The population of Argentina is the result of the intermixing between several groups, including Indigenous American, European and African populations. Despite the commonly held idea that the population of Argentina is of mostly European origin, multiple studies have shown that this process of admixture had an impact in the entire Argentine population. In the present study we characterized the distribution of Indigenous American, European and African ancestry among individuals from different regions of Argentina and evaluated the level of discrepancy between self-reported grandparental origin and genetic ancestry estimates. A set of 99 autosomal ancestry informative markers (AIMs) was genotyped in a sample of 441 Argentine individuals to estimate genetic ancestry. We used non-parametric tests to evaluate statistical significance. The average ancestry for the Argentine sample overall was 65% European (95%CI: 63–68%), 31% Indigenous American (28–33%) and 4% African (3–4%). We observed statistically significant differences in European ancestry across Argentine regions [Buenos Aires province (BA) 76%, 95%CI: 73–79%; Northeast (NEA) 54%, 95%CI: 49–58%; Northwest (NWA) 33%, 95%CI: 21–41%; South 54%, 95%CI: 49–59%; p<0.0001] as well as between the capital and immediate suburbs of Buenos Aires city compared to more distant suburbs [80% (95%CI: 75–86%) versus 68% (95%CI: 58–77%), p = 0.01]. European ancestry among individuals that declared all grandparents born in Europe was 91% (95%CI: 88–94%) compared to 54% (95%CI: 51–57%) among those with no European grandparents (p<0.001). Our results demonstrate the range of variation in genetic ancestry among Argentine individuals from different regions in the country, highlighting the importance of taking this variation into account in genetic association and admixture mapping studies in this population.

Ancient DNA recovered from 21 individuals excavated from burial sites in the Pampa Grande (PG) region (Salta province) of North-Western Argentina (NWA) was analyzed using various genetic markers (mitochondrial DNA, autosomal STRs, and Y chromosomal STRs). The results were compared to ancient and modern DNA from various populations in the Andean and North Argentinean regions, with the aim of establishing their relationships with PG. The mitochondrial haplogroup frequencies described (11% A, 47% B, and 42% D) presented values comparable to those found for the ancient Andean populations from Peru and San Pedro de Atacama. On the other hand, mitochondrial and Y chromosomal haplotypes were specific to PG, as they did not match any other of the South American populations studied. The described genetic diversity indicates homogeneity in the genetic structure of the ancient Andean populations, which was probably facilitated by the intense exchange network in the Andean zone, in particular among Tiwanaku, San Pedro de Atacama, and NWA. The discovery of haplotypes unique to PG could be due to a loss of genetic diversity caused by recent events affecting the autochthonous populations (establishment of the Inca Empire in the region, colonization by the Europeans).

A total of 495 individuals from five different Argentinian tribes was examined for variation in 23 blood group and protein genetic systems, and the results were integrated with previous data on some of these systems. These tribes generally present RH * R1, PGM1 * 1, and ACP * A frequencies lower and RH * R2, ESD * 1, and GLO * 1 prevalences higher than those observed in other South American Indian groups. Earlier studies with mitochondrial DNA showed that haplogroup A was present in low frequencies in these tribes, but haplogroup B showed a high prevalence among the Mataco. Average heterozygosities are very similar in the five tribes, while estimates of non-Indian ancestry are generally low. Both the blood group and protein, as well as the mtDNA data sets, divide the five tribes into two groups, and the relationships obtained with the blood group and protein systems are exactly those expected on the basis of geography and language. However, the topology obtained with the mtDNA results was different, possibly due to sampling effects or diverse patterns of exchange between the groups related to sex.

The population of Argentina today does not have a "visible" black African component. However, censuses conducted during most of the 19th century registered up to 30% of individuals of African origin living in Buenos Aires city. What has happened to this African influence? Have all individuals of African origin died, as lay people believe? Or is it possible that admixture with the European immigrants made the African influence "invisible?" We investigated the African contribution to the genetic pool of the population of Buenos Aires, Argentina, typing 12 unlinked autosomal DNA markers in a sample of 90 individuals. The results of this analysis suggest that 2.2% (SEM=0.9%) of the genetic ancestry of the Buenos Aires population is derived from Africa. Our analysis of individual admixture shows that those alleles that have a high frequency in populations of African origin tend to concentrate among 8 individuals in our sample. Therefore, although the admixture estimate is relatively low, the actual proportion of individuals with at least some African influence is approximately 10%. The evidence we are presenting of African ancestry is consistent with the known historical events that led to the drastic reduction of the Afro-Argentine population during the second half of the 19th century. However, as our results suggest, this reduction did not mean a total disappearance of African genes from the genetic pool of the Buenos Aires population.

Due to anthropogenic factors, the franciscana dolphin, Pontoporia blainvillei, is the most threatened small cetacean on the Atlantic coast of South America. Four Franciscana Management Areas have been proposed: Espiritu Santo to Rio de Janeiro (FMA I), São Paulo to Santa Catarina (FMA II), Rio Grande do Sul to Uruguay (FMA III), and Argentina (FMA IV). Further genetic studies distinguished additional populations within these FMAs. We analyzed the population structure, phylogeography, and demographic history in the southernmost portion of the species range. From the analysis of mitochondrial DNA control region sequences, 5 novel haplotypes were found, totalizing 60 haplotypes for the entire distribution range. The haplotype network did not show an apparent phylogeographical signal for the southern FMAs. Two populations were identified: Monte Hermoso (MH) and Necochea (NC)+Claromecó (CL)+Río Negro (RN). The low levels of genetic variability, the relative constant size over time, and the low levels of gene flow may indicate that MH has been colonized by a few maternal lineages and became isolated from geographically close populations. The apparent increase in NC+CL+RN size would be consistent with the higher genetic variability found, since genetic diversity is generally higher in older and expanding populations. Additionally, RN may have experienced a recent split from CL and NC; current high levels of gene flow may be occurring between the latter ones. FMA IV would comprise four franciscana dolphin populations: Samborombón West+Samborombón South, Cabo San Antonio+Buenos Aires East, NC+CL+Buenos Aires Southwest+RN and MH. Results achieved in this study need to be taken into account in order to ensure the long-term survival of the species.

Durante el Holoceno tardío la dinámica poblacional humana en Patagonia estuvo condicionada por factores ambientales, debido a que la tendencia hacia condiciones de mayor aridez afectó sustancialmente las cuencas hídricas y sus ambientes asociados. En particular, para la cuenca del Lago Salitroso (noroeste de la actual provincia de Santa Cruz, Argentina), se propuso una reducción de la movilidad residencial, con un consecuente nucleamiento poblacional en torno a esta fuente de agua permanente. En este trabajo se abordaron problemáticas arqueológicas sobre la población del Lago Salitroso a través del estudio del ADN mitocondrial antiguo. Con el fin de evaluar la composición genética de la población del lago, y detectar una posible expansión poblacional, se procesaron restos óseos y dentales de 28 individuos, con cronología entre 2600 y 300 años AP. Se logró extraer ADN y analizar la Región Hipervariable I en 16 muestras. Las secuencias obtenidas permitieron identificar cuatro linajes maternos: D1g (43,7%), B2 (31,3%), C1 (18,8%) y D4h3a (6,2%). Parte de los individuos presentaron haplotipos derivados, muchos de ellos hallados únicamente en la cuenca. Resulta interesante la presencia del linaje B2, ya que se encuentra escasamente descripto para poblaciones prehispánicas en Patagonia. Además, se observó una alta variabilidad genética en la muestra analizada, y una diferenciación respecto de otras poblaciones antiguas patagónicas. Por otro lado, si bien los análisis arqueológicos más recientes sugieren un crecimiento poblacional durante los últimos 500 años de ocupación de la cuenca, no se encontraron evidencias genéticas de dicho proceso.

Distintas disciplinas han intentado explicar el poblamiento y la evolución de las poblaciones cazadoras-recolectoras que habitaron la Patagonia argentina. La arqueología y la morfología craneal propusieron un escenario de poblamiento temprano caracterizado por una baja demografía, eventos de divergencias y efectos fundadores seriales. Estos postulados fueron avalados desde el análisis del ADN mitocondrial procedentes de poblaciones originarias actuales, siendo escasos aún los estudios en poblaciones precolombinas. Con el objeto de aumentar la información disponible, se analizaron un total de 50 muestras de individuos de sitios arqueológicos y colecciones de museos de diversas regiones patagónicas con temporalidades desde los ca. 5600 14C años AP hasta tiempos históricos. Se logró asignar el linaje materno en 27 de ellas por RFLP y en 23 de las mismas secuencias de la región hipervariable 1. Se detectaron los linajes A2, C1, D1, D1g, D1j y D4h3a. Los análisis estadísticos demuestran una disminución de la diversidad mitocondrial hacia el Sur. La comparación de las regiones geográficas analizadas ha demostrado la ausencia de diferencias estadísticamente significativas y de estructuración poblacional, lo cual puede indicar un origen común reciente y la existencia de flujo génico entre las regiones durante el Holoceno Tardío. Adicionalmente, puede proponerse un cambio en el acervo genético mitocondrial en las poblaciones nativas actuales representado por las altas frecuencias del linaje B2, posiblemente relacionado con el proceso de Araucanización a partir del Siglo XVI.

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