GENEWATCH
 
UNTANGLING POPULATION MIXTURE?
By Carlos Andrés Barragán
 

from GeneWatch 28-2 | June-Sept 2015

 

Human genomics is a burgeoning field of research in Latin America, enabled mostly by North-South and South-South collaborations among private and public laboratory networks. After the completion of the first sequence of the human genome in 2000, the promise that genomics would deliver humanity into an era of personalized medicine by mobilizing life scientists, pharmaceutical companies, and governments around the world into a frantic mapping agenda of genomic aspects of patients and the populations they represent. Latin America and the Caribbean have not been an exception. The region encompasses 32 countries and nearly 10% of the world's population. Scientists treat Latin America as a living laboratory to understand the branching of Homo sapiens out of Africa and the contemporary constitution of human genetic diversity itself; entrepreneurs, on the other hand, frame the region as an untapped source of human subjects for pharmaceutical trials and as a great consumer market to deliver medicine.

In recent years countries like Argentina, Brazil, Chile and Mexico have been channeling considerable public funds into the study of their respective populations. Perhaps the most notorious example is the creation in 2004 of the Instituto Nacional de Medicina Genómica (INMEGEN) en Mexico, framed as a biotechnological nationalist project whose main goals have been to produce first-class research specifically tailored for the Mexican population and to increase therapy efficacy.[1] But from all the different sorts of biological samples used in medicine, the collection of blood samples for genetic sequence and analysis is the one that causes more criticisms in Latin America. At stake are not only ethical dimensions (i.e. informed consent, inclusion), but also concerns over property rights and issues of representation, particularly about the scientific claims produced about the individuals sampled and the populations they represent. Let us consider how these efforts look from a university research network situated in the United Kingdom.

Delivering maps

On March 21, 2008, BBC's Science & Nature section featured an article on recent genetic findings on the history of its human populations.[2] The story explored the research of Andrés Ruiz Linares, a medical doctor at University College of London's Biology Department, whose work focuses on geographic patterns of genome admixture in Latin American "mestizos." According to the BBC story, Ruiz's study suggests a "clear [genetic] signature" among contemporary individuals representing mestizo populations from seven countries (Argentina, Brazil, Chile, Colombia, Costa Rica, Guatemala, and Mexico). Despite a great genetic admixture variation and the presence of Native American genetic "heritage" within the countries considered, the study found that three parental populations - Native American, African, and European - had, since the 16th century, changed into the singular mixed category of mestizos. The newsworthiness of Ruiz' findings was based in its potential to change how Latin Americans perceive themselves. The BBC article quotes Ruiz as saying: "It is very important in terms of rescuing the past and recognizing the roots of the population, and the living presence of natives within the current population." The BBC story also stated that, in addition to offering a window into the past, Ruiz's research agenda might hold medical value in understanding the genetic basis of complex human traits, like disease, within the Latin American mestizo populations.

Mestizos: What is in a name?

Ruiz and his research team had published their results in the scientific journal Public Library of Science Genetics. But a close reading of their article, "Geographic Patterns of Genome Admixture in Latin American Mestizos," brings to the table more questions and challenges than just a reminder of the historical deleterious political, economic and population effects of Europe's colonization of the New World.[3] The most obvious concerns the meaning of mestizo as a phenotypic category identifying a human being, and of mestizaje as a mixing process.

In Spanish-speaking areas of the Americas, mestizo has been exclusively used to describe in racial terms the offspring of Europeans and Native Americans. Later, it has been deployed to describe a general process and state of racial mixture, in a similar manner to the way in which "miscegenation" has been used to describe the interbreeding of people considered to be of different inferior racial types. In different contexts of Latin America the concept of mestizo stands also in contrast to cultural and biological identities of Native Americans, Whites, and Blacks/Afro-descendants. According to social science scholarship, however, the concept of race and racial categories are social constructions that are described as biological facts. Anthropologist Verena Stolcke argues that mestizos are not born, but are made. Stolcke's work describes how the category mestizo has been used to justify political and economic inequalities across the Americas, and that its meaning is flexible and made to adjust to local understandings of race and racial purity.[4] Mestizo as a racial and cultural category is one of those abstractions shifting in time and space in the imagination of laypeople, ascribed to biology and genetics in the work of social and life scientists since the late 18th century. But if we are to accept Stockle's argument, why can contemporary population geneticists like Ruiz find mestizos and genealogically measure them in time and space?

The key to this lies in understanding how scientists conceive of and sample the populations they study. Life-scientists are grounded in particular social contexts which inform their conceptual and methodological approaches. Admixture mapping traces genotypic differences when historically separated human populations reproduce. These separated human populations are described as "ancestral" or "parental" populations; in the context of the history of Latin America, these populations are defined as "Native American," "European," and "African." At the molecular level a mestizo is thus one that shows genetic imprints in different percentages of Native Americans (from Pre-Columbian and Colonial times), Europeans, and sometimes of Africans. But the problem with each of these geographical biological characterizations is that they have been produced since the 1990s using racial and ethnic categories that end up portraying parental populations as genetically homogenous. Thus the statistical apparatus that allows the comparison of "ancestry informative markers" (AIMs) can be misleading.

Data obtained in the case study considered here is not just objectively guiding us to identify a biological natural kind (i.e. Latin American mestizos). That would be impossible considering that the data is profoundly shaped by the very definitions of ancestral populations and the limitations of using them as a model, as an approximation to detect change or continuity in the genetic structure of a population. If we are to read Latin American mestizos as a natural kind (the embodiment of objective ancestry elements), can we ask how the authors' geographic characterization of mestizo populations distances itself or overlaps lay or legal racial/ethnic readings of mestizos across the region? In other words: Are scientists' geographic patterns of genome admixture for mestizos different or similar from the racial/ethnic realities perceived by the very same tissue donors and the populations they represent? Furthermore, what happens when the category "mestizo" travels within scientific networks in which it does not hold a common meaning, and then the donors and populations studied get standardized instead as Hispanics or Latin Americans?[5]

The proxying processes through which mestizos are translated into "Hispanic" or "Latino" deserve some attention. Normatively, the term "Hispanic" makes reference to Spanish-speaking countries and to those individuals coming from there and living in the United States. The term "Latino" is widely used in the United States to broadly identify individuals with origin or ancestry in Latin America. Nonetheless, Latino makes reference to someone that speaks old Latin or a language derived from it (this includes languages such as Catalan, French, Italian, Portuguese and Spanish). The use of Hispanic and Latino as ethno-linguistic categories is contested by Brazilians and Haitians because of the stereotype in the United States that all Latinos speak Spanish. The preference for the use of "Hispanic/Latino" for some researchers, editorial boards and funding agencies, rather than mestizo, gets primarily linked to the demographic and epidemiological potential to speak about Hispanics/Latinos, since they are a "growing segment of the U.S. population."[6] Mestizo, Hispanic and/or Latino proxy the emergence of admixed as a population category that facilitates the translation and comparison of human diversity, or in some cases the silencing of noise in scientific data.

Mapping the mapping is a key

Bio-geography and ancestry are no less contestable concepts just because on the surface they seem to be more neutral, more objective, or less controversial than race or ethnicity. Along with anthropologist Michael Montoya, I consider that the challenge is not to reflect whether AIMs are informative or not, but informative of what. While studying life scientists' biomolecular work on Type 2 Diabetes in the Mexican-US border, Montoya described a grafting process in which disease causality gets informed by the cultural identities and the socio-economic status of the persons being sampled.[7] Such examples of "ethnic constriction" enable most of the scientific value that individuals and populations across Latin America might embody as labor force in clinical trails, as tissue donors, or as potential markets for the consumption of genetic tests and pharmaceuticals.

If admixture mapping is possibly paving the way for a more individualized medicine, all the more reason biologists, biological and cultural anthropologists, medicine doctors, epidemiologists, and geneticists need to address and question the ways in which they are conceiving racial and ethnic groups, populations, and the very sampling strategies used to study them. Despite any altruistic motivations behind efforts to understand human diversity, we need to keep in mind that such enterprises are not only scientific ones but inherently socio-political and commercial as well. We cannot ignore the potential of such initiatives to unintentionally contribute to health disparity and the misrepresentation of populations. The possibility of building more robust scientific approaches to map the linkages between genotypes, phenotypes and environments demands a thorough analysis of how life scientists build taxonomies and how such taxonomies create realities for research participants or patients. Avoiding this task would make us close more locks around the ways we conceive and narrate our bodies in terms of belonging, purity and mixture and diminish what we can expect from human genomics.

 

Carlos Andrés Barragán is a Ph.D. student in the Science & Technology Studies Program and the Department of Anthropology at the University of California, Davis.

 

ENDNOTES

  1. Benjamin, Ruha (2009). "A lab of their own: genomic sovereignty as postcolonial science policy". Policy and Science 28(4): 341-355.
  2. BBC (2008). "Study unlocks Latin American past". Available at: http://news.bbc.co.uk/1/hi/7307563.stm (Accessed on Friday, March 21, 2008)
  3. {Wang et. al 2008}
  4. Stolcke, Verena (2008). "Los mestizos no nacen sino que se hacen". In: Stolcke, Verena and Alexandre Coello (eds.), Identidades ambivalentes en Ame´rica Latina (Siglos XVI-XXI), pp. 14-51. Barcelona, Bellaterra.
  5. See BEDOYA, Gabriel et al. (2006). "Admixture dynamics in Hispanics: a shift in the nuclear genetic ancestry of a South American population isolate". Proceedings of the National Academy of Sciences of the United States of America 103(19): 7234-7239.
  6. BRYC, Katarzyina et al. (2010). "Genome-wide patterns of population structure and admixture among Hispanic/Latino populations". Proceedings of the National Academy of Sciences of the United States of America 107(Supplement 2): 8954-8961.
  7. MONTOYA, Michael (2011). Making the Mexican diabetic. Race, science, and the genetics of inequality. Berkeley and Los Angeles, University of California Press.
 
 
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