d thought this was a persuasive argument a year or so ago when those first surprisingly-high European-ancestry numbers came out for American Latinos. But those samples were too small and isolated to be broadly determinative, which is why I’m so surprised the numbers seem so high throughout Mexico. 
     
    Another way of looking at these figures is that they mean that Mexicans might actually have a higher fraction of European ancestry than do “European” Jews. Maybe our census categories should therefore be switched around…

  6. Hmmm, 
     
    What does this say about the expected average intelligence among Mexican derived people?  
     
    Also, what about Y chromosomes? All European-derived?

  7. Also, what about Y chromosomes? All European-derived? 
     
    mostly (majority). the autosomal numbers don’t surprise me that much, impressionistically the Y’s were more exclusively euro than the mtDNA’s non-euro (though not always).

  8. Sorry for a stupid question, but I have to ask it. The story goes that Latin population basically is descended from Spanish males (the Conquistadores) and native females. Therefore, there should be a pronounced asymetry between autosomal and chromosomal proportion. European females were scarce in Medellin, so the population should be mostly native A and not European A. Something seems wrong or I am wrong.

  9. Y chromsome = all from males 
    mtDNA = all from females 
    X chromosome = 2/3 from females 
    autosomal = 1/2 from each sex 
     
    autosomal = all non sex chromosomal nuclear genome 
    i.e., ( not X & not Y & not mtDNA ), the disjoint set of the union of the aforementioned. 
     
    clear enough? 
     
    (no offense people, but you could look it up in wikipedia….)

  10. Thanks. One problem I have with this study is its (inexistent) definition of mestizo. It does not study the population of the country or a city (such as mexico City) as a whole (which some of the commenters seem to think), but only an undefined population called “mestizo”. Now I come from Latin America and there is nowhere any population that could be called mestizo, except in Bolivia (which does not participate in the study). Even in Bolivia, mestizo was – when existed – a social class, more than a racial group. In Argentina (Salta, Tucuman), there was never any separate mestizo group. I cant imagine how they selected the study individuals. On the other hand, Colombian population (Medellin) can be considered entirely “mestizo”.  
     
    Other that, the strong sexual bias of the African inflow into mestizo groups seems to mean something regarding Indian vis-a-vis African competition.

  11. Minor correction: 
     
     
    mtDNA = all from males 
     
     
    Make that females. 
     
    This seems to illustrate very well the precarious position males are in. It is most likely that the peopling of the Americas was driven my male desire to explore new lands and needs get away from other, dominant males. And yet their Y chromosomes have been replaced by those of other males. 
     
    Of course. quite a few of their autosomal genes might still be around.

  12. It is most likely that the peopling of the Americas was driven my male desire to explore new lands and needs get away from other, dominant males. And yet their Y chromosomes have been replaced by those of other males. 
     
     
    male haplotypes tend to be younger and exhibit more Fst from what i recall. IOW, every now and then “super male” lineages show up to clean out the dead wood….

  13.  
    male haplotypes tend to be younger and exhibit more Fst from what i recall. IOW, every now and then “super male” lineages show up to clean out the dead wood…. 
     
     
    Indeed. I have seen suggestions that they are half as young as female haplotypes. This is suggested here: Is There Anything Good About Males 
     
    That has certain implications for, ummm, infidelity rates and paternity …

  14. I’m being so well behaved right now.

  15. The Medellin area was characterized by heavy settlement during the 19th century from northern Spain, usually by families.

  16. i think a bigger issue, many americans see more native mestizos on the street, but might not recognize whiter looking american mestizos as latino at all. so there’s a strong bias in visual perception i think in terms of the image of what american latinos look like….. 
     
    A variation on this, applicable specifically to Mexicans, is that many of the more Indian-looking people Americans think are Mexican are actually Central American. As a result there’s a perception of Mexicans being more visibly Indian than they really are. It happens because Mexicans are the dominant Latin American group, with people assuming any Latin-looking person is Mexican. 
     
    Yet another variation happens in the Northeast, with its sizable population of Caribbean Hispanics. We tend to think of Puerto Ricans, the dominant group in the area, as being darker than they really are because many of the blacker-looking Hispanics assumed to be Puerto Rican are actually Dominican.

  17. It would be very interesting to see a similar regional genetic analysis for self-identified American “blacks.” In particular, I’d be curious about whether there’s any sort of gender-skewed ancestry in that group.

  18. As said, without a definition of the study population (mestizos) the whole thing is rather worthless. What I see, for example in Salta (an Argentine province bordering with heavily Indian Bolivia) is that the Indians have been making more babies to white women than white men to indian girls. And in Medellin something similar may have been going on. Regarding the accepted history of Medellin, few European women ever reached those remote mountains. Maybe the history is wrong. What is very salient that the great losers – to the Indians as well to the Europeans, are the Africans. The initial composition of AFricans was highly skewed toward males, so their relative position is even worse than shown in the graph.

  19. What does this say about the expected average intelligence among Mexican derived people? 
     
     
    I’m not sure how authoratative a source the GSS is, but Rob Guhname recently calculated that the average IQ for Mexican-Americans born in the U.S. rose from 85 to 95 in the last thirty years. If so, this puts them on par with some southeast Europeans.  
     
    http://inductivist.blogspot.com/search/label/Mexican%20Americans

  20. As said, without a definition of the study population (mestizos) the whole thing is rather worthless.  
     
    Unless I’m misreading this paper, it drew its samples from previous studies throughout Latin America. Perhaps those studies contained definition(s) for “mestizo?” I tried to look but I could only find the abstracts to those studies that this paper references, and the abstracts didn’t say.

  21. A breakdown by social class of the amount of European ancestry would be appreciated, instead of just an overall picture of the “mestizo” population.  
    In Mexico, everybody has an amount of Amerindian ancestry, except recent immigrants. Even in the upper classes who look the whitest. Same goes for Colombia. 
     
    The lower the class you would expect the less balance between autosomal and chromosomal analysis.

  22. Native mothers would mean the offspring look more like natives than European, wouldn’t it?

  23. @j:  
     
    Successive waves of European male immigrants would also increase the percentage European X-chr. In such cases, it would be (roughly) European guys mating with every generation more Europeanized American Mestizo women. This is an oversimplification, of course, but was suggested in some older study on Colombia.  
     
    But certainly you are right on the story not being as simple as “the white males took the native females and killed the native males”. There’s a tendency in that article’s interpretation to oversimplify and exaggerate. You are also possibly right in the problem of lack of definition of what is “Mestizo”. I assume they asked the sampled people for their self-identification as such but obviously a vast majority of Latin Americans self-define themselves as “Mestizo” (mixed race, specially from European and Native American).  
     
    I also noticed that some of the less “white” groups (4 out of 5) seem to be paternally more Native than Euro, while the sex bias is constant for the African input in all samples. I assume that these groups are very rural and had “problems” getting new (socially more acceptable, at least in the past) white males over time (possibly local mestizo males emigrated, while women stayed), so after an early standard mestization, native male input became bigger.  
     
    It’s not like all natives were wiped out nor anything close to that, though the situation varied a lot. What is clear is that the arrival of European women was for long very limited.

  24. Native mothers would mean the offspring look more like natives than European, wouldn’t it? 
     
    Why? They should look exactly intermediate in the simplest case of a European father and a Native mother, with the natural random variation. Of course, both Europeans and Native Americans show different phenotypes (it’s not like they are all made out of the same mould, you know) and some Mediterranean Euros are pretty dark featured, while some Native Americans approach somewhat the West Eurasian looks, so it’s not always easy to say.  
     
    Some of my cousins (half Basque, half Spaniard) look very very dark (for European standards) but it’s impossible to tell (at least without genetic analysis) if that’s because of Mediterranean ancestry or some other exotic one, like Native American or (as my mother has some times suggested) Filipino.  
     
    Looks can be very misleading.

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