Studies: Human Hunting Led to Extinctions

W A S H I N G T O N, June 8 -- For more than a century, scientists havedebated what killed off the big animals in Australia and theAmericas. Two new studies place the blame on squarely on ancienthuman hunters equipped with fire, spears and an appetite for meat.

The studies, appearing today in the journal Science, concludethat after early humans migrated into Australia and the Americas,the heavyweight animals of these new continents were driven toextinction within a few thousand years. In the Americas, 73 percent of the large plant-eaters, alongwith the saber-toothed cat, were gone within 1,200 years afterhumans migrated to the continents about 13,600 years ago. Wiped outwere animals like mammoths, camels, mastodons, large ground slothsand the glyptodont, a strange armored creature the size of a smallcar and weighing more than 1,400 pounds. In Australia, researchers precisely dated bone specimens ofelephant-sized marsupials, giant snakes, huge lizards and otherextinct animals. They found that the wildlife disappeared within10,000 years after humans arrived at the down-under continent.

Longstanding Question

The research contributes powerful new evidence to a century-olddebate among scientists intrigued by the question: What killed offthe big animals in newly settled continents of the world? Some have long blamed humans, but other experts say it couldhave been climate change, disease or a gradual change in habitat. The two new studies pin the blame firmly on humans. "Human population growth and hunting almost invariably leads tomajor mass extinctions," said John Alroy of the University ofCalifornia, Santa Barbara, author of the study of the Americanextinctions. "The results show how much havoc our species can cause, withoutanyone at the time having the slightest idea of what is going on,much less any intention of causing harm," Alroy said. Linda Ayliffe of the University of Utah in Salt Lake City saidprecise dating of rocks and fossils from 27 sites in Australia andWest Papua New Guinea clearly show that large animals theredisappeared around 46,000 years ago, or about 10,000 years or soafter the arrival of humans.