Ted Goebel

The Late Pleistocene Dispersal of Modern Humans in the Americas

When did humans colonize the Americas? From where did they come and what routes did they take? These questions have gripped scientists for decades, but until recently answers have proven difficult to find. Current genetic evidence implies dispersal from a single Siberian population toward the Bering Land Bridge no earlier than about 30,000 years ago (and possibly after 22,000 years ago), then migration from Beringia to the Americas sometime after 16,500 years ago. The archaeological records of Siberia and Beringia generally support these findings, as do archaeological sites in North and South America dating to as early as 15,000 years ago. If this is the time of colonization, geological data from western Canada suggest that humans dispersed along the recently deglaciated Pacific coastline.

Species-specific responses of Late Quaternary megafauna to climate and humans

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.

Genomic evidence for the Pleistocene and recent population history of Native Americans

Genetic history of Native Americans Several theories have been put forth as to the origin and timing of when Native American ancestors entered the Americas. To clarify this controversy, Raghavan et al. examined the genomic variation among ancient and modern individuals from Asia and the Americas. There is no evidence for multiple waves of entry or recurrent gene flow with Asians in northern populations. The earliest migrations occurred no earlier than 23,000 years ago from Siberian ancestors. Amerindians and Athabascans originated from a single population, splitting approximately 13,000 years ago. Science, this issue 10.1126/science.aab3884 Genetic variation within ancient and extant Native American populations informs on their migration into the Americas. INTRODUCTION The consensus view on the peopling of the Americas is that ancestors of modern Native Americans entered the Americas from Siberia via the Bering Land Bridge and that this occurred at least ~14.6 thousand years ago (ka). However, the number and timing of migrations into the Americas remain controversial, with conflicting interpretations based on anatomical and genetic evidence. RATIONALE In this study, we address four major unresolved issues regarding the Pleistocene and recent population history of Native Americans: (i) the timing of their divergence from their ancestral group, (ii) the number of migrations into the Americas, (iii) whether there was ~15,000 years of isolation of ancestral Native Americans in Beringia (Beringian Incubation Model), and (iv) whether there was post-Pleistocene survival of relict populations in the Americas related to Australo-Melanesians, as suggested by apparent differences in cranial morphologies between some early (“Paleoamerican”) remains and those of more recent Native Americans. We generated 31 high-coverage modern genomes from the Americas, Siberia, and Oceania; 23 ancient genomic sequences from the Americas dating between ~0.2 and 6 ka; and SNP chip genotype data from 79 present-day individuals belonging to 28 populations from the Americas and Siberia. The above data sets were analyzed together with published modern and ancient genomic data from worldwide populations, after masking some present-day Native Americans for recent European admixture. RESULTS Using three different methods, we determined the divergence time for all Native Americans (Athabascans and Amerindians) from their Siberian ancestors to be ~20 ka, and no earlier than ~23 ka. Furthermore, we dated the divergence between Athabascans (northern Native American branch, together with northern North American Amerindians) and southern North Americans and South and Central Americans (southern Native American branch) to be ~13 ka. Similar divergence times from East Asian populations and a divergence time between the two branches that is close in age to the earliest well-established archaeological sites in the Americas suggest that the split between the branches occurred within the Americas. We additionally found that several sequenced Holocene individuals from the Americas are related to present-day populations from the same geographical regions, implying genetic continuity of ancient and modern populations in some parts of the Americas over at least the past 8500 years. Moreover, our results suggest that there has been gene flow between some Native Americans from both North and South America and groups related to East Asians and Australo-Melanesians, the latter possibly through an East Asian route that might have included ancestors of modern Aleutian Islanders. Last, using both genomic and morphometric analyses, we found that historical Native American groups such as the Pericúes and Fuego-Patagonians were not “relicts” of Paleoamericans, and hence, our results do not support an early migration of populations directly related to Australo-Melanesians into the Americas. CONCLUSION Our results provide an upper bound of ~23 ka on the initial divergence of ancestral Native Americans from their East Asian ancestors, followed by a short isolation period of no more than ~8000 years, and subsequent entrance and spread across the Americas. The data presented are consistent with a single-migration model for all Native Americans, with later gene flow from sources related to East Asians and, indirectly, Australo-Melanesians. The single wave diversified ~13 ka, likely within the Americas, giving rise to the northern and southern branches of present-day Native Americans. Population history of present-day Native Americans. The ancestors of all Native Americans entered the Americas as a single migration wave from Siberia (purple) no earlier than ~23 ka, separate from the Inuit (green), and diversified into “northern” and “southern” Native American branches ~13 ka. There is evidence of post-divergence gene flow between some Native Americans and groups related to East Asians/Inuit and Australo-Melanesians (yellow). How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we found that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (ka) and after no more than an 8000-year isolation period in Beringia. After their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 ka, one that is now dispersed across North and South America and the other restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative “Paleoamerican” relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.

The Colonization of Beringia and the Peopling of the New World

The colonization of Beringia appears closely linked to the arrival of the oldest firmly documented archeological tradition in mid-latitude North America (Paleoindian). The discovery of a Paleoindian complex in central Alaska, combined with the recent redating of the Bering Land Bridge and key archeological sites, suggests that Beringia was settled during the final Pleistocene interstadial (12,000 to 11,000 years before present). Its population expanded rapidly into other parts of the New World. Beringia probably was colonized in response to changes in climate and vegetation that occurred during this interstadial. Access to the Americas was controlled by Beringian environments and not by changing sea levels or continental ice masses.

Genomic structure in Europeans dating back at least 36,200 years

The origin of contemporary Europeans remains contentious. We obtained a genome sequence from Kostenki 14 in European Russia dating from 38,700 to 36,200 years ago, one of the oldest fossils of anatomically modern humans from Europe. We find that Kostenki 14 shares a close ancestry with the 24,000-year-old Mal’ta boy from central Siberia, European Mesolithic hunter-gatherers, some contemporary western Siberians, and many Europeans, but not eastern Asians. Additionally, the Kostenki 14 genome shows evidence of shared ancestry with a population basal to all Eurasians that also relates to later European Neolithic farmers. We find that Kostenki 14 contains more Neandertal DNA that is contained in longer tracts than present Europeans. Our findings reveal the timing of divergence of western Eurasians and East Asians to be more than 36,200 years ago and that European genomic structure today dates back to the Upper Paleolithic and derives from a metapopulation that at times stretched from Europe to central Asia. An ancient human genome illuminates human demography in Eurasia and Europe. Secrets of human ancestor evolution revealed Studies of ancient humans help us understand the movement and evolution of modern populations of humans. Seguin-Orlando et al. present the genome of an ancient individual, K14, from northern Russia who lived over 36,000 years ago. K14 is more similar to west Eurasians and Europeans than to east Asians, indicating that these populations had already diverged. Science, this issue p. 1113

Ice Age Atlantis? Exploring the Solutrean-Clovis 'connection'

Abstract Bradley and Stanford (2004) have raised now, in several instances, the claim that European Upper Paleolithic Solutrean peoples colonized North America, and gave rise to the archaeological complex known as Clovis. They do so in the face of some obvious challenges – notably the several thousand miles of ocean and the 5000 radiocarbon years that separate the two. And yet they argue in their recent paper that the archaeological evidence in support of a historical connection is ‘overwhelming’. We are profoundly skeptical of this claim; we believe that the many differences between Solutrean and Clovis are far more significant than the few similarities, the latter being readily explained by the well-known phenomenon of technological convergence or parallelism. The origin and arrival time of the first Americans remain uncertain, but not so uncertain that we need to look elsewhere other than north-east Asia.

Accelerator radiocarbon dating of the initial Upper Palaeolithic in southeast Siberia

Across Eurasia and Africa new studies are encouraging archaeologists to rethink the age of of the Middle to Upper Palaeolithic transition. In the Lake Baikal region of southeast Siberia, new radiocarbon determinations on sites of difficult history suggest that the earliest Upper Palaeolithic emerged there as early as 39,000 years ago, 6000 years earlier than previously thought.

Faunal record identifies Bering isthmus conditions as constraint to end-Pleistocene migration to the New World

Human colonization of the New World is generally believed to have entailed migrations from Siberia across the Bering isthmus. However, the limited archaeological record of these migrations means that details of the timing, cause and rate remain cryptic. Here, we have used a combination of ancient DNA, 14C dating, hydrogen and oxygen isotopes, and collagen sequencing to explore the colonization history of one of the few other large mammals to have successfully migrated into the Americas at this time: the North American elk (Cervus elaphus canadensis), also known as wapiti. We identify a long-term occupation of northeast Siberia, far beyond the species’s current Old World distribution. Migration into North America occurred at the end of the last glaciation, while the northeast Siberian source population became extinct only within the last 500 years. This finding is congruent with a similar proposed delay in human colonization, inferred from modern human mitochondrial DNA, and suggestions that the Bering isthmus was not traversable during parts of the Late Pleistocene. Our data imply a fundamental constraint in crossing Beringia, placing limits on the age and mode of human settlement in the Americas, and further establish the utility of ancient DNA in palaeontological investigations of species histories.

Points in Time: Direct Radiocarbon Dates on Great Basin Projectile Points

Abstract Typological cross-dating is the primary means by which archaeological sites are placed into chronological frameworks. This approach relies on the assumption that artifacts at undated sites—usually projectile points—are coeval with similar artifacts found at Other, dated sites. While typological cross-dating is necessary in regions dominated by open-air lithic scatters, the approach can be problematic when undated and dated sites are separated by significant distances. Here, we present radiocarbon dates on projectile points with organic hafting material still attached or found within organic storage bags. Our results provide unequivocal ages for various morphological projectile point types at several Great Basin locales and should be useful to researchers seeking local age estimates for those point types, which often involves relying on chronological data from more distant sites. The results also highlight potential issues with uncritically applying typological cross-dating using typologies based on metric attributes, and in two cases, suggest the need to revise the age ranges for certain point styles in the western Great Basin.

Early Prehistoric Archaeology of the Middle Susitna Valley, Alaska

The early prehistory of the Susitna River region, near the place where three major rivers, the Susitna, Talkeetna, and the Chulitna, converge, provides important regional information about the movement of small-scale foraging societies in southcentral Alaska as well as specific data concerning lithic use. Since 2004, ongoing research at the Trapper Creek Overlook (TCO) and Susitna River Overlook (SRO) sites has revealed three primarily lithic artifact assemblages from stratigraphically sealed cultural occupations spanning the early to middle Holocene (ca. 10,000–5000 cal B.P.). Radiocarbon, tephrochronology, and optically stimulated luminescence (OSL) dating techniques provide context for interpreting these sites with a focus on geomorphic and stratigraphic contexts, geochronology, and lithic analyses. Results suggest an initial migration from the north and similarities between early and middle Holocene lithic industries in the period prior to the development of riverine salmon economies.