Walter A. Neves

Craniofacial morphology of the first Americans : Pattern and process in the peopling of the New World

The peopling of the New World has been the focus of anthropological attention since the last century. Proponents of multiple migration models have claimed that patterns of variation among extant New World populations reflect ancient, discrete migrations to the Americas during the terminal Pleistocene. Although multiple migration models appear to explain patterns of both past and present craniometric variation, this interpretation rests on a number of key assumptions that require further investigation. We examined a series of Paleoindian (n = 11) and Archaic (n = 384) crania from North and South America, and compare these early samples to a large world-wide sample of late Holocene (n = 6,742) remains to assess within- and among-group variability in early samples, and to determine how patterns of variation could be viewed as a reflection of both population history and population structure. Analyses included univariate and multivariate analysis of variance, principal component analysis, calculation of biological distances, and multivariate allocation methods. We also performed model-bound analyses of these data, including Relethford-Blangero analysis and calculation of F(ST). Our results indicate that under the assumptions of migration/founder models, the data are consistent with Paleoindians having derived from an undifferentiated Asian population that was not ancestral to modern American Indians. This view can be accommodated into existing models of multiple founders (migrations) in the New World. However, the assumptions required for such an interpretation are not realistic, and the diversity of early populations could as easily reflect population structuring processes such as genetic drift, demographic growth, and other phenomena. When the data were analyzed controlling for the effects of genetic drift (i.e., with smaller long-term effective population sizes for Paleoindians), the Paleoindian samples were no longer distinct from modern Native American populations. Other factors that need to be considered include processes involved in craniofacial change and adaptation during the past 10,000 years. Finally, patterns of variation in the North and South American Paleoindian samples are different, suggesting that the process of New World colonization is more complex than previously assumed.

Morphological affinities of the first Americans: an exploratory analysis based on early South American human remains

Abstract The cranial morphology of early South American human remains are compared with Late Pleistocene and Early Holocene worldwide human morphological variation by means of a principal components analysis applied to 13 craniometric variables. Two modern Mongoloid populations and one Australoid population were also included as controls. The morphological affinities obtained showed evidence of a marked biological similarity between early South Americans and early and modern Australians, and a considerable distance between both populations and the Mongoloid groups used as control. These results call for more detailed investigations about human micro-evolution in the Americas, including time of entry and number of migrations involved.

Cladistic analysis of continuous modularized traits provides phylogenetic signals in Homo evolution

Evolutionary novelties in the skeleton are usually expressed as changes in the timing of growth of features intrinsically integrated at different hierarchical levels of development. As a consequence, most of the shape-traits observed across species do vary quantitatively rather than qualitatively, in a multivariate space and in a modularized way. Because most phylogenetic analyses normally use discrete, hypothetically independent characters, previous attempts have disregarded the phylogenetic signals potentially enclosed in the shape of morphological structures. When analysing low taxonomic levels, where most variation is quantitative in nature, solving basic requirements like the choice of characters and the capacity of using continuous, integrated traits is of crucial importance in recovering wider phylogenetic information. This is particularly relevant when analysing extinct lineages, where available data are limited to fossilized structures. Here we show that when continuous, multivariant and modularized characters are treated as such, cladistic analysis successfully solves relationships among main Homo taxa. Our attempt is based on a combination of cladistics, evolutionary-development-derived selection of characters, and geometric morphometrics methods. In contrast with previous cladistic analyses of hominid phylogeny, our method accounts for the quantitative nature of the traits, and respects their morphological integration patterns. Because complex phenotypes are observable across different taxonomic groups and are potentially informative about phylogenetic relationships, future analyses should point strongly to the incorporation of these types of trait.

Testing Evolutionary and Dispersion Scenarios for the Settlement of the New World

Background Discussion surrounding the settlement of the New World has recently gained momentum with advances in molecular biology, archaeology and bioanthropology. Recent evidence from these diverse fields is found to support different colonization scenarios. The currently available genetic evidence suggests a “single migration” model, in which both early and later Native American groups derive from one expansion event into the continent. In contrast, the pronounced anatomical differences between early and late Native American populations have led others to propose more complex scenarios, involving separate colonization events of the New World and a distinct origin for these groups. Methodology/Principal Findings Using large samples of Early American crania, we: 1) calculated the rate of morphological differentiation between Early and Late American samples under three different time divergence assumptions, and compared our findings to the predicted morphological differentiation under neutral conditions in each case; and 2) further tested three dispersal scenarios for the colonization of the New World by comparing the morphological distances among early and late Amerindians, East Asians, Australo-Melanesians and early modern humans from Asia to geographical distances associated with each dispersion model. Results indicate that the assumption of a last shared common ancestor outside the continent better explains the observed morphological differences between early and late American groups. This result is corroborated by our finding that a model comprising two Asian waves of migration coming through Bering into the Americas fits the cranial anatomical evidence best, especially when the effects of diversifying selection to climate are taken into account. Conclusions We conclude that the morphological diversity documented through time in the New World is best accounted for by a model postulating two waves of human expansion into the continent originating in East Asia and entering through Beringia.

Early Holocene human skeletal remains from Santana do Riacho, Brazil: implications for the settlement of the New World

In this study we compare the cranial morphology of several late Paleoindian skeletons uncovered at Santana do Riacho, Central Brazil, with worldwide human cranial variation. Mahalanobis Distance and Principal Component Analysis are used to explore the extra-continental morphological affinities of the Brazilian Paleoindian sample. Santana do Riacho is a late Paleoindian burial site where approximately 40 individuals were recovered in varying states of preservation. The site is located at Lagoa Santa/Serra do Cipó, State of Minas Gerais. The first human activities in this rockshelter date back to the terminal Pleistocene, but the burials are bracketed between circa 8200 and 9500BP. The collection contains only six skulls well-enough preserved to be measured. The Santana do Riacho late Paleoindians present a cranial morphology characterized by long and narrow neurocrania, low and narrow faces, with low nasal apertures and orbits. The multivariate analyses show that they exhibit strong morphological affinities with present day Australians and Africans, showing no resemblance to recent Northern Asians and Native Americans. These findings confirm our long held opinion that the settlement of the Americas was more complicated in terms of biological input than has been widely assumed. The working hypothesis is that two very distinct populations entered the New World by the end of the Pleistocene, and that the transition between the cranial morphology of the Paleoindians and the morphology of later Native Americans, which occurred around 8-9ka, was abrupt. This, in our opinion, is a more parsimonious explanation for the diversity detected than a long, local microevolutionary process mediated by selection and drift. The similarities of the first South Americans with sub-Saharan Africans may result from the fact that the non-Mongoloid Southeast Asian ancestral population came, ultimately, from Africa, with no major modification in the original cranial bau plan of the first modern humans.

Incidence and distribution of postcranial fractures in the prehistoric population of San Pedro de Atacama, Northern Chile

Trauma incidence analysis in skeletal populations has been very popular among skeletal biologists during the last two decades. In this context, the work of Lovejoy and Heiple ([1981] Am. J. Phys. Anthropol. 55:529-541) has been quoted as a landmark because their analysis rested on a populational approach, avoiding simple assumptions about cause and etiology. In this study, we apply to the prehistoric population of San Pedro de Atacama, northern Chile, an approach similar to that carried out by Lovejoy and Heiple (1981). The results obtained point to a peak of risk of fractures among old people, estimated age around 45 years. The distribution of fractures by sex and age suggests that the prevailing etiology is related to accidents and not violence. When the frequencies of fractures are compared, the Libben population shows a much higher incidence than the Atacamenean population. It is suggested that this difference can be explained by peculiarities of the subsistence economies of the two populations.

Paleoamerican morphology in the context of European and East Asian late Pleistocene variation: Implications for human dispersion into the new world

Early American crania show a different morphological pattern from the one shared by late Native Americans. Although the origin of the diachronic morphological diversity seen on the continents is still debated, the distinct morphology of early Americans is well documented and widely dispersed. This morphology has been described extensively for South America, where larger samples are available. Here we test the hypotheses that the morphology of Early Americans results from retention of the morphological pattern of Late Pleistocene modern humans and that the occupation of the New World precedes the morphological differentiation that gave rise to recent Eurasian and American morphology. We compare Early American samples with European Upper Paleolithic skulls, the East Asian Zhoukoudian Upper Cave specimens and a series of 20 modern human reference crania. Canonical Analysis and Minimum Spanning Tree were used to assess the morphological affinities among the series, while Mantel and Dow-Cheverud tests based on Mahalanobis Squared Distances were used to test different evolutionary scenarios. Our results show strong morphological affinities among the early series irrespective of geographical origin, which together with the matrix analyses results favor the scenario of a late morphological differentiation of modern humans. We conclude that the geographic differentiation of modern human morphology is a late phenomenon that occurred after the initial settlement of the Americas.

Dental health in Northern Chile's Atacama oases: evaluating the Middle Horizon (AD 500-1000) impact on local diet.

As one of the few areas apt for horticulture in Northern Chiles arid landscape, the prehistory of the Atacama oases is deeply enmeshed with that of the inter-regional networks that promoted societal development in the south central Andes. During the Middle Horizon (AD 500-1000), local populations experienced a cultural apex associated with a substantial increase in inter-regional interaction, population density, and quantity and quality of mortuary assemblages. Here, we test if this cultural peak affected dietary practices equally among the distinct local groups of this period. We examine caries prevalence and the degree of occlusal wear in four series recovered from three cemeteries. Our results show a reduction in the prevalence of caries for males among an elite subsample from Solcor 3 and the later Coyo 3 cemeteries. Dental wear tends to increase over time with the Late Middle Horizon/Late Intermediate Period cemetery of Quitor 6 showing a higher average degree of wear. When considered in concert with archaeological information, we concluded that the Middle Horizon was marked by dietary variability wherein some populations were able to obtain better access to protein sources (e.g., camelid meat). Not all members of Atacameño society benefited from this, as we note that this dietary change only affected men. Our results suggest that the benefits brought to the San Pedro oases during the Middle Horizon were not equally distributed among local groups and that social status, relationship to the Tiwanaku polity, and interment in particular cemeteries affected dietary composition.

Influencia de Tiwanaku en la calidad de vida biológica de la población prehistórica de San Pedro de Atacama 1

We examine four prehistorical moments in San Pedro de Atacama with the purpose of qualifying the impact that Tiwanaku had on the local population. To this end, we carried out osteobiographic studies on 161 individuals from the cemeteries of Solcor-3, Coyo-3 and Quitor-6, which are representative of pre-Tiwanaku (Sequitor and Quitor Phases), Tiwanaku (Coyo Phase; with a rise of altiplano influence), Final Tiwanaku (final Coyo Phase) and post-Tiwanaku (Yaye-Solor Phase). The results for three of the indicators that we used, suggest an improvement in the biological quality of life of the local population, expressed in greater height and sexual dimorphism, the lesser occurrence of caries, occlusal abrasion and loss of teeth during the individual’s life, all of this possibly owing to the increase in the consumption of animal protein that took place under Tiwanaku influence. Although, on a first impression, hyperostosis and the systemic hypoplasia of tooth enamel would indicate a negative impact on the population, it is conceivable that the greater incidence of these variables results from an improved diet that made individuals more resistant to attacks by pathogenic agents. The last indicator we used relates to body use, which reveals that, notwithstanding the changes that would have been propitiated by altiplano influence, the local population kept to its traditional daily activities throughout.

LAGOA SANTA REVISITED: AN OVERVIEW OF THE CHRONOLOGY, SUBSISTENCE, AND MATERIAL CULTURE OF PALEOINDIAN SITES IN EASTERN CENTRAL BRAZIL

Lagoa Santa, a karstic area in eastern Central Brazil, has been subject to research on human paleontology and archaeol ogy for 175 years. Almost 300 Paleoindian human skeletons have been found since Danish naturalist Peter Lund’s pio neering work. Even so, some critical issues such as the role of rockshelters in settlement systems, and the possible paleoclimatic implications of the peopling of the region have yet to be addressed. We present some results obtained from recent excava tions at four rockshelters and two open-air sites, new dates for human Paleoindian skeletons, and a model to explain the cultural patterns observed so far. It is also argued that the Paleoindian subsistence system at Lagoa Santa was similar to other locations in South America: generalized small-game hunting complemented by fruits, seed, and root gathering. Lagoa Santa, un area karstica en Brasil Central, ha sido objeto de investigacion en paleontologia humana y arqueologia durante 170 anos. Casi 300 esqueletos humanos paleoindios se han encontrado desde que el naturalista dinamarques Peter Lund empezo su trabajo pionero en la mitad del siglo XIX. Sin embargo, problemas criticos como el papel de las cuevas en los patrones de asentamiento y las posibles implicaciones paleoclimaticas en el poblamiento del area todavia tienen que ser mejor estudiados. Nosotros presentamos los resultados obtenidos de las recientes excavaciones de cuatro cuevas y dos yacimien tos a cielo abierto, nuevas feches de esqueletos humanos paleoindios, y un modelo para explicar los patrones culturales obser vados. Tambien propone mas que el sistema de subsistencia paleoindio en Lagoa Santa fue, asi como en otros sitios de Sudamerica, bastante generalizado, incluyendo la caza de pequenos animales y la recoleccion de frutos, semillas y raices.