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Let's say there's a disaster that sends humanity back to the Stone Age.
假如有一天，灾难使得人类文明倒退回了石器时代。
Can our knowledge and history survive?
我们的知识和历史能否得以保存？
The printed page will decompose. Hard drive storage will deteriorate. Even stones will eventually crumble.
印刷的纸张会分解。电脑硬盘的存储会退化。甚至连石头最终也会碎裂。
But we might have something inside us that can outlast these physical limitations: deoxyribonucleic acid.
但是也许我们体内有些东西能超越这些物理的极限：脱氧核糖核酸（DNA）。
DNA already stores our biological information.
DNA已经存储了我们的生物信息。
From eye color to skin tone, it programs our entire bodies.
从眼球颜色到肤色，它通过编码构造了我们整个身体。
DNA is made of four organic bases: adenine, guanine, cytosine, and thymine, or A, G, C, and T.
DNA是由四种碱基组成的：腺嘌呤、鸟嘌呤、胞嘧啶以及胸腺嘧啶，或简略地用A、G、C和T表示。
The specific sequence of these bases into groups of three, known as codons,
这些碱基每三个为一组形成的序列，称为密码子，
gives our cells instructions to make each of the proteins in our bodies.
这些密码子会指引细胞以形成体内各种蛋白质。
But this code can be used for other things, too, like secret messages.
但是这种编码也可做他用，比如编写秘密信息。
In 1999, scientists in New York created an alphabet
1999年，纽约科学家创建了一个字母表，
in which each of the 64 possible DNA codons substituted for a specific letter, number, or grammar symbol.
这个字母表包含了64种可能的DNA密码子，每个密码子都代表一个特定字母、数字或语法符号。
They spliced a 22-character message into a long strand of DNA and surrounded it with specific genetic markers.
他们根据这个字母表，将一段22个字符的信息转译成一段长的DNA链，并且在周围加上特定的基因标记。
They then hid the DNA over a period in a type-written letter with only a small smudge to give the location away.
他们将这段DNA隐藏在一封打印信件的一个句号上，仅仅使用了一个小污渍来提示这段信息的位置。
They mailed the letter back to themselves. Then they examined the letter looking for the DNA strand.
他们将这封信件寄回自己。再次收到信件，他们检查了这封信件来寻找那段DNA链。
Once the DNA strand was located, they found the genetic markers.
他们找到了DNA链，也找到了基因标记。
Then, they sequenced the DNA and successfully decoded the message.
而后，他们将这段DNA排序并且成功地破译了这段信息。
It soon became obvious that DNA cryptography could code for much more than simple text.
很快，科学家发现DNA编码不仅限于编译简单的文本。
By translating the 1's and 0's of binary code into DNA codons,
通过将二进制的1和0翻译成DNA密码子，
digital data could be programmed into synthetic DNA, then decoded back into its original form.
我们可以将数码信息编译进人工合成的DNA，然后再将它们解码到原来的形式。
In 2012, UK scientists encoded 739 kilobytes of computer files into DNA strands,
2012年，英国科学家将739KB的电脑文件编译入DNA链，
including all 154 Shakespeare sonnets and an excerpt from Martin Luther King's "I Have a Dream" speech.
其中包括莎士比亚所有的十四行诗（154首）以及一段节选摘自马丁·路德·金“我有一个梦想”的演讲。
And four years later, researchers at Microsoft and the University of Washington broke that record.
四年之后，来自微软和华盛顿大学的研究者打破了这项纪录。
They used binary coding to capture a whopping 200 megabytes of data,
他们将200MB由二进制编码译制的数据，
including the Universal Declaration of Human Rights and a high-def OK Go music video, all in strings of DNA.
包括“世界人权宣言”和一部高清的OK Go乐团的音乐录像，全部编入了DNA序列中。
As far as storage capacity goes, DNA stands out because of the surprising amount of information it can hold in so little space.
随着存储空间的增大，DNA因其特点“极小存储空间，惊人信息存量”而越发受到关注。
The current theoretical limit of DNA'S storage capacity is so high that you could fit 100 million HD movies on a pencil eraser.
现今DNA存储空间的极限，理论上可以达到将1亿部高清电影存储到一块橡皮大小的空间。
It's even conceivable that one day we could fit all of the information currently on the Internet into the space of a shoe box.
甚至可以想象有一天，我们能将所有当今网络上的信息，存入一个鞋盒大小的空间中。
Also, computers and the magnetic tape and discs that their information is stored on only last for a few decades,
而且，那些存储在电脑，磁带和光碟中的信息在降解且变得不可靠之前，
at most, before degrading and becoming unreliable.
最多仅仅能维持几十年。
Meanwhile, DNA has a half-life of 500 years, meaning that's how long it takes for half of its bonds to break.
与此同时，DNA的半衰期高达500年，这意味着DNA要经过500年，其中一半的连接才会断裂。
And if left in a cold and dark environment, DNA could potentially last for hundreds of thousands of years.
而如果保存在冰冷和阴暗的环境中，DNA有可能维持几十万年。
And if that isn't long enough, scientists experimented with having synthetic DNA auto-reproduce.
如果这还不够持久，科学家们还进行了人工合成DNA的自动复制实验。
After creating their own strands of DNA that spelled out the lyrics to the children's song "It's a Small World,"
他们合成了自己的DNA链，包含了儿童歌曲“这是一个小小的世界”的歌词信息，
they placed them into the genome of a microbe nicknamed Conan the Bacterium.
并且将这段DNA链放入了一个昵称为柯南细菌的微生物的基因中。
Conan belongs to a species which can survive in a vacuum, or without water, for six years,
柯南细菌是一种能够在真空或在无水环境中生存六年，
or come out unscathed after being exposed to a dose of radiation 1,000 times that which would kill a human.
或暴露在高于致命辐射剂量1000倍的环境中仍能毫发无损的物种。
According to the experiment, the bacterium was able to reproduce at least 100 generations without data loss.
根据这个实验结果，这个细菌能至少复制100代而无任何数据丢失。
Theoretically, if the organism had redundant copies of the information
理论上来说，如果生物体留有多余的拷贝信息，
that could be used to automatically correct mistakes, the information could stay preserved even longer.
这些信息能被主动用来进行自我修复错误，而这段信息也因此能被保存更长时间。
So one day, you might be able to create a living, growing, knowledge archive in your own backyard,
所以有一天，你也许能在自己的后院“种”一个鲜活的、发展的知识库，
and its seeds might carry your family's history, a detailed breakdown of the world's political upheavals,
它的种子可能将携带你的家族史，世界政治动荡的详解，
or the sum of humanity's knowledge into forests and across continents.
或是深入丛林，横跨大陆的人类全部知识。
Perhaps even into the far reaches of space.
甚至能够触及宇宙深处。
Though we might one day disappear, perhaps our legacy can still live on, if anyone would think to find it.
尽管有一天我们会消失，但或许我们的知识遗产将得以传承，如果任何人有意探寻的话。
