New research suggests that human beings may have been partly responsible for the disappearance of cave bears thousands of years ago, when the plant-loving animals lived. Some experts believed that the cooling climate during the Ice Age was to blame for their extinction.
Scientists reported last week they had studied genetic data from 59 cave bears. Their bones were recovered from seven countries: France, Germany, Italy, Poland, Serbia, Spain and Switzerland. From the genetic information, the scientists noted a decrease in the cave bear population beginning about 50, 000 years ago. That is around the time of the arrival of Homo sapiens (现代人), or modern humans, in Eastern Europe. The researchers said they observed a sharp drop in the bears' numbers about 40, 000 years ago. That coincides with(与……同时发生) the spread of Homo sapiens throughout Europe.
The animals disappeared about 20, 000 years ago. The cave bear lived in the Ice Age at the same time as other now extinct creatures. The bear was as big as a modern polar bear, but ate only plants. It appears often in prehistoric(史前的) cave paintings.
There has been a scientific debate about what led to the extinction of the cave bear. Some scientists believe that the climate change greatly reduced the plants they needed, while others have blamed it on human activities, including hunting and taking over the caves where the bears gave birth and slept during winter. The bear's population remained largely unchanged for long periods before climate cooling, including during two noticeably cold periods and other cooling events.
Homo sapiens appeared in Africa more than 300, 000 years ago and later moved to other areas. The study offered new evidence that the arrival of Homo sapiens led to ruin for many kinds of animals across Eurasia, the Americas and Australia.
