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, 100 (1), 177-82

Color and Genomic Ancestry in Brazilians

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Color and Genomic Ancestry in Brazilians

Flavia C Parra et al. Proc Natl Acad Sci U S A.

Abstract

This work was undertaken to ascertain to what degree the physical appearance of a Brazilian individual was predictive of genomic African ancestry. Using a panel of 10 population-specific alleles, we assigned to each person an African ancestry index (AAI). The procedure was able to tell apart, with no overlaps, 20 males from northern Portugal from 20 males from São Tomé Island on the west coast of Africa. We also tested 10 Brazilian Amerindians and observed that their AAI values fell in the same range as the Europeans. Finally, we studied two different Brazilian population samples. The first consisted of 173 individuals from a rural Southeastern community, clinically classified according to their Color (white, black, or intermediate) with a multivariate evaluation based on skin pigmentation in the medial part of the arm, hair color and texture, and the shape of the nose and lips. In contrast to the clear-cut results with the African and European samples, our results showed large variances and extensive overlaps among the three Color categories. We next embarked on a study of 200 unrelated Brazilian white males who originated from cosmopolitan centers of the four major geographic regions of the country. The results showed AAI values intermediate between Europeans and Africans, even in southern Brazil, a region predominantly peopled by European immigrants. Our data suggest that in Brazil, at an individual level, color, as determined by physical evaluation, is a poor predictor of genomic African ancestry, estimated by molecular markers.

Figures

Figure 1
Figure 1
Geographic localization of Brazilian localities selected for study: north region (states of Amazonas, Acre, Rondônia, and Pará), northeast region (Pernambuco), southeast region (Minas Gerais), and south region (Paraná, Santa Catarina, and Rio Grande do Sul). In the state of Minas Gerais (southeast) the approximate location of Queixadinha is indicated (⊗).
Figure 2
Figure 2
Box plot graph showing the distribution of values of AAI in samples of the northern Portuguese population (n = 20), Africans from São Tomé Island (n = 20), and Amerindians (n = 10). Each group is represented as a box whose top and bottom are drawn at the lower and upper quartiles, with a small square at the median. Thus, the box contains the middle half of the scores in the distribution. Vertical lines outside the box extend to the largest and the smallest observations within 1.5 interquartile ranges from the box (20).
Figure 3
Figure 3
Slot plot graphic [GraphPad (San Diego) prism software, version 2.01] of the AAIs from the three rural samples grouped according to their phenotype (30 black, 114 intermediate, and 29 white individuals) as well as from two of the Brazilian parental populations (20 Africans from São Tomé and 20 Europeans from Northern Portugal). Each symbol indicates the AAI value from one individual.
Figure 4
Figure 4
Box plot graph showing the distribution of values of AAI in samples from Brazil (n = 200) and from the main regions of the country (NE = northeast, N = north, SE = southeast, and S = south). For comparison we included the data obtained from northern Portuguese and from the rural sample of white Brazilians already shown in Fig. 3. Each group is represented as a box whose top and bottom are drawn at the lower and upper quartiles, with a small square at the median. Thus, the box contains the middle half of the scores in the distribution. Vertical lines outside the box extend to the largest and the smallest observations within 1.5 interquartile ranges from the box (20).

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