更多好文章的沪江博客： 星座下的神迹
手指非常灵巧，他们帮你拿咖啡，打字，或是拉裤子。但是你有没有想过：手指是怎么进化来的？上世纪90年代，科学家深入思考了这一问题。他们得出结论：手指基本上是第一个四足动物（有四肢的动物）的发明。原因之一就是古代鱼类的化石骨骼看似没有手指——至少在胸鳍上没有明显的趾结构。但是从鱼类进化来的四足动物却有这种结构。

但如今，科学家在9月21日的《自然》杂志在线版上撰文指出，以前的想法并不正确。这些科学家发掘出的化石证明，古代鱼类的鳍上的确长有“手指”。他们对3亿8千万年的一个标本进行了CT扫描，发现在保存非常完整的鱼右鳍上，确实有趾形的鱼骨。这些科学家认为，以前的科学家之所以没有发现这种鱼骨，是因为他们的标本上的“手指”被鱼鳞留下的痕迹掩盖了。所以，看起来鱼儿身上也有手指的雏形。让我们为这一发现竖起两跟大拇指。

科技词汇：
tetrapod n. 四足动物
a vertebrate (as an amphibian, a bird, or a mammal) with two pairs of limbs 有四肢的脊椎动物（例如：两栖动物、鸟类和哺乳动物）
fossilize v. 变成化石
skeleton n. 骨骼
digit : finger or toe 手指; 脚趾
pectoral adj. 胸部的
evolve v. 进化
CT scan : CT扫描（Computerized Tomography 计算机层析术，简称CT）
CT是一种功能齐全的病情探测仪器，它是电子计算机X射线断层扫描技术简称。
CT的工作程序是这样的：它根据人体不同组织对X线的吸收与透过率的不同，应用灵敏度极高的仪器对人体进行测量，然后将测量所获取的数据输入电子计算机，电子计算机对数据进行处理后，就可摄下人体被检查部位的断面或立体的图像，发现体内任何部位的细小病变。
specimen n. 样本;标本

其它词汇整理：
nifty : clever; skilful
grab : (infml joc 口, 谑) have or take (sth) esp in a casual or hasty manner 取或拿（某物）（尤指随便地或匆匆地）
latte : a hot drink made from espresso (= strong coffee) and milk 拿铁咖啡
critter n. 生物（经常参加【科学60秒】的童鞋应该已经认识这个单词了吧^^）
limb : leg, arm or wing 肢（腿﹑ 臂或翼）
fishy : creating doubt or suspicion : QUESTIONABLE
fin : thin flat projecting part of a fish, used for swimming and steering 鳍
incipient : beginning to come into being or to become apparent


Fish Gave Us the Finger

Fingers are pretty nifty. They let you to grab a latte, type on a keyboard, even pull up your pants. But did you ever wonder: where do fingers come from? In the 1990s, scientists gave this problem a lot of thought. And they concluded that fingers were pretty much invented by the first tetrapods: that is, critters with four limbs. One reason they thought that is because a fossilized skeleton of an ancient fish didn’t appear to have any fingers. Or at least any distinct digits in its pectoral fin. But tetrapods, which evolved from fish, did.

Now scientists writing in the September 21st online issue of Nature say that that thinking was…a little fishy. Because they’ve unearthed evidence that suggests that that ancient fish did indeed have fingers in its fins. The researchers did a CT scan on a specimen about 380 million years old. And they found that the fish’s right fin, which was unusually well-preserved, does appear to have digitlike bones. The reason other researchers previously missed them, they think, is because in their samples the fingers were hidden behind marks left by the fish’s scales. So fish, too, seem to have incipient fingers. A finding we give two thumbs up.

—Karen Hopkin

原文链接： http://www.sciam.com/podcast/episode.cfm?id=fish-gave-us-the-finger-08-09-22