【科学60秒】脖子有助大脑进化_英语听力练习mp3下载-科学-沪江听力酷

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【科学60秒】脖子有助大脑进化

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What's in a neck? Well, it's a good place to hang a pendant or a tie. Or to rest your head. Now scientists say that by separating our heads from our bodies, the neck give our brains ____1____ in evolution. Their findings appear in the online journal Nature Communications.
Not all animals have necks. A fish's head is pretty much ____2____ its body. And a fish ____3____ just fine. Nerves based in the fish's brain instruct its fins to move, and ____4____.
But something happened when our aquatic ancestors first slithered onto the land. The source of the nerve cells that power the animals' forelimbs shifted, from the brain to the spinal cord. That move allowed the body to grow more distant from the head, taking the arms with it. And so the neck was born.
That neck, say the scientists, was more than just a way to ____5____ the head off the shoulders. The anatomical relocation improved dexterity by leaving the arms free to move in new ways. And the resulting flexibility helped shape the evolution of our heads and our hands, and how we can use them together to do all sorts of ____6____ things -- like tie a perfect Windsor knot.