How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we find that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia. Following their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 KYA, one that is now dispersed across North and South America and the other is restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative ‘Paleoamerican’ relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.

Native American population history is reexamined using a large data set of pre-Columbian mitochondrial genomes.

The purpose of this study was to describe the prenatal formation of the human mandibular canal. Since bony canals develop in prenatal life around the nerve paths, it was assumed that the canal pattern could reflect the pattern of innervation of the dentition. Mapping of this early canal pattern does not appear to have been undertaken before. The material consisted of anthropological mandibles from the National Institute of Anthropology and History, Mexico City. A total of 302 human hemimandibles from the latter half of the prenatal period was investigated. The length, measured from the mental symphysis to the mandibular condyle, ranged from 28 to 60 mm. The dento-alveolar maturity was classified in two stages according to the appearance of alveolar sockets of deciduous and first permanent molars. The mandibles were radiographed with guttapercha points inserted into the canal openings (foramina) on the lingual surfaces of the mandibular rami. The study showed that the canal to the incisors appeared first, followed by the canal to the primary molars, and last by the one or more canals to the first permanent molars. In the most mature group, three different canals always occurred in each hemimandible. The canals were directed from the lingual surface of the mandibular ramus toward the different tooth groups. The inferior alveolar nerve presumably occurs in the mandible as three individual nerve paths originating at different stages of development. It is suggested that rapid prenatal growth and remodeling in the ramus region result in a gradual coalescence of the canal entrances that is obvious at birth. It is hypothesized that the pattern of tooth agenesis within the three groups of teeth is related to the three separate paths of innervation of the dentition.

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Contemporary and mummy hair samples are characterized and compared, using modern chemical and physical characterization methods. It is found that in cave conditions mummy hair can be preserved even if it interacts with environmental dirt or soil, X-ray diffraction and infrared spectroscopy results. Hair is an ion exchanger and the exposure to earth and water can facilitate the interaction of some elements with hair as shown by X-ray fluorescence, energy dispersive spectroscopy and neutron activation analysis. Post mortem degradation is detected through the reaction of cystine and through the partial collapse of the scale arrangement. The mummy hair scales become less ordered and the hair surface less smooth, such features were clearly observed by scanning electron microscopy and atomic force microscopy. The presented interdisciplinary results show that alteration of hair initiates in the core but scales are often well preserved. The features found in mummy hair suggest that the correlation between chemical composition and health or nutrition of ancient people should be carefully evaluated due to environmental contamination.Key words: Hair, mummy, human, scalp, cuticle, cortex, keratin. Muestras de pelo de momia y también contemporáneo se compararon y caracterizaron por métodos espectroscópicos y fisicoquí-micos. Se encontró que el pelo de la momia en una cueva se puede conservar, incluso si interactúa con el medio ambiente o la suciedad del suelo. El cabello es un intercambiador de iones y la exposición a la tierra y el agua puede facilitar la interacción de algunos elementos con el pelo como se mostró por fluorescencia de rayos X, espectroscopía de energía dispersiva y análisis