September 15, 2009

Variable genetic ancestry in Brazilians

Braz J Med Biol Res. 2009 Sep 11. pii: S0100-879X2009005000026.

DNA tests probe the genomic ancestry of Brazilians.

Pena SD, Bastos-Rodrigues L, Pimenta JR, Bydlowski SP.

We review studies from our laboratories using different molecular tools to characterize the ancestry of Brazilians in reference to their Amerindian, European and African roots. Initially we used uniparental DNA markers to investigate the contribution of distinct Y chromosome and mitochondrial DNA lineages to present-day populations. High levels of genetic admixture and strong directional mating between European males and Amerindian and African females were unraveled. We next analyzed different types of biparental autosomal polymorphisms. Especially useful was a set of 40 insertion-deletion polymorphisms (indels) that when studied worldwide proved exquisitely sensitive in discriminating between Amerindians, Europeans and Sub-Saharan Africans. When applied to the study of Brazilians these markers confirmed extensive genomic admixture, but also demonstrated a strong imprint of the massive European immigration wave in the 19th and 20th centuries. The high individual ancestral variability observed suggests that each Brazilian has a singular proportion of Amerindian, European and African ancestries in his mosaic genome. In Brazil, one cannot predict the color of persons from their genomic ancestry nor the opposite. Brazilians should be assessed on a personal basis, as 190 million human beings, and not as members of color groups.

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2 comments:

Kepler said...

Well, results are no surprise. I found the last sentence a bit superfluous.
"Brazilians should be assessed on a personal basis, as 190 million human beings, and not as members of color groups."
As opposed to what other nation?
Another thing is to say Brazilians, as most Latin Americans, have a lot of recent genetic admixture.

Ponto said...

I think the researchers have proven their hypothesis: A person's phenotype, i.e race or sub racial physical appearance, has only a small part to do with most of a person's individual genome. Most are common to humanity as a whole, and found in every human racial group.

It just proves to me that studying genes, SNPs or indels may prove illuminating to some on admixture in humans with a capital A, but basically boils down to genes, SNPs and indels that are more based on geography with a capital G, and are basically meaningless when it comes to actual racial or sub racial physical appearance. Many Europeans, sub Saharan Africans, and the peoples living in Asia already contained many of those admixture indicators before immigrating to the Americas from their home continents. Amerindians are similar to Eastern Asians. Europeans of the main racial types are closest to sub Saharan Africans genetically anyway.

I prefer those studies using many thousands of SNPs which show how groups of humans, ethnic groups, nationalities differ from each other in a clinal way and show change of sub groups in main racial groups from continents to continents e.g. Europeans from Southwest Asians to South Asians into Central and East Asia.