They encode the molecules that make up your body, from the keratin in your toenails, to the collagen at the tip of your nose, to the dopamine surging around inside your brain.

它們將你身體的分子編碼，包含腳指甲的角質、鼻尖上的膠原蛋白，以及腦中翻湧的多巴胺。

Other species have genes of their own.

其它物種也有牠們自己的基因。

A spider has genes for spider silk.

蜘蛛有製造蜘蛛絲的基因。

An oak tree has genes for chlorophyll, which turns sunlight into wood.

橡樹有將陽光轉換為木材的葉綠素基因。

So where did all those genes come from?

那麼，那些基因都是從哪來的呢？

It depends on the gene.

這取決於各個基因。

Scientists suspect that life started on Earth about 4 billion years ago.

科學家推測，地球上生命起源於約 40 億年前。

The early life forms were primitive microbes with a basic set of genes for the basic tasks required to stay alive.

早期的生命體是原始微生物，擁有一組基本基因，處理維持生命的簡單工作。

They passed down those basic genes to their offspring through billions of generations.

牠們再將那些基本基因，經過數十億個世代，傳給後代。

Some of them still do the same jobs in our cells today, like copying DNA.

其中一些基因，至今在我們的細胞中仍然擁有同樣的功能，如複製 DNA。

But none of those microbes had genes for spider silk or dopamine.

但那些微生物中，沒有能製造蜘蛛絲或多巴胺的基因。

There are a lot more genes on Earth today than there were back then.

現今地球上的基因數，比當時多出很多。

It turns out that a lot of those extra genes were born from mistakes.

原來那些多出來的基因中，很多都是因為錯誤而誕生的。

Each time a cell divides, it makes new copies of its DNA.

一個細胞每次分裂，都會複製新的 DNA。

Sometimes it accidentally copies the same stretch of DNA twice.

有時候，它會不小心將同一段 DNA 複製兩次。

In the process, it may make an extra copy of one of its genes.

在這過程中， 它可能會額外複製其中一個基因。

At first, the extra gene works the same as the original one.

起初，額外基因和原基因的運作方式相同。

But over the generations, it may pick up new mutations.

但經過世代變化，它可能會獲得新的基因突變。

Those mutations may change how the new gene works, and that new gene may duplicate again.

那些突變可能會改變新基因的功能，而這個新基因可能會再進行複製。

A surprising number of our mutated genes emerged more recently; many in just the past few million years.

數量驚人的基因突變發生在較近期，其中許多都只是近數百萬年的事。

The youngest evolved after our own species broke off from our cousins, the apes.

最新的演變，發生在人類與近親猿猴分開進化後。

While it may take over a million years for a single gene to give rise to a whole family of genes,

雖然一個基因演變成一個基因家族需要超過一百萬年以上的時間，

scientists are finding that once the new genes evolve, they can quickly take on essential functions.

科學家發現，一旦新基因進化，它們很快就能承擔基本功能。

For example, we have hundreds of genes for the proteins in our noses that grab odor molecules.

舉例而言，我們的鼻子裡有幾百個捕捉氣味分子的蛋白質基因。

The mutations let them grab different molecules, giving us the power to perceive trillions of different smells.

基因突變使它們能捕捉不同的分子，讓我們能感受到無數種氣味。

Sometimes mutations have a bigger effect on new copies of genes.

有時候，突變對新複製基因有更大的影響。

They may cause a gene to make its protein in a different organ, or at a different time of life, or the protein may start doing a different job altogether.

突變可能導致一個基因在不同的器官中或不同的生命時間點製造蛋白質，這個蛋白質也可能開始做完全不同的工作。

In snakes, for example, there's a gene that makes a protein for killing bacteria.

例如，蛇的體內有一個基因，專門製造可殺死細菌的蛋白質。

Long ago, the gene duplicated and the new copy mutated.

這個基因在很久以前進行了複製，而新複製基因產生了突變。

That mutation changed the signal in the gene about where it should make its protein.

那個突變更改了該基因要在哪裡製造蛋白質的信號。

Instead of becoming active in the snake's pancreas, it started making this bacteria-killing protein in the snake's mouth.

原本應該在蛇的胰腺中運作的基因，開始在蛇的口中製造可殺菌的蛋白質。

So when the snake bit its prey, this enzyme got into the animal's wound.

所以當蛇咬著獵物時， 這種酶會侵入該動物的傷口。

And when this protein proved to have a harmful effect, and helped the snake catch more prey, it became favored.

而當這個蛋白質被證明有害，且能幫助蛇捕捉更多獵物後，它成為了一項優勢。

So now what was a gene in the pancreas makes a venom in the mouth that kills the snake's prey.

所以原本曾是在胰腺裡運作的基因，轉變為在蛇的口中製造殺死獵物的毒液。

And there are even more incredible ways to make a new gene.

還有更多令人難以置信的新基因製造方式。

The DNA of animals and plants and other species contain huge stretches without any protein coding genes.

動物、植物，及其它物種的 DNA 含有大量沒有蛋白質編碼基因的片段。

As far as scientists can tell, it's mostly random sequences of genetic gibberish that serve no function.

據科學家所知，這些大多是隨機序列且不具任何功能的基因亂碼。

These stretches of DNA sometimes mutate, just like genes do.

如同基因，這些 DNA 片段有時也會突變。

Sometimes those mutations turn the DNA into a place where a cell can start reading it.

有時，那些突變會將 DNA 轉換成為細胞能讀取的編碼。

Suddenly, the cell is making a new protein.

突然地，該細胞開始製造新蛋白質。

At first, the protein may be useless, or even harmful, but more mutations can change the shape of the protein.

起先，這蛋白質可能是沒用，甚或有害的，但更多的突變能改變蛋白質結構。

The protein may start doing something useful, something that makes an organism healthier, stronger, better able to reproduce.

蛋白質可能開始做一些有用的事，能讓生物體更健康、更強大，並提升其繁衍能力。

Scientists have found these new genes at work in many parts of animal bodies.

科學家已在動物體內多處發現這些新基因正在運作中。

So our 20,000 genes have many origins, from the origin of life, to new genes still coming into existence from scratch.

所以說，我們的 2 萬個基因有很多來源，從生命的起源至不斷從零開始的新基因。

As long as life is here on Earth, it will be making new genes.

只要地球上有生命，新基因就會不斷誕生。