Claudio M. Bravi

An alternative model for the early peopling of southern South America revealed by analyses of three mitochondrial DNA haplogroups.

After several years of research, there is now a consensus that America was populated from Asia through Beringia, probably at the end of the Pleistocene. But many details such as the timing, route(s), and origin of the first settlers remain uncertain. In the last decade genetic evidence has taken on a major role in elucidating the peopling of the Americas. To study the early peopling of South America, we sequenced the control region of mitochondrial DNA from 300 individuals belonging to indigenous populations of Chile and Argentina, and also obtained seven complete mitochondrial DNA sequences. We identified two novel mtDNA monophyletic clades, preliminarily designated B2l and C1b13, which together with the recently described D1g sub-haplogroup have locally high frequencies and are basically restricted to populations from the extreme south of South America. The estimated ages of D1g and B2l, about ∼15,000 years BP, together with their similar population dynamics and the high haplotype diversity shown by the networks, suggests that they probably appeared soon after the arrival of the first settlers and agrees with the dating of the earliest archaeological sites in South America (Monte Verde, Chile, 14,500 BP). One further sub-haplogroup, D4h3a5, appears to be restricted to Fuegian-Patagonian populations and reinforces our hypothesis of the continuity of the current Patagonian populations with the initial founders. Our results indicate that the extant native populations inhabiting South Chile and Argentina are a group which had a common origin, and suggest a population break between the extreme south of South America and the more northern part of the continent. Thus the early colonization process was not just an expansion from north to south, but also included movements across the Andes.

Brief communication: Restricted geographic distribution for Y-Q* paragroup in South America.

We analyzed 21 paragroup Q* Y chromosomes from South American aboriginal and urban populations. Our aims were to evaluate the phylogenetic status, geographic distribution, and genetic diversity in these groups of chromosomes and compare the degree of genetic variation in relation to Q1a3a haplotypes. All Q* chromosomes from our series and five samples from North American Q* presented the derivate state for M346, that is present upstream to M3, and determined Q1a3* paragroup. We found a restrictive geographic distribution and low frequency of Q1a3* in South America. We assumed that this low frequency could be reflecting extreme drift effects. However, several estimates of gene diversity do not support the existence of a severe bottleneck. The mean haplotype diversity expected was similar to that for South American Q1a3* and Q1a3a (0.478 and 0.501, respectively). The analysis of previous reports from other research groups and this study shows the highest frequencies of Q* for the West Corner and the Grand Chaco regions of South America. At present, there is no information on whether the phylogenetic status of Q* paragoup described in previous reports is similar to that of Q1a3* paragroup though our results support this possibility.

Demographic expansions in South America: enlightening a complex scenario with genetic and linguistic data.

Native Americans are characterized by specific and unique patterns of genetic and cultural/linguistic diversities, and this information has been used to understand patterns of geographic dispersion, and the relationship between these peoples. Particularly interesting are the Tupi and Je speaker dispersions. At present, a large number of individuals speak languages of these two stocks; for instance, Tupi-Guarani is one of the official languages in Paraguay, Bolivia, and the Mercosul economic block. Although the Tupi expansion can be compared in importance to the Bantu migration in Africa, little is known about this event relative to others. Equal and even deeper gaps exist concerning the Je-speakers expansion. This study aims to elucidate some aspects of these successful expansions. To meet this purpose, we analyzed Native American mtDNA complete control region from nine different populations and included HVS-I sequences available in the literature, resulting in a total of 1,176 samples investigated. Evolutionary relationships were explored through median-joining networks and genetic/geographic/linguistic correlations with Mantel tests and spatial autocorrelation analyses. Both Tupi and Je showed general traces of ancient or more recent fission-fusion processes, but a very different pattern of demographic expansion. Tupi populations displayed a classical isolation-by-distance pattern, while Je groups presented an intricate and nonlinear mode of dispersion. We suggest that the collective memory and other cultural processes could be important factors influencing the fission-fusion events, which likely contributed to the genetic structure, evolution, and dispersion of Native American populations.

Phylogeography of mitochondrial haplogroup D1: An early spread of subhaplogroup D1j from Central Argentina

We analyzed the patterns of variation of haplogroup D1 in central Argentina, including new data and published information from other populations of South America. Almost 28% (107/388) of the individuals sampled in the region belong to haplogroup D1, whereas more than 52% of them correspond to the recently described subhaplogroup D1j (Bodner et al.: Genome Res 22 (2012) 811-820), defined by the presence of additional transitions at np T152C-C16242T-T16311C to the nodal D1 motif. This lineage was found at high frequencies across a wide territory with marked geographical-ecological differences. Additionally, 12 individuals present the mutation C16187T that defines the recently named subhaplogroup D1g (Bodner et al.: Genome Res 22 (2012) 811-820), previously described in populations of Patagonia and Tierra del Fuego. Based on our results and additional data already published, we postulate that the most likely origin of subhaplogroup D1j is the region of Sierras Pampeanas, which occupies the center and part of the northwestern portion of Argentina. The extensive yet restricted geographical distribution, the relatively large internal diversity, and the absence or low incidence of D1j in other regions of South America suggest the existence of an ancient metapopulation covering the Sierras Pampeanas, being this lineage its genetic signature. Further support for a scenario of local origin for D1j in the Sierras Pampeanas stems from the fact that early derivatives from a putative ancestral lineage carrying the transitions T16311C-T152C have only been found in this region, supporting the hypothesis that it might represent an ancestral motif previous to the appearance of D1j-specific change C16242T.

Estudio del ADN mitocondrial de una muestra de la ciudad de La Plata

RESUMEN: xa0Un objetivo de la Antropologia Biologica consiste en estudiar el crecimiento y desarrollo dentro del concepto de intravariacion. Entre los analisis cefalometricos empleados en Argentina para valorar el crecimiento y su correccion por medio de la ortodoncia u ortopedia funcional de los maxilares, figura el de Ricketts y colaboradores. Estos autores determinaron tres modelos de crecimiento: mesofacial, braquifacial y dolicofacial. Sin embargo, la existencia de variabilidad como producto de la interaccion genetico-ambiental puede conducir a que cada poblacion difiera de los modelos estandarizados. El presente trabajo tiene por objeto contrastar el modelo facial de una muestra de La Plata y areas de influencia con los construidos por Ricketts y colaboradores de la poblacion estadounidense considerada como internacional. La muestra estuvo constituida por escolares de ambos sexos comprendidos entre los 8 y 14 anos de edad. A cada individuo se le practico una telerradiografia lateral en oclusion, sobre la cual fueron relevadas mediciones diametrales y angulares. El procesamiento estadistico consistio en analisis de varianza y pruebas de LSD. Los resultados obtenidos indicaron variacion porcentual significativa en la mayoria de las mediciones del modelo mesofacial analizado. Se concluye que deben reformularse estandares de las mediciones que definen dicho caracter, para posteriormente ajustar las constantes correspondientes a braquifaciales y dolicofaciales. Rev. Arg. Antrop. Biol. 2(1): 91-106, 1999. ABSTRACT: xa0One of the aims of Biological Anthropology is to study growth and development under the concept of intravariation. That of Ricketts et al. is among the cephalometric analyses employed in Argentina for evaluating -and correcting- growth by means of functional maxillary orthodontic and orthopedic techniques. According to these authors, three patterns of craniofacial growth can be isolated: brachyfacial, mesofacial, and dolichofacial. Variability as the product of genetic-environmental interactions, however, can lead to differences among populations and the consequent deviation from their normal patterns of craniofacial structure. In the present study, the facial model belonging to a sample from La Plata city and areas of influence was tested against the North-American one by Ricketts methodology, considered as an international standard. The sample involved schoolchildren of both sexes, between 8 and 14 years of age. A lateral teleradiography was taken to each child in occlusion, and several linear and angular measurements were made. Statistics consisted in the analysis of variance and post-hoc LSD tests. A significant percentage variation in almost all mesofacial variables was evident. As a conclusion, the mesofacial standard must be redefined for La Plata region, in order to recalculate the coefficients belonging to the brachyfacial and dolichofacial ones. Rev. Arg. Antrop. Biol. 2(1): 91-106, 1999.

Mitochondrial DNA control region data reveal high prevalence of Native American lineages in Jujuy province, NW Argentina

Mitochondrial control region (16024-576) sequences were generated from 180 individuals of four population nuclei from the province of Jujuy (NW Argentina), located at different altitudes above sea level. The frequency at which a randomly selected mtDNA profile would be expected to occur in the general population (random match probability) was estimated at 0.011, indicating a relatively high diversity. Analysis of the haplogroup distribution revealed that Native American lineages A2 (13.9%), B (56.7%), C1 (17.8%), D1 (8.9%) and D4h3a (1.1%) accounted for more than 98% of the total mtDNA haplogroup diversity in the sample examined. We detected a certain degree of genetic heterogeneity between two subpopulations located at different points along the altitudinal gradient (Valles and Puna), suggesting that altitude above sea level cannot be ruled out as a factor promoting divergences in mtDNA haplogroup frequencies, since altitude is closely associated with human living conditions, and consequently, with low demographic sizes and the occurrence of genetic drift processes in human communities. In all, mitochondrial DNA database obtained for Jujuy province strongly points to the need for creating local mtDNA databases, to avoid bias in forensic estimations caused by genetic substructuring of the populations.

Technical Note: A Method for Assignment of the Weight of Characters

The weight of characters is a crucial step in different population analyses. We propose a new formula to facilitate this while establishing a scale that follows the criteria of the probability of change in each character. This method is described for drawing of median-joining networks, yet it could also be used for other methods in which the weight of the characters is required.

Genealogical surveys show a high rate of non-paternal surname transmission with regional differences in Argentina.

Surnames are a vertically transmitted cultural trait that in Argentina follows the paternal line of descent when the paternity is known. There was a lack of empirical information regarding non-paternal surname transmissions among the general population, so we performed 2,550 genealogical interviews, which included 6,954 surname passes, in different regions of this country. We compared the proportion of non-paternal transmissions between the propositus and parental generation and found no significant difference between them (p<0.01). Inter-population comparisons allowed us to describe 4 regional groups. We also drew models and simulations to estimate how many generations it would take to find that only half of the population maintained the paternal transmission. The lowest proportion of non-paternal transmission was 7.3%, estimating 9 generations (between 225 and 315 years) to find that, at most, half its population keeps following the paternal transmission; the highest proportion was 23%, taking 3 generations (75-105 years). Our results show a high proportion of unrecognized paternities among the general population, a very quick loss of association between male lineages and surnames, and regional proportions with significant differences between each other.

Latin Americans show wide-spread Converso ancestry and the imprint of local Native ancestry on physical appearance

Historical records and genetic analyses indicate that Latin Americans trace their ancestry mainly to the admixture of Native Americans, Europeans and Sub-Saharan Africans. Using novel haplotype-based methods here we infer the sub-populations involved in admixture for over 6,500 Latin Americans and evaluate the impact of sub-continental ancestry on the physical appearance of these individuals. We find that pre-Columbian Native genetic structure is mirrored in Latin Americans and that sources of non-Native ancestry, and admixture timings, match documented migratory flows. We also detect South/East Mediterranean ancestry across Latin America, probably stemming from the clandestine colonial migration of Christian converts of non-European origin (Conversos). Furthermore, we find that Central Andean ancestry impacts on variation of facial features in Latin Americans, particularly nose morphology, possibly relating to environmental adaptation during the evolution of Native Americans.

Ethnic origin of y-chromosome haplotypes in subpopulations located at different altitudes in northwest Argentina

Se analizo sobre la base del polimorfismo del cromosoma Y del ADN, el origen etnico de linaje paterno en dos subpoblaciones amerindias del nordeste argentino exindidas de un mismo ancestro. Una de las subpoblaciones fue obtenida en San Salvador de Jujuy ubicado a 1.200 m sobre el nivel del mar y la segunda en los habitantes de Humahuaca con una altitud que fluctua entre 2.500 a 3.500 metros. Encontramos un porcentaje de 40,5% de integracion del cromosoma Y de origen hispano en el total de muestras de amerindios. Sin embargo esta integracion fue de un 64,3% en SS de Jujuy (1.200 m aproximadamente) que es el nivel andino de menor altura y de 27.6% en Humahuaca (2.500 m o mas sobre el nivel del mar) definiendo una menor integracion hispanica en concordancia con la altura. (P< 0.05). La subpoblacion que habita a 1.200 m mostro tambien una variacion genetica del cromosoma Y significativamente alta. Estos hallazgos, tienen una buena correlacion con la informacion historica de la conquista de America, que fue hecha por hombres que mantenian uniones poligamicas con mujeres amerindias. SS de Jujuy es la region mas noreste donde se encuentra una mezcla genetica de amerindios, en Argentina.