“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? It was only in college, when I read Douglas Hofstadter’s Godel, 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?“
That’s exactly right, and that’s why I think all school kids should read Gödel, Escher, Bach. I was lucky to buy myself a copy at 16 (I had seen the book mentioned in very different contexts that had not much to do with each other, and that made me curious), and it is fair to say it changed my life.