英语听力：猛玛象进城记—3

But even on its own, a mammoth was still highly dangerous and an attack required stealth and teamwork. One of the hunters may have acted as a decoy, distracting the animal while others surrounded it. These hunters had another trick up their sleeve. Using a specially crafted wooden stick called an atlatl, they were able to launch sharp pointed darts more than 40 meters. So we know these people were efficient hunters, but could they really have wiped out all the mammoths of the North American continent?

Today the remains of mammoths, in particular their tusks, may help answer that question. To read the clues contained within these tusks, you need to look at the mammoths’ closest living relative, the elephant.

Elephant tusks grow throughout their lives, with the tip being the oldest part. Mammoth tusks show the same pattern of growth as modern elephants. Each year of life is represented by a ring, just like tree rings.

But tusks can also be a record of the most stressful period in an elephant’s life. As bulls mature, they are forced out of the family group and have to fight to survive. During this stressful time, they don’t have so much energy for growth, so the space between each ring is narrower.