Go to Brilliant.org/SciShow to learn more.

到 Brilliant.org/SciShow 了解更多資訊。

When you hear the word “scurvy,” you probably think of

當你聽到「壞血症」時，你可能會想到

jokes about pirates, but this disease

某些有關海盜的笑話，但這個疾病

can actually be really serious.

其實非常嚴重。

Its symptoms include bleeding gums;

其症狀包括牙齦出血

bumpy, rashy skin; and joint pain,

皮膚粗糙、關節疼痛，

and if it's not treated, it can be deadly.

而且如果不治療的話，可能會致命。

It's not just a thing of the past, either.

這不只是以前的疾病。

Scurvy still shows up in developing nations,

壞血症仍出現在發展中國家，

and dozens of cases were reported in

而且在過去十年，

the United States in the last decade.

美國就傳出數十例。

Thankfully, it is relatively easy to treat —

幸好，這種疾病相對好治療。

all you need is a high dose of Vitamin C.

你只需要高劑量的維他命 C。

But here's the thing:

但問題是：

If it weren't for a quirk of evolution,

如果不是因為怪異的演化，

nobody would have ever gotten scurvy in the first place.

一開始根本沒人會得壞血症。

The reason Vitamin C cures scurvy is because

維他命Ｃ 可以治療壞血症的原因是，

the disease is actually caused by a Vitamin C deficiency.

壞血症其實是由於缺乏維他命 Ｃ 所造成。

Without this vitamin, the body can't properly form collagen.

沒有這種維他命，身體就無法正常形成膠原蛋白。

Collagen is the protein that makes up

膠原蛋白是構成

the vast majority of our connective tissues,

我們絕大多數結締組織的蛋白質，

so without enough of it, things can go seriously wrong.

所以要是沒有足夠的膠原蛋白，身體就會變得很糟。

For example, scurvy patients can develop skin

例如，壞血症患者的皮膚

that's thin and fragile, where any wounds they get

會變得又薄又脆弱，得到的任何傷口

stay open and can't heal.

都會變開放性且無法痊癒。

That can make them more likely to contract a life-threatening infection.

這讓患者更有可能感染威脅生命的傳染病。

Scurvy can also cause the collagen supporting

壞血症也會造成由膠原蛋白

blood vessels to fall apart, which can lead to hemorrhages.

支撐的血管破裂，進而導致出血。

So this protein is a pretty big deal

所以，這種蛋白質非常重要。

and by extension, so is Vitamin C.

此外，維他命 C 當然也是。

To be clear, this vitamin isn't the only thing we need to make collagen.

坦白說，這種維他命不是製作膠原蛋白的唯一物質。

But it is the only component of the collagen

但它是膠原蛋白在合成過程中

synthesis process our bodies can't naturally produce.

身體無法自然產生的成分。

We need to consume it somehow.

我們需要以某種方式攝取。

That's why a lack of it leads to scurvy,

這就是為什麼缺乏維他命 C 會導致壞血症，

and why a high dose of it can cure the disease.

而且為什麼高劑量的維他命 C 可以治療壞血症。

But what's interesting is that most of nature doesn't have to deal with this.

但有趣的是，自然界的大多數生物都不必應付這問題。

Lots of animals can make their own Vitamin C

很多動物可以自己製造維他命 C，

without consuming it in their diets.

而不需要從食物中攝取。

And here's the kicker:

更重要的是：

Our very distant primate ancestors could do this, too.

我們久遠的靈長類祖先也能這麼做。

More than 60 million years ago,

在 6000 多萬年前，

the branch of primates that now includes humans

靈長類的分支，包含現在的人類

did have the ability to make Vitamin C.

確實有能力製作維他命 C。

But then we lost it.

但我們後來失去這種能力。

More specifically, we lost the ability to make an enzyme called GULO.

更具體來說，我們失去製作一種叫 GULO 酵素的能力

Just like with collagen, the process of making

就像製作膠原蛋白一樣，製作

Vitamin C is... a process.

維他命 C 的過程...是一個過程。

But for this story, all you need to know

但在這裡，你要知道的是

is that the last step depends on GULO.

最後一個步驟仰賴於 GULO。

When you look at different animals' genomes,

你在看不同動物的基因組時，

you'll see that most animals have the gene that codes for this enzyme.

你會發現大多動物都有編碼這種酵素的基因。

And those that do can tweak how much

牠們可以調整

or how little Vitamin C they produce.

維他命 C 產生的多寡。

Like, rabbits pump out way more GULO enzymes

例如，在冬天，富含維他命 C 的食物

during the winter months when Vitamin C-rich foods

供給短缺時，兔子會產生大量的 GULO 酵素。

are in short supply, and goats can really crank it out

而山羊也會在生病或緊張時

when they're sick or stressed.

製造這種酵素。

Even animals toward the bottom of the evolutionary tree,

就算是在演化樹底層的那些動物，

like sponges and jellyfish, have the gene

像是海綿和水母，也有產生

responsible for GULO, which means

GULO 的基因，這代表

it's existed for a very long time.

GULO 已經存在很久了。

The only members of the no-GULO club are

無-GULO 俱樂部的成員只有

guinea pigs, some bats and birds, most fish...

天竺鼠、某些蝙蝠、大多數的魚類...

and many primates, including humans.

還有很多靈長類，包括人類。

So in our evolutionary past, our very distant ancestors

所以在我們演化史上，我們的遠祖

had the ability to make GULO and therefore Vitamin C.

都有能力製作 GULO 和維他命 C。

But somewhere in primate evolution, a random mutation broke it.

但靈長類演化的某個時間點，有個隨機突變破壞了這能力。

This might seem more than a little unfair,

這可能好像有點不公平，

but you have to remember, mutations are random.

但你要記住，突變是隨機的。

Most of the time, they're harmless and unnoticeable,

大多時候都無害且不明顯，

but sometimes they affect an important gene.

但有時會影響重要的基因。

And when they do… well, it just kind of stinks.

如果影響到...好吧，會有點遭。

We can tell this happened to GULO

我們可以知道 GULO 發生的事。

because its gene is actually still in our genetic code —

因為它的基因其實仍在我們的遺傳編碼中。

although these days, it's just something called a pseudogene.

雖然現在是叫作假基因。

That's a copy of a DNA sequence

那是 DNA 序列的複製品。

that accumulated enough mutations that it can't

它累積了足夠突變，導致無法

perform its original job — or in the case of the GULO gene,

完成原本的工作，或是在 GULO 基因下，

accumulated enough that it's totally nonfunctional.

累積足夠完全喪失功能的突變。

Pseudogenes actually crop up all the time,

假基因其實一直都在，

and the GULO gene is one of about 20,000 others in our genome.

而 GULO 基因是基因組中，其他 20,000 個基因中的一個。

For reference, we have about 27,000 genes

我們有大約 27,000 個基因做為參考，

that actually make what they're supposed to.

它們其實可以製造原本該製造的物質。

So, you know… our genomes are kind of a mess.

所以說…我們的基因組有點亂。

But that's a little beside the point here.

但這有點離題了。

The real question is, why did the nonfunctional

真正的問題是，為何失去作用的

GULO gene get passed down in the first place?

GULO 基因一開始會遺傳下來？

After all, we can literally die without Vitamin C.

畢竟，我們沒有維他命 C 確實會死。

So it seems like the first primates to get this

所以似乎第一批獲得這些

broken gene should have died before they could pass it along to their offspring.

殘缺基因的靈長類，應該在遺傳給後代前死亡。

Well, scientists have looked into it,

科學家已經研究過了

and they've come up with a hypothesis about what happened.

而他們對此提出一個假設。

A part of it could be that there is some benefit to ditching the GULO gene.

其中部分原因可以是，丟掉 GULO 基因可能有其他好處。

GULO can create hydrogen peroxide as a

GULO 可以製造過氧化氫

byproduct of its reaction, which can form particles

作為其反應的副產品，當過氧化氫分解時，

called free radicals when it breaks down.

會形成叫自由基的分子。

These are little free-floating electrons

這些微小、自由浮動的電子

that have the potential to harm cells

可能會傷害細胞，

and make certain diseases more likely.

讓某些疾病更可能產生。

So it seems helpful to produce as few of them as possible.

所以盡可能減少產生它們，似乎對我們有好處。

But then again… that's a marginal benefit at best,

但一樣… 這是考慮到沒有維他命 C 的情況，

considering what happens without Vitamin C.

充其量只是邊際效益。

So the better explanation seems to be that

比較好的解釋是，

the GULO pseudogene wasn't eliminated

GULO 的假基因沒有受到清除，

because there just wasn't enough selective pressure.

是因為進化壓力還不夠的關係。

Not making GULO is easy to compensate for

如果是可以在飲食中大量攝取維生素 C 的動物，

if you're an animal that consumes plenty of Vitamin C in your diet.

即使沒有製作 GULO 的能力也能得到補償。

And at the point in our ancestry where primates lost the GULO gene,

在我們的祖先，靈長類失去 GULO 的基因時，

they lived mostly in tropical environments,

他們主要生活在熱帶環境，

so their diets contained plenty of fruits and vegetables.

因此他們的飲食中，含有大量的水果和蔬菜。

So we probably never noticed the ability to

所以，我們大概沒注意到

synthesize this vitamin was gone because,

這種合成維他命的能力失去了，因為

well, we got it pretty easily in our diets.

嗯，我們可以輕鬆從飲食中獲得。

Today, that seems pretty rough,

現在，情況還是很遭，

considering that scurvy is still a problem.

因為壞血症仍是個問題。

But unfortunately, that's just how evolution plays out sometimes.

但不幸的是，有時演化就是這樣。

The best we can do now is try and

我們能做的就是努力

make sure everyone gets what they need.

確保每個人能得到他們需要的。

Scurvy isn't anything to joke about,

壞血症不是什麼玩笑話

but there are plenty of other great jokes you

但你還能從故事書中的海盜

can make about storybook pirates.

找到很多其他笑話。

Like, anything about booty is a good time.

像是，任何戰利品都會讓人愉快。

Pirates are always collecting it, counting it,

海盜總是收集、數數它們的數量，

and divvying it up among their crew.

然後分給其他船員。

And if you want to experience some of that

如果你想自己體驗一下，

for yourself, you can check out the Logic course from Brilliant.

你可以在 Brilliant 那了解邏輯課程。

It features a quiz that's all about pirates,

它是以海盜為特色的小測驗，

where you use your new logic skills to

可以使用新的邏輯技巧，

figure out who's cheating whom out of the most booty.

在大多數的戰利品中，找出誰在欺騙人。

It's a fun time, and Brilliant also has a bunch

這很有趣，而且 Brilliant 還有其他

of other courses that can help you cultivate

課程可以幫你培養

your math and scientific thinking skills.

數學和科學的思維能力。

They're also available offline using

Brilliants iOS 和 Android 的應用程式

Brilliants iOS and Android app.

都可以離線使用。

So whether you're stuck on the subway

所以不論你是在地下鐵坐車，

or sailing the seven seas, you'll be able to keep learning.

還是航行於七海中，你都能持續學習。

If you're one of the first 200 people to sign up

如果你是前 200 名

at Brilliant.org/SciShow, you'll also get 20% off an annual Premium subscription.

在 Brilliant.org/SciShow 註冊的人，你也會得到年度高級訂閱的 20% 折扣。

And you'll be helping SciShow make more content, too!

同時也是在幫 SciShow 製作更多內容！