Hungry prehistoric hunters, not climate change, drove elephants to extinction during the Pleistocene era (更新世), new research suggests.
At least 12 kinds of elephants 31 to wander about the African, Eurasian, and American continents. Today, only two 32 of elephants are left in South Asia and Africa. One theory for this dramatic death holds that rapid climate shifts at the end of the most recent major ice age, some 10,000 years ago, 33 vegetation and broke up habitats (栖息地), causing the death of those unable to adapt to the new conditions. Another 34 blames prehistoric humans, whose improved weapons and hunting techniques allowed them to wipe out whole herds of elephants.
To help 35 the debate, archaeologist Todd Surovell of the University of Wyoming, and col- leagues tested two assumptions, If humans caused the elephant extinction, Surovell reasoned, the timing of the die-off in 36 regions should match human expansion into those regions. On the contrary, if the extinction was 37 to climate change, elephants should remain in regions 38 colonized by humans and would only begin to die off once climate change occurred.
The team tested both theories by yzing where and when elephants were killed. In all, the study included 41 archaeological sites on five continents. The researchers found that, as humans 39 out of Africa, they left a trail of dead elephants behind them. The creatures disappear from the fossil record of a region once it became colonized by humans. Modern elephants survived in rerfuges 40 to humans, such as tropical forests, says Surovell.
A. uninviting B. migrated C. declined D. due
E. memorial F. specific G. already H. casually
I. hypothesis J. endurance K. resolve L polish
M. altered N. used O. species