Gustavo G. Politis

Ancient mitochondrial DNA provides high-resolution time scale of the peopling of the Americas.

Native American population history is reexamined using a large data set of pre-Columbian mitochondrial genomes. The exact timing, route, and process of the initial peopling of the Americas remains uncertain despite much research. Archaeological evidence indicates the presence of humans as far as southern Chile by 14.6 thousand years ago (ka), shortly after the Pleistocene ice sheets blocking access from eastern Beringia began to retreat. Genetic estimates of the timing and route of entry have been constrained by the lack of suitable calibration points and low genetic diversity of Native Americans. We sequenced 92 whole mitochondrial genomes from pre-Columbian South American skeletons dating from 8.6 to 0.5 ka, allowing a detailed, temporally calibrated reconstruction of the peopling of the Americas in a Bayesian coalescent analysis. The data suggest that a small population entered the Americas via a coastal route around 16.0 ka, following previous isolation in eastern Beringia for ~2.4 to 9 thousand years after separation from eastern Siberian populations. Following a rapid movement throughout the Americas, limited gene flow in South America resulted in a marked phylogeographic structure of populations, which persisted through time. All of the ancient mitochondrial lineages detected in this study were absent from modern data sets, suggesting a high extinction rate. To investigate this further, we applied a novel principal components multiple logistic regression test to Bayesian serial coalescent simulations. The analysis supported a scenario in which European colonization caused a substantial loss of pre-Columbian lineages.

Earliest hunters and gatherers of South America

Traditional syntheses of the archaeology of the late Pleistocene period in South America have focused primarily on the peopling of the continent by North American cultural groups and on identifying associations among regional sites. This focus has tended to ignore the widespread culture diversity of the period and the possible effects of different paleolandscapes on human migration and colonization, such as the presence of unglaciated tropical and temperate environments in the northern lowlands, the gateway to the interior. The earliest known cultural assemblages are characterized by various unifacial and bifacial lithic industries that may represent regional processes reminiscent of an Archaic lifeway. The major archaeological sites and associated artifact assemblages are examined in terms of regional and continental patterns of environmental and cultural change. Results suggest that the Pleistocene archaeological record of South America must be explained in its own terms and that the events and processes producing this record either occurred earlier than previously thought or are very different from those in North America.

Moving to produce: Nukak mobility and settlement patterns in Amazonia

Abstract This paper presents original information on the mobility and settlement patterns of the Nukak, who live between the Guaviare and Inirida rivers in the Colombian Amazon. The objective of this paper is to provide a better understanding of how egalitarian societies produce spatial arrangements in order to organize their settlements and to exploit the tropical rain forest resources. Traditional Nukak subsistence is based on hunting and the gathering of plants and animal products such as honey, turtle eggs and palm grubs; fishing and small‐scale horitculture are also practised. High residential mobility is practised in both the rainy and the dry season; it is estimated that bands make between seventy and eighty residential moves per year. Residential camps comprise two to five domestic units and usually cover under 130 m2. The Nukak case shows that forager mobility in tropical rain forests is not exclusively the consequence of avoiding over‐exploitation of an easily depleted environment. On the contra...

Discrepancy between cranial and DNA data of early Americans: implications for American peopling.

Currently, one of the major debates about the American peopling focuses on the number of populations that originated the biological diversity found in the continent during the Holocene. The studies of craniometric variation in American human remains dating from that period have shown morphological differences between the earliest settlers of the continent and some of the later Amerindian populations. This led some investigators to suggest that these groups—known as Paleomericans and Amerindians respectively—may have arisen from two biologically different populations. On the other hand, most DNA studies performed over extant and ancient populations suggest a single migration of a population from Northeast Asia. Comparing craniometric and mtDNA data of diachronic samples from East Central Argentina dated from 8,000 to 400 years BP, we show here that even when the oldest individuals display traits attributable to Paleoamerican crania, they present the same mtDNA haplogroups as later populations with Amerindian morphology. A possible explanation for these results could be that the craniofacial differentiation was a local phenomenon resulting from random (i.e. genetic drift) and non-random factors (e.g. selection and plasticity). Local processes of morphological differentiation in America are a probable scenario if we take into consideration the rapid peopling and the great ecological diversity of this continent; nevertheless we will discuss alternative explanations as well.

El poblamiento temprano de las llanuras pampeanas de Argentina y Uruguay

Based on available information, the early peopling (c. 12,300 to 8,000 BP) of the Pampean plains of Argentina and Uruguay is summarized and discussed within the broader context of the human population of the continent. The evidence presented here indicates that humans initially occupied the plains around 12,300 BP. Data obtained in recent decades within the framework of a regional research project do not support a model of late entry into the continent (known as the “Clovis First” model); neither do they support an extremely early human occupation of the region (i.e. tens of thousands of years). The information obtained indicates that Late Pleistocene hunter-gatherer bands had high residential mobility, exploited a variety of environments, and used both local and exotic raw materials. These foragers based part of their diet on the generalized consumption of land mammals, among which some extinct megamammals, such as American horse and giant ground sloth, could have been key resources. These bands shared with other contemporary groups of the Southern Cone a particular projectile point model, known as “fishtail” projectile point, which was dominant in the technology of the region between ca. 11,000 and 10,000 BP.

Montículos, Jerarquía Social y Horticultura en las sociedades indígenas del delta del Río Paraná (Argentina)

Son fragmentos de rocas de textura granular utilizadas directamente o previo formateo somero, y utilizadas directamente como pulidores (especialmente para mangos de madera u objetos de hueso).Existen 5 en las colecciones de Tierra del Fuego. Es posible que, alguno, sea etnografico, puesto que su uso ha sido descrito y es una piedra que, de no ser reconocida como instrumento, probablemente no hubiesen recogido en un conchero. De ellos, 2 estan etiquetados como de procedencia “ona”. (MHP-Col. Rousson/Willem y MVB col. Mallmann); 2 mas como “Tierra del Fuego” sin mas especificacion (BMML col. Crawshay), y otro (MVV col. Gusinde) como “yamana”.Fotografias del yacimiento, proceso de excavacion y detalles del sitio Tunel VII. Anos: 1989. Complementan los items de los protocolos de excavacion y las Plantas y estratigrafias del sitio Tunel VIIArchivos en jpg y en pdf de fotografias de bloques y laminas de micromorfologia de los yacimientos Lanashuaia y Alashawaia. Comprende muestras de columnas estratigraficas, y de la zona central de la ocupacion de Lanashuaiaincluyendo tambien los hogares centrales.Documentos y correspondencia con museos etnograficos. Seleccion de cartas de solictud y bienvenidas para estudiar los materiales en Museos europeos.La resistencia a la corrosion de aceros inoxidables en medios acuosos neutros, acidos y ricos en Cl- mejora notablemente con la aplicacion de recubrimientos hibridos de SiO2 preparados por sol-gel. La incorporacion de ZrO2 a estos recubrimientos permitiria su empleo en medios alcalinos, siempre que se obtenga una composicion homogenea. En este trabajo se ha estudiado dentro del sistema ZrO2/SiO2 el efecto de la variacion de las condiciones de preparacion del sol precursor y de sinterizacion en las caracteristicas finales de las capas. Se prepararon soles por hidrolisis y policondensacion de tetrabutoxido de Zr y metiltrietoxisilano (MTES). La naturaleza hibrida de los recubrimientos permitio obtener espesores criticos aproximados a 0.5�Em para la composicion con mayor contenido de MTES. Por FT-IR y DRX se determinaron altas concentraciones de enlaces Si-O-Zr para temperaturas de sintesis Ts<700oC, con cristalizacion de ZrO2(t) a temperaturas superiores. La resistencia electroquimica, evaluada mediante polarizacion ciclica del acero AISI304 recubierto con estas capas, revela estabilidad en medio alcalino, conservando la resistencia a medios ricos en Cl- caracteristica de los recubrimientos de SiO2.Fotografias de una muestra de metapodios de lobo marino de Tunel VII, Se incluyen tambien microfotografias de trazas sobre estos huesos.Los objetos fueguinos ubicados actualmente en museos etnograficos fueron analizados segun el modelo de analisis para objetos arqueologicos (caracteres morfologicos y tecnicos que nos revelan los elementos de su proceso tecnico de produccion), obteniendo asi una vision apta para su utilizacion comparativa con los materiales provenientes de yacimientos arqueologicos. Cada pieza fue objeto de una ficha informatizada en un programa estandar, comercial, de bases de datos. En ella se incluian datos morfotecnicos, metricos, materiales con los que fue confeccionada y modo de fabricacion. De tal modo pudieron aplicarse posteriormente paquetes estadisticos para analisis de busqueda de posibles estandars de fabricacion con implicaciones tecnicas o sociales comparables a las surgentes del registro arqueologico. Se anadio tambien la informacion etnografica de funcion y procedencia registrada en los museos. Asi se incluian los siguientes campos comunes: Museo, n.o de inventario, coleccion, adscripcion etnica (especificando si procede del Museo, canoeros/yamana p. ej...: o es conclusion propia), observaciones del Museo, clase de material (p.ej.: arco, punta de arpon, peine), descripcion morfotecnica y metrica estandartizada jerarquizando el proceso de produccion y la morfometria conseguida, no de inventario fotografico y miniatura de la foto. Ademas de estos campos comunes hemos recogido hasta un total de otros 32 campos con informacion especifica, metrica y de materia prima. Este item contiene varios archivos ADJUNTOS: - Documento en pdf con la relacion de las colecciones en los Museos etnograficos europeos, - Documento en pdf con las Fichas individuales (pagina a pagina) - Documento en texto txt con las mismas fichas. Los campos del archivo (separados por tabuladores) son: URI/ Palabras clave/ Nombre de la Pieza/ Institucion donde se conserva/ referencia Museo/ referencia foto/ DESCRIPCION/ Tipo de trenzado/ Numero de asas/ Altura/ Anchura/ diam. Max./ boca/ Anch base/ Materia punta/ Anch pedunculo/ Anchura/ Anch pedunculo/ Color punta/ longitud/ material cuerda/ long cuerda/ Diam trans/ Diam AP/ Anch. Min traba/ Long. Tot. Mango/ Espesor/ Long Lengueta/ Long.base/ long diente/ Long. Punta/ Anch 4/ No dientes/ Sobresalienza dientes/ sobresal. Min dientes/ Notrabas/ Sobres max. Traba/ min. Traba/ Fondo. Las fotos de cada objeto en buena calidad estan en los items correspondientes en esta misma Coleccion y pueden identificarse por la referencia al numero de foto. - Documento en pdf con la copia de las fichas de objetos etnograficos fueguinos del Museo Etnografico de Gotemburgo. (proporcionado por el museo). - Documento en pdf con el listado de los objetos etnograficos del Museo de Manchester (proporcionado por el museo). - Documento en pdf con el listado de los objetos etnograficos del Museo de Florencia (proporcionado por el museo) - Documento en pdf con el listado de los objetos de Patagonia y Tierra del Fuego del Museo de America de Madrid (proporcionado por el museo con anotaciones propias).6 paginas, 1 tabla y 1 figura.-Trabajo presentado en el III Congreso Iberico de Ciencias Horticolas, celebrado en Vilamoura, Algarve, entre el 11 y el 15 de marzo de 1997.Se incluyen articulos publicados y textos ineditos: J. Estevez y Vila, A. 2006 “Colecciones de museos etnograficos en Arqueologia” En: Etnoarqueologia de la Prehistoria: mas alla de la Analogia :241-254 Treballs d’Etnoarqueologia 6. CSIC. Madrid J. Estevez y Vila, A. 2013 “Analysis of palaeolithic barbed points from the Mediterranean Coast of the Iberian Peninsula: an ethnoarchaeological approach.” En: Andreas Pastoors & Barbel Auffermann (eds.): Pleistocene foragers on the Iberian Peninsula: Their culture and environment. :283-308 Wissenschaftliche Schriftendes Neanderthal Museums 7, Mettmann J. A. Barcelo, I. Briz, I. Clemente, J. Estevez, L. Mameli, A. Maximiano, F. Moreno, J. Pijoan, R. Pique, X. Terradas, A. Toselli, E. Verdun, A. Vila, D. Zurro 2006 “Analisis etnoarqueologico del valor social del producto en sociedades cazadoras-recolectoras”. En: Etnoarqueologia de la Prehistoria: mas alla de la Analogia :189-208 Treballs d’Etnoarqueologia 6. CSIC. Madrid. A.Vila y J.Estevez 2003 “Sociedades fueguinas, ?desapariciones inevitables?” En: R.Pique & M.Ventura (eds.) America Latina. Historia y Sociedad. :X-XI y 107-118. ICCI y UAB, Barcelona J. Barcelo, J.; A. Vila, y T. Argeles 1994 KIPA: A computer program to analize the social position of women in hunter-gatherer societies. En: I.Johmson (ed.) Methods In The Mountains. Sydney Univ. Archaeological Methods Series, 2 (1994) A.Vila y J.Estevez (ms.) Analisis arqueologico de las colecciones etnograficas.Fotografias de las canoas y modelos fueguinos en museos europeos. Sabemos que existen dos canoas seguramente yamanas: una en el MELPR y otra en el MEPGL. No nos permitieron acceder a la del MEPGL. Existe otra canoa pequena en el MBML. Por desgracia su delicado estado de conservacion nos hizo desistir de analizarla. Hemos fotografiado tambien una canoa en el Museo de Gottemburgo que estaba desmontada. A parte de estas hemos analizado 21 modelos de canoas que por su construccion reproducen las canoas yamana.Studies carried out in different outcrops of La Manga Formation (middle Callovian-middle Oxfordian) in southern Mendoza province, have allowed the recognition of an internal discontinuity characterized by the presence of a paleokarst. This surface was mentioned by Groeber as alveolar limestones. He also recognized surfaces displaying shades of yellow, brown alteration colors and honeycomb erosion (alveolation processes) in the “blue limestones wih Gryphaea ”. These surfaces appear on the top of reefal and oolitic barrier facies which define a shallowing-upward succession, or in intertidal-supratidal facies. Paleokarst deposits are represented by mantling breccias, collapse breccias and sinkhole breccias. Breccias are chaotic, with grain-supported to matrix supported fabrics. Some breccias can appear stratified. They are composed by clasts that vary between few millimeters to boulders, with irregular limits produced by dissolution. Sedimentology, morphology and diagenesis let recognize the epikarst in peritidal facies showing shorten shallowing-upward cycles in an internal ramp with low gradient. Fluctuations of the phreatic level during periods of subaerial exposure controlled the development of pendant cementation and drusy calcite cement with negative values of δ 18 O (-5.08 to -6.21‰) evidencing the action of meteoric waters. The epikarst shows dissolution cavities that reach 3 to 5 cm below surface, usually indicated by the presence of iron oxides and pisolites with an irregular distribution. The discontinuity is indicated by the paleokarst and by epikarst features, which are produced by subareal exposure and intense dissolution processes as a consequence of sea level fall.

Early Holocene Human Remains From the Argentinean Pampas: Additional Evidence for Distinctive Cranial Morphology of Early South Americans

The cranial morphology of Early Holocene American human samples is characterized by a long and narrow cranial vault, whereas more recent samples exhibit a shorter and wider cranial vault. Two hypotheses have been proposed to account for the morphological differences between early and late-American samples: (a) the migratory hypothesis that suggests that the morphological variation between early and late American samples was the result of a variable number of migratory waves; and (b) the local diversification hypothesis, that is, the morphological differences between early and late American samples were mainly generated by local, random (genetic drift), and nonrandom factors (selection and phenotypic plasticity). We present the first craniometric study of three early skulls from the Argentinean Pampas, dated ∼8,000 cal. years BP (Arroyo Seco 2, Chocorí, and La Tigra), and one associated with mega-faunal remains (Fontezuelas skull). In addition, we studied several Late Holocene samples. We show that the skulls from the Argentinean Pampas are morphologically similar to other Early Holocene American skulls (i.e., Lagoa Santa from Brazil, Tequendama, Checua, and Aguazuque from Colombia, Lauricocha from Peru, and early Mexicans) that exhibit long and narrow cranial vaults. These samples differ from the Late Holocene American samples that exhibit a shorter and wider cranial vault. Our results underscore the important differences in cranial morphology between early and late-American samples. However, we emphasize the need for further studies to discuss alternative hypotheses regarding such differences.

bammds: a tool for assessing the ancestry of low-depth whole-genome data using multidimensional scaling (MDS)

Summary: We present bammds, a practical tool that allows visualization of samples sequenced by second-generation sequencing when compared with a reference panel of individuals (usually genotypes) using a multidimensional scaling algorithm. Our tool is aimed at determining the ancestry of unknown samples—typical of ancient DNA data—particularly when only low amounts of data are available for those samples. Availability and implementation: The software package is available under GNU General Public License v3 and is freely available together with test datasets https://savannah.nongnu.org/projects/bammds/. It is using R (http://www.r-project.org/), parallel (http://www.gnu.org/software/parallel/), samtools (https://github.com/samtools/samtools). Contact: bammds-users@nongnu.org Supplementary information: Supplementary data are available at Bioinformatics online.

Early Holocene Human Remains from the Argentinean Pampas: Cranial Variation in South America and the American Peopling

Abstract Morphological comparisons between the earliest and latest human skeletons of America have suggested the existence of a complex scenario underlying the biological diversification of American populations. In the late nineteenth and early twentieth centuries Florentino Ameghino initiated the debate on the antiquity of humans in the Argentinean Pampas, which has been reviewed recently due to new radiocarbon dates obtained. Morphometric analyses from these Argentinean Pampas samples are presented together with early samples from Chile, Brazil, and Colombia. Results show that while there is no clear separation between early and late samples from Chile, samples from Brazil, Colombia, and Argentina show more pronounced differences, the latter presenting the largest morphological variation among early American samples. However, the hypotheses that morphological differences between early and late American samples are related to evolutionary processes are difficult to support using cranial morphometric differences alone. Future studies need to consider a combination of additional evidence (e.g., archaeological and molecular).

Acerca de la Etnoarqueología en América del Sur

Despite all of the potential that South America has for ethnoarchaeo-logical research, the development of Ethnoarchaeology is still very limited in this region. Only in the last decade ethnoarchaeological projects have grown, specially among South American archeologists. The present article revises the conceptual foundations of this field of study and analyses its present tendencies in South America. A discussion of the fields potential is made, not only as to what it can bring to the study of the relationship between human conduct and material derivations, but also as to the conditions in which we can expect to find certain types of archeological data. At last, the present article explores the uses that can be made out of Ethnoarchaeology in the study of other forms of thought and other patterns of rationality - forms and patterns that are hard to be identified in archeological data but are essential to understanding fundamental aspects of past societies.