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Mud from the ancient riverbanks is good for building nests.
古老河岸边的泥浆有利于筑巢。
lt also holds more evidence that will help us to reconstruct the ice age past.
很多证据表明，这将帮助我们重现过去的冰河世纪。
Every now and then,new clues surface, hinting at what else might lie beneath.
新的线索表面有时暗示着其他可能深藏的东西。
ln this dried-up pond in South Dakota, known as Hot Springs, scientists unearthed great piles of bones.
在被称为温泉的南达科达州干涸的池塘边，科学家发掘了成堆的骨头。
What kind of creature died here? The bones reveal it stood four metres tall and weighed more than 10 tonnes.
什么生物死在这里？骨头揭示了它有四米高，重达10吨。
There's nothing fitting that description living here today.
今天没有这样大小的生物存在。
Here's the give-away, a pair of tusks two metres long, the trademark of a Columbian mammoth, the biggest animal to roam the ice age plains.
这是赠品，一对两米长的象牙，一个哥伦比亚猛犸象的商标，冰河时代的平原上最大的动物。
By comparing it to elephants in Africa today, can we shed light on how those ice age elephants lived and what they lived on?
和今天的非洲象相比，我们能够解释冰河时期的大象生活和它们如何生活的吗？
These are mammoth teeth, huge molars the size of bricks.
这些是猛犸象的牙齿，巨大的臼齿和砖块差不多大。
They have deep ridges very similar to those of modern elephants, suggesting mammoths, too, survived by grinding vast amounts of grass.
它们有深深的脊，和现代大象十分相似，表明猛犸象也靠磨大量的草为生。
Plant fragments trapped between the ridges can still be identified today.
今天还能看见在脊骨中间的残留的植物碎片。
Thousands of years after this mammoth died, we know exactly what it ate for its last meal.
在猛犸象死了，几千年之后，我们很明确地知道它的最后一餐吃的是什么。
Grass is a tough, abrasive food. Even with protective enamel ridges, these teeth would gradually have worn down.
草是强硬和需要研磨的食物。即使是有保护釉质的脊，这些牙齿也会逐渐被磨损。
But just like modern elephants, the mammoths had evolved a way to deal with this.
但是如同现代象一样，猛犸象进化到可以处理这一切。
As one set of teeth was eroded, another grew up to take its place.
一套牙齿被侵蚀了，新的一套又出现了。
The evidence suggests they had six sets in all, to last a lifetime, up to 60 years.
证据表明在它们60多年的人生中，有六套牙齿。
The South Dakota mammoth didn't make it to old age and it was not alone.
南达科他州的猛犸象没能活到晚年，它并不孤独。
The site turned out to be a mammoth graveyard, hiding more than 50 skeletons, all from animals in their prime.
这片遗址变成了猛犸象的墓地，有超过50具骨骼在此，都是处于它们的鼎盛时期。
There's no sign they were killed by hunters, so how did so many healthy mammoths die?
没有迹象表明它们被猎人杀害，这么多健康的猛犸象是怎么死的呢？
