Redefining the age of Clovis: implications for the peopling of the Americas

New age constraints for human entry into the Americas on the north Pacific coast

The timing of the initial peopling of the Americas is unresolved. Because the archaeological record necessitates discussion of human entry from Beringia into southern North America during the last glaciation, addressing this problem routinely involves evaluating environmental parameters then targeting areas suitable for human settlement. Vertebrate remains indicate landscape quality and are a key dataset for assessing coastal migration theories and the viability of coastal routes. Here, radiocarbon dates on vertebrate specimens and archaeological sites are calibrated to document species occurrences and the ages of human settlements across the western expansion and decay of the Cordilleran Ice Sheet (CIS) during the Late Wisconsin Fraser Glaciation in four subregions of the north Pacific coast of North America. The results show archaeological sites occur after glacial maxima and are generally consistent with the age of other securely dated earliest sites in southern North America. They also highlight gaps in the vertebrate chronologies around CIS maxima in each of the subregions that point to species redistributions and extirpations and signal times of low potential for human settlement and subsistence in a key portion of the proposed coastal migration route. This study, therefore, defines new age constraints for human coastal migration theories in the peopling of the Americas debate.

The "Greenberg Controversy" and the Interdisciplinary Study of Global Linguistic Relationships

This paper examines the controversy that followed the 1987 publication of Joseph Greenberg's book, Language in the Americas, attending to the role of language and linguistic research within overlapping disciplinary traditions. With this text, Greenberg presented a macro-level tripartite classification that opposed then dominant fine-grained analyses recognizing anywhere from 150 to 200 distinct language families. His proposal was the subject of a landmark conference, examining strengths and weaknesses, the unpublished proceedings of which are presented here for the first time. For specialists in the anthropological and comparative-historical study of Indigenous American languages, Greenberg's intervention highlighted the tension between language, conceived as an abstract object of study, and languages, understood to be carriers of specific cultural knowledge. For physical anthropologists and archaeologists, his theory was initially fortuitous on programmatic, substantive, and methodological grounds. The essay will show how interdisciplinary appeals were figured by supporters as a virtue, and by critics as a vice. The essay further highlights ethical reasons for integrating historical narratives of science and the humanities.

Human Occupation of the North American Colorado Plateau ∼37,000 Years Ago

Calibrating human population dispersals across Earth’s surface is fundamental to assessing rates and timing of anthropogenic impacts and distinguishing ecological phenomena influenced by humans from those that were not. Here, we describe the Hartley mammoth locality, which dates to 38,900–36,250 cal BP by AMS 14C analysis of hydroxyproline from bone collagen. We accept the standard view that elaborate stone technology of the Eurasian Upper Paleolithic was introduced into the Americas by arrival of the Native American clade ∼16,000 cal BP. It follows that if older cultural sites exist in the Americas, they might only be diagnosed using nuanced taphonomic approaches. We employed computed tomography (CT and μCT) and other state-of-the-art methods that had not previously been applied to investigating ancient American sites. This revealed multiple lines of taphonomic evidence suggesting that two mammoths were butchered using expedient lithic and bone technology, along with evidence diagnostic of controlled (domestic) fire. That this may be an ancient cultural site is corroborated by independent genetic evidence of two founding populations for humans in the Americas, which has already raised the possibility of a dispersal into the Americas by people of East Asian ancestry that preceded the Native American clade by millennia. The Hartley mammoth locality thus provides a new deep point of chronologic reference for occupation of the Americas and the attainment by humans of a near-global distribution.

Late date of human arrival to North America: Continental scale differences in stratigraphic integrity of pre-13,000 BP archaeological sites

By 13,000 BP human populations were present across North America, but the exact date of arrival to the continent, especially areas south of the continental ice sheets, remains unclear. Here we examine patterns in the stratigraphic integrity of early North American sites to gain insight into the timing of first colonization. We begin by modeling stratigraphic mixing of multicomponent archaeological sites to identify signatures of stratigraphic integrity in vertical artifact distributions. From those simulations, we develop a statistic we call the Apparent Stratigraphic Integrity Index (ASI), which we apply to pre- and post-13,000 BP archaeological sites north and south of the continental ice sheets. We find that multiple early Beringian sites dating between 13,000 and 14,200 BP show excellent stratigraphic integrity. Clear signs of discrete and minimally disturbed archaeological components do not appear south of the ice sheets until the Clovis period. These results provide support for a relatively late date of human arrival to the Americas.

The age of Clovis-13,050 to 12,750 cal yr B.P

Thirty-two radiocarbon ages on bone, charcoal, and carbonized plant remains from 10 Clovis sites range from 11,110 ± 40 to 10,820 ± 10 ¹⁴C years before the present (yr B.P.). These radiocarbon ages provide a maximum calibrated (cal) age range for Clovis of ~13,050 to ~12,750 cal yr B.P. This radiocarbon record suggests that Clovis first appeared at the end of the Allerød and is one of at least three contemporary archaeological complexes in the Western Hemisphere during the terminal Pleistocene. Stemmed projectile points in western North America are coeval and even older than Clovis, and the Fishtail point complex is well established in the southern cone of South America by ~12,900 cal yr B.P. Clovis disappeared ~12,750 cal yr B.P. at the beginning of the Younger Dryas, coincident with the extinction of the remaining North American megafauna (Proboscideans) and the appearance of multiple North American regional archaeological complexes.

Examining variation in skeletal tuberculosis in a late pre-contact population from the eastern mountains of Peru

OBJECTIVE AND MATERIALS

This research evaluates the presence and chronology of tuberculosis (TB) in the northeastern highlands of Peru (CE 800-1535) through the analysis of osseous lesions from Pre-Contact Kuelap, Chachapoyas.

METHODS

We examined macroscopic lesion morphology and distribution from the skeletal series (MNI = 207).

RESULTS

We determined that skeletal evidence was highly consistent with advanced multifocal and spinal tuberculosis in 13 individuals. Destructive lesions of the lower thoracic and/or lumbar vertebra bodies and sacroiliac joints are evident in most cases, but we also observed lesions within the manubriosternal, hip, and knee joints. Both adult males (n = 7) and females (n = 6) present skeletal lesions from young adult to older adults, but there is only one late adolescent. Only three individuals demonstrate similar lesion distributions.

CONCLUSIONS

Variation in lesion distribution in this population-based study shows the importance of identifying extra-vertebral tuberculosis and suggests that the disease may have manifested differently than at other coastal sites. These cases confirm the presence of tuberculosis both before and after Inca occupation across this central Andean highlands region.

SIGNIFICANCE

This evidence for the likely endemic presence of TB in the New World prior to European Contact furthers our understanding of the distribution of this infectious disease across the region as well as elucidating lesion distribution.

LIMITATIONS

The diagnosis of tuberculosis is based on skeletal lesions and it should be confirmed by molecular analysis.

FUTURE RESEARCH

Additional examination of vertebral bodies (including juvenile remains) for evidence of earlier manifestations of infection.

Optimization of subsampling, decontamination, and DNA extraction of difficult peat and silt permafrost samples

This study aims to act as a methodological guide for contamination monitoring, decontamination, and DNA extraction for peaty and silty permafrost samples with low biomass or difficult to extract DNA. We applied a biological tracer, either only in the field or both in the field and in the lab, via either spraying or painting. Spraying in the field followed by painting in the lab resulted in a uniform layer of the tracer on the core sections. A combination of bleaching, washing, and scraping resulted in complete removal of the tracer leaving sufficient material for DNA extraction, while other widely used decontamination methods did not remove all detectable tracer. In addition, of four widely used commercially available DNA extraction kits, only a modified ZymoBIOMICS DNA Microprep kit was able to acquire PCR amplifiable DNA. Permafrost chemical parameters, age, and soil texture did not have an effect on decontamination efficacy; however, the permafrost type did influence DNA extraction. Based on these findings, we developed recommendations for permafrost researchers to acquire contaminant-free DNA from permafrost with low biomass.

Fluted-point technology in Neolithic Arabia: An independent invention far from the Americas

New World archaeologists have amply demonstrated that fluted point technology is specific to Terminal Pleistocene American cultures. Base-fluted, and rarer tip-fluted, projectile points from the Americas have been well-documented by archaeologists for nearly a century. Fluting is an iconic stone tool manufacturing method and a specific action that involves the extraction of a channel flake along the longitudinal axis of a bifacial piece. Here we report and synthesize information from Neolithic sites in southern Arabia, demonstrating the presence of fluting on a variety of stone tool types including projectile points. Fluted projectile points are known from both surface sites and stratified contexts in southern Arabia. Fluting technology has been clearly identified at the Manayzah site (Yemen) dating to 8000-7700 cal. BP. Examination of fluted points and channel flakes from southern Arabia enable a reconstruction of stone tool manufacturing techniques and reduction sequences (chaines opératoires). To illustrate the technological similarities and contrasts of fluting methods in Arabia and the Americas, comparative studies and experiments were conducted. Similarities in manufacturing approaches were observed on the fluting scars of bifacial pieces, whereas technological differences are apparent in the nature and localization of the flute and, most probably, the functional objective of fluting in economic, social and cultural contexts. Arabian and American fluted point technologies provide an excellent example of convergence of highly specialized stone tool production methods. Our description of Arabian and American fluting technology demonstrates that similar innovations and inventions were developed under different circumstances, and that highly-skilled and convergent production methods can have different anthropological implications.

The timing and effect of the earliest human arrivals in North America

The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed 'Clovis-first')-suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points¹-has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5-19 thousand years ago)^2,3 but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7-12.9 thousand years before AD 2000)⁴. We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.

Late Pleistocene exploration and settlement of the Americas by modern humans

North and South America were the last continents to be explored and settled by modern humans at the end of the Pleistocene. Genetic data, derived from contemporary populations and ancient individuals, show that the first Americans originated from Asia and after several population splits moved south of the continental ice sheets that covered Canada sometime between ~17.5 and ~14.6 thousand years (ka) ago. Archaeological evidence shows that geographically dispersed populations lived successfully, using biface, blade, and osseous technologies, in multiple places in North and South America between ~15.5 and ~14 ka ago. Regional archaeological complexes emerged by at least ~13 ka ago in North America and ~12.9 ka ago in South America. Current genetic and archaeological data do not support an earlier (pre-17.5 ka ago) occupation of the Americas.

Late Upper Paleolithic occupation at Cooper's Ferry, Idaho, USA, ~16,000 years ago

Radiocarbon dating of the earliest occupational phases at the Cooper's Ferry site in western Idaho indicates that people repeatedly occupied the Columbia River basin, starting between 16,560 and 15,280 calibrated years before the present (cal yr B.P.). Artifacts from these early occupations indicate the use of unfluted stemmed projectile point technologies before the appearance of the Clovis Paleoindian tradition and support early cultural connections with northeastern Asian Upper Paleolithic archaeological traditions. The Cooper's Ferry site was initially occupied during a time that predates the opening of an ice-free corridor (≤14,800 cal yr B.P.), which supports the hypothesis that initial human migration into the Americas occurred via a Pacific coastal route.

Paleoamerican Occupation, Stone Tools from the Cueva del Medio, and Considerations for the Late Pleistocene Archaeology in Southern South America

Archaeological excavations at the Cueva del Medio performed during the 1980s and 1990s yielded an important record of both faunal and stone tool remains, as well as data, to discuss issues that occurred during the Terminal Pleistocene. Due to that, the shaped Paleoamerican artifacts collected in the author’s excavations were partially informed. The present article provides unpublished data on the field-work, the results of a techno-morphological analysis of the stone tools, and considerations about early hunter-gatherer societies along with their regional paleo-environmental interactions, as well other topics regarding the regional archaeological process during the last millennium of the Pleistocene. Findings from there have been extremely useful for discussing diverse paleo-ecological and archaeological topics and have extended the knowledge and discussions about different Pleistocene scientific issues, mainly related with flora, fauna, and the colonization of southern Patagonia.

Linking late Paleoindian stone tool technologies and populations in North, Central and South America

From the perspective of Central and South America, the peopling of the New World was a complex process lasting thousands of years and involving multiple waves of Pleistocene and early Holocene period immigrants entering into the neotropics. These Paleoindian colonists initially brought with them technologies developed for adaptation to environments and resources found in North America. As the ice age ended across the New World people adapted more generalized stone tools to exploit changing environments and resources. In the neotropics these changes would have been pronounced as patchy forests and grasslands gave way to broadleaf tropical forests. We document a late Pleistocene/early Holocene stone tool tradition from Belize, located in southern Mesoamerica. This represents the first endogenous Paleoindian stone tool technocomplex recovered from well dated stratigraphic contexts for Mesoamerica. Previously designated Lowe, these artifacts share multiple features with contemporary North and South American Paleoindian tool types. Once hafted, these bifaces appear to have served multiple functions for cutting, hooking, thrusting, or throwing. The tools were developed at a time of technological regionalization reflecting the diverse demands of a period of pronounced environmental change and population movement. Combined stratigraphic, technological, and population paleogenetic data suggests that there were strong ties between lowland neotropic regions at the onset of the Holocene.

Early human dispersals within the Americas

Studies of the peopling of the Americas have focused on the timing and number of initial migrations. Less attention has been paid to the subsequent spread of people within the Americas. We sequenced 15 ancient human genomes spanning from Alaska to Patagonia; six are ≥10,000 years old (up to ~18× coverage). All are most closely related to Native Americans, including those from an Ancient Beringian individual and two morphologically distinct “Paleoamericans.” We found evidence of rapid dispersal and early diversification that included previously unknown groups as people moved south. This resulted in multiple independent, geographically uneven migrations, including one that provides clues of a Late Pleistocene Australasian genetic signal, as well as a later Mesoamerican-related expansion. These led to complex and dynamic population histories from North to South America.

Ancient human parallel lineages within North America contributed to a coastal expansion

Little is known regarding the first people to enter the Americas and their genetic legacy. Genomic analysis of the oldest human remains from the Americas showed a direct relationship between a Clovis-related ancestral population and all modern Central and South Americans as well as a deep split separating them from North Americans in Canada. We present 91 ancient human genomes from California and Southwestern Ontario and demonstrate the existence of two distinct ancestries in North America, which possibly split south of the ice sheets. A contribution from both of these ancestral populations is found in all modern Central and South Americans. The proportions of these two ancestries in ancient and modern populations are consistent with a coastal dispersal and multiple admixture events.

Paternal origin of Paleo-Indians in Siberia: insights from Y-chromosome sequences

The expansion of modern humans to the American continent after the Last Glacial Maximum led the way to the present-day distribution of American aborigines. Recent advances in autosomal DNA research and expanded testing of mtDNA lineages has provided a clearer picture of the number and timing of founding lineages. However, both autosomal DNA and mtDNA research have provided unresolved competing theories between the short-term and the long-term models of the Beringian standstill hypothesis. Further, the source of founding paternal lineages of American aborigines and their relationship with ancient Siberia populations remains ambiguous. In this study, we reanalyzed a 7.0 Mbp region of 132 paternal Y-chromosome sequences, including 39 newly reported ones, of male samples from American aborigines and Eurasian populations. Among Eurasian samples, we identified Y-chromosome branches that are most closely related to known American aborigine founding lineages, that is, Q1-L804 links to Q1-M3, Q1-L330 links to Q1-Z780, Q1-M120 links to Q1-B143, and C2-F1756 links to C2-P39. The revised phylogenetic tree and age estimates indicate a narrow timeframe (~15.3-14.3 kya) for the upper time limit of human entry to the American continent. Our analysis suggests that the in situ differentiation of Q-M242 in Central Eurasia and South Siberia region gave rise to numerous sub-lineages older than 15.3 kya, and the founding of Paleo-Indian paternal lineages is part of the great Q1-L53 diffusion throughout the Eurasia after the Last Glacial Maximum. The results of our study will assist in future studies of the history of modern populations in Eurasia and the Americas.

Evidence of an early projectile point technology in North America at the Gault Site, Texas, USA

American archeology has long been polarized over the issue of a human presence in the Western Hemisphere earlier than Clovis. As evidence of early sites across North and South America continues to emerge, stone tool assemblages appear more geographically and temporally diverse than traditionally assumed. Within this new framework, the prevailing models of Clovis origins and the peopling of the Americas are being reevaluated. This paper presents age estimates from a series of alluvial sedimentary samples from the earliest cultural assemblage at the Gault Site, Central Texas. The optically stimulated luminescence age estimates (~16 to 20 thousand years ago) indicate an early human occupation in North America before at least ~16 thousand years ago. Significantly, this assemblage exhibits a previously unknown, early projectile point technology unrelated to Clovis. Within a wider context, this evidence suggests that Clovis technology spread across an already regionalized, indigenous population.

Reassessing the chronology of the archaeological site of Anzick

Found in 1968, the archaeological site of Anzick, Montana, contains the only known Clovis burial. Here, the partial remains of a male infant, Anzick-1, were found in association with a Clovis assemblage of over 100 lithic and osseous artifacts-all red-stained with ochre. The incomplete, unstained cranium of an unassociated, geologically younger individual, Anzick-2, was also recovered. Previous chronometric work has shown an age difference between Anzick-1 and the Clovis assemblage (represented by dates from two antler rod samples). This discrepancy has led to much speculation, with some discounting Anzick-1 as Clovis. To resolve this issue, we present the results of a comprehensive radiocarbon dating program that utilized different pretreatment methods on osseous material from the site. Through this comparative approach, we obtained a robust chronometric dataset that suggests that Anzick-1 is temporally coeval with the dated antler rods. This implies that the individual is indeed temporally associated with the Clovis assemblage.

Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America

Predator-prey interactions revealed by vertebrate trace fossils are extremely rare. We present footprint evidence from White Sands National Monument in New Mexico for the association of sloth and human trackways. Geologically, the sloth and human trackways were made contemporaneously, and the sloth trackways show evidence of evasion and defensive behavior when associated with human tracks. Behavioral inferences from these trackways indicate prey selection and suggest that humans were harassing, stalking, and/or hunting the now-extinct giant ground sloth in the terminal Pleistocene.

Terminal Pleistocene epoch human footprints from the Pacific coast of Canada

Little is known about the ice age human occupation of the Pacific Coast of Canada. Here we present the results of a targeted investigation of a late Pleistocene shoreline on Calvert Island, British Columbia. Drawing upon existing geomorphic information that sea level in the area was 2-3 m lower than present between 14,000 and 11,000 years ago, we began a systematic search for archaeological remains dating to this time period beneath intertidal beach sediments. During subsurface testing, we uncovered human footprints impressed into a 13,000-year-old paleosol beneath beach sands at archaeological site EjTa-4. To date, our investigations at this site have revealed a total of 29 footprints of at least three different sizes. The results presented here add to the growing body of information pertaining to the early deglaciation and associated human presence on the west coast of Canada at the end of the Last Glacial Maximum.

Cultural learning and the Clovis colonization of North America

The timing of the earliest colonization of North America is debatable, but what is not at issue is the point of origin of the early colonists: Humans entered the continent from Beringia and then made their way south along or near the Pacific Coast and/or through a corridor that ran between the Cordilleran and Laurentide ice sheets in western North America. At some point, they abandoned their Arctic-based tool complex for one more adapted to an entirely different environment. That new techno-complex is termed "Clovis"; its dispersal allows us to examine, at a fine scale, how colonization processes played out across a vast continent that at the time had, at best, a very small resident population. Clovis has figured prominently in American archeology since the first Clovis points were identified in eastern New Mexico in the 1930s. However, the successful marriage of learning models grounded in evolutionary theory and modern analytical methods that began roughly a decade ago has begun to pay significant dividends in terms of what we know about the rapid spread of human groups across the last sizable landmass to witness human occupation.

Fire history on the California Channel Islands spanning human arrival in the Americas

Recent studies have suggested that the first arrival of humans in the Americas during the end of the last Ice Age is associated with marked anthropogenic influences on landscape; in particular, with the use of fire which, would have given even small populations the ability to have broad impacts on the landscape. Understanding the impact of these early people is complicated by the dramatic changes in climate occurring with the shift from glacial to interglacial conditions. Despite these difficulties, we here attempt to test the extent of anthropogenic influence using the California Channel Islands as a smaller, landscape-scale test bed. These islands are famous for the discovery of the 'Arlington Springs Man', which are some of the earliest human remains in the Americas. A unifying sedimentary charcoal record is presented from Arlington Canyon, Santa Rosa Island, based on over 20 detailed sedimentary sections from eight key localities. Radiocarbon dating was based on thin, fragile, long fragments of charcoal in order to avoid the 'inbuilt' age problem. Radiocarbon dating of 49 such fragments has allowed inferences regarding the fire and landscape history of the Canyon ca 19-11 ka BP. A significant period of charcoal deposition is identified approximately 14-12.5 ka BP and bears remarkable closeness to an estimated age range of the first human arrival on the islands.This article is part of the themed issue 'The interaction of fire and mankind'.

Tracing social interactions in Pleistocene North America via 3D model analysis of stone tool asymmetry

Stone tools, often the sole remnant of prehistoric hunter-gatherer behavior, are frequently used as evidence of ancient human mobility, resource use, and environmental adaptation. In North America, studies of morphological variation in projectile points have provided important insights into migration and interactions of human groups as early as 12-13 kya. Using new approaches to 3D imaging and morphometric analysis, we here quantify bifacial asymmetry among early North American projectile point styles to better understand changes in knapping technique and cultural transmission. Using a sample of 100 fluted bifaces of Clovis and post-Clovis styles in the eastern United States ca. 13,100-9,000 cal BP (i.e., Clovis, Debert-Vail, Bull Brook, Michaud-Neponset/Barnes, and Crowfield), we employed two different approaches for statistical shape analysis: our previously presented method for analysis of 2D flake scar contours, and a new approach for 3D surface analysis using spherical harmonics (SPHARM). Whereas bifacial asymmetry in point shape does not vary significantly across this stylistic sequence, our measure of asymmetric flake scar patterning shows temporal variation that may signify the beginning of regionalization among early New World colonists.

Environment-induced changes in selective constraints on social learning during the peopling of the Americas

The weaponry technology associated with Clovis and related Early Paleoindians represents the earliest well-defined evidence of humans in Pleistocene North America. We assess the technological diversity of these fluted stone points found at archaeological sites in the western and eastern halves of North America by employing statistical tools used in the quantification of ecological biodiversity. Our results demonstrate that the earliest hunters in the environmentally heterogeneous East used a more diverse set of points than those in the environmentally homogenous West. This and other evidence shows that environmental heterogeneity in the East promoted the relaxation of selective constraints on social learning and increased experimentation with point designs.

Different kinds of genetic markers permit inference of Paleolithic and Neolithic expansions in humans

Recent population genetic studies have provided valuable insights on the demographic history of our species. However, some issues such as the dating of the first demographic expansions in human populations remain puzzling. Indeed, although a few genetic studies argued that the first human expansions were concomitant with the Neolithic transition, many others found signals of expansion events starting during the Palaeolithic. Here we performed a simulation study to show that these contradictory findings may result from the differences in the genetic markers used, especially if two successive expansion events occurred. For a large majority of replicates for each scenario tested, microsatellite data allow only detecting the recent expansion event in that case, whereas sequence data allow only detecting the ancient expansion. Combined with previous real data analyses, our results bring support to the ideas that (i) a first human expansions started during the Palaeolithic period, (ii) a second expansion event occurred later, concomitantly with the Neolithic transition.

Resilience and the population history of the Kuril Islands, Northwest Pacific: A study in complex human ecodynamics

Living in remote places can strain the adaptive capacities of human settlers. It can also protect communities from external social, political and economic forces. In this paper, we present an archaeological population history of the Kuril Islands. This string of small volcanic islands on the margins of the Northwest Pacific was occupied by maritime hunting, fishing and gathering communities from the mid-Holocene to recent centuries. We bring together (1) 380 new and previously published archaeological radiocarbon dates, (2) a new paleodemographic model based on a radiocarbon-timestamped temporal frequency distribution of archaeological deposits, (3) recently published paleoclimate trends, and (4) recently published archaeological proxy evidence for changes in the extent of social networks. We demonstrate that, over the last two millennia, inhabitants of the Kuril Islands underwent dramatic demographic fluctuations. Explanations of these fluctuations are considered in the context of environmental hazards, social networks and the emergence of an East Asian "World System", elucidating the tension between local and external adaptive strategies to social and ecological uncertainty. Results suggest that population resilience to local climate and environmental variability was achieved by virtue of social networks that maintained non-local support in times of crisis. Conversely, the expansion of the East Asian political economy into neighboring regions of the southern margin of the Kuril Islands perhaps in conjunction with exposure to epidemic diseases appears to have undermined the adaptive strategies, resulting in an increase in the vulnerability of Kuril populations to environmental fluctuations.

The Arrival of Homo sapiens into the Southern Cone at 14,000 Years Ago

The Arroyo Seco 2 site contains a rich archaeological record, exceptional for South America, to explain the expansion of Homo sapiens into the Americas and their interaction with extinct Pleistocene mammals. The following paper provides a detailed overview of material remains found in the earliest cultural episodes at this multi-component site, dated between ca. 12,170 ¹⁴C yrs B.P. (ca. 14,064 cal yrs B.P.) and 11,180 ¹⁴C yrs B.P. (ca. 13,068 cal yrs B.P.). Evidence of early occupations includes the presence of lithic tools, a concentration of Pleistocene species remains, human-induced fractured animal bones, and a selection of skeletal parts of extinct fauna. The occurrence of hunter-gatherers in the Southern Cone at ca. 14,000 cal yrs B.P. is added to the growing list of American sites that indicate a human occupation earlier than the Clovis dispersal episode, but posterior to the onset of the deglaciation of the Last Glacial Maximum (LGM) in the North America.

Test of Martin's overkill hypothesis using radiocarbon dates on extinct megafauna

Following Martin [Martin PS (1973) Science 179:969-974], we propose the hypothesis that the timing of human arrival to the New World can be assessed by examining the ecological impacts of a small population of people on extinct Pleistocene megafauna. To that end, we compiled lists of direct radiocarbon dates on paleontological specimens of extinct genera from North and South America with the expectation that the initial decline of extinct megafauna should correspond in time with the initial evidence for human colonization and that those declines should occur first in eastern Beringia, next in the contiguous United States, and last in South America. Analyses of spacings and frequency distributions of radiocarbon dates for each region support the idea that the extinction event first commenced in Beringia, roughly 13,300-15,000 BP. For the United States and South America, extinctions commenced considerably later but were closely spaced in time. For the contiguous United States, extinction began at ca. 12,900-13,200 BP, and at ca. 12,600-13,900 BP in South America. For areas south of Beringia, these estimates correspond well with the first significant evidence for human presence and are consistent with the predictions of the overkill hypothesis.

Bayesian chronological analyses consistent with synchronous age of 12,835-12,735 Cal B.P. for Younger Dryas boundary on four continents

The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835-12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼ 100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer.

On Vastness and Variability: Cultural Transmission, Historicity, and the Paleoindian Record in Eastern South America

Eastern South America, or what is today Brazilian territory, poses interesting questions about the early human occupation of the Americas. Three totally distinct and contemporaneous lithic technologies, dated between 11,000 and 10,000 14C BP, are present in different portions of the country: the Umbu tradition in the south, with its formal bifacial industry, with well-retouched scrapers and bifacial points; the Itaparica tradition in the central-west / northwest, totally unifacial, whose only formal artifacts are limaces; and the "Lagoa Santa" industry, completely lacking any formal artifacts, composed mainly of small quartz flakes. Our data suggests that these differences are not related to subsistence or raw-material constraints, but rather to different cultural norms and transmission of strongly divergent chaînes opératoires. Such diversity in material culture, when viewed from a cultural transmission (CT) theory standpoint, seems at odds with a simple Clovis model as the origin of these three cultural traditions given the time elapsed since the first Clovis ages and the expected population structure of the early South American settlers.

Late Pleistocene horse and camel hunting at the southern margin of the ice-free corridor: reassessing the age of Wally's Beach, Canada

The only certain evidence for prehistoric human hunting of horse and camel in North America occurs at the Wally's Beach site, Canada. Here, the butchered remains of seven horses and one camel are associated with 29 nondiagnostic lithic artifacts. Twenty-seven new radiocarbon ages on the bones of these animals revise the age of these kill and butchering localities to 13,300 calibrated y B.P. The tight chronological clustering of the eight kill localities at Wally's Beach indicates these animals were killed over a short period. Human hunting of horse and camel in Canada, coupled with mammoth, mastodon, sloth, and gomphothere hunting documented at other sites from 14,800-12,700 calibrated y B.P., show that 6 of the 36 genera of megafauna that went extinct by approximately 12,700 calibrated y B.P. were hunted by humans. This study shows the importance of accurate geochronology, without which significant discoveries will go unrecognized and the empirical data used to build models explaining the peopling of the Americas and Pleistocene extinctions will be in error.

Dating human occupation at Toca do Serrote das Moendas, São Raimundo Nonato, Piauí-Brasil by electron spin resonance and optically stimulated luminescence

Excavation of Toca do Serrote das Moendas, in Piauí state, Brazil revealed a great quantity of fossil wild fauna associated with human remains. In particular, fossils of a cervid (Blastocerus dichotomus) were found, an animal frequently pictured in ancient rock wall paintings. In a well-defined stratum, two loose teeth of this species were found in close proximity to human bones. The teeth were independently dated by electron spin resonance (ESR) in two laboratories. The ages obtained for the teeth were 29 ± 3 ka (thousands of years) and 24 ± 1 ka. The concretion layer capping this stratum was dated by optically stimulated luminescence (OSL) of the quartz grains to 21 ± 3 ka. As these values were derived independently in three different laboratories, using different methods and equipment, these results are compelling evidence of early habitation in this area.

The genetic prehistory of the New World Arctic

The New World Arctic, the last region of the Americas to be populated by humans, has a relatively well-researched archaeology, but an understanding of its genetic history is lacking. We present genome-wide sequence data from ancient and present-day humans from Greenland, Arctic Canada, Alaska, Aleutian Islands, and Siberia. We show that Paleo-Eskimos (~3000 BCE to 1300 CE) represent a migration pulse into the Americas independent of both Native American and Inuit expansions. Furthermore, the genetic continuity characterizing the Paleo-Eskimo period was interrupted by the arrival of a new population, representing the ancestors of present-day Inuit, with evidence of past gene flow between these lineages. Despite periodic abandonment of major Arctic regions, a single Paleo-Eskimo metapopulation likely survived in near-isolation for more than 4000 years, only to vanish around 700 years ago.

Human (Clovis)-gomphothere (Cuvieronius sp.) association ∼ 13,390 calibrated yBP in Sonora, Mexico

The earliest known foragers to populate most of North America south of the glaciers [∼ 11,500 to ≥ ∼ 10,800 (14)C yBP; ∼ 13,300 to ∼ 12,800 calibrated (Cal) years] made distinctive "Clovis" artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼ 11,550 yBP (∼ 13,390 Cal years) at "El Fin del Mundo," an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction.

A review and synthesis of late Pleistocene extinction modeling: progress delayed by mismatches between ecological realism, interpretation, and methodological transparency

Late Pleistocene extinctions occurred globally over a period of about 50,000 years, primarily affecting mammals of > or = 44 kg body mass (i.e., megafauna) first in Australia, continuing in Eurasia and, finally, in the Americas. Polarized debate about the cause(s) of the extinctions centers on the role of climate change and anthropogenic factors (especially hunting). Since the late 1960s, investigators have developed mathematical models to simulate the ecological interactions that might have contributed to the extinctions. Here, we provide an overview of the various methodologies used and conclusions reached in the modeling literature, addressing both the strengths and weaknesses of modeling as an explanatory tool. Although late Pleistocene extinction models now provide a solid foundation for viable future work, we conclude, first, that single models offer less compelling support for their respective explanatory hypotheses than many realize; second, that disparities in methodology (both in terms of model parameterization and design) prevent meaningful comparison between models and, more generally, progress from model to model in increasing our understanding of these extinctions; and third, that recent models have been presented and possibly developed without sufficient regard for the transparency of design that facilitates scientific progress.

Genetic diversity of a late prehispanic group of the Quebrada de Humahuaca, northwestern Argentina

This palaeogenetic study focused on the analysis of a late prehispanic Argentinean group from the Humahuaca valley, with the main aim of reconstructing its (micro)evolutionary history. The Humahuaca valley, a natural passageway from the eastern plains to the highlands, was the living environment of Andean societies whose cultural but especially biological diversity is still poorly understood. We analyzed the DNA extracted from 39 individuals who populated this upper valley during the Regional Development period (RDP) (between the 11th and 15th centuries CE), to determine their maternal and paternal genetic ancestry. Some mitochondrial and Y-chromosomal haplotypes specific to the Andean region are consistent with an origin in the highlands of Central Andes. On the other hand, a significant genetic affinity with contemporary admixed communities of the Chaco area was detected. Expectedly, recent demographic events, such as the expansion of the Inca Empire or the European colonization, have changed the original mitochondrial gene pool of the ancient Humahuaca Valley community. Finally, we identified a particular geographical organization of the prehispanic populations of Northwestern Argentina. Our results suggest that the communities of the region were divided between two different spheres of interaction, which is consistent with assumptions made by means of craniometric traits.

The genome of a Late Pleistocene human from a Clovis burial site in western Montana

Clovis, with its distinctive biface, blade and osseous technologies, is the oldest widespread archaeological complex defined in North America, dating from 11,100 to 10,700 (14)C years before present (bp) (13,000 to 12,600 calendar years bp). Nearly 50 years of archaeological research point to the Clovis complex as having developed south of the North American ice sheets from an ancestral technology. However, both the origins and the genetic legacy of the people who manufactured Clovis tools remain under debate. It is generally believed that these people ultimately derived from Asia and were directly related to contemporary Native Americans. An alternative, Solutrean, hypothesis posits that the Clovis predecessors emigrated from southwestern Europe during the Last Glacial Maximum. Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site in western Montana. The human bones date to 10,705 ± 35 (14)C years bp (approximately 12,707-12,556 calendar years bp) and were directly associated with Clovis tools. We sequenced the genome to an average depth of 14.4× and show that the gene flow from the Siberian Upper Palaeolithic Mal'ta population into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years bp. We also show that the Anzick-1 individual is more closely related to all indigenous American populations than to any other group. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly ancestral to many contemporary Native Americans. Finally, we find evidence of a deep divergence in Native American populations that predates the Anzick-1 individual.

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world's premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.

Distinguishing between selective sweeps from standing variation and from a de novo mutation

An outstanding question in human genetics has been the degree to which adaptation occurs from standing genetic variation or from de novo mutations. Here, we combine several common statistics used to detect selection in an Approximate Bayesian Computation (ABC) framework, with the goal of discriminating between models of selection and providing estimates of the age of selected alleles and the selection coefficients acting on them. We use simulations to assess the power and accuracy of our method and apply it to seven of the strongest sweeps currently known in humans. We identify two genes, ASPM and PSCA, that are most likely affected by selection on standing variation; and we find three genes, ADH1B, LCT, and EDAR, in which the adaptive alleles seem to have swept from a new mutation. We also confirm evidence of selection for one further gene, TRPV6. In one gene, G6PD, neither neutral models nor models of selective sweeps fit the data, presumably because this locus has been subject to balancing selection.

Clovis age Western Stemmed projectile points and human coprolites at the Paisley Caves

The Paisley Caves in Oregon record the oldest directly dated human remains (DNA) in the Western Hemisphere. More than 100 high-precision radiocarbon dates show that deposits containing artifacts and coprolites ranging in age from 12,450 to 2295 (14)C years ago are well stratified. Western Stemmed projectile points were recovered in deposits dated to 11,070 to 11,340 (14)C years ago, a time contemporaneous with or preceding the Clovis technology. There is no evidence of diagnostic Clovis technology at the site. These two distinct technologies were parallel developments, not the product of a unilinear technological evolution. "Blind testing" analysis of coprolites by an independent laboratory confirms the presence of human DNA in specimens of pre-Clovis age. The colonization of the Americas involved multiple technologically divergent, and possibly genetically divergent, founding groups.