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Narrator:Listen to part of a lecture in a Marine Biology Class
獨白:聽下面一段海洋生物學的講座。
Professor:We know whales are mammals and that they evolved from land creatures.
演講者:我們知道鯨魚是哺乳動物，而且是從陸地生物進化而來。
So the mystery is figuring out how they became ocean dwellers.
所以需要解開的謎團是他們怎樣變成海洋生物。
Because until recently there was no fossil record of what we call “the missing link”-that is evidence of species that show the transition between land-dwelling mammals and today's whales.
因為至今為止，我們還沒有發現所謂關于二者聯系消失的化石證據。這是很重要的證據來證明陸上生物到鯨魚的進化。
Fortunately, some recent fossil discoveries have made the picture a little bit clearer.
幸運的是最近一些化石證據能使這一“進化圖”稍顯清晰了。
For example, a few years back in Pakistan, they found a skull of a wolf-like creature.
比如幾年前在巴基斯坦，發現了一具像狼一樣的頭蓋骨，
It's about 50 million years old. Scientists had seen this wolf-like creature before, but this skull was different.
距今 15 百萬年，科學家以為這和以前的化石一樣，但事實上，它有所不同。
The ear area of the skull had characteristics seen only in aquatic mammals, specifically whales.
在它耳朵區域的頭骨是有水聲哺乳動物的特點，特別像鯨。
Err, well, then also in Pakistan they found a fossil of another creature, which we call Ambulocetus natans.
而且也在巴基斯坦，我們找到了另一具生物化石，稱為陸行鯨。
The name Ambulocetus natans comes from Latin of course, and means “walking whale that swims”.
那很。陸行鯨這個名字來自于拉丁語，意為能行走的游泳鯨。
It clearly had four limbs that couldn't have been used for walking. It also had a long thin tail, typical of mammals, something we don't see in today's whales.
它有四肢可以行走，也有一個和哺乳動物一樣的長細尾巴，盡管現代鯨沒有了。
But, it also had a long skeletal structure.
而且還有一副修長骨架結構，
And that long skeletal structure suggests that it was aquatic.
而且這個骨架結構表明它是水生生物。
And very recently in Egypt, they found a skeleton of Basilosaurus.
而且最近在埃及，他們發現了一具骨架，稱之為龍王鯨。
Basilosaurus was a creature that we've already known about for over a hundred years.
龍王鯨是我們已經知道百年的生物了，
And it has been linked to modern whales because of its long whale-like body.
而且他們也與鯨有關系，因為他們有著修長的鯨一樣的身體。
But this new fossil find showed a full set of leg bones, something we didn't have before.
但這具新化石有 4 個腿骨，這是之前所沒有過的。
The legs were too small to be useful.
它們腿骨太小而無用，
They weren't even connected to its Power San and couldn't have supported its weight.
而且沒有鏈接到手掌，也不能支撐那么大的軀體重量。
But it clearly shows Basilosaurus an evolution from land creature.
但能很清楚的證明龍王鯨是由陸地生物進化而來。
So that's a giant step in the right direction.
所以這是在正確研究方向上的重大進步。
Even better, it established Ambulocetus natans as a clear link between the wolf-like creature and Basilosaurus.
更有甚者，這指明了陸行鯨這樣的狼型生物與龍王鯨之間的關系。
Now these discoveries don't completely solve the mystery.
但這發現不能完全將謎團解開。
I mean, Ambulocetus natans is a mammal that shows a sort of bridge between walking on land and swimming.
我的意思是，盡管陸行鯨已經指明一個路上行走動物和水中游泳動物的清晰聯系，
But it also is very different from the whales who know today.
但陸行鯨與今天的鯨魚仍有很大不同。
So really we are working just a few pieces of a big puzzle.
所以我們在幾個大困惑上兜圈子。
Emm…a related debate involved some recent DNA studies.
有一個包涵最近關于ＤＮＡ研究的話題。
Remember, DNA is the genetic code for any organism.
記住，ＤＮＡ是有關任何生物的基因密碼，
And when the DNA from two different species is similar, it suggests that those two species are related.
當兩種不同種類的生物ＤＮＡ相似是，這說明二者是有一定關聯的。
And when we compared some whale DNA with DNA from some other species, we got quite a surprise. The DNA suggests that whales are descendants of the hippopotamus.
當我們拿鯨的ＤＮＡ與其他生物比對時，我們驚奇的發現，鯨魚竟然是河馬的后代！
Yes, the hippopotamus!Well, it came as a bit of a shock.
對，就是河馬，這一定讓你們大吃一驚了。
I mean, that a four-legged land and river dweller could be the evolutionary source of a completely aquatic creature up to 25 times its size.
我是說，一個在河里生活有四條腿的陸生生物能成為比自己大２５倍的水生生物的進化源么？
Unfortunately this evolution of the hippopotamus apparently contradicts the fossil record, which suggests that the hippopotamus is only a very distant relative of the whale, not an ancestor.
很不幸，河馬進化理論與化石是有沖突的。我們只能說，河馬是鯨魚的一個遠親，并不是祖先。
And of course as I mentioned, that whales are descendent not from hippos but from that distant wolf-like creatures.
當然我提到了，鯨并不是河馬的后代，而是由那個久遠的狼型化石的后代。
So we have contradictory evidences.
所以我們有了個相矛盾的證據，
And more research might just raise more questions and create more controversies. At any rate, we have a choice.
隨著更多的研究衍生出更多的問題，繼而得到更多的辯駁，總之，我們可以選擇，
We can believe the molecular data- the DNA, or we can believe the skeleton trail, but unfortunately, not both.
我們可以相信分子數據—DNA 理論，也可以相信骨架結構蹤跡理論，但事實上，都不是。
Err… and there have been some other interesting findings from DNA research.
有一些 DNA 研究有趣的發現。
For a long time, we assumed that all whales that had teeth including sperm whales and killer whales were closely related to one another.
以前我們認為，有牙齒的鯨魚，比如巨頭鯨和虎鯨，他們是有一定聯系的，
And the same for the toothless whales, like the blue whale and other baleen whales, we assumed that they be closely related.
沒有牙齒的鯨魚，比如藍鯨和須鯨，他們是有一定聯系的，
But recent DNA studies suggest that that's not the case at all.
但DNA 研究表明，根本就沒這回事兒。
The sperm whale was actually closely related to the baleen whale, and it's only distantly related to the toothed-whales.
現在 DNA 表明，巨頭鯨與須鯨有關聯，而且僅僅與有齒鯨有遙遠的關系，
So that's the real surprise to all of us.
所以這讓我們都很驚奇。
