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Researcher Moves Closer to Understanding Cause of Mass Extinction

26.11.2009
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.

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.

A particular issue that has also contributed to this debate focuses on the chronology of extinctions. The existing fossil record is incomplete, making it more difficult to tell whether or not the extinctions occurred in a gradual process, or took place as a synchronous event. In addition, it was previously unclear whether species are missing from the terminal Pleistocene because they had already gone extinct or because they simply have not been found yet.

However, new findings from Faith indicate that the extinction is best characterized as a sudden event that took place between 13.8 and 11.4 thousand years ago. Faith’s findings support the idea that this mass extinction was due to human overkill, comet impact or other rapid events rather than a slow attrition.

“The massive extinction coincides precisely with human arrival on the continent, abrupt climate change, and a possible extraterrestrial impact event” said Faith. “It remains possible that any one of these or all, contributed to the sudden extinctions. We now have a better understanding of when the extinctions took place and the next step is to figure out why.”

The article, "Synchronous Extinction of North America's Pleistocene Mammals" appears in the Nov. 23 edition of Proceedings of the National Academy of Sciences.

The nationally-ranked doctoral program in Hominid Paleobiology, established in 1998, trains students to apply multidisciplinary techniques and approaches to the study of human origins. The program is part of GW's Columbian College of Arts and Sciences, the largest of the University's academic units with more than 40 departments and programs for undergraduate, graduate and professional studies.

Columbian College provides the foundation for GW's commitment to education, research and outreach, providing courses ranging from the traditional disciplines to a wide variety of interdisciplinary and applied fields for students in all the undergraduate degree programs across the University. An internationally recognized faculty and active partnerships with prestigious research institutions place Columbian College at the forefront in advancing policy, enhancing culture and transforming lives through scientific research and discovery.

Located four blocks from the White House, The George Washington University was created by an Act of Congress in 1821. Today, GW is the largest institution of higher education in the nation's capital. The university offers comprehensive programs of undergraduate and graduate liberal arts study, as well as degree programs in medicine, public health, law, engineering, education, business, and international affairs. Each year, GW enrolls a diverse population of undergraduate, graduate, and professional students from all 50 states, the District of Columbia, and more than 130 countries.

Jill Sankey | Newswise Science News
Further information:
http://www.gwu.edu

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