Let's talk about evolution.

讓我們談談演化。

You've probably heard that some people consider it controversial, even though most scientists don't.

你可能聽說有些人認為它具爭議性，雖然多數科學家不如此認為。

But even if you aren't one of those people and you think you have a pretty good understanding of evolution,

即使你不是反對人士之一且認為自己非常瞭解演化，

chances are you still believe somethings about it that aren't entirely right, things like,

你仍可能相信ㄧ些不完全正確的觀念像是，

"Evolution is organisms adapting to their environment."

「演化是生物個體適應它們的生存環境。」

This was an earlier, now discredited, theory of evolution.

這是一個老舊，現在已被推翻的演化理論。

Almost 60 years before Darwin published his book, Jean-Baptiste Lamarck proposed that creatures evolve by developing certain traits over their lifetimes and then passing those on to their offspring.

在達爾文發表它的巨作的 60 年前，拉馬克提出物種於一生中可能發展各種特徵然後將之傳給後代。

For example, he thought that because giraffes spent their lives stretching to reach leaves on higher branches, their children would be born with longer necks.

例如：他認為由於長頸鹿一生都在伸長脖子吃樹梢的葉子，牠們的後裔將會擁有更長的脖子。

But we know now that's not how genetic inheritance works.

現在我們知道基因遺傳並不是這樣。

In fact, individual organisms don't evolve at all.

事實上，生物個體並不會演化。

Instead, random genetic mutations cause some giraffes to be born with longer necks, and that gives them a better chance to survive than the ones who weren't so lucky,

而是基因突變隨機使得有些長頸鹿生來就有較長的脖子，那使牠們生存的機率提升而其它的就沒那麼幸運，

which brings us to "survival of the fittest".

這觀念帶我們到「適者生存」。

This makes it sound like evolution always favors the biggest, strongest, or fastest creatures, which is not really the case.

這聽起來好像演化總是偏好最大、最強壯，或最快的動物，事實並不如此。

For one thing, evolutionary fitness is just a matter of how well-suited they are to their current environment.

首先，演化適存度只反應生物是否適合現在的環境。

If all the tall trees suddenly died out and only short grass was left, all those long-necked giraffes would be at a disadvantage.

如果所有的樹突然消失只剩下短草，所有的長頸鹿都會處於不利。

Secondly, survival is not how evolution occurs, reproduction is.

其次，演化的延續靠的不是生存，而是生殖。

And the world is full of creatures like the male anglerfish, which is so small and ill-suited for survival at birth that it has to quickly find a mate before it dies.

世界上多的是物種像是雄性的鮟鱇魚，牠們出生時既小又不適生存，必須迅速於死亡前找到配偶。

But at least we can say that if an organism dies without reproducing, it's evolutionarily useless, right?

那這樣我們可以說如果有一個物種沒生殖就死亡，那在演化上就沒用，對吧？

Wrong!

錯！

Remember, natural selection happens not at the organism level, but at the genetic level, and the same gene that exists in one organism will also exist in its relatives.

記住，天擇並不是針對物種個體，而是在基因層面，而存在於一個個體中的基因也會存在於其親屬。

So, a gene that makes an animal altruistically sacrifice itself to help the survival and future reproduction of its siblings or cousins,

所以使生物犧牲自我來幫助後代子孫或親屬的生存或生殖的基因，

can become more widespread than one that is solely concerned with self-preservation.

繁衍的數目可大於只在乎保存自我的基因。

Anything that lets more copies of the gene pass on to the next generation will serve its purpose, except evolutionary purpose.

任何能使更多基因複製並傳給後代的機制都可以達到這個目的，除了演化目的。

One of the most difficult things to keep in mind about evolution is that when we say things like,

演化論其中一個最困難的概念就是當我們說：

"Genes want to make more copies of themselves," or even, "natural selection," we're actually using metaphors.

「基因想要增加自己的數目」，或甚至「天擇」，這些其實都是比喻。

A gene doesn't want anything, and there's no outside mechanism that selects which genes are best to preserve.

基因並不想要作任何事，並沒有一個外來的機制選擇哪些基因是最適合保存。

All that happens is that random genetic mutations cause the organisms carrying them to behave or develop in different ways.

真正發生的是，隨機基因突變會使得生物個體產生不同行為或發展。

Some of those ways result in more copies of the mutated gene being passed on, and so forth.

而其中有些行為最後使某些突變基因被傳到下一代，如此而已。

Nor is there any predetermined plan progressing towards an ideal form.

並沒有一個使物種演化並臻至完美的計畫。

It's not ideal for the human eye to have a blind spot where the optic nerve exits the retina, but that's how it developed, starting from a simple photoreceptor cell.

例如：人視神經與視網膜接觸點會產生不完美的盲點，但是人眼就是這樣，自一個簡單的感光細胞發展出來。

In retrospect, it would have been much more advantageous for humans to crave nutrients and vitamins rather than just calories.

以現代角度思考，人類如果能著重營養和維生素的攝取，而不單是熱量那該有多好。

But over the millennia, during which our ancestors evolved, calories were scarce, and there was nothing to anticipate that this would later change so quickly

但是在我們祖先這幾百萬年來的演化過程之中，熱量是很難取得的，而沒有任何人能預料情況將改變得如此快速。

So, evolution proceeds blindly, step by step by step, creating all of the diversity we see in the natural world.

所以演化是盲目的一步，接著一步，創造我們所見的多樣自然界。