英語(yǔ)聽力：冰河綠洲—11

It's likely giant ground sloths used their claws in a similiar way to hook branches and pull them within reach. Like tree sloths, they were vegetarians and probably not fussy about what they ate, chewing their way through leaves, fruits, twigs and all. The big difference between the two is their size. Giant ground sloths were 500 times bigger than their modern relatives. Andstanding up right on their back legs, they towered as tall as a giraffe.

So far we have pieced together something of the people who first explored the southeast of the continent and the wildlife they must have encountered and hunted. But what about the climate and the landscape they all lived in?

Florida is tropical today, but how warm was it 13,000 years ago? This is Little Salt Spring in central Florida, the source of one of the most unlikely clues to the climate of the past. Brought up from aledge more than 20 metres below the surface was the fossilized shell of a tortoise, a giant tortoise, much like this one. Giant tortoises are now only found basking in the heat of a few islands along the equator.