I’m re-reading a couple of science books I read a few years ago — The Violinist’s Thumb by Sam Kean and Microcosm by Carl Zimmer. Both are about cell biology, and while they’re addressed to the intelligent layman, they’re not gee-whiz pop science books. They really do present a fairly clear picture of what happens inside cells, and how we’ve learned about it all. Kean is far too fond of anthropomorphizing; his descriptions of DNA and other molecules give them very human intentions, and that’s bogus. In reality, the molecules are just bumping around at random, but the process happens so quickly that the results (one molecule fitting into another so as to catalyze a reaction) operate as if they were intentional.
Cells don’t reproduce sexually. They sometimes swap genetic material with one another, but that’s not quite the same thing. Cells reproduce by dividing in two. And no new cells are ever assembled from raw molecular ingredients — that hasn’t happened for billions of years, and may in fact have happened only once. All of the cells in all of the animals and plants that are alive today have arisen through the splitting of previously existing cells. And from the point of view of a cell (if we can speak of such a thing), in splitting it has budded off a daughter cell. A daughter cell isn’t a new-born: It’s still the same cell as before.
This fact has a dizzying consequence: That very first cell that somehow assembled itself 3.8 billion years ago is still alive. It’s you. It’s me. It’s all of life on Earth. With the possible exception of viruses, but I’ve read a theory that viruses evolved from the breakdown of more complete cells. They aren’t a separate creation, they’re just efficient parasites. Be that as it may, it’s humbling to realize that every single cell in your body is 3.8 billion years old. For the last 550 million years or so it was continuously an egg cell; each time an embryo differentiated, the cell that became you was one that remained an egg cell. Before that, you were just swimming around, being a cell.
That’s mind-blowing enough, but once we peer inside cells to discover what makes them tick. what we find is a vast array of chemical reactions, a constantly bubbling stew of molecules bumping against one another and catalyzing reactions. All behavior — all human behavior and all of the other behavior of every living thing on the planet — is ultimately a chemical process that occurs when molecules interact. We can’t even say that behavior is the result of chemical reactions. Behavior IS chemical reactions. Unimaginably complex chemical reactions, to be sure, but there’s nothing else going on. It’s all proteins and methyl groups and whatnot bumping into one another. That’s how you get Shakespeare; it’s also how you get a common garden slug. In fact, many of the same chemical processes that happened in Shakespeare also happen in a slug.
Of course, molecules pass in and out of cells all the time. A cell that couldn’t pass molecules in and out through its membrane would soon be dead. No cell is an island. Once you realize this, if you twist the zoom control all the way out and look at life on Earth as a whole, what you discover is that life on Earth is all one ongoing chemical reaction. It has been going on for 3.8 billion years, constantly stirred by energy from the sun. If we say, “That’s a redwood tree,” or, “That’s a sonnet by Shakespeare,” what we’re doing is giving a name to some small part of this single enormous chemical reaction.
This is humbling, but it’s also freeing. You and I are nothing but burbling masses of chemicals. The molecules are going to do whatever they’re going to do. Nobody is in control, so there’s no blame. Just relax and burble along.