Washington D.C. - A group of U.S. and Australian researchers have used the eggshells of an enormous flightless bird to show that humans were probably responsible for a major extinction event that saw the demise of more than 85% of Australia's large animals. In the 8 January 1999 issue of Science, Gifford Miller of the University of Colorado and his colleagues report that the extinction probably occurred about 50,000 years ago and speculate that its cause may have been ecological disruption from burning by the continent's early human inhabitants. This evidence should help clear up a decades-old debate as to whether human activity or climate change was behind the extinction events that rocked ecosystems around the world during the Quaternary period (1.8 million years ago to the present).
Over a century ago, explorer Alfred Russell Wallace wrote that "we live in a zoologically impoverished world, from which all the hugest, and fiercest, and strangest forms have recently disappeared...." The dearth of these animal species (collectively known as "megafauna," for their moderate to large size) is a result of the mass extinction events of the Quaternary period, which Timothy Flannery of Harvard University describes in a Perspective that accompanies the Report by Miller and his colleagues. These events were mild or absent in some regions of the world, such as Africa and Southeast Asia, moderate in others such as Europe, and extreme in the Americas, Australia, and many oceanic islands.
However, in recent decades, agreement as to why the megafaunal extinctions
occurred has been as non-existent as the long-gone giant sloth. Parts of the
Quaternary were periods of rapid and extensive climatic change that could have
been capable of driving many species to extinction. On the other hand, modern
humans, who first spread across the globe during this time, might also have
brought about the megafauna's demise, either through hunting or less direct
Contact: Gabriel Paal
American Association for the Advancement of Science