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More than 12,000 years ago, in one of the greatest triumphs of prehistory, humans colonized North America, a continent that was then truly a new world. Just when and how they did so has been one of the most perplexing and controversial questions in archaeology. This dazzling, cutting-edge synthesis, written for a wide audience by an archaeologist who has long been at the center of these debates, tells the scientific story of the first Americans: where they came from, when they arrived, and how they met the challenges of moving across the vast, unknown landscapes of Ice Age North America. David J. Meltzer pulls together the latest ideas from archaeology, geology, linguistics, skeletal biology, genetics, and other fields to trace the breakthroughs that have revolutionized our understanding in recent years. Among many other topics, he explores disputes over the hemisphere's oldest and most controversial sites and considers how the first Americans coped with changing global climates. He also confronts some radical claims: that the Americas were colonized from Europe or that a crashing comet obliterated the Pleistocene megafauna. Full of entertaining descriptions of on-site encounters, personalities, and controversies, this is a compelling behind-the-scenes account of how science is illuminating our past.

Clovis groups in Late Pleistocene North America occasionally hunted several now extinct large mammals. But whether their hunting drove 37 genera of animals to extinction has been disputed, largely for want of kill sites. Overkill proponents argue that there is more archaeological evidence than we ought to expect, that humans had the wherewithal to decimate what may have been millions of animals, and that the appearance of humans and the disappearance of the fauna is too striking to be a mere coincidence. Yet, there is less to these claims than meets the eye. Moreover, extinctions took place amid sweeping climatic and environmental changes as the Pleistocene came to an end. It has long been difficult to link those changes to mammalian extinctions, but the advent of ancient DNA, coupled with high-resolution paleoecological, radiocarbon, and archeological records, should help disentangle the relative role of changing climates and people in mammalian extinctions.

During the Last Glacial Maximum, continental ice sheets isolated Beringia (northeast Siberia and northwest North America) from unglaciated North America. By around 15 to 14 thousand calibrated radiocarbon years before present (cal. kyr bp ), glacial retreat opened an approximately 1,500-km-long corridor between the ice sheets. It remains unclear when plants and animals colonized this corridor and it became biologically viable for human migration. We obtained radiocarbon dates, pollen, macrofossils and metagenomic DNA from lake sediment cores in a bottleneck portion of the corridor. We find evidence of steppe vegetation, bison and mammoth by approximately 12.6 cal. kyr bp , followed by open forest, with evidence of moose and elk at about 11.5 cal. kyr bp , and boreal forest approximately 10 cal. kyr bp . Our findings reveal that the first Americans, whether Clovis or earlier groups in unglaciated North America before 12.6 cal. kyr bp , are unlikely to have travelled by this route into the Americas. However, later groups may have used this north–south passageway. During much of the last ice age, continental ice sheets prevented humans from migrating into North America from Siberia; an environmental reconstruction of the corridor that opened up between the Cordilleran and Laurentide ice sheets reveals that it would have been inhospitable to the initial colonizing humans, who therefore probably entered North America by a different route. A coastal migration route to the Americas During much of the last ice age, continental ice sheets prevented humans from migrating into North America from Beringia, the area between Siberia and what is now the Bering Strait. At some point, a route opened up between the Cordilleran and Laurentide ice sheets, but it is thought that this 1,500-kilometre-long ice-free corridor may have been too cold to act as a human migration route. Eske Willerslev and colleagues present a series of environmental reconstructions based on coring of lake sediments in what was once the ice-free corridor. Their data indicate that the corridor would have still been inhospitable even after humans are known to have arrived in the Americas south of the ice. This implies that humans migrated by a coastal route, now submerged by the risen sea.

Kennewick Man, a 8,500-year-old male human skeleton discovered in Washington state, USA, has been the subject of scientific and legal controversy; here a DNA analysis shows that Kennewick Man is closer to modern Native Americans than to any other extant population worldwide. Who was Kennewick Man? Kennewick Man is a 9,000-year-old male human skeleton discovered in Washington state, USA in 1996. The population affinities of the remains have been the subject of scientific and legal controversy. Initial studies based on morphology suggested that the skeleton was not of Native American affinity. Eske Willerslev and colleagues now present DNA analysis showing that Kennewick Man is in fact closer to modern Native Americans than to any other extant population worldwide. Kennewick Man, referred to as the Ancient One by Native Americans, is a male human skeleton discovered in Washington state (USA) in 1996 and initially radiocarbon dated to 8,340–9,200 calibrated years before present ( bp ) 1 . His population affinities have been the subject of scientific debate and legal controversy. Based on an initial study of cranial morphology it was asserted that Kennewick Man was neither Native American nor closely related to the claimant Plateau tribes of the Pacific Northwest, who claimed ancestral relationship and requested repatriation under the Native American Graves Protection and Repatriation Act (NAGPRA). The morphological analysis was important to judicial decisions that Kennewick Man was not Native American and that therefore NAGPRA did not apply. Instead of repatriation, additional studies of the remains were permitted 2 . Subsequent craniometric analysis affirmed Kennewick Man to be more closely related to circumpacific groups such as the Ainu and Polynesians than he is to modern Native Americans 2 . In order to resolve Kennewick Man’s ancestry and affiliations, we have sequenced his genome to ∼1× coverage and compared it to worldwide genomic data including for the Ainu and Polynesians. We find that Kennewick Man is closer to modern Native Americans than to any other population worldwide. Among the Native American groups for whom genome-wide data are available for comparison, several seem to be descended from a population closely related to that of Kennewick Man, including the Confederated Tribes of the Colville Reservation (Colville), one of the five tribes claiming Kennewick Man. We revisit the cranial analyses and find that, as opposed to genome-wide comparisons, it is not possible on that basis to affiliate Kennewick Man to specific contemporary groups. We therefore conclude based on genetic comparisons that Kennewick Man shows continuity with Native North Americans over at least the last eight millennia.

The end of the Pleistocene in North America saw the extinction of 38 genera of mostly large mammals. As their disappearance seemingly coincided with the arrival of people in the Americas, their extinction is often attributed to human overkill, notwithstanding a dearth of archaeological evidence of human predation. Moreover, this period saw the extinction of other species, along with significant changes in many surviving taxa, suggesting a broader cause, notably, the ecological upheaval that occurred as Earth shifted from a glacial to an interglacial climate. But, overkill advocates ask, if extinctions were due to climate changes, why did these large mammals survive previous glacial–interglacial transitions, only to vanish at the one when human hunters were present? This question rests on two assumptions: that previous glacial–interglacial transitions were similar to the end of the Pleistocene, and that the large mammal genera survived unchanged over multiple such cycles. Neither is demonstrably correct. Resolving the cause of large mammal extinctions requires greater knowledge of individual species’ histories and their adaptive tolerances, a fuller understanding of how past climatic and ecological changes impacted those animals and their biotic communities, and what changes occurred at the Pleistocene−Holocene boundary that might have led to those genera going extinct at that time. Then we will be able to ascertain whether the sole ecologically significant difference between previous glacial−interglacial transitions and the very last one was a human presence.

In less than a decade, analyses of ancient genomes have transformed our understanding of the Indigenous peopling and population history of the Americas. These studies have shown that this history, which began in the late Pleistocene epoch and continued episodically into the Holocene epoch, was far more complex than previously thought. It is now evident that the initial dispersal involved the movement from northeast Asia of distinct and previously unknown populations, including some for whom there are no currently known descendants. The first peoples, once south of the continental ice sheets, spread widely, expanded rapidly and branched into multiple populations. Their descendants—over the next fifteen millennia—experienced varying degrees of isolation, admixture, continuity and replacement, and their genomes help to illuminate the relationships among major subgroups of Native American populations. Notably, all ancient individuals in the Americas, save for later-arriving Arctic peoples, are more closely related to contemporary Indigenous American individuals than to any other population elsewhere, which challenges the claim—which is based on anatomical evidence—that there was an early, non-Native American population in the Americas. Here we review the patterns revealed by ancient genomics that help to shed light on the past peoples who created the archaeological landscape, and together lead to deeper insights into the population and cultural history of the Americas. A review of the ancient human genomic record sheds light on the peopling processes of the Americas.

In the late 1920s outside a sleepy remote New Mexico village, prehistory was made. Spear points, found embedded between the ribs of an extinct Ice Age bison at the site of Folsom, finally resolved decades of bitter scientific controversy over whether the first Americans had arrived in the New World in Ice Age times. Although Folsom is justly famous in the history of archaeology for resolving that dispute, for decades little was known of the site except that it was very old. This book for the first time tells the full story of Folsom. David J. Meltzer deftly combines the results of extensive new excavations and laboratory analyses from the late 1990s, with the results of a complete examination and analysis of all the original artifacts and bison remains recovered in the 1920s - now scattered in museums and small towns across the country. Using the latest in archaeological method and technique, and bringing in data from geology and paleoecology, this interdisciplinary study provides a comprehensive look at the adaptations and environments of the late Ice Age Paleoindian hunters who killed a large herd of bison at this spot, as well as a measure of Folsom's pivotal role in American archaeology.

According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age–depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas.