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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.
a leg up continuous with gets around off it goes keep nifty
脖子有什么用？嗯，脖子是个挂项链吊坠或打领带的好地方。当然，脖子也一直架着我们脑袋让它能够倚靠休息。如今，科学家们在《自然通讯》网络版上发表的研究成果里称，脖子将脑袋跟躯体分离开，从而协助了我们的大脑进化。 并不是所有的动物都有脖子。鱼的脑袋就直接连在躯体上，它们在水中时总是来去自如。鱼的大脑掌控着神经来指挥鱼鳍摆动，这样鱼儿就能到处游动了。 然而，当我们的祖先从水中蹒跚着爬上陆地时，事情就发生了变化。驱使动物前肢移动的神经细胞源从大脑转到了脊髓。这种转变使得躯体长得离头部越来越远，同时还进化出前臂来。这样，脖子就应运而生了。 科学家们说，这个脖子可不仅仅是让脑袋从肩膀“独立”出来。这种解剖学上的重新定位使前臂得以解放并发展出新的运动方式，进而改进了灵活敏捷程度。而且，由此产生的适应性反过来帮助形成了我们的头与手的进化，而在手脑配合下，我们就可以做出一切巧夺天工的玩意儿来——比如打出一个漂亮的温莎领结。