Serpentine Hot Springs, Alaska: results of excavations and implications for the age and significance of northern fluted points
Ted GoebelHeather L. SmithLyndsay M. DiPietroMichael R. WatersBryan HockettKelly E. GrafRóbert Iván GálSergei B. SlobodinRobert J. SpeakmanSteven G. DrieseDavid Rhode
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Keywords:
Beringia
Land bridge
Megafauna
Beringia
Megafauna
Rhinoceros
Chronology
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During the last glacial period, the Bering Land Bridge was inhabited by a diverse bestiary of large mammals, many now extinct (1), and covered by the steppe-tundra, a widespread, now largely vanished biome (2). Given the twinned losses of big animals and a major ecosystem during the last deglaciation, a central question is to understand whether and how these events were connected. Did bottom-up processes rule, in which changing climates led to changing habitats, which then triggered population declines and, ultimately, extinctions of Arctic megaherbivores? Did top-down processes govern, in which declining populations of megaherbivores, pressured by the regional arrival of humans by at least 32,000 y ago (3), led to altered nutrient cycling and reduced grazing strength, facilitating a widespread replacement of a grass–forb steppe-tundra (4) with a shrub tundra dominated by willow ( Salix ), birch ( Betula ), and alder ( Alnus ) (5)? Or, given that these are complex ecosystems governed by multiple interacting processes, were extinctions and ecosystem transformations all part of one larger positive feedback loop? In PNAS, Monteath et al. (6) shed light on these questions of top-down and bottom-up processes through a careful analysis of the temporal and spatial patterns of late Quaternary megafaunal extinctions and vegetation transformation in eastern Beringia, now known as Alaska. Better answers to these questions have clear implications for contemporary global change ecology and conservation biology. For, if climate was the ultimate driver of Beringian ecosystem transformations and extinctions, then this adds urgency to today’s efforts to conserve habitats and helping species adapt to climate change, for example, via the resist–accept–direct framework (7). Conversely, evidence that top-down trophic processes were decisive would add impetus to efforts to restore ecosystem functioning through rewilding efforts (8), by either reintroducing extirpated species to their former range … [↵][1]1Email: jwwilliams1{at}wisc.edu. [1]: #xref-corresp-1-1
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Beringia
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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.
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Abstract More than 375 14 C dates from 150 fossil sites in North America have been analyzed to evaluate the question of extinction of Late Pleistocene megafauna. When critically evaluated, no 14 C ages for any extinct Pleistocene genera are younger than 10,000 yr B.P.
Megafauna
Extinction (optical mineralogy)
Early Pleistocene
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