[Science Report]:Ancient Human Hunters


This is the VOA SpecialEnglish SCIENCE REPORT.

Scientists have long debated what caused many kinds of largeanimals in North America and Australia to disappear. Two new studiesblame ancient humans for the disappearance. They say human hunterson both continents may have killed the animals for food. Sciencemagazine reported the findings.

Thirteen-thousand years ago, North America was home to many largemammals. They included woolly mammoths, several kinds of horses,camels and oxen. However, these and many other animals died out soonafter. More than seventy percent of the continent's large mammalswere affected.

John Alroy of the University of California at Santa Barbara ledone of the studies. He developed a computer program to study theeffect of human hunters on forty-one kinds of large mammals.

Mister Alroy based his study on evidence that humans firstarrived in North America about thirteen-thousand years ago. Heexamined how a group of about one-hundred humans could grow innumber over a period of one-thousand-two-hundred years. Mister Alroyestimated such things as reproduction rates and the amount of foodhumans need to survive. He found that it was possible for the smallgroup of humans to expand to about three-hundred-thousand membersduring the period.

Mister Alroy said ancient humans could have killed off many kindsof large animals native to North America. He said the animals thatdisappeared had low rates of reproduction. This would have preventedthem from recovering from the attacks by humans.

Science magazine also reported the findings of a study byAustralian, French and American scientists. They studied fossilremains from twenty-eight areas across Australia and Papua NewGuinea. The scientists said the fossils show that large animals inthe area disappeared about forty-six-thousand years ago. That is afew thousand years after humans arrived.

More than thirty years ago, Paul Martin of the University ofArizona described how the disappearance of large animals was linkedwith human expansion. He says the two studies support his position.Mister Martin adds that local climate may have influenced thedisappearance of some animals.

This VOA Special English SCIENCE REPORT was written by GeorgeGrow.

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