CHERSKY, Russia — During the last ice age, shaggy mammoths, woolly rhinos and bison lumbered across northern Siberia. Then, about 10,000 years ago — in the span of a geological heartbeat, or a few hundred years — they disappeared.
Many scientists think a shift in climate drove these giant grazers to extinction. But two scientists who live in the frigid Siberian plains say that man — either for food, fuel or fun — hunted the animals to extinction.
Paleontologists have been squabbling for decades over how these animals met their demise. The most persuasive theories say it was humanity and nature: Dramatically warming temperatures caused a changing habitat and brought a migration of men armed with deep-piercing spears.
No one knows for sure what set off global warming back then — perhaps solar activity or a slight shift in the Earth’s orbit.
But, in an echo of the global warming debate today, Sergey Zimov, director of the internationally funded Northeast Science Station, and his son Nikita say that man, and not warming temperatures, was the real agent of change.
For the Siberian grasses to provide nutrition in winter, they needed to be grazed in summer to produce fresh shoots in autumn. The hooves of millions of reindeer, elk and moose as well as the larger beasts also trampled choking moss, while their waste promoted the blossoming of summer meadows.
As the ice retreated at the end of the Pleistocene era — the final millennia of a 1.8 million year-long epoch — it cleared the way for man’s expansion into previously inaccessible lands.
When humans arrived, they hunted not only for food but for the fat that kept the northern animals insulated against the subzero cold. The hunters burned the fat for fuel, say the scientists. They might also have killed for prestige or for sport, in the same way buffalo were heedlessly felled.
The wholesale slaughter allowed the summer fodder to dry up, destroying the winter supply, they say.
“We don’t look at animals just as animals. We look at them as a system, with vegetation and the whole ecosystem,” said the younger Zimov. “You don’t need to kill all the animals to kill an ecosystem.”
During the transition from the ice age to the modern climate, global temperatures rose 5 degrees Celsius, or 9 Fahrenheit. But in Siberia’s northeast, the temperature soared 7 degrees C, or nearly 13 degrees F, in just three years, the elder Zimov said.
The theory of human overkill is much disputed. Advocates of climate theory say the warm, wet weather spawned forests that overwhelmed the habitats of the bulky grass eaters.
Adrian Lister of the paleontology department of London’s Natural History Museum said humans might have delivered the final blow, but rapid global warming was primarily responsible for the mammoth’s extinction.
It brought an abrupt change in vegetation that squeezed the last mammoths into isolated pockets, where hunters could pick them off, he said.
