Abstract
Brazil never had segregation laws defining membership of an ethnoracial group. Thus, the composition of the Brazilian population is mixed, and its ethnoracial classification is complex. Previous studies showed conflicting results on the correlation between genome ancestry and ethnoracial classification in Brazilians. We used 370,539 Single Nucleotide Polymorphisms to quantify this correlation in 5,851 community-dwelling individuals in the South (Pelotas), Southeast (Bambui) and Northeast (Salvador) Brazil. European ancestry was predominant in Pelotas and Bambui (median = 85.3% and 83.8%, respectively). African ancestry was highest in Salvador (median = 50.5%). The strength of the association between the phenotype and median proportion of African ancestry varied largely across populations, with pseudo R2 values of 0.50 in Pelotas, 0.22 in Bambui and 0.13 in Salvador. The continuous proportion of African genomic ancestry showed a significant S-shape positive association with self-reported Blacks in the three sites, and the reverse trend was found for self reported Whites, with most consistent classifications in the extremes of the high and low proportion of African ancestry. In self-classified Mixed individuals, the predicted probability of having African ancestry was bell-shaped. Our results support the view that ethnoracial self-classification is affected by both genome ancestry and non-biological factors.
Highlights
Brazil never had segregation laws defining membership of an ethnoracial group
With regards to Native American ancestry, there was no clear pattern: in Pelotas, persons self-reported as Mixed and Black had significant higher median of Native American ancestry than Whites; in Bambuı, only persons self-reporting as Mixed showed higher level of Native ancestry, while in Salvador this was true only for persons self-reporting as White
Self-classified Mixed individuals showed a bell-shaped predicted probability of having African ancestry in all sites. This is the first large community-based multicenter study to investigate the association between individual proportions of genome-wide based African, European and Native American ancestries and likelihood of ethnoracial self-classification in Brazil
Summary
Brazil never had segregation laws defining membership of an ethnoracial group. the composition of the Brazilian population is mixed, and its ethnoracial classification is complex. Brazil never had segregation laws defining who should belong to an ethnoracial group, as the United States and South Africa had This was probably a result of the Brazilian elite decision to ‘‘whiten’’ the Brazilian population through miscegenation rather than impose segregation; and ethnoracial classification was left to individual perception[2]. The composition of the Brazilian population is more mixed, and its ethnoracial classification is more complex and fluid than in those countries where segregation was imposed by law[2] This was to such a degree that it has been questioned whether – and how – ethnoracial classification in Brazil correlates with genomic ancestry. We used 370,539 Single Nucleotide Polymorphisms (SNPs) to quantify the association between likelihood of self-classification as White, Mixed and Black and genome-wide based individual proportions of African, European and Native American ancestry in 5,851 participants of these cohorts
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