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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In 2002, we assessed all sites known to us that had been suggested to provide evidence for the association of Clovis-era archaeological material with the remains of extinct Pleistocene mammals in North America. We concluded that, of the 76 sites we assessed, 14 provided compelling evidence for human involvement in the death and/or dismemberment of such mammals. Of these sites, 12 involved mammoth ( Mammuthus ), the remaining two mastodon ( Mammut ). Here, we update that assessment. We examine Clovis-era, and earlier, sites reported since 2002, as well as sites examined previously but for which additional information has become available. Our assessment leads us to exclude Hebior (Wisconsin) from the list of accepted sites, and to add El Fin del Mundo (Sonora) and Wally's Beach (Alberta). There are now 15 sites on our list, providing what we find to be compelling evidence for human involvement in the death and/or dismemberment of five genera of now-extinct late Pleistocene mammals: Equus , Camelops , Cuvieronius , Mammut , and Mammuthus . As in 2002, however, we note this is a small fraction of the 37 genera that disappeared at the end of the Pleistocene, and for this and other reasons we remain highly skeptical that human overkill was responsible for their extinction. [ABSTRACT FROM AUTHOR]

Abstract: The Great Plains of the United States was the setting for some of the earliest research in North America into patterns and changes in the character of late Pleistocene environments and their effects on contemporary human populations. Many localities in the region have well-stratified records of terminal Pleistocene and early Holocene human (Paleoindian) activity and past environments. These have proven important in debates over the character of the Younger Dryas Chronozone (YDC; 11,000–10,000 14C BP; 12,900–11,700 cal BP) in the continental interior. This paper reviews the lithostratigraphic record of the YDC on the Central and Southern Great Plains and summarizes paleobiological records (largely isotopic). The goal is to determine if there is any uniformity in the timing, character, direction and/or magnitude of changes in depositional environments or broader geomorphic systems before, during or after the YDC in order to address the question of the character of environments through this time. The stratigraphic records of the late Pleistocene to early Holocene transition, and in particular, the stratigraphic records of the YDC vary through time and space. The data clearly show that a host of geomorphic processes produced the terminal Pleistocene and early Holocene stratigraphic records of the Great Plains. Moreover, the YDC is not necessarily manifest as a distinct lithostratigraphic or biostratigraphic entity in these different types of deposits and soils. The various geomorphic systems of the Great Plains did not behave synchronously in response to any common climate driver. These stratigraphic records reflect local environmental conditions and probably a complex response to the reorganization of mid-latitude climates in the terminal Pleistocene and early Holocene. [Copyright &y& Elsevier]

A hypothesized extraterrestrial impact in North America at -~12,900 calendar years BP (12.9 ka) has been proposed as the cause of Younger Dryas climate changes, terminal Pleistocene mammalian extinctions, and a supposed "termination" of the Clovis archaeological culture. In regard to the latter, however, an examination of archaeological, geochronological, and stratigraphic evidence fails to provide evidence of a demographic collapse of post-Clovis human populations, especially where the Clovis and post-Clovis site records are reasonably well constrained chronologically. Although few Clovis sites contain evidence of an immediate post-Clovis occupation, interpreting that absence as population collapse is problematic because the great majority of Paleoindian sites also lack immediately succeeding occupations. Where multiple occupations do occur, stratigraphic hiatuses between them are readily explained by geomorphic processes. Furthermore, calibrated radiocarbon ages demonstrate continuous occupation across the time of the purported "Younger Dryas event." And, finally, the relatively few sites purported to provide direct evidence of the 12.9-ka impact are not well constrained to that time. Whether or not the proposed extraterrestrial impact occurred is matter for empirical testing in the geological record. Insofar as concerns the archaeological record, an extra- terrestrial impact is an unnecessary solution for an archaeological problem that does not exist. [ABSTRACT FROM AUTHOR]

The Hot Tubb site, located in the Monahans Dunes just off the southern High Plains of west Texas, has yielded Folsom and Midland projectile points, as well as badly fragmented and occasionally burned remains of Bison antiquus. Because these materials occur primarily on the surface of a deflation basin. within an active sand dune, which also contains artifacts of later age, the Paleoindian component cannot be easily isolated, nor have attempts to determine its radiocarbon age been successful. Nonetheless, the distribution and density of the bone and diagnostic Folsom material indicate there is spatial and possibly stratigraphic integrity to this component, which makes it possible to discern where and what Paleoindian activity may have occurred on site. We infer this was a small Folsom-age bison kill and processing locality of an estimated six animals. The lithic assemblage is marked by intensive reworking and even refluting of projectile points, suggesting that the supply of stone, originally acquired at sources at least 150 km distant, was low by the time of this occupation. That dearth of stone, the presence of Midland points, as well as a possible Midland point preform, may also shed some light on the longstanding 'Folsom-Midland Problem.' [ABSTRACT FROM AUTHOR]

North American archaeologists have spent much effort debating whether Early Paleoindian foragers were specialized hunters of megafauna or whether they pursued more generalized subsistence strategies. In doing so, many have treated the foraging practices of early North Americans as if they must have been uniform across the continent, even though others have pointed out that adaptations appear to have varied among groups inhabiting different kinds of environments. Resolving these issues fully requires referring to archaeofaunal data and evaluating those data critically. In this paper, we conduct such an evaluation of the existing Early Paleoindian faunal record, which we then use to test the hypothesis that early Americans across the continent specialized in the hunting of megafauna. After detailed attention is given to taphonomic issues, to the limited geographical distribution of sites with secure associations between humans and prey taxa, and to differences among sites in the roles that they likely played in settlement and subsistence systems, it becomes clear that the faunal record provides little support for the idea that all, or even any, Early Paleoindian foragers were megafaunal specialists. It does appear, however, that there was considerable variability in Early Paleoindian prey choice across the continent, which was likely related to variability in the environments that different groups inhabited. [Copyright &y& Elsevier]

The "associational critique" holds that there are too few archaeological kill/scavenging sites to support the hypothesis that human hunting caused the late Pleistocene extinction of 38 genera of primarily large mammals. Wolfe and Broughton (2020) assessed this critique on both theoretical and empirical grounds and found it wanting, with a focus on the arguments presented in Grayson and Meltzer (2015). We welcome their evaluation, including their effort to improve on our prior analyses. However, we are unconvinced by their assertion that hunters will always pursue large ungulates on encounter. We also reject their conclusion there is no systematic difference in the abundance of extant and extinct taxa in terminal Pleistocene archaeological contexts since they made two errors that undermine their analysis. First, they confounded calibrated and uncalibrated radiocarbon years. Second, they failed to note the parameters of the Cannon and Meltzer (2004) study on which their tally of archaeological kill/scavenging sites of extant taxa is based. With these mistakes corrected, the results confirm what we showed previously: extant large mammals occur in kill/scavenging sites far more often than extinct forms. This result also supports our previous suggestion that the now-extinct fauna had either already disappeared or was much reduced in abundance by the time people arrived on the landscape. • Extant large mammals are more common than extinct ones in North American late Pleistocene kill/scavenging sites. • Of the extinct taxa found in kill/scavenging sites, only mammoth occur more often than expected based on fossil abundances. • The vast majority of the 38 extinct large mammal genera were gone or nearly so, by the time people arrived in North America. [ABSTRACT FROM AUTHOR]

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., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Waters and Stafford (Reports, 23 February 2007, p. 1122) provided useful information about the age of some Clovis sites but have not definitively established the temporal span of this cultural complex in the Americas. Only a continuing program of radiometric dating and careful stratigraphic correlations can address the lingering ambiguity about the emergence and spread of Clovis culture.