The genetic discourse of continuity of the Uros ethnic group

It was precisely Wachtel’s research on the Aymarisation of the Uros that led Fujita, Sandoval and colleagues to the hypothesis of the Uros’ biological continuity. Referring to this process, they argue that ‘these antecedents suggest that the inhabitants of the Uros islands would still preserve part of the genetic pool of the original Urus’.

In 1998, geneticist José Sandoval – himself an Aymara born in a community on the southern shore of Lake Titicaca – collected 28 samples among the Uros. In addition, he also collected samples from one Aymara and two Quechua island communities of Lake Titicaca. Analyses were performed in collaboration with medical geneticist Ricardo Fujita, of the Universidad San Martin de Porres in Lima. They focused on mitochondrial DNA (mtDNA), which is integrally transmitted from a mother to her children and therefore makes it possible to identify the most remote ancestor on the maternal side. Over the course of research, the samples collected among the Uros were resignified in important ways. Drawing on the aforementioned equivalence between language and ethnic belonging that is frequently made in the Andes, Sandoval initially chose to focus on the inhabitants of the floating islands as ‘Aymara isolates’.

However, the awareness of the intense debate surrounding the Uros’ identity together with the differential component found in the analysis of their mtDNA led him and Fujita to redefine these samples as Uros. It is with this label that they were featured in the resulting publications.These publications established genetic continuity between the Uros of the Bay of Puno and the ancient Urus in the following way. Among Amerindian populations of South America, there are four main haplogroups – or sets of individuals that share genetic ancestry markers indicating a common ancestor: A, B, C and D12 (Schurr, 2004). Genetic analyses revealed that the samples of the three Quechua and Aymara communities collected by Sandoval could be almost entirely placed within haplogroup B. In contrast, the Uros were the only ones with a significant proportion – 18 percent – of haplogroup A2.

After establishing this difference from surrounding populations, the next step was to trace it to a distinct origin. While in genetic research, haplogroup B is mainly associated with the Pacific coast, haplogroups A, C and D are predominantly found in the Amazon region. The vast majority of Aymaras and Quechuas have haplogroup B, suggesting they are descendents of populations that originally reached the Andes from the Pacific coast. In contrast, haplogroup A2 is almost entirely absent among Andean populations. For Fujita, Sandoval and their colleagues, the presence of this haplogroup among the Uros would indicate a remote Amazonian origin. They corroborated this hypothesis by referring to linguistic studies and research with blood groups, which also suggest a differentiated peopling of the Andes, with the first population movement coming from the Amazon region and a distant kinship between the Urus and the Amazonian Arawak population . These considerations led the geneticists to the conclusion that ‘the inhabitants of the Uros islands still conserve an important Uru genetic component … contradicting the idea of their extinction’. In a subsequent publication, they affirm that the results of their research ‘could suggest greater antiquity’ of the Uros in comparison to Aymaras and Quechuas.

In 2007, Fujita and Sandoval began to collaborate with the Genographic Project, with Fujita becoming the project’s national coordinator for Peru. The Genographic Project – an initiative of the National Geographic Society and coordinated by geneticist Spencer Wells – started in 2005, with a large-scale effort to collect samples from indigenous populations across the world, with the objective to map ancient patterns of human migration.

Its methodology includes mtDNA and Y-chromosome analysis, which serve to reveal, respectively, the direct maternal and paternal lineages of sampled populations. The Uros were among the first populations in Peru sampled by the project. The project’s coordinator for South America, Fabrício Santos, acknowledged the Uros’ identity claims from the outset, while establishing an explicit distinction between genetic ancestry and the domains of culture and ethnic identity.

Analyses of their samples revealed the existence of ‘private alleles’ among the Uros, as well as lineages of a distinctly Amazonian origin in both mtDNA and the Y chromosome.

According to the geneticists, this would suggest that the Uros indeed have partial Uru ancestry, thus corroborating the idea of genetic continuity. However, while the geneticists tried to keep ethnic identity and genetic ancestry separate, the Uros were precisely interested in establishing articulations between the two.

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