Gabriela Russo

The sudden proliferation in ancient DNA (aDNA) studies has prompted critical thinking on the subject and the development of recommendations that can be framed within the “Ethics, Legal and Social Implications”. The outcomes of these self-reviewing exercises have regional particularities in terms of their application and regulation. Aiming to contribute to these debates in South America, we focused on examining two aspects of aDNA studies: the use of ethnonyms and the evidence of collaborative research. We compiled 68 articles reporting genetic data from South American archaeological sites. First, we recorded edition and research-related general characteristics. Second, the discourse was analyzed searching for ethical-related issues like the use of ethnonyms, the justification for its usage, and evidences of collaborative approaches. Many articles included no information on the permits granted for analysis (44%) and the custody of the human remains (49%). Besides, ethnonyms were used in 41% of the studies mostly without any explicit justification. Finally, only 7% of the studies exhibited some evidence of a collaborative approach. These results help problematize and reflect on the ways of undertaking aDNA studies in the South American context, the limitations of scientific communication, and the social repercussions of these studies.

En este trabajo se analizó la variabilidad y diferenciación genética en poblaciones prehispánicas del Área Centrosur Andina bajo la hipótesis de que las relaciones de intercambio mantenidas durante todos los períodos de ocupación habrían estado acompañadas por flujo génico. Se recopilaron secuencias de la Región Hipervariable I del ADN mitocondrial de 415 individuos y se agruparon en 18 grupos poblacionales de diversas regiones.
Los resultados obtenidos indicaron, por un lado, que las poblaciones prehispánicas del noroeste argentino no se diferenciaron de las de los actuales territorios de Bolivia y norte de Chile, hecho que podría asociarse a las relaciones de intercambio que mantuvieron. Por otra parte, la distancia entre los grupos estudiados del Área Centrosur Andina no parece explicar la diferenciación hallada. En cambio, existen evidencias de que otros factores, como la temporalidad o las características sociopolíticas y culturales de cada población, pudieron haber tenido mayor influencia. Las poblaciones que más se diferenciaron del resto correspondieron tanto a momentos tempranos de ocupación, como a comunidades pequeñas que se habrían mantenido más aisladas y probablemente con altos niveles de endogamia. Al contrario, las poblaciones que fueron capitales estatales o grandes centros ceremoniales presentaron valores más altos de diversidad y una menor diferenciación.

During the Late Holocene, human population dynamics in Patagonia was conditioned by environmental factors, since a climate shift towards more arid conditions affected watersheds and their associated environments. In particular, for the Salitroso Lake basin (northwest of Santa Cruz province, Argentina) has been proposed a reduction in residential mobility, with a consequent population nucleation around this permanent water source. In this study, some archaeological concerns about the Salitroso Lake population were addressed through the study
of ancient mitochondrial DNA. In order to evaluate the genetic composition of the lake’s inhabitants and detect a possible population expansion, skeletal remains of 28 individuals (dated between 2,600 and 300 years BP) were processed. We were able to extract DNA and analyze the Hipervariable Region I of the mitochondrial genome in 16 samples. Four maternal lineages were found: D1g (43,7%), B2 (31,3%), C1 (18,8%) and D4h3a (6,2%). Some individuals presented derived haplotypes, many
of them only found in the basin. The presence of the B2 lineage is interesting, since it has been scarcely described in pre-Hispanic groups in Patagonia. In addition, high levels of genetic variability were observed in the analyzed sample, which was also different from other ancient Patagonian populations. Although the most recent archaeological analyses suggest a population growth during the last 500 years of occupation of the basin, no genetic evidence of this process was found.

Objectives

The main aim of this work was to contribute to the knowledge of pre‐Hispanic genetic variation and population structure among the South‐central Andes Area by studying individuals from Quebrada de Humahuaca, North‐western (NW) Argentina.

Materials and methods

We analyzed 15 autosomal STRs in 19 individuals from several archaeological sites in Quebrada de Humahuaca, belonging to the Regional Developments Period (900–1430 AD). Compiling autosomal, mitochondrial, and Y‐chromosome data, we evaluated population structure and differentiation among eight South‐central Andean groups from the current territories of NW Argentina and Peru.

Results

Autosomal data revealed a structuring of the analyzed populations into two clusters which seemed to represent different temporalities in the Andean pre‐Hispanic history: pre‐Inca and Inca. All pre‐Inca samples fell into the same cluster despite being from the two different territories of NW Argentina and Peru. Also, they were systematically differentiated from the Peruvian Inca group. These results were mostly confirmed by mitochondrial and Y‐chromosome analyses. We mainly found a clearly different haplotype composition between clusters.

Discussion

Population structure in South America has been mostly studied on current native groups, mainly showing a west‐to‐east differentiation between the Andean and lowland regions. Here we demonstrated that genetic population differentiation preceded the European contact and might have been more complex than thought, being found within the South‐central Andes Area. Moreover, divergence among temporally different populations might be reflecting socio‐political changes occurred in the evermore complex pre‐Hispanic Andean societies.

Objectives: The aim of this study was to contribute to the knowledge of pre-Hispanic Andean mitochondrial diversity by analyzing an individual from the archaeological site Pukara de La Cueva (North-western Argentina). The date of the discovery context (540±60 BP) corresponds to the Regional Developments II period.
Methods: Two separate DNA extractions were performed from dentin powder of one tooth. HVR I was amplified by PCR from each extract in three overlapping fragments and the haplotype was determined by consensus among all obtained sequences. The procedures were carried out under strict protocols developed for working with ancient DNA.
Results: The individual belonged to the A2ah lineage due to the presence of the 16097C and 16098G transitions, which constitute its distinctive motif. This lineage is very rare in Native American populations and was described in four individuals from current groups inhabiting the Bolivian Llanos, two from South-eastern Brazil and one from the Gran Chaco region. In addition, two other mutations (16260T and 16286T) were shared with one of the individuals from the Bolivian Llanos region.
Conclusions: Considering that the origin of this lineage was postulated for the South American lowlands, the present pre-Hispanic discovery in the Andean area could be taken as a new evidence of gene flow between these regions. Also, it allows to questioning the geographical origin of this mitochondrial lineage.

The  archaeological  site  Esquina  de  Huajra (south-central area of the Quebrada de Humahuaca) is a location chronologically assigned to the Inca phase (ca. 500-420 AP)  and  to  the  Hispanic-indigenous  phase  or  initial  period of contact with the Spanish (ca. 420-320 AP). In the context
of the Incaic economic system, Esquina de Huajra may have been a key settlement in the exploitation and distribution of goods from the eastern forests (Yungas). In addition, its material  culture  suggests  major  interaction  networks  with  the highlands, raising questions about its inhabitants’ origin. In this work maternal lineages of individuals from Esquina de Huajra were analyzed in comparison to other sites in southcentral Andes to assess possible foreign origins, considering
that population resettlement under Inca dominion was a common practice. DNA was extracted from the teeth of six individuals and mitochondrial hypervariable region I (HVRI) was successfully sequenced in four samples, resulting in two of them assigned to lineage A2 and the other two to C1. Absence of  B2  disagrees  with  data  from  most Andean  sites,  where this lineage is the most frequent. Two of the four haplotypes are only shared with individuals from other sites located in
Quebrada de Humahuaca (Los Amarillos and San Jose), and a nodal C1 variant was reported in samples from Juella and several pre-Inca and Inca Peruvian sites. These results represent the first contribution to genetic studies on the population of Esquina de Huajra and are also further evidence of the complex population processes in the Andean region.

Almost all pre-Hispanic societies from Quebrada de Humahuaca (north-western Argentina) buried their defuncts in domestic areas, demonstrating the importance of death and its daily presence among the living. Presumably, the collective graves contained related individuals, a hypothesis that can be tested through the study of ancient DNA. This study analyzes autosomal and uniparental genetic markers in individuals from two archaeological sites in Quebrada de Humahuaca occupied during the Late Formative (1450–1050 BP) and Regional Developments I (1050–700 BP) periods. Mitochondrial and Y-chromosome haplotypes were compared in order to establish possible maternal and paternal relatedness. Genotypes for 15 autosomal STRs were used to calculate pairwise relatedness coefficients and pedigree probabilities. High kinship levels among individuals buried in the same graves were found in both sites. Although only two particular cases were analyzed, these results represent an important contribution to the study of mortuary practices in the region by means of ancient DNA.

La estimación de ancestría individual posee gran relevancia en el estudio de la composición poblacional en regiones como Sudamérica, que han atravesado intensos procesos de mestizaje, lo que también tiene implicancia en ciencias de la salud. Debido a esto, es importante conocer los factores que influyen en la confiabilidad de los resultados obtenidos. En este trabajo se evalúa el número mínimo de marcadores informativos de ancestría (AIMs) a partir del cual las estimaciones resultarían aceptables. Se toma como ejemplo el cálculo en individuos provenientes de una muestra poblacional de diferentes regiones de Argentina. Considerando un modelo de tres componentes (nativo americano, euroasiático y subsahariano), se calculó la ancestría de 441 individuos utilizando 10, 20, 30 y 50 AIMs. Los resultados indican que el número de marcadores influye sobre la estimación de ancestría y su precisión aumenta al incrementarse la cantidad de AIMs. Al comparar con las estimaciones obtenidas en un trabajo previo a partir de 99 AIMs, se observó que para el componente minoritario (en este caso subsahariano) se obtiene una buena correlación utilizando al menos 30 marcadores. Se concluye que es necesario considerar en los estudios de ancestría individual el número de marcadores, su capacidad informativa y las características de la población bajo estudio.

Estimation of individual ancestry has great relevance when studying population composition in regions like South America, where intensive admixture processes have occurred, being also important in biomedical sciences. For that reason, it is important to assess the factors that may affect the reliability of results. In this work, we investigate the minimum number of ancestry informative markers (AIMs) for obtaining acceptable estimations of ancestry. As an example, we take individuals from a population sample of different Argentinean regions. Considering a three component model (Native American, Eurasian and Sub-Saharan), we calculated ancestry of 441 individuals using 10, 20, 30 and 50 AIMs. The results indicate that the number of markers affects ancestry estimation and its accuracy increases with AIMs number. When compared to previous estimations obtained from 99 AIMs, the result shows that at least 30 markers are needed to achieve good correlation values for the minority component (Sub-Saharan in this case). For individual ancestry studies, we suggest to take into account not only the number of markers, but also its informativeness and the background of the studied population.

Pampa Grande (PG) y Los Amarillos (LA) son
dos sitios arqueológicos del noroeste argentino (NOA), en
los que el estudio de ADN antiguo ha permitido determinar
el sexo de los individuos y analizar los linajes paternos y
maternos presentes. PG (Salta) se ha adjudicado al Periodo
Formativo y LA ubicado en la Quebrada de Humahuaca
(Jujuy), habría tenido una masiva ocupación hacia el Período
de Desarrollos Regionales. El objetivo de este trabajo es
comparar ambos sitios en cuanto a su diversidad genética
analizando los haplogrupos y haplotipos de ADN mitocondrial
estudiados en dichas poblaciones. Se incluyeron en el
análisis 19 individuos de PG y 18 de LA. Al analizar los linajes mitocondriales, se observa que los únicos haplogrupos
compartidos entre ambas poblaciones son los haplogrupos
A2 y D1, encontrados habitualmente en poblaciones
amerindias. Por otro lado, no se detectó el haplogrupo
B2 en LA, ni el C1 en PG. Los análisis de variación génica
realizados a partir de la Región Hipervariable I indican una
diferenciación genética significativa entre ambos sitios,
siendo PG el más variable. Mecanismos microevolutivos
asociados a la distancia geográfica y temporal parecen haber
moldeado la diversidad intra e interpoblacional entre
estos dos sitios prehispánicos del NOA.

El Noroeste de la Provincia de Santa Cruz presenta un registro arqueológico de gran importancia. En particular, en la cuenca del Lago Salitroso se ha recuperado y estudiado una de las colecciones osteológicas más numerosas de poblaciones cazadoras-recolectoras, ubicándose temporalmente en el Holoceno Tardío. En el presente trabajo se exhiben los resultados obtenidos del estudio del ADN mitocondrial (ADNmt) de 6 piezas dentales de cuatro adultos y dos subadultos en buen estado de preservación. Todos provienen de  la modalidad de entierro en chenque: uno corresponde al grupo de chenques iniciales de 1600-1200 AP, mientras que los cinco restantes a los tardíos de 800-350 años AP. Se logró determinar el linaje materno a través de la secuenciación de la Región Hipervariable I de 5 de los 6 individuos analizados (83% de recuperación). Las secuencias preliminares obtenidas permitieron identificar dos linajes maternos: D1g (60%) y B2 (40%). En el primero de los casos, los individuos poseen polimorfismos típicamente patagónicos y descriptos en poblaciones antiguas y actuales. Con respecto al segundo linaje, resulta interesante su presencia ya que se encuentra escasamente descripto para poblaciones prehispánicas en Patagonia. Estos resultados actualizan los datos de ADN mitocondrial obtenidos recientemente en la colección para 12 individuos de distintos bloques cronológicos y se discuten en el marco de las investigaciones paleogenéticas  vigentes a nivel local y regional.