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Genetic research fights disease but it can be hijacked by politics

There’s a huge variety in physical appearance in Latin America: there are indigenous native Americans, descendants of African slaves, Europeans and Middle Easterners of all kinds, and Chinese and Japanese…

Supermodel Gisele Bündchen: sixth generation German, 100% Brazilian. Bob Bekian, CC BY-SA

There’s a huge variety in physical appearance in Latin America: there are indigenous native Americans, descendants of African slaves, Europeans and Middle Easterners of all kinds, and Chinese and Japanese people – plus all those descended from the mixtures of these native and immigrant groups.

While social scientists are quick to point out that this image of racial tolerance is undermined by big problems with racism, biological scientists are interested in Latin American mixture for different reason: genetics. But it’s clear that even between these sciences, a mixing of concepts is also taking place.

Health of a nation

Mapping genetic mixture can be helpful in disease research. Admixture mapping, based on the idea that some health disorders are more common in some populations than others, can be used by scientists to locate disease-causing genetic variants, often for complex diseases such as diabetes – that may have environmental as well as biological underpinnings.

So when the genomes of patients and healthy people are compared, for example, a high level of European ancestry might indicate where on the genome a particular genetic variant might be found. This can narrow the search down from millions of genetic variants. Admixture mapping uses a limited number of markers to analyse ancestry, so it is cheaper and quicker than studies that scope large areas of the genome.

Geneticists’ main aim is to improve human well-being by locating disease-causing genetic variants. And in the process, they produce a lot of data about human diversity, in Latin America and elsewhere. While you might imagine that this all exists within a neutral space, genetic findings can be used to argue much more than whether whole nations, such as Mexico or Brazil, are genetically distinctive enough to need specific drug treatments.

To geneticists, the data usually indicate the non-existence of biological races. But to other groups the same data can be used to support existing ideas about racial differences in society.

Mixing it up

“Genetic admixture” happens when individuals from two or more previously separated populations come together, and in Latin America this comes from African, Native American and European populations. Numerous genetics studies have analysed the ancestry of local populations, generating vast quantities of data about the diversity of the nation, and there is great genetic diversity between and even within countries.

In Mexico, the government’s National Institute of Genomic Medicine mapped Mexicans’ genomes and showed that all Mexicans had some proportion of all three original populations, though the percentages of ancestries varied from region to region. In Colombia, where most people are mixed, regional diversity is very marked, with particular areas having high levels of African, European or Amerindian ancestry.

Quilombolas of Brazil: descendents of Afro-Brazilian slaves. Antônio Cruz/ABr, CC BY-NC-SA

In Brazil, genetic testing has shown that even white Brazilians carry African and Amerindian ancestry informative markers (AIMs) in their DNA. Differences between regions are also noticeable here: the far south of the country has very European ancestry, because of extensive immigration from countries like Italy and Germany. In contrast the north-east has a lot of African ancestry.

Reinforcing racial difference

Geneticists have generally – although not universally – emphasised that the concept of race is not valid in understanding this biological diversity. Although humans vary genetically, most scientists agree it is not possible to divide up that variety into distinct “races”. This is particularly evident in Latin America, because of the history of extensive mixture. Although people in the region may talk about blacks, whites, Indians and mestizos (mixed people), these social categories cannot be defined genetically in a clear way (although this does not stop some people discriminating against others on the basis of their appearance).

Paradoxically, social science research shows that the results of genetic research can have the unexpected consequence of reinforcing everyday ideas about racial difference.

Although geneticists dismiss the validity of biological race, they still talk in terms of European, African and Amerindian genetic ancestries in ways that can indicate, to people less versed in genetic science, that as whole populations, these groups are genetically very separate. Genetic studies also present specific populations and regions within Latin America as quite distinctive in terms of their genetic ancestry, which can suggest that, overall, they are genetically very different from each other.

So although it’s a well-known fact that all humans are genetically more than 99% the same, genetics can feed into existing popular ideas about racial difference and even exacerbate racism.

In Brazil, for example, there have been heated debates about the rights and wrongs of race-based admissions quotas for black people in some public universities. Those in favour argue that such policies help correct decades of racial injustice, while those against say the quotas just reinforce racial divisions and that social injustice should be tackled with colour-blind reforms.

Some critics of the scheme have used genetic research showing that black people in Brazil have substantial amounts of European heritage to argue that there is no “real” black population in Brazil that should benefit from race-based affirmative action policies: all Brazilians are mixed, they say. Defenders of the quotas instead counter that genetics are irrelevant: being black is a social, not a genetic fact. Policemen do not ask for a DNA test before deciding to harass a person who looks black to them.

Genetics don’t exist in a social vacuum. Genetic data may be intended by scientists to simply improve well-being, but the data can also be used – including by the scientists themselves – to support very different positions about human diversity, racial difference and national distinctiveness.

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