Credit: Dragon Horse
The Pith: Brazil is often portrayed as the second largest black nation in the world, after Nigeria. But it turns out that the majority of the ancestors for non-white Brazilians are European.
One of the more popular sources of search engine traffic to this website has to do with the population genomics of Latin America. For example, my post showing that Argentina is not quite as European a country as it likes to consider itself is regularly cited in online arguments (people of various “persuasions” are invested in the racial status of the Argentine people). But last week in PLoS ONE a paper looking at the patterns of ancestry in the Brazilian population came to a somewhat inverse conclusion as to the self-conception or perception of the preponderant racial identity of that nation. Let me quote from the conclusion of the paper:
Among the actions of the State in the sphere of race relations are initiatives aimed at strengthening racial identity, especially “Black identity” encompassing the sum of those self-categorized as Brown or Black in the censuses and government surveys. The argument that non-Whites constitute more than half of the population of the country has been routinely used in arguing for the introduction of public policies favoring the no-White population, especially in the areas of education (racial quotas for entrance to the universities), the labor market, access to land, and so on . Nevertheless, our data presented here do not support such contention, since they show that, for instance, non-White individuals in the North, Northeast and Southeast have predominantly European ancestry and differing proportions of African and Amerindian ancestry.
The idea that Brazil is majority non-white, that is black, is one I’ve seen elsewhere. Using the American model of hypodescent, where children inherit the racial status of their most stigmatized ancestral component, no matter its magnitude, well over half of Brazilians are “black.” On the other hand, there’s the persistent trend in the recent analyses which show that black Brazilians have a much higher load of European ancestry than black Americans, while white Brazilians have a much higher load of Amerindian and African, than white Americans.
Let’s jump to the paper first. The Genomic Ancestry of Individuals from Different Geographical Regions of Brazil Is More Uniform Than Expected:
Based on pre-DNA racial/color methodology, clinical and pharmacological trials have traditionally considered the different geographical regions of Brazil as being very heterogeneous. We wished to ascertain how such diversity of regional color categories correlated with ancestry. Using a panel of 40 validated ancestry-informative insertion-deletion DNA polymorphisms we estimated individually the European, African and Amerindian ancestry components of 934 self-categorized White, Brown or Black Brazilians from the four most populous regions of the Country. We unraveled great ancestral diversity between and within the different regions. Especially, color categories in the northern part of Brazil diverged significantly in their ancestry proportions from their counterparts in the southern part of the Country, indicating that diverse regional semantics were being used in the self-classification as White, Brown or Black. To circumvent these regional subjective differences in color perception, we estimated the general ancestry proportions of each of the four regions in a form independent of color considerations. For that, we multiplied the proportions of a given ancestry in a given color category by the official census information about the proportion of that color category in the specific region, to arrive at a “total ancestry” estimate. Once such a calculation was performed, there emerged a much higher level of uniformity than previously expected. In all regions studied, the European ancestry was predominant, with proportions ranging from 60.6% in the Northeast to 77.7% in the South. We propose that the immigration of six million Europeans to Brazil in the 19th and 20th centuries – a phenomenon described and intended as the “whitening of Brazil” – is in large part responsible for dissipating previous ancestry dissimilarities that reflected region-specific population histories. These findings, of both clinical and sociological importance for Brazil, should also be relevant to other countries with ancestrally admixed populations.
If you don’t know, the cartoon cut-out is that the northeast of Brazil is the most African inflected region, while the far South is predominantly European. Amazonia has more Amerindian influence, while there is local variation in other parts of the country due to rural to urban migration. Because the ancestry components that the authors were looking for are very distinctive, with the parent populations being separated for tens of thousands to hundreds of thousands of years, I assume 40 well selected markers are sufficient. Over 900 individuals is a large number. I jumped to the detailed methods, and was a little curious as to possible sampling bias introduced by their locations of collection, universities. Nevertheless, after 10 years of these sorts of papers I am convinced that there really does seem to be a fair amount of admixture in the Brazilian population across color lines.
The authors focused on three major color categories, white, brown, and black. These are self-descriptions for most of the participants, though the methods indicate that the southern sample was classified visually by the researchers. To get a sense of the relevance of these categories quantitatively the book Race in Another America: The Significance of Skin Color in Brazil, is useful (the low stars given on Amazon to this book seem to do with the reviewers being dumb or angry that the author didn’t have a big enough axe to grind). Roughly, Brazil shakes out as a “layer cake,” with (on average) blacks on the bottom, whites on top, and browns in the middle.
To the left you see the excepted triangle plots, with each vertex representing an ancestral component. The apex is European on each triangle (don’t deconstruct that!), with African to the bottom left and Amerindian to the bottom right. The leftmost column consists of self-identified whites, the right-most column self-identified blacks, and the middle column browns. Each row consists of a set of samples from a specific geographic region. To get a sense of national patterns the authors report that a 2008 survey indicated that of Brazilians 48.4% identified as white, 43.8% as brown, 6.8% as black, 0.6% as yellow, and 0.3% indigenous. These are social constructs. In fact, it seems likely that the indigenous genetic contribution to the total Brazilian population is actually 10-15%, relatively evenly distributed across the white, black, and brown categories. Additionally, American sociologists have generally observed that while very light-skinned individuals with some African ancestry self-identify as black in the USA, in Brazil the same individuals would probably identify as white. That’s a function of the differences between North American and Brazilian societies.
In any case, as you can see above there are differences between the color categories. Whites have more European ancestry, blacks more African, and browns are more mixed, with those in the north having more Amerindian quantum than those elsewhere. Here are the summary statistics by region & self-identification:
|South (Rio Grande do Sul)||European||0.86||0.44||0.43|
There’s nothing that surprising in this. The rank order is as you’d expect…except that blacks in the far south, where they are a much smaller minority, have less, not more, European ancestry. This is counter-intuitive because the presumption is that in blacker regions the threshold for being white is lower, while in whiter regions the threshold for being black is lower. You see the first in Bahia, where the typical white is about 2/3 European in ancestry, vs. Rio Grande do Sul, where European ancestry is at the level of Argentina genetically. I don’t think the authors have a good explanation for this, and even at their N there might be issues with representativeness that is distorting the results.
A common finding, which shows up in this research, is that there isn’t that big of a difference in the averages between some of the color categories in terms of ancestry. You can see that clearly in the figure to the left, from the paper Color and genomic ancestry in Brazilians: a study with forensic microsatellites. Again you have the three color categories, with their position on the y axis proportional to their “index of African ancestry.” The average rank order is perfectly correct, but there’s a great deal of overlap. The sample was from Sao Paulo. This is not typical in the United States. African Americans may be about ~20-25% European, with 10% being more than 50%, but the rate of non-European admixture in American whites is generally rather low. Only a small minority of American whites have anywhere near the median among of non-European ancestry among Brazilian or Argentine whites.
The main argument of the paper, which is in line with that of a long line of papers coming out of Brazil over the past ten years, is that assortative mating over the past 300 years has maintained phenotypic races, despite ancestral admixture. In other words, the physical difference between the color categories is much clearer than their ancestral quanta. Why? Because skin color, and perhaps traits like hair curl and nose form, as controlled by a small number of genes. In the case of skin color most of the variance is accounted for by less than half a dozen genes! We all know that among mixed-race siblings some individuals will resemble one race much more than the other, despite similar ancestral quanta. Rashida Jones regularly “passes” for white for her television roles, while her sister Kidada looks a bit more African American. As long as humans fix upon salient characteristics the “post-racial” idea is probably a delusion of idealism.
In any case, probably the most interesting and original aspect of the paper is the demographic one. I’ll quote:
We believe that the regional disparities in mtDNA ancestry were maintained because, once again, in the immigratory wave of Europeans there was a significant excess of males. When they admixed with the Brazilian women there was rapid europeanization of the genomic ancestry, but preservation of the established matrilineal pattern. There is demographic information to corroborate this possibility. First, of 1,222,282 immigrants from all origins that arrived in the Port of Santos in the period 1908–1936 the sex ratio (males/females) was 1.76…Second. the two most abundant immigrants, Portuguese and Italians, had sex rations of 2.12 and 1.83, respectively. census data of 1910 showed concordant results: there were 1,138,582 foreigners in Brazil, with a male/female ratio of 1.74, while there were 22,275,595 Brazilians with an even sex ratio of 1.0.
I’ve poked around for this sort of data before, and it is often hard to find. The Brazilian pattern, with a huge bias toward male migration, has probably been the pattern across much of human history with long distance travel. The United States is a great exception, with intact families settling New England early on (though the South exhibited a more Brazil like pattern, the admixed element was reabsorbed into the slave population). I think this has resulted in some weird inferences from historical population genetics derived from mitochondrial DNA, which passed through the maternal lineage (example: mtDNA of India didn’t predict very well how much closer Indians were going to be to West Eurasian populations when autosomal studies utilizing hundreds of thousands of markers came online).
Finally, a lot of these authors in these papers coming out of Brazil seem rather political when it comes to genomics, race, etc. I have no knowledge of the detailed back story, and I don’t believe that anything but conspiratorial manipulation could result in the consistent pattern in the data. But, in a heterogeneous population there’s always going to be worries about representativeness. From what little I know an awful lot of Brazilians are like Gisele Bündchen, the grandchildren or great-grandchildren of European immigrants. If so, they shouldn’t have any non-European ancestry. So I do wonder if there’s some conscious or unconscious undersampling going on because the researchers want to promote the idea of a racially admixed population.
Citation: Pena SDJ, Di Pietro G, Fuchshube-Moraes M, Genro JP, & Hutz MH (2011). The Genomic Ancestry of Individuals from Different Geographical Regions of Brazil Is More Uniform Than Expected PLoS ONE : 10.1371/journal.pone.0017063
Links to this Post
- Linkage is Good for You: Last of the Old Edition | February 27, 2011