Man exterminated animals already in prehistory

Researchers: hunting and self-initiated fires destroyed large animals

by Tamara Traubman

In the last hundred years, man is responsible for the mass extinction of animal species. But now it turns out that man harmed the living world already in prehistoric times, about 50 thousand years ago. Two new studies, published today in the scientific journal "Science" present evidence that man is responsible for the disappearance of the mammoth from North America and dozens of other animal species in Australia. The extinction processes, which took place 35 thousand years apart, happened near the time of man's arrival on the continents.

The new evidence may bring to an end a long-standing debate about the factors that led to the mass extinction, and also clear other suspects, such as climate change.

Paleontologists estimate that 28 genera and 55 species of vertebrates became extinct in Australia, among them a kangaroo with a terrifying appearance, armed with strong claws, which weighed 300 kilograms, and the Newernis, a bird that weighed 100 kilograms. As far as is known, the Newarinis is the heaviest bird that ever lived.

In an attempt to find the cause of the extinction, geochronologist Dr. Richard Roberts and his colleagues from the University of Melbourne checked the age of the remains of large animals from 28 different sites around Australia. The researchers used two new methods for determining the dates of ancient materials, which together gave more accurate dates than those that can be obtained with traditional dating methods. The test revealed that the large animals tested were buried 51,200-39,800 years ago, just as humans began to settle in Australia.

Roberts believes that man dealt a fatal blow to the large animals, albeit indirectly. According to him, "Man changed the vegetation by burning areas, possibly to facilitate hunting and movement. The result was less food for large herbivorous animals. Also, hunting and climate change might have pushed them to the kidney."

A variety of exotic animals also lived in America, including the giant saber-toothed tiger, the downy bison, the giant antelope and the mammoth. About 11 years ago, more than two-thirds of the large mammals in America died out. Dr. John Ellroy, a researcher in biological evolution at the University of California, Santa Barbara, used a computer simulation of North American ecology that looked at the human impact on 41 large herbivores. According to the simulation, Ellroy wrote, from the moment man arrived on the continent mass extinctions were "inevitable".

Ellroy included in the simulation variables such as the efficiency of man's hunting, the speed of his spread on the continent, and the number of animal species that competed with each other for the same type of food. According to the simulation, even the slowest and clumsiest hunters caused ecological disaster.

In an article accompanying the studies, Dr. Gifford Miller, a geochronologist from the University of Colorado, wrote that "the bulk of the evidence indicates that the human factor is the explanation for the extinction events. If humans hadn't come to Australia, the big animals would still be roaming there today."

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