I should have loved biology (2020)

我本该热爱生物学 (2020)

By James Somers 作者：James Somers

I should have loved biology but I found it to be a lifeless recitation of names: the Golgi apparatus and the Krebs cycle; mitosis, meiosis; DNA, RNA, mRNA, tRNA. In the textbooks, astonishing facts were presented without astonishment. Someone probably told me that every cell in my body has the same DNA. But no one shook me by the shoulders, saying how crazy that was. 我本该热爱生物学，但我发现它不过是枯燥的名词背诵：高尔基体、克雷布斯循环；有丝分裂、减数分裂；DNA、RNA、mRNA、tRNA。在教科书中，那些令人惊叹的事实被平淡地陈述出来，毫无惊奇感。或许有人曾告诉我，我体内的每个细胞都拥有相同的 DNA，但没有人曾摇着我的肩膀，告诉我这有多么疯狂。

I needed Lewis Thomas, who wrote in The Medusa and the Snail: For the real amazement, if you wish to be amazed, is this process. You start out as a single cell derived from the coupling of a sperm and an egg; this divides in two, then four, then eight, and so on, and at a certain stage there emerges a single cell which has as all its progeny the human brain. The mere existence of such a cell should be one of the great astonishments of the earth. People ought to be walking around all day, all through their waking hours calling to each other in endless wonderment, talking of nothing except that cell. 我需要的是刘易斯·托马斯（Lewis Thomas），他在《水母与蜗牛》（The Medusa and the Snail）中写道：如果你想感受真正的惊奇，那么这个过程本身就是。你最初只是一个由精子和卵子结合而成的单细胞；它分裂成两个，然后是四个、八个，以此类推。在某个阶段，会出现一个单细胞，它所有的后代最终构成了人类的大脑。仅仅是这样一个细胞的存在，就应该是地球上最伟大的奇迹之一。人们本该整天走来走去，在清醒的每一刻都怀着无尽的惊叹互相呼唤，除了谈论那个细胞，别无他话。

I wish my high school biology teacher had asked the class how an embryo could possibly differentiate—and then paused to let us really think about it. The whole subject is in the answer to that question. A chemical gradient in the embryonic fluid is enough of a signal to slightly alter the gene expression program of some cells, not others; now the embryo knows “up” from “down”; cells at one end begin producing different proteins than cells at the other, and these, in turn, release more refined chemical signals; …; soon, you have brain cells and foot cells. How come we memorized chemical formulas but didn’t talk about that? 我真希望我的高中生物老师能问问全班，胚胎究竟是如何分化的——然后停下来让我们真正思考一下。整个学科的精髓就在这个问题的答案里。胚胎液中的化学梯度足以成为一种信号，去改变部分细胞而非全部细胞的基因表达程序；于是胚胎分清了“上下”；一端的细胞开始产生与另一端不同的蛋白质，而这些蛋白质反过来又释放出更精细的化学信号；……很快，你就有了脑细胞和足细胞。为什么我们背诵了化学公式，却从不讨论这些？

It was only in college, when I read Douglas Hofstadter’s Gödel, Escher, Bach, that I came to understand cells as recursively self-modifying programs. The language alone was evocative. It suggested that the embryo—DNA making RNA, RNA making protein, protein regulating the transcription of DNA into RNA—was like a small Lisp program, with macros begetting macros begetting macros, the source code containing within it all of the instructions required for life on Earth. Could anything more interesting be imagined? 直到大学读到道格拉斯·侯世达（Douglas Hofstadter）的《哥德尔、艾舍尔、巴赫》（Gödel, Escher, Bach）时，我才理解了细胞作为递归自修改程序的本质。单是这种语言描述就足以引人深思。它暗示了胚胎——DNA 生成 RNA，RNA 生成蛋白质，蛋白质调节 DNA 到 RNA 的转录——就像一个微小的 Lisp 程序，宏生成宏，宏再生成宏，其源代码中包含了地球生命所需的所有指令。还能想象出比这更有趣的事物吗？

Someone should have said this to me: Imagine a flashy spaceship lands in your backyard. The door opens and you are invited to investigate everything to see what you can learn. The technology is clearly millions of years beyond what we can make. This is biology. –Bert Hubert, “Our Amazing Immune System” 有人本该这样告诉我：想象一下，一艘炫酷的宇宙飞船降落在你的后院。舱门打开，你被邀请去调查一切，看看你能学到什么。这些技术显然领先我们所能制造的几百万年。这就是生物学。——Bert Hubert，《我们神奇的免疫系统》

In biology class, biology wasn’t presented as a quest for the secrets of life. The textbooks wrung out the questing. We were nowhere acquainted with real biologists, the real questions they had, the real experiments they did to answer them. We were just given their conclusions. 在生物课上，生物学并没有被呈现为一场对生命奥秘的探索。教科书榨干了探索的乐趣。我们根本没有接触过真正的生物学家，不知道他们面临的真正问题，也不知道他们为了解答这些问题所做的真正实验。我们得到的仅仅是他们的结论。

For instance I never learned that a man named Oswald Avery, in the 1940s, puzzled over two cultures of Streptococcus bacteria. One had a rough texture when grown in a dish; the other was smooth, and glistened. Avery noticed that when he mixed the smooth strain with the rough strain, every generation after was smooth, too. Heredity in a dish. What made it work? This was one of the most exciting mysteries of the time—in fact of all time. Most experts thought that protein was somehow responsible, that traits were encoded soupily, via differing concentrations of chemicals. Avery suspected a role for nucleic acid. 例如，我从未听说过 20 世纪 40 年代一位名叫奥斯瓦尔德·艾弗里（Oswald Avery）的人，他曾对两种链球菌培养物感到困惑。一种在培养皿中生长时质地粗糙；另一种则光滑且有光泽。艾弗里注意到，当他将光滑菌株与粗糙菌株混合时，之后每一代的菌株都是光滑的。这是培养皿中的遗传现象。是什么在起作用？这是当时——甚至是有史以来——最令人兴奋的谜团之一。大多数专家认为蛋白质在其中起作用，认为性状是通过不同浓度的化学物质以“汤”的形式编码的。艾弗里则怀疑核酸在其中扮演了角色。

So, he did an experiment, one we could have replicated on our benches in school. Using just a centrifuge, water, detergent, and acid, he purified nucleic acid from his smooth strep culture. Precipitated with alcohol, it became fibrous. He added a tiny bit of it to the rough culture, and lo, that culture became smooth in the following generations. This fibrous stuff, then, was “the transforming principle”—the long-sought agent of heredity. Avery’s experiment set off a frenzy of work that, a decade later, ended in the discovery of the double helix. 于是，他做了一个实验，一个我们在学校实验台上就能复现的实验。他仅用离心机、水、洗涤剂和酸，就从光滑的链球菌培养物中提纯了核酸。用酒精沉淀后，它变成了纤维状。他将少量这种物质加入到粗糙的培养物中，瞧，该培养物在随后的几代中变得光滑了。这种纤维状物质，就是“转化因子”——人们苦苦寻找的遗传介质。艾弗里的实验引发了一场研究狂潮，十年后，这场狂潮最终导致了双螺旋结构的发现。

In his “Mathematician’s Lament,” Paul Lockhart describes how school cheapens mathematics by robbing us of the questions. We’re not just asked, hey, how much of the triangle takes up the box? That’s a puzzle we might delight in. (If you drop a vertical from the top of the triangle, you end up with two rectangles cut in half; you discover that the area inside the triangle is equal to the area outside.) Instead, we’re told that if you ever find yourself wanting the area of a triangle, here’s the procedure: 保罗·洛克哈特（Paul Lockhart）在《数学家的哀歌》（Mathematician’s Lament）中描述了学校是如何通过剥夺我们的提问权来贬低数学的。我们不仅仅是被问到：嘿，三角形占了盒子的多少面积？那是一个我们可能会乐在其中的谜题。（如果你从三角形的顶点画一条垂线，你会得到两个被对半切开的矩形；你会发现三角形内部的面积等于外部的面积。）相反，我们被告知的是：如果你想求三角形的面积，请按这个步骤操作：

Biology is like that, but worse because it’s a messier subject. The facts seem extra arbitrary. We’re told to distinguish “lipid bilayers” from “endoplasmic reticula” without understanding why we care about either in the first place. 生物学也是如此，甚至更糟，因为它是一门更混乱的学科。事实显得格外武断。我们被要求区分“脂质双分子层”和“内质网”，却根本不理解我们为什么要关心这两者。

Enormous subjects are best approached in thin, deep slices. I discovered this when first learning how to program. The textbooks never worked; it all only started to click when I started to do little projects for myself. The project wasn’t just motivation but an organizing principle, a magnet to arrange the random iron filings I picked up along the way. I’d care to learn about some abstract concept, like “memoization,” because I needed it to solve my problem; and these concepts would lose their abstractness in the light of my example. 宏大的学科最好通过细致而深入的切片来学习。我在初学编程时发现了这一点。教科书从来没用；直到我开始自己做一些小项目，一切才开始变得清晰。项目不仅是动力，更是一种组织原则，像磁铁一样将我沿途收集到的随机铁屑排列整齐。我会主动去学习一些抽象概念，比如“记忆化”（memoization），因为我需要它来解决我的问题；而在我实际案例的映照下，这些概念就不再抽象了。

Biology is no different. Learning begins with questions. How do embryos differentiate? Why are my eyes blue? How does a hamster turn cheese into muscle? Why does the coronavirus make some people much sicker than others? 生物学也不例外。学习始于问题。胚胎是如何分化的？为什么我的眼睛是蓝色的？仓鼠是如何把奶酪变成肌肉的？为什么冠状病毒会让某些人比其他人病得更重？