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SSS 2009-02-16

时间:2010-05-17 03:28来源:互联网 提供网友:木渐浅。   字体: [ ]
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    (单词翻译:双击或拖选)

This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

 

Expectant moms can have very different ideas when it comes to where they plan to have their babies. Some women even choose to give birth in a warm tub of water. But 50 million years ago, whales, it seems, crawled out of the ocean to give birth on land.

You’ve probably heard that whales evolved from animals that lived on terra firma. But what were things like during the transition, when early whales spent some time on shore and the rest in the sea? A new report in the journal Public Library of Science ONE offers one idea. Because scientists from the University of Michigan Museums of Natural History recently unearthed1 the first fossil of an ancient pregnant whale. And they found that the footlong fetus2, who was probably only a day or two from being born, was positioned for a head-first delivery. That’s how land mammals tend to give birth, so their babies can breathe as soon as they arrive. Modern whales, on the other hand, come out tail-first, to make sure they don’t drown during delivery.

So it looks like ancient whales lived in the water but gave birth on the beach. Then they most likely headed back to sea for baby’s first bite of sushi. Which sounds like a whale of a birth plan.

 

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.

 


点击收听单词发音收听单词发音  

1 unearthed e4d49b43cc52eefcadbac6d2e94bb832     
出土的(考古)
参考例句:
  • Many unearthed cultural relics are set forth in the exhibition hall. 展览馆里陈列着许多出土文物。
  • Some utensils were in a state of decay when they were unearthed. 有些器皿在出土时已经残破。
2 fetus ekHx3     
n.胎,胎儿
参考例句:
  • In the fetus,blood cells are formed in different sites at different ages.胎儿的血细胞在不同时期生成在不同的部位。
  • No one knows why a fetus is not automatically rejected by the mother's immune system. 没有人知道为什么母亲的免疫系统不会自动排斥胎儿。
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