SummaryWe report genome-wide ancient DNA from 49 individuals forming four parallel time transects in Belize, Brazil, the Central Andes, and the Southern Cone, each dating to at least ∼9,000 years ago. The common ancestral population radiated rapidly from just one of the two early branches that contributed to Native Americans today. We document two previously unappreciated streams of gene flow between North and South America. One affected the Central Andes by ∼4,200 years ago, while the other explains an affinity between the oldest North American genome associated with the Clovis culture and the oldest Central and South Americans from Chile, Brazil, and Belize. However, this was not the primary source for later South Americans, as the other ancient individuals derive from lineages without specific affinity to the Clovis-associated genome, suggesting a population replacement that began at least 9,000 years ago and was followed by substantial population continuity in multiple regions.

The ability of cranial morphology to reflect population/phylogenetic history, and the degree to which it might be influenced by environmental factors and selection pressures have been widely discussed. Recent consensus views cranial morphology as largely indicative of population history in humans, with some anatomical cranial regions/measurements being more informative on population history, while others being under selection pressure. We test earlier findings using the largest and most diverse cranial dataset available as yet: 7,423 male specimens from 135 geographic human population samples represented by 33 standard craniometric linear measurements. We calculated Mahalanobis D 2 for three datasets: complete cranial dataset; facial measurement dataset; and neurocranial measurement dataset; these morphological distance matrices were then compared to matrices of geographic distances as well as of several climatic variables. Additionally, we calculated Fst values for our cranial measurements and compared the results to the expected Fst values for neutral genetic loci. Our findings support the hypothesis that cranial, and especially neurocranial morphology, is phylogenetically informative, and that aspects of the face and cranium are subject to selection related to climatic factors. The Fst analysis suggest that selection to climate is largely restricted to groups living in extremely cold environments, including Northeast Asia, North America, and Northern Europe, though each of these regions appears to have arrived at their morphology through distinct adaptive pathways. Anat Rec, 292:1720Rec, 292: -1733Rec, 292: , 2009. Key words: Fst; craniometrics; adaptation; population history; human variation; NeanderthalsThe degree to which human cranial morphology reflects population history or adaptive and developmental changes related to environmental conditions is the subject of ongoing scientific discussion in anthropology. Our understanding of the evolutionary processes affecting morphological variation directly impacts both the study of modern human geographic diversity as well as the interpretation of the human fossil record. The relevance of cranial morphology to phylogenetic reconstruction has been questioned in the past (see e.g., Collard and Wood, 2000), and convergence, parallelism, reversals, and environmen-

Comparative morphological studies of the earliest human skeletons of the New World have shown that, whereas late prehistoric, recent, and present Native Americans tend to exhibit a cranial morphology similar to late and modern Northern Asians (short and wide neurocrania; high, orthognatic and broad faces; and relatively high and narrow orbits and noses), the earliest South Americans tend to be more similar to present Australians, Melanesians, and Sub-Saharan Africans (narrow and long neurocrania; prognatic, low faces; and relatively low and broad orbits and noses). However, most of the previous studies of early American human remains were based on small cranial samples. Herein we compare the largest sample of early American skulls ever studied (81 skulls of the Lagoa Santa region) with worldwide data sets representing global morphological variation in humans, through three different multivariate analyses. The results obtained from all multivariate analyses confirm a close morphological affinity between SouthAmerican Paleoindians and extant Australo-Melanesians groups, supporting the hypothesis that two distinct biological populations could have colonized the New World in the Pleistocene͞Holocene transition.Paleoamericans ͉ Paleoindian morphology ͉ Paleoindians

BackgroundDiscussion 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 FindingsUsing 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.ConclusionsWe 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.

The goal of this longitudinal study was to assess the impact of economic change and increased market integration on subsistence strategies, living conditions, growth, and nutritional status of Ribeirinhos living in the rural Amazon, Brazil. Data on weight, height, skinfolds, and circumferences, as well as data on economic strategies and living conditions were collected from 469 individuals in 2002 and 429 in 2009. Of these, 204 individuals were measured on both occasions. Independent and paired t-tests were used to identify changes in nutritional status over time in the larger sample and smaller, longitudinal subsample, respectively. Multiple linear regressions were used to examine the relationship between changes in economic/living conditions and nutritional status in the longitudinal subsample. Results indicate modest improvements in linear growth (HAZ) and among male children the observed increase was related to enrollment in the Brazilian conditional cash transfer program, Bolsa Família (P = 0.03). In terms of short-term measures of nutritional status, we found a significant increase in ZTSF and a reduction in ZUMA in most age/sex groups. Among subadults, there was a negative relationship between ZUMA and access to electricity (P = 0.01) and positive relationship between ZUMA and the sale of the açaí fruit (P = 0.04). Significant changes in weight and BMI (P < 0.01) were found among adult females and both were negatively related to household cash income (P = 0.02 and P = 0.03, respectively). Despite significant changes in economic strategies and lifestyle, changes in nutritional status were modest which may be explained by increased food insecurity documented during this early stage of transition.

As one of the few areas apt for horticulture in Northern Chile's 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.

Human skeletal remains of the first Americans are scarce, especially in North America. In South America the situation is less dramatic. Two important archaeological regions have generated important collections that allow the analysis of the cranial morphological variation of the Early Americans: Lagoa Santa, Brazil, and Sabana de Bogotá, Colombia. Human crania from the former region have been studied by one of us (WAN) and collaborators, showing that the cranial morphology of the first South Americans was very different from that prevailing today in East Asia and among Native Americans. These results have allowed for proposing that the New World may have been colonized by two different biological populations in the final Pleistocene/early Holocene. In this study, 74 human skulls dated between 11.0 and 3.0 kyr, recovered in seven different sites of Sabana de Bogotá, Colombia, were compared with the world cranial variation by different multivariate techniques: Principal Components Analysis, Multidimensional Scaling, and Cluster of Mahalanobis distance matrices. The Colombian skeletal remains were divided in two chronological subgroups: Paleocolombians (11.0-6.0 kyr) and Archaic Colombians (5.0-3.0 kyr). Both quantitative techniques generated convergent results: the Paleocolombians show remarkable similarities with Lagoa Santa and with modern Australo-Melanesians. Archaic Colombians exhibited the same morphological patterns and associations. These findings support our long-held proposition that the early American settlement may have involved two very distinct biological populations coming from Asia. On the other hand, they suggest the possibility of late survivals of the Paleoamerican pattern not restricted to isolated or marginal areas, as previously thought.

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.