title: American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change.
abstract: Existing radiocarbon ((14)C) dates on American mastodon (Mammut americanum) fossils from eastern Beringia (Alaska and Yukon) have been interpreted as evidence they inhabited the Arctic and Subarctic during Pleistocene full-glacial times (∼ 18,000 (14)C years B.P.). However, this chronology is inconsistent with inferred habitat preferences of mastodons and correlative paleoecological evidence. To establish a last appearance date (LAD) for M. americanum regionally, we obtained 53 new (14)C dates on 36 fossils, including specimens with previously published dates. Using collagen ultrafiltration and single amino acid (hydroxyproline) methods, these specimens consistently date to beyond or near the ∼ 50,000 y B.P. limit of (14)C dating. Some erroneously "young" (14)C dates are due to contamination by exogenous carbon from natural sources and conservation treatments used in museums. We suggest mastodons inhabited the high latitudes only during warm intervals, particularly the Last Interglacial [Marine Isotope Stage (MIS) 5] when boreal forests existed regionally. Our (14)C dataset suggests that mastodons were extirpated from eastern Beringia during the MIS 4 glacial interval (∼ 75,000 y ago), following the ecological shift from boreal forest to steppe tundra. Mastodons thereafter became restricted to areas south of the continental ice sheets, where they suffered complete extinction ∼ 10,000 (14)C years B.P. Mastodons were already absent from eastern Beringia several tens of millennia before the first humans crossed the Bering Isthmus or the onset of climate changes during the terminal Pleistocene. Local extirpations of mastodons and other megafaunal populations in eastern Beringia were asynchrononous and independent of their final extinction south of the continental ice sheets.
authors.affiliation: Yukon Palaeontology Program, Department of Tourism & Culture, Government of Yukon, Whitehorse, YT Y1A 2C6, Canada; grant.zazula@gov.yk.ca.
authors.forename: Grant D
authors.initials: GD
authors.lastname: Zazula
authors.affiliation: Department of Mammalogy, Division of Vertebrate Zoology, and Gilder Graduate School, American Museum of Natural History, New York, NY 10024;
authors.forename: Ross D E
authors.initials: RD
authors.lastname: MacPhee
authors.affiliation: Department of Anthropology, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada;
authors.forename: Jessica Z
authors.initials: JZ
authors.lastname: Metcalfe
authors.affiliation: Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada;
authors.forename: Alberto V
authors.initials: AV
authors.lastname: Reyes
authors.affiliation: Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology & History of Art, University of Oxford, Oxford OX1 3QY, United Kingdom;
authors.forename: Fiona
authors.initials: F
authors.lastname: Brock
authors.affiliation: Department of Earth Sciences, University of Alaska Museum, Fairbanks, AK 99775; Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK 99775;
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Druckenmiller
authors.affiliation: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775;
authors.forename: Pamela
authors.initials: P
authors.lastname: Groves
authors.affiliation: Research Division (Paleobiology), Canadian Museum of Nature, Ottawa, ON K1P 6P4, Canada;
authors.forename: C Richard
authors.initials: CR
authors.lastname: Harington
authors.affiliation: Arizona AMS Facility, Department of Physics, and School of Anthropology, University of Arizona, Tucson, AZ 85721-0081;
authors.forename: Gregory W L
authors.initials: GW
authors.lastname: Hodgins
authors.affiliation: School of Natural Resources and Agricultural Science, University of Alaska Fairbanks, Fairbanks, AK 99775;
authors.forename: Michael L
authors.initials: ML
authors.lastname: Kunz
authors.affiliation: Department of Earth Sciences, The University of Western Ontario, London, ON N6A 5B7, Canada;
authors.forename: Fred J
authors.initials: FJ
authors.lastname: Longstaffe
authors.affiliation: Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK 99775;
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Mann
authors.affiliation: Museum Management Program, National Park Service, Fort Collins, CO 80525; and.
authors.forename: H Gregory
authors.initials: HG
authors.lastname: McDonald
authors.affiliation: Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology & History of Art, University of Oxford, Oxford OX1 3QY, United Kingdom;
authors.forename: Shweta
authors.initials: S
authors.lastname: Nalawade-Chavan
authors.affiliation: Keck-CCAMS Group, Earth System Science Department, University of California, Irvine, CA 92697-3100.
authors.forename: John R
authors.initials: JR
authors.lastname: Southon
mesh_terms: D000413:Alaska; D000818:Animals; D001110:Arctic Regions; D057231:Climate Change; D065928:Forests; D005580:Fossils; D006801:Humans; D056666:Mastodons / Q000502:physiology*
keywords: Beringia; Pleistocene; extinctions; megafauna; radiocarbon