These are my parents, they're clearly humans too.

他們是我的父母，也很明顯都是人類。

My grandfather, human.

我的祖父，還是人類。

My great-grandfather and great-great-grandfather?

那我的曾祖父和曾曾祖父呢？

Humans without a doubt.

絕對都是人類。

But my grandfather 185 million generations removed?

但是我那一億八千五百萬年前的祖先呢？

Not a human.

牠不是人類。

He was a fish.

牠是條魚。

So imagine you could take a picture of every ancestor down the line and put them in a big stack.

想像一下我們能把自己過去的每一代祖先都拍照下來，整理成一大疊照片。

Every father's father's father's father's [etc.] father.

每一代的爸爸的爸爸的爸爸的爸爸的... (不斷重複) 爸爸。

And well, that would be a very big stack, with me at the top and my fishy forefather all the way down at the bottom.

最後手邊會有非常厚的一疊照片，我在最上面，而我的魚類祖先則在最下面。

Maybe we should lay this stack down on its side, that would be a little safer.

或許我們應該把這疊照片橫著放，這樣比較安全。

As we journey back in this stack, let's pull out a few snapshots from history.

隨著我們越往這疊照片的後面走去，讓我們也一邊記錄下來歷史的進展吧。

1,000 generations back we're just a few inches in, and we find a human.

才在照片堆前幾英吋的一千代以前，我們到了一名人類。

10,000 generations ago, just two steps further and well, still human but not like we'd recognize.

僅是兩步之遙的一萬代以前，仍然是名人類，但和我們一般認知的人類有些不同。

75,000 generations ago, that's a million and a half years back, not a human.

七萬五千代以前，也就是一百五十萬年前，就不是人類了。

That's Homo erectus.

這是直立猿人 (Homo erectus)。

Now here we are just a few hundred steps back in our journey, a million and a half generations ago.

現在我們來到了距離起點數百步的距離，大約是我們的一百五十萬代以前。

This ancestor looks more like today's Old World monkeys, but still a primate.

這位祖先看起來更像是我們現今稱為舊世界猴的猴科動物，但仍然是靈長類。

15 million generations ago and this ancestor looks more like a tree rodent than a monkey.

來到一千五百萬代以前，比起猴子，這位祖先看起來則更像是隻樹鼠。

Let's jump all the way back to my 120 millionth great-grandparent, this is 12 kilometers back down the line.

讓我們再繼續跳到一億兩千萬代祖先以前，也就是離起點十二公里的地方。

This is a decidedly non-human, non-primate shrew-like mammal, but it's kinda cute!

這是隻絕對既不是人類也不是靈長類，長得像是隻尖鼠的哺乳類動物。不過看起來挺可愛的！

My 165 millionth great-grandparent is not even a mammal, it's a prehistoric lizard that predates even the dinosaurs.

我的一億六千五百萬代前的祖先甚至不是哺乳類，而是比恐龍還更早出現的史前蜥蜴。

They've got their own photo album, their own stack, that joins up with ours somewhere around here.

牠們有著屬於自己的相簿，屬於自己的照片堆，並且在大約這裡與我們的相片堆交會。

In fact, every species has their own stack that branches off somewhere down the line.

實際上，每個物種都有屬於自己的照片堆，並且會在途中分枝散葉。

And here we are 185 million generations ago at our ancestral fish.

現在我們來到了一億八千五百萬代以前，看到了我們的魚類祖先。

You see the resemblance?

你覺得我們看起來像嗎？

So where along the stack was the first human?

所以世界上第一名人類出現在哪裡呢？

There wasn't one.

其實並沒有這樣的存在。

Photo #4,632?

第 4,632 張照片？

Human.

是人類。

Photo #79,221?

第 79,221 張照片？

Well, that's Homo erectus.

嗯，這個是直立猿人。

There's no single point where one became the other.

猿人演變到人類的過程並不是單一的時間點。

Every photo that we pull from this stack looks pretty much like the photo on either side.

我們從照片堆中拿出的每一張照片看起來都可能屬於其中一邊。

Every generation is the same species as its parents, and the same species as its children.

每一代都有著相同的物種做為牠們的父母，並生出相同物種的後代。

Homo erectus had Homo erectus parents and Homo erectus kids.

直立猿人有著直立猿人的父母，還有直立猿人的小孩。

Our fishy ancestor?

我們的魚類祖先呢？

Had fishy fathers and fishy children.

一樣有著魚類父親和魚類小孩。

You can never pinpoint the exact moment that a species came to be, because it never did.

我們沒辦法準確標明一個物種轉變成另一個物種的瞬間，因為實際上這種事情並不會發生。

It's just like how you used to be a baby, and now you're older.

這就好像你過去是個小嬰兒，但現在變老了一些。

But there was no single day when you went to bed young and woke up old, although sometimes it feels that way.

但你不會某天上床睡覺的時候還是個年輕人，但起床之後就變成老人了。雖然有時候是會有這種感覺啦。

There was no first human.

史上並沒有所謂的第一位人類。

It sounds like a paradox, it sounds like it breaks the whole theory of evolution.

這聽起來或許有些矛盾，而且好像違背了進化論。

But it's really a key to truly understanding how evolution works.

但這卻是真正理解演化機制運作方式的關鍵。

Evolution happens like a movie, with frames moving by both quickly and gradually, and we often can't see the change while it's occurring.

演化的過程就好像一部電影一樣，每一個影格都快速且逐漸地播放下去，而我們很常沒有辦法及時看到當中所發生的變化。

Every time we find a fossil, it's a snapshot back in time, often with thousands of frames missing in between, and we're forced to reconstruct the whole film.

每當我們找到一個化石，就好像是找到過去一個瞬間的畫面，中間缺失了數以千計的影格，而我們則被迫要自己重新建構出整部電影。

Life is what happens in between the snapshots.

生命進化的過程就在這一個個瞬間之間。

Instead of a nice smooth road, this is a journey on stepping stones, and we give each one their own name.

它不是一個平坦的過程，而我們都是在摸著石頭過河，給予每一個化石屬於它們自己的名字。

Stay curious.

保持好奇心。

This journey was inspired by Richard Dawkins' book "The Magic of Reality" and there is a link down in the description.

本次的影片的靈感來自理查·道金斯的著作《現實的魔力》。該書的連結放在影片資訊欄位中了。