The known languages of the Americas comprise nearly half of the world\'s language families and a wide range of structural types, a level of diversity that required considerable time to develop. This paper proposes a model of settlement and expansion designed to integrate current linguistic analysis with other prehistoric research on the earliest episodes in the peopling of the Americas. Diagnostic structural features from phonology and morphology are compared across 60 North American languages chosen for coverage of geography and language families and adequacy of description. Frequency comparison and graphic cluster analysis are applied to assess the fit of linguistic types and families with late Pleistocene time windows when entry from Siberia to North America was possible. The linguistic evidence is consistent with two population strata defined by early coastal entries ~24,000 and ~15,000 years ago, then an inland entry stream beginning ~14,000 ff. and mixed coastal/inland ~12,000 ff. The dominant structural properties among the founder languages are still reflected in the modern linguistic populations. The modern linguistic geography is still shaped by the extent of glaciation during the entry windows. Structural profiles imply that two linguistically distinct and internally diverse ancient Siberian linguistic populations provided the founding American populations.
OBJECTIVE: Describe early North American linguistic population structure and chronology; align distribution of structural types with archeological and paleoclimatological evidence on the earliest settlements. Propose an improved model of early settlement and expansion and pose some priority research questions.
METHODS: Classification of languages based on a tripartite geolinguistic division based on geographical and linguistic evidence. Survey of phonological and morphological patterns of 60 languages representing the structural, geographical, and genealogical diversity of North America. Survey of 16 morphological and phonological features of known or likely high stability and family-identifying value across those languages. Frequency comparison and cluster analysis to elucidate the tripartite analysis and compare to the chronology and geolinguistics implied by paleoclimatological and archeological work.
RESULTS: There is enough evidence (linguistic, archeological, genetic, and geological) to indicate four glacial-age openings allowing entries to North America: coastal c. 24,000 and 15,000 years ago; inland c. 14,000 years ago and continuing; and coastal c. 12,000 years ago and continuing. Geographical distribution of modern languages reflects the geography and chronology of the openings and the two human and linguistic population strata they formed, and plausibly also the structural types of the founding languages.
CONCLUSIONS: Improved model of North American settlement (two chronological strata, four entries); comparison to other proposed models. Further questions and research issues for linguistic, genetic, and archeological research.

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.

Megafauna paintings have accompanied the earliest archaeological contexts across the continents, revealing a fundamental inter-relationship between early humans and megafauna during the global human expansion as unfamiliar landscapes were humanized and identities built into new territories. However, the identification of extinct megafauna from rock art is controversial. Here, we examine potential megafauna depictions in the rock art of Serranía de la Lindosa, Colombian Amazon, that includes a giant sloth, a gomphothere, a camelid, horses and three-toed ungulates with trunks. We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas. Our findings contribute to the emerging picture of considerable geographical and stylistic variation of geometric and figurative rock art from early human occupations across South America. Lastly, we discuss the implications of our findings for understanding the early human history of tropical South America. This article is part of the theme issue \'Tropical forests in the deep human past\'.

Uniparental genetic systems are unique sex indicators and complement the study of autosomal diversity by providing landmarks of human migrations that repeatedly shaped the structure of extant populations. Our knowledge of the variation of the male-specific region of the Y chromosome in Native Americans is still rather scarce and scattered, but by merging sequence information from modern and ancient individuals, we here provide a comprehensive and updated phylogeny of the distinctive Native American branches of haplogroups C and Q. Our analyses confirm C-MPB373, C-P39, Q-Z780, Q-M848, and Q-Y4276 as the main founding haplogroups and identify traces of unsuccessful (pre-Q-F1096) or extinct (C-L1373*, Q-YP4010*) Y-chromosome lineages, indicating that haplogroup diversity of the founder populations that first entered the Americas was greater than that observed in the Indigenous component of modern populations. In addition, through a diachronic and phylogeographic dissection of newly identified Q-M848 branches, we provide the first Y-chromosome insights into the early peopling of the South American hinterland (Q-BY104773 and Q-BY15730) and on overlying inland migrations (Q-BY139813).

The aim of this study was to create a comprehensive summary of available mtDNA and Y-chromosome data for Native Americans from North, Central, and South America, including both modern and ancient DNA. To illustrate the usefulness of this dataset we present a broad picture of the genetic variation for both markers across the Americas.
We searched PubMed, ResearchGate, Google Scholar for studies about mtDNA or Y-chromosome variation in Native American populations, including geographic, linguistic, ecological (ecoregion), archeological and chronological information. We used AMOVA to estimate the genetic structure associated with language and ecoregion grouping and Mantel tests to evaluate the correlation between genetic and geographic distances.
Genetic data were obtained from 321 primary sources, including 22,569 individuals from 298 contemporary populations, and 3628 individuals from 202 archeological populations. MtDNA lineages of probable non-Amerindian origin were rare, in contrast with Y-chromosome lineages. Mantel tests showed a statistically significant correlation for the whole continent considering mtDNA but not the Y-chromosome. Genetic structure between groups was always stronger for mtDNA than for the Y-chromosome.
This study summarizes decades of research conducted in Native American populations for both mtDNA and the Y-chromosome. Continental or sub-continental patterns of variation reveal that most of the genetic variation occurs within populations rather than among linguistic or ecoregional groups, and that isolation by distance is barely detectable in most population sets. The genetic structure among groups was always larger for mtDNA than for the Y-chromosome, suggesting between-sex differences in gene flow.

Advances in the isolation and sequencing of ancient DNA have begun to reveal the population histories of both people and dogs. Over the last 10,000 y, the genetic signatures of ancient dog remains have been linked with known human dispersals in regions such as the Arctic and the remote Pacific. It is suspected, however, that this relationship has a much deeper antiquity, and that the tandem movement of people and dogs may have begun soon after the domestication of the dog from a gray wolf ancestor in the late Pleistocene. Here, by comparing population genetic results of humans and dogs from Siberia, Beringia, and North America, we show that there is a close correlation in the movement and divergences of their respective lineages. This evidence places constraints on when and where dog domestication took place. Most significantly, it suggests that dogs were domesticated in Siberia by ∼23,000 y ago, possibly while both people and wolves were isolated during the harsh climate of the Last Glacial Maximum. Dogs then accompanied the first people into the Americas and traveled with them as humans rapidly dispersed into the continent beginning ∼15,000 y ago.

Recent genome studies of modern and ancient samples have proposed that Native Americans derive from a subset of the Eurasian gene pool carried to America by an ancestral Beringian population, from which two well-differentiated components originated and subsequently mixed in different proportion during their spread in the Americas. To assess the timing, places of origin and extent of admixture between these components, we performed an analysis of the Y-chromosome haplogroup Q, which is the only Pan-American haplogroup and accounts for virtually all Native American Y chromosomes in Mesoamerica and South America.
Our analyses of 1.5 Mb of 152 Y chromosomes, 34 re-sequenced in this work, support a \"coastal and inland routes scenario\" for the first entrance of modern humans in North America. We show a major phase of male population growth in the Americas after 15 thousand years ago (kya), followed by a period of constant population size from 8 to 3 kya, after which a secondary sign of growth was registered. The estimated dates of the first expansion in Mesoamerica and the Isthmo-Colombian Area, mainly revealed by haplogroup Q-Z780, suggest an entrance in South America prior to 15 kya. During the global constant population size phase, local South American hints of growth were registered by different Q-M848 sub-clades. These expansion events, which started during the Holocene with the improvement of climatic conditions, can be ascribed to multiple cultural changes rather than a steady population growth and a single cohesive culture diffusion as it occurred in Europe.
We established and dated a detailed haplogroup Q phylogeny that provides new insights into the geographic distribution of its Eurasian and American branches in modern and ancient samples.

Fluted projectile points have long been recognized as the archaeological signature of early humans dispersing throughout the Western Hemisphere; however, we still lack a clear understanding of their appearance in the interior \"Ice-Free Corridor\" of western Canada and eastern Beringia. To solve this problem, we conducted a geometric morphometric shape analysis and a phylogenetic analysis of technological traits on fluted points from the archaeological records of northern Alaska and Yukon, in combination with artifacts from further south in Canada, the Great Plains, and eastern United States to investigate the plausibility of historical relatedness and evolutionary patterns in the spread of fluted-point technology in the latest Pleistocene and earliest Holocene. Results link morphologies and technologies of Clovis, certain western Canadian, and northern fluted points, suggesting that fluting technology arrived in the Arctic from a proximate source in the interior Ice-Free Corridor and ultimately from the earliest populations in temperate North America, complementing new genomic models explaining the peopling of the Americas.

A long-standing debate in Pleistocene archaeology concerns the sources of variation in the technology of colonizing hunter-gatherers. One prominent example of this debate is Clovis technology (13,350-12,500 calendar years before present), which represents the earliest widespread and currently recognizable remains of hunter-gatherers in North America. Clovis projectile points appear to have been made the same way regardless of region, but several studies have documented differences in shape that appear to be regional. Two processes have been proposed for shape variation: (1) stochastic mechanisms such as copy error (drift) and (2) Clovis groups adapting their hunting equipment to the characteristics of prey and local habitat. We used statistical analysis of Clovis-point flake-scar pattern and geometric morphometrics to examine whether drift alone could cause significant differences in the technology of Stone Age colonizing hunter-gatherers. Importantly, our analysis was intraregional to rule out a priori environmental adaptation. Our analysis confirmed that the production technique was the same across the sample, but we found significant shape differences in Clovis point populations made from distinct stone outcrops. Given that current archaeological evidence suggests stone outcrops were \"hubs\" of regional Clovis activity, our dichotomous, intraregional results quantitatively confirm that Clovis foragers engaged in two tiers of social learning. The lower, ancestral tier relates to point production and can be tied to conformist transmission of tool-making processes across the Clovis population. The upper, derived tier relates to point shape, which can be tied to drift that resulted from increased forager interaction at different stone-outcrop hubs and decreased forager interaction among groups using different outcrops. Given that Clovis artifacts represent the earliest widespread and currently recognizable remains of hunter-gatherers in North America, our results suggest that we need to alter our theoretical understanding of how quickly drift can occur within a colonizing population and create differences among socially learned technological characters.