英语听力：探索发现 2012-09-16 长毛象王国 Mammoth—4（在线收听）

 Of all these creatures, the woolly mammoth is the undisputed symbol of the Ice Age. But what do we really know about how this giant lived. How did it use its massive spiral tusks? Modern-day elephants, the mammoth’s closest living relatives, may provide some answers. They use tusks to break and lever branches in their search for food, and also to dig for minerals, which all leaves telltale scratches on their tusks. Similar marks found on mammoth’s tusks suggest they too were use as tools. But these tusks are huge. They reach 4 metres long and can weigh more than 80 kilos, equal to a full grown man. So why were mammoth’s tusks so big? Bull elephants fight for the right to mate. The strongest males win access to females and pass on their genes. It was the same for mammoth’s bulls, and over time, this competition led to the development of the ever-larger tusks. Sheer size didn’t save mammoth from extinction. But another of Beringia’s woolly beasts is still around today, the musk ox.