Genetic continuity and change among the Indigenous peoples of California.

Before the colonial period, California harboured more language variation than all of Europe, and linguistic and archaeological analyses have led to many hypotheses to explain this diversity1. We report genome-wide data from 79 ancient individuals from California and 40 ancient individuals from Northern Mexico dating to 7,400-200 years before present (BP). Our analyses document long-term genetic continuity between people living on the Northern Channel Islands of California and the adjacent Santa Barbara mainland coast from 7,400 years BP to modern Chumash groups represented by individuals who lived around 200 years BP. The distinctive genetic lineages that characterize present-day and ancient people from Northwest Mexico increased in frequency in Southern and Central California by 5,200 years BP, providing evidence for northward migrations that are candidates for spreading Uto-Aztecan languages before the dispersal of maize agriculture from Mexico2-4. Individuals from Baja California share more alleles with the earliest individual from Central California in the dataset than with later individuals from Central California, potentially reflecting an earlier linguistic substrate, whose impact on local ancestry was diluted by later migrations from inland regions1,5. After 1,600 years BP, ancient individuals from the Channel Islands lived in communities with effective sizes similar to those in pre-agricultural Caribbean and Patagonia, and smaller than those on the California mainland and in sampled regions of Mexico.

An Insight to the Composition of Pre-Hispanic Mayan Funerary Pigments by 1H-NMR Analysis.

The funerary rites of particular members of the pre-Hispanic Mayan society included the pigmentation of the corpse with a red color. In order to understand this ritual, it is first necessary to identify the constituents of the pigment mixture and then, based on its properties, analyze the possible form and moment of application. In the present approach, 1H-NMR analysis was carried to detect organic components in the funerary pigments of Xcambó, a small Maya settlement in the Yucatan Peninsula. The comparison of the spectra belonging to the pigment found in the bone remains of seven individuals, and those from natural materials, led to the identification of beeswax and an abietane resin as constituents of the pigment, thus conferring it agglutinant and aromatic properties, respectively. The 1H-NMR analysis also allowed to rule out the presence of copal, a resin found in the pigment cover from paramount chiefs from the Mayan society. Additionally, a protocol for the extraction of the organic fraction from the bone segment without visible signs of analysis was developed, thus broadening the techniques available to investigate these valuable samples.

Place of origin of the sacrificial victims in the sacred Cenote, Chichén Itzá, Mexico.

OBJECTIVES: The ancient city of Chichén Itzá in the northern Yucatán of Mexico was one of the most important in the Maya area, but its origins and history are poorly understood. A major question concerns the origins of the peoples who founded and later expanded the ancient city. Hundreds of people were ritually executed and their bodies thrown into the waters of the Sacred Cenote at Chichén. MATERIALS AND METHODS: In this study, we use strontium and oxygen isotopes to study the place of origin of a large sample of these individuals. Isotopes are deposited in human tooth enamel. Enamel forms during the first years of life, remains largely unchanged long past death, and can provide a signature of the place of birth. If the isotope ratios in enamel are different from the place of death, the individual must have moved during his/her lifetime. RESULTS: Comparison of our results from the cenote with information on isotope ratios across the Maya region and elsewhere suggests that the individuals in the cenote came from a number of different parts of Mexico and possibly beyond. DISCUSSION: It is not known if all of the sacrificial victims resided in Chichén Itzá, but their suggested origins likely reflect patterns of population movement and social networks that existed between Chichén Itzá and both neighboring and distant regions. Various lines of evidence point to places in the Yucatán, along the Gulf Coast, Central America, or even in the Central Highlands of Mexico.

Root canal morphology of the mandibular first premolars in a Yucatecan population using cone beam computed tomography: an in vitro study / Morfología del conducto radicular de primeros premolares mandibulares en una población yucateca usando tomografía computarizada: estudio in vitro

A successful endodontic treatment requires knowledge of the internal configuration of dental root canals. Most of the people who live in Yucatan are of Maya origin, characterized by a Mongoloid dental pattern. Because of their ethnicity, variations are expected. The purpose of this investigation is to assess the morphological characteristics and variability of this population. One hundred and five extracted first mandibular premolars of Mexican Maya population were analyzed; the sample was obtained from the Oral Surgery Clinic in the School of Dentistry at the Autonomous University of Yucatan with written informed consent. Analyses were performed by means of Cone Beam Computed Tomography. Vertucci´s Type I was the most prevalent configuration with 51.4 %, but 41 cases (39.1 %) presented a radicular groove and a C-shaped canal configuration. Overall, we documented 1, 2, 3, and 4 root canals. Mandibular first premolars are very variable in the Yucatecan population. The variability and frequency of C-shape is similar to mandibular second molars confirming the importance of the ethnic background for the endodontic treatments.

El éxito en el tratamiento endodóntico requiere el conocimiento profundo de la configuración interna del sistema de conductos radiculares. La mayoría de las personas que viven en Yucatán son de origen Maya y poseen el patron dental Mongoloide; por lo tanto, se esperan variaciones debido a su etnicidad. El propósito de esta investigación fue evaluar las características morfológicas y la variabilidad del conducto radicular en la población yucateca. Se analizaron ciento cinco primeros premolars mandibulares extraídos de pacientes provenientes de una muestra Maya mexicana; la muestra fue obtenida de la Clínica de Cirugía Oral de la Facultad de Odontología de la Universidad Autónoma de Yucatán. Con consentimiendo informado escrito. Se utilizaron Tomografías Computarizadas para el análisis de la muestra. La configuración más prevalente fue la Tipo I de Vertucci con 51,4 %. Sin embargo, 41 de 105 casos (39,1 %) presentaron un surco radicular y la configuración en forma de "C". Se documentaron casos con 1, 2, 3 y 4 conductos radiculares. Los primeros premolares mandibulares de la población Yucateca son muy variables. La variabilidad y frecuencia de conductos en forma de "C" concuerda con estudios realizados en segundos molars mandibulares en esta zona confirmando la importancia del origen étnico de las poblaciones para los tratamientos endodónticos.

Morfología radicular y mediciones apicales en primeros molares en una población maya / Root morphology and apical measurements of first molars in a Mayan population

El conocimiento preciso de la morfología radicular dental son claves para el éxito en las terapias endodónticas. El objetivo de este estudio fue evaluar las distintas variaciones de la morfología radicular y apical en primeros molares superiores e inferiores de una población maya moderna. Se observaron microfotografías provenientes de 80 primeros molares superiores e inferiores, presentadas en cortes transversales a 1 y 2,5 mm del vértice apical, así como de las porciones 1/3, 1⁄2, 2/3 del largo radicular y en la unión amelocementaria. Se determinó el número de raíces, conductos y configuración de Vertucci, así como forma y medidas de diámetro mayor y menor a 1 mm del vértice apical. El 90 % de primeros molares superiores reportó la presencia de 3 raíces y el 10 % mostró 2. En tanto que el total de primeros molares inferiores (100 %) reportó 2 raíces. En general, en las raíces mesiales prevaleció el Tipo II de Vertucci mientras que en las distales y palatinas la Tipo I. En el corte a 1 mm del vértice apical la forma redonda fue la de mayor prevalencia en los conductos de primeros molares superiores (44,5 %), seguida de la irregular (34,1 %) y la oval (21,4 %); mientras que en los primeros molares inferiores la más prevalente fue la irregular (54, 5 %), seguida de la redonda (23,9 %) y oval (21,6 %). Los diámetros mayor y menor de los conductos mesiales a 1 mm apical midieron 0,46 y 0,23 mm y 0,64 y 0,25 mm en molares superiores e inferiores respectivamente. La frecuencia de MB2 en primeros molares superiores fue del 77,8 %. Los conductos con mayor variabilidad fueron los mesiales. Se observó baja frecuencia de conductos ovales. Los diámetros mayores de los conductos mesiales en general, fueron superiores a 0,45 mm.

Accurate knowledge of dental root morphology is a key to success in endodontic therapies. The aim of this study was to evaluate the different variations of the root and apical morphology in upper and lower first molars of a modern Mayan population. Photomicrographs were taken from 80 upper and lower first molars, presented in cross sections at 1 and 2.5 mm from the apical vertex, as well as from the 1/3, 1⁄2, 2/3 portions of the root length and at the cementoenamel junction. The number of roots, canal and Vertucci`s configuration was determined, as well as the shape and measurements of the major and minor diameters at 1 mm from the apex. In this study 90 % of upper first molars reported the presence of 3 roots and 10 % showed 2, while the total lower first molars (100 %) reported 2 roots. In general, Vertucci`s Type II prevailed in the mesial roots while Type I was prevalent in the distal and palatal ones. In the 1 mm cut of the apical vertex, the round shape was the most prevalent in the canal of the first upper molars (44.5 %), followed by irregular (34.1 %) and oval (21.4 %); while in the first lower molars the most prevalent one was irregular (54.5 %), followed by round (23.9 %) and oval (21.6 %). The major and minor diameters of the mesial canals at 1 mm apical recorded 0.46 and 0.23 mm and 0.64 and 0.25 mm in upper and lower molars respectively. The frequency of MB2 in upper first molars was 77.8 %. The canals with greater variability were the mesial ones. Low frequency of oval canals was observed. The largest diameters of the mesial canal in general were greater than 0.45 mm.

New linear regression equations to calculate body height from tibial length in modern Maya populations.

Height cannot always be measured directly, hence the need for height estimation formulae. This study presents two new linear regression equations for estimating height from tibial length among Maya populations. Body height and percutaneous tibial length were measured in two living Maya samples from the state of Yucatan, Mexico. The first sample comprises 100 adults (63 females and 37 males) from the community of Dzemul, (Group 1) and the second sample comprises 71 adults (26 females and 45 males) from the city of Mérida (Group 2). A linear regression model equation was then adjusted to estimate height from tibia length for each group. These models were then compared using 95% confidence intervals for the estimated variables. No differences were observed between the equations at this interval. Thus, both equations appear adequate for estimating body height from tibia length in contemporary Yucatecan populations. While the formula of Group 1 is applicable also to bioarcheological studies, the formula of Group 2 is more appropriate for studies in living populations.

Comparison of two ancient DNA extraction protocols for skeletal remains from tropical environments.

OBJECTIVES: The tropics harbor a large part of the world's biodiversity and have a long history of human habitation. However, paleogenomics research in these climates has been constrained so far by poor ancient DNA yields. Here we compare the performance of two DNA extraction methods on ancient samples of teeth and petrous portions excavated from tropical and semi-tropical sites in Tanzania, Mexico, and Puerto Rico (N = 12). MATERIALS AND METHODS: All samples were extracted twice, built into double-stranded sequencing libraries, and shotgun sequenced on the Illumina HiSeq 2500. The first extraction protocol, Method D, was previously designed for recovery of ultrashort DNA fragments from skeletal remains. The second, Method H, modifies the first by adding an initial EDTA wash and an extended digestion and decalcification step. RESULTS: No significant difference was found in overall ancient DNA yields or post-mortem damage patterns recovered from samples extracted with either method, irrespective of tissue type. However, Method H samples had higher endogenous content and more mapped reads after quality-filtering, but also higher clonality. In contrast, samples extracted with Method D had shorter average DNA fragments. DISCUSSION: Both methods successfully recovered endogenous ancient DNA. But, since surviving DNA in ancient or historic remains from tropical contexts is extremely fragmented, our results suggest that Method D is the optimal choice for working with samples from warm and humid environments. Additional optimization of extraction conditions and further testing of Method H with different types of samples may allow for improvement of this protocol in the future.

Methods and theory in bone modeling drift: comparing spatial analyses of primary bone distributions in the human humerus.

This study compares two novel methods quantifying bone shaft tissue distributions, and relates observations on human humeral growth patterns for applications in anthropological and anatomical research. Microstructural variation in compact bone occurs due to developmental and mechanically adaptive circumstances that are 'recorded' by forming bone and are important for interpretations of growth, health, physical activity, adaptation, and identity in the past and present. Those interpretations hinge on a detailed understanding of the modeling process by which bones achieve their diametric shape, diaphyseal curvature, and general position relative to other elements. Bone modeling is a complex aspect of growth, potentially causing the shaft to drift transversely through formation and resorption on opposing cortices. Unfortunately, the specifics of modeling drift are largely unknown for most skeletal elements. Moreover, bone modeling has seen little quantitative methodological development compared with secondary bone processes, such as intracortical remodeling. The techniques proposed here, starburst point-count and 45° cross-polarization hand-drawn histomorphometry, permit the statistical and populational analysis of human primary tissue distributions and provide similar results despite being suitable for different applications. This analysis of a pooled archaeological and modern skeletal sample confirms the importance of extreme asymmetry in bone modeling as a major determinant of microstructural variation in diaphyses. Specifically, humeral drift is posteromedial in the human humerus, accompanied by a significant rotational trend. In general, results encourage the usage of endocortical primary bone distributions as an indicator and summary of bone modeling drift, enabling quantitative analysis by direction and proportion in other elements and populations.

Drifting Diaphyses: Asymmetry in Diametric Growth and Adaptation Along the Humeral and Femoral Length.

This study quantifies regional histomorphological variation along the human humeral and femoral diaphysis in order to gain information on diaphyseal growth and modeling drift patterns. Three thin sections at 40, 50, and 60% bone length were prepared from a modern Mexican skeletal sample with known age and sex to give a longitudinal perspective on the drifting cortex (12 adults and juveniles total, 7 male and 5 female). Point-count techniques were applied across eight cross-sectional regions of interest using the starburst sampling pattern to quantify percent periosteal and endosteal primary lamellar bone at each diaphyseal level. The results of this study show a posterio-medial drift pattern in the humerus with a posterior rotational trend along the diaphysis. In the femur, we observed a consistent lateral to anteriolateral drift and an increase in primary lamellar bone area of both, periosteal and endosteal origin, towards the distal part of the diaphysis. These observations characterize drifting diaphyses in greater detail, raising important questions about how to resolve microscopic and macroscopic cross-sectional analysis towards a more complete understanding of bone growth and mechanical adaptation. Accounting for modeling drift has the potential to positively impact age and physical activity estimation, and explain some of the significant regional variation in bone histomorphology seen within (and between) bone cross-sections due to differing ages of tissue formation. More study is necessary, however, to discern between possible drift scenarios and characterize populational variation.

Studing cranial vault modifications in ancient Mesoamerica.

The artificial modification of infant cranial vaults through massages or by means of constriction and compression devices constitutes a readily visible, permanent body modification that has been employed cross-culturally to express identity, ethnicity, beauty, status and gender. For those ancient societies that staged head shaping, these cultural correlates may be ascertained by examining cranial shapes together with other data sets from the archaeological record. Studies of skulls modified for cultural reasons also provide important clues for understanding principles in neural growth and physiopathological variation in cranial expansion. This paper focuses on head shaping techniques in Mesoamerica, where the practice was deeply rooted and widespread before the European conquest. It provides a comprehensive review of the Mesoamericanistic research on shaping techniques, implements and taxonomies. An up-dated, interdisciplinary examination of the physiological implications and the cultural meanings of artificially produced head shapes in different times and culture areas within Mesoamerica leads to a discussion of the scope, caveats, and future directions involved in this kind of research in the region and beyond.

Carious lesions and maize consumption among the Prehispanic Maya: an analysis of a coastal community in northern Yucatan.

Patterns of carious lesions were analyzed in the Classic period coastal Maya population of Xcambó, a salt production and administration center in northern Yucatan. To this end, the study investigated caries in the permanent dentitions of 163 adult skeletons, 23 from the Early Classic (AD 250-550) and 140 from the Late Classic period (AD 550-750), equally distributed between sexes. The archaeological and bioarchaeological evidence indicates a wealthy and socially homogeneous population dedicated to salt production and administration in the Early Classic that switched to pure administrative functions in the Late Classic. The results indicate an increase in caries from 7.4% and 21.2% (males and females respectively) from the Early Classic to 14.0% in males and 27.4% in females from the Late Classic period. The rate of caries in the Early and in the Late Classic phases of continuous occupation is not consistent with a simple interpretation of a heavier reliance on maize during the latter phase, characterized by a sedentary lifestyle, particularly for the male segment of the society now dedicated completely to the administration of the salt mines. Rather, the increase in caries rates in both sexes is best explained within a broader context of overall food habits, new cariogenic foods for both sexes, and the changes in lifestyle imposed by the increased socioeconomic role of the site. Our conclusions stress the limitations imposed by interpreting carious lesions solely in terms of single dietary components, such as maize consumption, without taking into account broader aspects of cultural and socioeconomic relevance.

New formulas to estimate age at death in Maya populations using histomorphological changes in the fourth human rib*.

This study develops new histomorphological algorithms for Maya populations' human ribs and tests the applicability of published algorithms. Thin sections from the fourth rib of 36 individuals of known age were analyzed under polarized light microscopy. Osteon population density (OPD, the concentration of intact and fragmented osteons per mm(2)), cortical area (CA), and osteon size (OS) were recorded. Seven algorithms were calculated, using all combinations of variables, and compared to the performance of published formulas. The OPD-based formulas deviate from the known age 8.7 years on average, while those from OS and CA deviate between 10.7 and 12.8 years. In comparison, our OPD-based algorithms perform better than the one by Stout and Paine and much better than Cho et al. In conclusion, algorithms should be developed using OPD for different ethnic groups; although Stout and Paine's can be used for Maya and maybe Mesoamerican individuals.

Early African Diaspora in colonial Campeche, Mexico: strontium isotopic evidence.

Construction activities around Campeche's central park led to the discovery of an early colonial church and an associated burial ground, in use from the mid-16th century AD to the late 17th century. Remains of some individuals revealed dental mutilations characteristic of West Africa. Analyses of strontium isotopes of dental enamel from these individuals yielded unusually high (87)Sr/(86)Sr ratios, inconsistent with an origin in Mesoamerica, but consistent with an origin in West Africa in terrain underlain by the West Africa Craton, perhaps near the port of Elmina, a principal source of slaves for the New World during the 16th century. These individuals likely represent some of the earliest representatives of the African Diaspora in the Americas.

Dental caries and antemortem tooth loss in the Northern Peten area, Mexico: a biocultural perspective on social status differences among the Classic Maya.

Dental caries and antemortem tooth loss (AMTL) are investigated in a Classic Maya sample obtained from the sites of Calakmul, Dzibanché, and Kohunlich (Mexico). This study aims at assessing the effect that sex and social status had on the prevalence of oral pathologies. The lack of a direct relationship between caries, AMTL, and age-at-death led us to interpret the results in terms of the biological, socioeconomic, and behavioral conditions prevailing in these ancient Maya settlements. Benefits related to sex and social status are evident in the frequency of carious lesions, which appear less frequently in elite males than in low-status individuals of both sexes and in elite females. Individuals from problematic mortuary contexts and isolated bone assemblages, who could not be ascribed to any status group, showed the highest rates of caries. Sex discrimination in dietary preferences appears in the elite sample, while the homogeneity encountered between sexes in the low-status segment suggests a more uniform access to resources. Tooth loss clearly distinguishes elite individuals from commoners, regardless of sex, with the former bearing a much higher rate of loss. In individuals from the undefined mortuary assemblages and sacrificial contexts, it was even more pronounced than in the other groups, although its interpretation is problematic due to a lack of associated funerary data. The overall evidence from oral pathologies is interpreted to be the result of deficient oral hygiene coupled with a softer and more refined diet in the high-status population, particularly males. Whereas elite males' subsistence was apparently based more on animal proteins and relatively soft and refined foods, a diet relying on carbohydrates may account for the observed rate of oral pathologies in elite females and commoners.