Humans off the Hook for Alaskan Mastodon Extinction

听力音频

听力原文

This is Scientific American 60-Second Science. I'm Emily Schwing. Got a minute?
It's long been thought mammoths and mastodons rambled over North America's arctic and subarctic realms between 75,000 and 100,000 years ago, and were made extinct by hungry new arrivals on the scene: human beings.
But new evidence indicates mastodons probably roamed the region as far back as 120,000 years ago, and they were gone before the first people showed up.
"For at the least the story of the mastodon, we now know for what we call Beringia, Alaska, parts of Yukon and over into northeastern Asia,
they were wiped out in those areas for things that had nothing to do with humans, because they all died out before there were humans there."
Pat Druckenmiller is the Curator of Earth Science at the University of Alaska Museum of the North.
"Humans could not have been part of the story and that's pretty interesting."
The research is in the Proceedings of the National Academy of Sciences.
Druckenmiller and co-authors were led to these conclusions after colleagues at the Yukon Paleontology Program in Canada decided to redate nearly forty thousand specimens,
because American mastodons are often mistaken for their much hairier wooly mammoth cousins, who hung around the area later.
"A mammoth and a mastodon can be immediately distinguished on the basis of their teeth, their big cheek teeth.
The surface of a mammoth tooth looks like a washboard, perfect for grinding grasses that grew during the last ice age.
But mastodon teeth have much lumpier, bumpier cusps: ideal for chewing twigs and leaves.
"People in the past when they found these teeth and bones, they put glue and other kinds of strange things on them,
that glue can mess up the dates, gives you a wrong date.
In fact, it gives you a date that's too young."
The new dates corroborate what mastodon teeth show:
They ambled over Beringia when the region was warmer and forested, long before mammoths and earlier than humans.
So, if humans didn't wipe out the mastodon, what did?
That mystery remains for scientists to sink their teeth into.
For Scientific American 60-Second Science. I'm Emily Schwing.

题目讨论

如果对题目有疑问,欢迎来提出你的问题,热心的小伙伴会帮你解答。

用户头像
已经输入0个字

精听听写练习

最新提问

  • 一碗熱雞湯

    一碗熱雞湯针对READING题目

    发表了一个提问 去解答>>

  • 呆sy

    呆sy针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员fSryra

    学员fSryra针对READING题目

    发表了一个提问 去解答>>

  • 学员fSryra

    学员fSryra针对LISTENING题目

    发表了一个提问 去解答>>

  • ru1126

    ru1126针对READING题目

    发表了一个提问 去解答>>

  • 夕梦谢

    夕梦谢针对题目

    发表了一个提问 去解答>>

  • oliover

    oliover针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员1fZwMi

    学员1fZwMi针对READING题目

    发表了一个提问 去解答>>

  • got96

    got96针对READING题目

    发表了一个提问 去解答>>

  • got96

    got96针对READING题目

    发表了一个提问 去解答>>

  • mia24killa2025

    mia24killa2025针对SPEAKING题目

    发表了一个提问 去解答>>

  • 学员npTapM

    学员npTapM针对题目

    发表了一个提问 去解答>>

  • 学员aa7hj3

    学员aa7hj3针对题目

    发表了一个提问 去解答>>

  • 学员0q8RRQ

    学员0q8RRQ针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员zF91Vt

    学员zF91Vt针对题目

    发表了一个提问 去解答>>

  • 李培兴

    李培兴针对题目

    发表了一个提问 去解答>>

  • wendyzixu

    wendyzixu针对题目

    发表了一个提问 去解答>>

  • pinheadlarry

    pinheadlarry针对READING题目

    发表了一个提问 去解答>>

  • 学员lpXOZs

    学员lpXOZs针对题目

    发表了一个提问 去解答>>

  • 口说29我来啦

    口说29我来啦针对LISTENING题目

    发表了一个提问 去解答>>

  • 一碗熱雞湯

    一碗熱雞湯针对READING题目

    发表了一个提问 去解答>>

  • 呆sy

    呆sy针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员fSryra

    学员fSryra针对READING题目

    发表了一个提问 去解答>>

  • 学员fSryra

    学员fSryra针对LISTENING题目

    发表了一个提问 去解答>>

  • ru1126

    ru1126针对READING题目

    发表了一个提问 去解答>>

  • 夕梦谢

    夕梦谢针对题目

    发表了一个提问 去解答>>

  • oliover

    oliover针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员1fZwMi

    学员1fZwMi针对READING题目

    发表了一个提问 去解答>>

  • got96

    got96针对READING题目

    发表了一个提问 去解答>>

  • got96

    got96针对READING题目

    发表了一个提问 去解答>>

  • mia24killa2025

    mia24killa2025针对SPEAKING题目

    发表了一个提问 去解答>>

  • 学员npTapM

    学员npTapM针对题目

    发表了一个提问 去解答>>

  • 学员aa7hj3

    学员aa7hj3针对题目

    发表了一个提问 去解答>>

  • 学员0q8RRQ

    学员0q8RRQ针对LISTENING题目

    发表了一个提问 去解答>>

  • 学员zF91Vt

    学员zF91Vt针对题目

    发表了一个提问 去解答>>

  • 李培兴

    李培兴针对题目

    发表了一个提问 去解答>>

  • wendyzixu

    wendyzixu针对题目

    发表了一个提问 去解答>>

  • pinheadlarry

    pinheadlarry针对READING题目

    发表了一个提问 去解答>>

  • 学员lpXOZs

    学员lpXOZs针对题目

    发表了一个提问 去解答>>

  • 口说29我来啦

    口说29我来啦针对LISTENING题目

    发表了一个提问 去解答>>

Get Microsoft Silverlight
查词 | 笔记