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, 6 (2), e17063

The Genomic Ancestry of Individuals From Different Geographical Regions of Brazil Is More Uniform Than Expected

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The Genomic Ancestry of Individuals From Different Geographical Regions of Brazil Is More Uniform Than Expected

Sérgio D J Pena et al. PLoS One.

Abstract

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.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Map of Brazil showing the five geographical regions of the country.
The regions with a square label were analyzed in this work. The cities and respective states where the samples were collected are shown with a star.
Figure 2
Figure 2. Triangular plots of the genomic proportions of African, European and Amerindian ancestry in three self-reported color groups of 934 Brazilian individuals from four different regions of the country, self-categorized White, Brown and Black individuals.
Each point represents a separate individual and the ancestral proportions can be determined by dropping a line parallel to each of the three axes. The graphs were drawn using the Tri-Plot program .
Figure 3
Figure 3. Triangular plot and table of the genomic proportions of African, European and Amerindian ancestry in four different regions of Brazil, independent of color category.
Each point represents a separate region, as follows (1) North (Pará), (2) Northeast (Bahia), (3) Southeast (Rio de Janeiro) and (4) South (Rio Grande do Sul). The graph was drawn using the Tri-Plot program .

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