DNA antigo revela a última sobrevivência de mamute e cavalo no interior do Alasca

Ancient DNA reveals late survival of mammoth and horse in interior Alaska

James Haile a, Duane G. Froese b, Ross D. E. MacPhee c, Richard G. Roberts d, Lee J. Arnold d,1, Alberto V. Reyes b, Morten Rasmussen a, Rasmus Nielsen e, Barry W. Brook f, Simon Robinson b, Martina Demuro d, M. Thomas P. Gilbert a, Kasper Munch e, Jeremy J. Austin g, Alan Cooper g, Ian Barnes h, Per Möller i and Eske Willerslev a,2

- Author Affiliations

aCentre for GeoGenetics, University of Copenhagen, Copenhagen 2100, Denmark;

bDepartment of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada;

cDivision of Vertebrate Zoology, American Museum of Natural History, New York, NY 10024;

dCentre for Archaeological Science, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia;

eDepartment of Integrative Biology, University of California, Berkeley, CA 94720;

fThe Environment Institute, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia;

gAustralian Centre for Ancient DNA, University of Adelaide, Adelaide, SA 5005, Australia;

hSchool of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom; and

iGeoBiosphere Science Centre, Department of Geology/Quaternary Sciences, Lund University, S-223 62 Lund, Sweden

↵1Present address: Centro Nacional de Investigación sobre la Evolución Humana, CENIEH, 09002 Burgos, Spain.

Communicated by P. Buford Price, University of California, Berkeley, CA, October 31, 2009 (received for review June 30, 2009)

Abstract

Causes of late Quaternary extinctions of large mammals (“megafauna”) continue to be debated, especially for continental losses, because spatial and temporal patterns of extinction are poorly known. Accurate latest appearance dates (LADs) for such taxa are critical for interpreting the process of extinction. The extinction of woolly mammoth and horse in northwestern North America is currently placed at 15,000–13,000 calendar years before present (yr BP), based on LADs from dating surveys of macrofossils (bones and teeth). Advantages of using macrofossils to estimate when a species became extinct are offset, however, by the improbability of finding and dating the remains of the last-surviving members of populations that were restricted in numbers or confined to refugia. Here we report an alternative approach to detect ‘ghost ranges’ of dwindling populations, based on recovery of ancient DNA from perennially frozen and securely dated sediments (sedaDNA). In such contexts, sedaDNA can reveal the molecular presence of species that appear absent in the macrofossil record. We show that woolly mammoth and horse persisted in interior Alaska until at least 10,500 yr BP, several thousands of years later than indicated from macrofossil surveys. These results contradict claims that Holocene survival of mammoths in Beringia was restricted to ecologically isolated high-latitude islands. More importantly, our finding that mammoth and horse overlapped with humans for several millennia in the region where people initially entered the Americas challenges theories that megafaunal extinction occurred within centuries of human arrival or were due to an extraterrestrial impact in the late Pleistocene.

extinction permafrost megafauna Beringia

Footnotes

2To whom correspondence should be addressed: E-mail: ewillerslev@bio.ku.dk

Author contributions: D.G.F., R.D.E.M., R.G.R., and E.W. designed research; J.H., D.G.F., L.J.A., A.V.R., M.R., S.R., M.D., M.T.P.G., J.J.A., A.C., I.B., and P.M. performed research; J.H., D.G.F., R.D.E.M., R.G.R., L.J.A., R.N., B.W.B., M.D., and K.M. analyzed data; and D.G.F., R.D.E.M., R.G.R., and E.W. wrote the paper.

The authors declare no conflict of interest.

This article contains supporting information online at www.pnas.org/cgi/content/full/0912510106/DCSupplemental.

↵* In this paper, calibrated radiocarbon ages (and OSL ages) are reported in calendar years (yr BP), whereas uncalibrated radiocarbon ages are reported as 14C yr BP.

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