英语听力：猛玛象进城记—5

But there is a problem with the idea that hunting caused the mass extinction. Mammoths were not the only animals to disappear.

Camels survived for millions of years in North America, but disappeared around the same time as the mammoths. Wild horses first evolved here and became dominant grazers. Yet they, too, vanished soon after the Ice Age ended. But there’s little evidence to suggest that humans hunted horses or camels. This seems to go against the hunting argument.

So what else would have triggered such large-scale extinctions?

The other major possibility is climate change. The end of the Ice Age was a turbulent, erratic period. In some areas, rain patterns were shifting, bringing moisture back to dry landscapes and turning grassland into forest.

Other regions of the continent were plunged into prolonged periods of draught. For grazers such as horses, this led to a massive change in habitat, one they were not flexible enough to overcome.

As the land dried out, many grass eaters disappeared. We may never know for certain what killed off most of the larger animals at the end of the Ice Age. We do know that there was a time of coincidence—people were arriving just as the climate was in a state of change. Both may have played their part. Whichever was responsible, more than 70 species vanished for good, but some large animals did survive and still live here today.