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Thanks to Brilliant for supporting this whole week of SciShow. Go to Brilliant.org/SciShow to learn more.
感谢Brilliant对本周《科学秀》的支持，登陆Brilliant.org/SciShow了解更多。
When you hear the word "scurvy", you probably think of jokes about pirates, but this disease can actually be really serious.
当你听到‘坏血病’这个词的时候，你可能会想到关于海盗的笑话，但这种疾病真的会很严重。
Its symptoms include bleeding gums, bumpy, rashy skin, and joint pain, and if it's not treated, it can be deadly.
其症状包括牙龈出血、皮肤起疹子以及关节疼痛，如果不接受治疗，甚至可以致死。
It's not just a thing of the past, either.
这也不仅仅是过去的事情。
Scurvy still shows up in developing nations, and dozens of cases were reported in the United States in the last decade.
坏血病仍出现在发展中国家，美国在过去十年中也有几十起相关报道。
Thankfully, it is relatively easy to treat, all you need is a high dose of Vitamin C.
幸好这种疾病相对容易治疗，你只需要高剂量的维生素C就行了。
But here's the thing: If it weren't for a quirk of evolution, nobody would have ever gotten scurvy in the first place.
但问题是，如果不是因为进化的怪癖，没有人会得坏血病。
The reason Vitamin C cures scurvy is because the disease is actually caused by a Vitamin C deficiency.
维生素C可以治愈坏血病的原因是因为这种疾病其实是由于维生素C缺乏所引起的。
Without this vitamin, the body can't properly form collagen.
没了这种维生素，身体就不能正常形成胶原。
Collagen is the protein that makes up the vast majority of our connective tissues,
胶原是一种蛋白质，构成了我们绝大部分的结缔组织，
so without enough of it, things can go seriously wrong.
所以没有这种物质，事情会变得非常糟糕。
For example, scurvy patients can develop skin that's thin and fragile, where any wounds they get stay open and can't heal.
例如，坏血病病人的皮肤会变得很薄很脆弱，任何伤口都会无法愈合。
That can make them more likely to contract a life-threatening infection.
这会使得病人更容易感染致命的传染病。
Scurvy can also cause the collagen supporting blood vessels to fall apart, which can lead to hemorrhages.
坏血病还会导致支撑血管的胶原分解，从而导致出血。
So this protein is a pretty big deal and by extension, so is Vitamin C.
所以这种蛋白质很重要，维生素C也是。
To be clear, this vitamin isn't the only thing we need to make collagen.
要说明的是，这种维生素不是我们制造胶原所需的唯一物质。
But it is the only component of the collagen synthesis process our bodies can't naturally produce.
但它是胶原合成过程中唯一一种我们的身体无法自然生产的成分。
We need to consume it somehow. That's why a lack of it leads to scurvy, and why a high dose of it can cure the disease.
但我们需要消耗这一成分。因此少了它会导致坏血病，也因此高剂量维生素C可以治愈这种疾病。
But what's interesting is that most of nature doesn't have to deal with this.
但最有趣的是大部分自然生物并不要应付这种疾病。
Lots of animals can make their own Vitamin C without consuming it in their diets.
许多动物可以自己制造维生素C，而不需要在饮食中摄入。
And here's the kicker: Our very distant primate ancestors could do this, too.
更奇妙的是，我们非常遥远的灵长类祖先也能做到这一点。
More than 60 million years ago, the branch of primates that now includes humans did have the ability to make Vitamin C.
六千万年前，灵长类动物的一个分支，现在包括人类，确实有能力制造维生素C。
But then we lost it. More specifically, we lost the ability to make an enzyme called GULO.
但我们失去了这种能力。更准确的说，我们失去了制造Gulo酶的能力。
Just like with collagen, the process of making Vitamin C is a process.
就像胶骨一样，制造维生素C的进程是有一个过程的。
But for this story, all you need to know is that the last step depends on GULO.
但在这个故事中，你所需要知道的是过程的最后一步取决于Gulo。
When you look at different animals' genomes, you'll see that most animals have the gene that codes for this enzyme.
当你观察不同动物的基因组时，你会看到大部分的动物都有编码这种酶的基因。
And those that do can tweak how much or how little Vitamin C they produce.
有这种能力的动物都可以调整它们生产维生素C的量。
Like, rabbits pump out way more GULO enzymes during the winter months
比如，兔子在冬天的几个月里会分泌更多的Gulo
when Vitamin C-rich foods are in short supply, and goats can really crank it out when they're sick or stressed.
因为此时维生素C丰富的食物不多，在生病或压力大的时候真的很容易生产出维生素C。
Even animals toward the bottom of the evolutionary tree, like sponges and jellyfish,
甚至是进化树底层的动物，如海绵和水母，
have the gene responsible for GULO, which means it's existed for a very long time.
都有负责生产Gulo的基因，这意味着Gulo已经存在很长时间了。
The only members of the no-GULO club are guinea pigs, some bats and birds, most fish and many primates, including humans.
无Gulo俱乐部的唯一一批成员是豚鼠、一些蝙蝠和鸟类、大部分鱼类以及很多灵长类动物，包括人类。
So in our evolutionary past, our very distant ancestors had the ability to make GULO and therefore Vitamin C.
所以在我们的进化历史中，我们非常遥远的祖先有制造Gulo的能力，因此也有制造维生素C的能力。
But somewhere in primate evolution, a random mutation broke it.
但在灵长类进化的某个阶段，一种随机突变打破了它。
This might seem more than a little unfair, but you have to remember, mutations are random.
这似乎不太公平，但大家要记住，突变是随机的。
Most of the time, they're harmless and unnoticeable, but sometimes they affect an important gene.
大多数时候，它们是无害且不明显的，但有时它们会影响到一个重要的基因。
And when they do… well, it just kind of stinks.
当被影响到时，就会让人厌恶。
We can tell this happened to GULO because its gene is actually still in our genetic code
当Gulo受影响时，我们可以辨别的出来，因为其基因仍在我们的遗传密码中
although these days, it's just something called a pseudogene.
虽然如今，它只是一种叫做假基因的东西。
That's a copy of a DNA sequence that accumulated enough mutations
这是一组基因序列的复制品，这组基因序列聚集了充足的且
that it can't perform its original job or in the case of the GULO gene,
无法执行原本工作的突变或是在Gulo的情况中，
accumulated enough that it's totally nonfunctional.
聚集了充足的且完全失去功能的突变。
Pseudogenes actually crop up all the time, and the GULO gene is one of about 20,000 others in our genome.
假基因实际上一直在出现，并且Gulo基因是我们基因组中约两万个基因之一。
For reference, we have about 27,000 genes that actually make what they're supposed to.
作为参考，我们有大约27000个基因，它们实际上可以产生它们应该有的东西。
So, you know… our genomes are kind of a mess. But that's a little beside the point here.
所以我们的基因组有点混乱，但这有点离题了。
The real question is, why did the nonfunctional GULO gene get passed down in the first place?
真正的问题是，为什么无功能的Gulo基因遗传了下来？
After all, we can literally die without Vitamin C.
毕竟，没有维生素C，我们真的会死。
So it seems like the first primates to get this broken gene should have died before they could pass it along to their offspring.
因此，似乎第一批获得这种断裂基因的灵长类动物应该在将其传给后代之前就已经死亡了。
Well, scientists have looked into it, and they've come up with a hypothesis about what happened.
科学家对此进行了调查，他们提出了一种假设。
A part of it could be that there is some benefit to ditching the GULO gene.
部分原因可能是抛弃Gulo基因有一些好处。
GULO can create hydrogen peroxide as a byproduct of its reaction,
作为其反应的副产品，Gulo可以创造过氧化氢，
which can form particles called free radicals when it breaks down.
当它分解时可以形成叫做自由基的粒子。
These are little free-floating electrons that have the potential to harm cells and make certain diseases more likely.
这是一些小小的自由浮动的电子，可能会伤害细胞，更有可能造成某些疾病。
So it seems helpful to produce as few of them as possible.
因此，尽可能少地生产它们似乎是有帮助的。
But then again, that's a marginal benefit at best, considering what happens without Vitamin C.
但考虑到没有维生素C会发生什么情况，这充其量只是一个边际效益。
So the better explanation seems to be that the GULO pseudogene wasn't eliminated
所以更好的解释似乎是Gulo假基因没有被消除
because there just wasn't enough selective pressure.
因为没有足够的选择压力。
Not making GULO is easy to compensate for if you're an animal that consumes plenty of Vitamin C in your diet.
如果你是那种在饮食中消耗大量维生素C的动物，那么Gulo很容易得到弥补。
And at the point in our ancestry where primates lost the GULO gene,
回到我们的灵长类祖先失去Gulo基因那个点上，
they lived mostly in tropical environments, so their diets contained plenty of fruits and vegetables.
他们大部分住在热带环境中，所以他们的饮食中含有充足的水果和蔬菜。
So we probably never noticed the ability to synthesize this vitamin was gone because,well, we got it pretty easily in our diets.
所以我们或许从未注意到合成这种维生素的能力消失了，因为我们能从饮食中轻易获取。
Today, that seems pretty rough, considering that scurvy is still a problem.
如今，考虑到坏血病仍然是个问题，这种想法似乎相当粗略。
But unfortunately, that's just how evolution plays out sometimes.
但不幸的是，这就是进化的过程。
The best we can do now is try and make sure everyone gets what they need.
现在我们能做的就是确保每个人都得到他们需要的东西。
Scurvy isn't anything to joke about, but there are plenty of other great jokes you can make about storybook pirates.
坏血病可不能拿来开玩笑，但关于故事书中的海盗，你还可以开很多其他有趣的玩笑。
Like, anything about booty is a good time.
比如，和战利品有关的都不错。
Pirates are always collecting it, counting it, and divvying it up among their crew.
海盗们总是把战利品收集起来，数数，然后分给他们的船员。
And if you want to experience some of that for yourself, you can check out the Logic course from Brilliant.
如果你想亲自体验，你可以去看看Brilliant的逻辑课程。
It features a quiz that's all about pirates,
这门课的特色是关于海盗的小测试，
where you use your new logic skills to figure out who's cheating whom out of the most booty.
在测试中，你可以使用新学的逻辑技巧找出谁骗了谁并拿走了最多的战利品。
It's fun a time, and Brilliant also has a bunch of other courses that can help you cultivate your math and scientific thinking skills.
这是一段有趣的时光，Brilliant还有很多其他课程，可以帮助你培养数学课科学思考技巧。
They're also available offline using Brilliants iOS and Android app.
Brilliants iOS和安卓均可使用。
So whether you're stuck on the subway or sailing the seven seas, you'll be able to keep learning.
所以，无论你是困在地铁里，还是在七大洋航行，你都能继续学习。
If you're one of the first 200 people to sign up at Brilliant.org/SciShow, you'll also get 20% off an annual Premium subscription.
前200名注册Brilliant.org/SciShow的观众，可以获得年度会员8折优惠。
And you'll be helping SciShow make more content, too!
注册该网站也是在帮助我们制作更多内容！
