SSS 2009-02-16

（单词翻译）

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.