Extinção em massa: por que metade dos maiores mamíferos da América do Norte desapareceu entre 40.000 e 10.000 anos atrás?

domingo, novembro 29, 2009

Mass Extinction: Why Did Half of N. America's Large Mammals Disappear 40,000 to 10,000 Years Ago?

ScienceDaily (Nov. 27, 2009) — Years of scientific debate over the extinction of ancient species in North America have yielded many theories. However, new findings from J. Tyler Faith, GW Ph.D. candidate in the hominid paleobiology doctoral program, and Todd Surovell, associate professor of anthropology at the University of Wyoming, reveal that a mass extinction occurred in a geological instant.

Artist's rendering of a woolly mammoth family. (Credit: iStockphoto/KIM FREITAS)

During the late Pleistocene, 40,000 to 10,000 years ago, North America lost over 50 percent of its large mammal species. These species include mammoths, mastodons, giant ground sloths, among many others. In total, 35 different genera (groups of species) disappeared, all of different habitat preferences and feeding habits.

What event or factor could cause such a mass extinction? The many hypotheses that have been developed over the years include: abrupt change in climate, the result of comet impact, human overkill and disease. Some researchers believe that it may be a combination of these factors, one of them, or none.

Read more here/Leia mais aqui.


Synchronous extinction of North America's Pleistocene mammals

J. Tyler Faith a,1 and Todd A. Surovell b

- Author Affiliations

aHominid Paleobiology Doctoral Program, Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, 2110 G Street NW, Washington, DC 20052; and

bDepartment of Anthropology, University of Wyoming, P.O. Box 3431, 1000 East University Avenue, Laramie, WY 82071

Edited by Steven M. Stanley, University of Hawaii, Honolulu, HI, and approved October 12, 2009 (received for review July 27, 2009)


The late Pleistocene witnessed the extinction of 35 genera of North American mammals. The last appearance dates of 16 of these genera securely fall between 12,000 and 10,000 radiocarbon years ago (≈13,800–11,400 calendar years B.P.), although whether the absence of fossil occurrences for the remaining 19 genera from this time interval is the result of sampling error or temporally staggered extinctions is unclear. Analysis of the chronology of extinctions suggests that sampling error can explain the absence of terminal Pleistocene last appearance dates for the remaining 19 genera. The extinction chronology of North American Pleistocene mammals therefore can be characterized as a synchronous event that took place 12,000–10,000 radiocarbon years B.P. Results favor an extinction mechanism that is capable of wiping out up to 35 genera across a continent in a geologic instant.

climate change extraterrestrial impact overkill Quaternary extinctions radiocarbon dates


1To whom correspondence should be addressed. E-mail: tfaith@gwmail.gwu.edu

Author contributions: J.T.F. and T.A.S. designed research; J.T.F. and T.A.S. performed research; J.T.F. and T.A.S. analyzed data; and J.T.F. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.