Image: Lithops stone plant, UNB greenhouse, © Stephen Heard
I love used-book sales. A little while ago I went to one at a local church, where I was amused to find all the science fiction on the children’s table*. I didn’t ask why they’d sorted it there, but I can guess, because I’ve always read a lot of science fiction and I’ve gotten used to it being routinely dismissed as beneath the dignity of serious readers. The knock is frequently that it’s just not believable: methane-breathing aliens, intelligent gas clouds, galactic civilizations, and planet-sized toroidal starships are all so improbable that they’re for childish play, not adult attention.
But I’m a biologist, and that means I know a bit about improbability. Let me tell you, as improbability goes, science fiction has nothing on nature. I got thinking about this because I was up in our greenhouse, and walked by the stone plant (Lithops sp.) in the photo above. Lithops is a southern African plant that looks just like a little pebble. It has a single pair of fleshy leaves coloured to match the substrate. Most of the leaf is actually buried – just the tips poke above ground – but it can photosynthesize nonetheless because the leaf tips have transparent “leaf windows” that let the sun shine underground. Improbable enough for you? Pffft – those aren’t even close to the most improbable things about Lithops. Think about photosynthesis. Like every plant**, Lithops can extract energy from sunlight at an efficiency human engineers are still dreaming of. It does this with a body self-assembled from nothing but air, water, and dirt under the control of a program encoded by the order of four tiny molecules repeated in a string several metres long, curled up in a nucleus much, much, much smaller than the dot over the i in Lithops.
And Mr. Spock is improbable. Right.
I’ve learned never to bet against the occurrence in nature of improbable things. Woodpeckers with tongues so long their supports curl all the way around the skull? Check. A beetle that defends itself by using rocket fuel to spray boiling-hot poison from its anus? Check. Fish that change sex from male to female, then back to male? Check. You can’t make this stuff up; or rather, you could, but you wouldn’t be taken seriously, and they’d put your books on the kid’s table at church book sales.
That’s the power of evolution and time: it makes the improbable virtually certain. There may be a nearly infinite parameter space of imaginable creatures, but that parameter space is accessible to the powerful search engine of natural selection. Genetic mechanisms generate variety, selection sifts that variety so that a rare but advantageous new phenotype becomes common, and the process iterates generation by generation over millions of years. Evolution finds solutions to Earth’s problems that our most clever engineers wouldn’t think of. Those solutions can be elegant or kludgy, beautiful or horrifying – but almost no matter how improbable they might be, they are found. That’s how evolution has made Nature the endless source of jawdropping wonder that biologists love to explore***.
So I know where the church ladies put the improbable science fiction. I wonder where they would have put the stone plant?
This post is dedicated to the memory of Lewis Thomas (1913-1993), whose birthday was today. Thomas was a physician, a scientist, a poet, and especially a brilliant essayist. If you haven’t read his essays, you should: start with Lives of a Cell: Notes of a Biology Watcher. I hope he’d see “Science fiction, stone plants, and the certainty of improbable things” as an appreciation, not an appropriation, of his perspective on nature.
© Stephen Heard (firstname.lastname@example.org) November 25, 2015
***^That woodpecker tongues and bombardier beetles are sometimes held up as “evidence” for creationism betrays the awesome silliness of that movement. It’s not that strange and complex things couldn’t evolve – it’s that only evolution could produce the kind of strange and complex things that populate the Earth!