How Evolution Works

I’m back at my alma mater, like a sea turtle finding his home beach, and have been conducting interviews with people who often answer a question by going to the blackboard and scribbling an equation. I grasp the fundamental concept that God is a mathematician, but when someone goes to the equations to clarify a point we are typically venturing from the difficult to the incomprehensible. It becomes theater. “Scientist scribbles equations,” I write in my notebook. It becomes a scene. No actual data, much less what you’d call knowledge, is being transmitted at this point. I keep wanting to interject, “You missed a minus sign before the Lambda,” or some such impertinent jibe.

As I get older the camera pans back to reveal even more that I do not know and may never understand — more vast territory of knowledge of which I have only the dimmest awareness. Will I ever learn? Probably not. But we can always chart a course and bluster forward into the unknown. My father had a Ph.D. and I always wanted to have that credential, too, though without having to go through the fuss and bother of actually earning it. But it would be nice to have a deep-field look at some piece of the universe rather than always going wide.

Which is, perhaps, a decent segue to today’s excerpt of an article I recently wrote for my alumni magazine, [the Princeton Alumni Weekly,] about Peter and Rosemary Grant. They’re the famed evolutionary biologists who have spent their careers studying Darwin’s finches in the Galapagos. I had mentioned them a few months ago here on the blog.


An early explorer, the bishop of Panama, wrote after a 1535 visit to the volcanic archipelago, “It looked as though God had caused it to rain stones.” In his novel Galápagos,Kurt Vonnegut wrote of the Spanish explorers: “They did not claim the islands for Spain, any more than they would have claimed hell for Spain … ”

In the middle part of the 20th century, the biologist David Lack visited the Galápagos and stuck around only for a matter of months. Evidently he did not care for the place, as he wrote in Darwin’s Finches in 1947: “The biological peculiarities are offset by an enervating climate, monotonous scenery, dense thorn scrub, cactus spines, loose sharp lava, food deficiencies, water shortages, black rats, fleas, jiggers, ants, mosquitoes, scorpions, Ecuadorean Indians of doubtful honesty, and dejected, disillusioned European settlers….”

I assumed the Grants had made allowances for the harshness of the environment by jumping into a boat now and again for a quick trip to civilization to take in a movie or enjoy a fine meal with a glass of wine poured from the napkined wrist of a sommelier. But no. There were no daily departures. There wasn’t a boat at all. Without elaborate preparations, they could not leave. They had to bring all their supplies, including water, for months at a time. Still, the Grants loved what they were doing. Peter remembers that one time when he got off the island of Genovesa (another site for long-term fieldwork) he was asked, repeatedly, if he was grateful that he finally could take a hot shower. He said he’d prefer to finish his fieldwork. People persisted: Surely he was happy to be in civilized society! After protesting a few times, the scientist decided to play along. Sure, great to be back, he’d say — not meaning it at all.

The climate ranged from awful to brutal. There were prolonged droughts and prolonged, soaking, miserable rainy seasons. They would have to do much of their work early in the morning, before the heat became unbearable, the lava rock heating up under the equatorial sun. Weiner writes in The Beak of the Finch, “On many days the little island feels like the solar face of Mercury.”…

We all know how evolution works — or we think we know. Here’s what I would have told you (before interviewing the Grants) about the origin of new species: It involves “natural selection.” There are ecological niches. There’s competition. There’s genetic mutation. Life is hard and nasty and at some point you have the “survival of the fittest.” Is that good enough? No? OK. Time is a key factor: Lots and lots of time will allow evolution to happen. It’s like the secret ingredient, the sugar, in the recipe. With enough time your original species will turn into two species, including one that has horns or a tusk or dorsal spines or some kind of scary frill on the back of the head like a triceratops.

The truth is more complicated than that.

Evolution isn’t linear. There are always many species in the mix, and they are co-evolving, competing, innovating, reproducing, dying, sometimes even going extinct. You have variations within species. There is simultaneous divergence and convergence. There are contrary winds. There are genetic drifts and back-currents. There is hybridization. There are invasive species and a changing competitive landscape. Evolutionary change when viewed in the fossil record looks slow only because the oscillations — the herky-jerky improvisations — are hard to discern, and just the longer-term trends are readily preserved.

[Here's the whole story from the start.]

Joel Achenbach writes on science and politics for the Post's national desk and on the "Achenblog."
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Joel Achenbach · April 25