For years, scientists have argued about what caused the great extinction of large mammals in the New World at the end of the last ice age. Our desert region lost mammoths, ground sloths, and camels, among many others. This extinction occurred around 11,000 radiocarbon years ago, close to the time that hunting man becomes prominent in the archaeological record. The question has been, extinction because of the vast climatic changes or because of overkill by humans. Now, by analogy, perhaps some new light is shone on the subject.
In Australia, where man was widespread by about 45,000 years ago, many large animals became extinct around that date. Judging from the results of analyzing carbon isotopes of Emu fossil eggshells, it appears that near the time of the great extinction, Emus switched from a mixed diet of non-grasses and grasses to a diet that almost lacked grasses. Grazing herbivores without grass are dead herbivores. In the absence of strong climatic change, the likely diagnosis is human-caused ecological change; the verdict? "Death by man". Could it have happened here?
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
A modern-day Emu. Image courtesy of Dennis Haugen, 1082 Shryer Avenue, www.forestryimages.org.
Johnson, C. N. 2005. The remaking of Australia's ecology. Science 309:255-256.
Miller, G. H., M. L. Fogel, J. W. Magee, M. K. Gagan, S. J. Clarke, and B. J. Johnson. 2005. Ecosystem collapse in Pleistocene Australia and a human role in megafaunal extinction. Science 309:287-290.