November 2005

The Illusion of DesignDarwin’s ShrinkEvolution in ActionThe Origins of FormUniverse
Image by Jac Depczyk,;

Evolution in Action

Finches, monkeyflowers, sockeye salmon, and bacteria are changing before our eyes.

harles Darwin’s wife, Emma, was terrified that they would be separated for eternity, because she would go to heaven and he would not. Emma confessed her fears in a letter that Charles kept and treasured, with his reply to her scribbled in the margin: “When I am dead, know that many times, I have kissed and cryed over this.”

Close as they were, the two could hardly bear to talk about Darwin’s view of life. And today, those of us who live in the United States, by many measures the world’s leading scientific nation, find ourselves in a house divided. Half of us accept Darwin’s theory, half of us reject it, and many people are convinced that Darwin burns in hell. I find that old debate particularly strange, because I’ve spent some of the best years of my life as a science writer peering over the shoulders of biologists who actually watch Darwin’s process in action. What they can see casts the whole debate in a new light—or it should.

Darwin himself never tried to watch evolution happen. “It may metaphorically be said,” he wrote in the Origin of Species,

that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers. . . . We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages.

Darwin was a modest man who thought of himself as a plodder (one of his favorite mottoes was, “It’s dogged as does it”). He thought evolution plodded too. If so, it would be more boring to watch evolution than to watch drying paint. As a result, for several generations after Darwin’s death, almost nobody tried. For most of the twentieth century the only well-known example of evolution in action was the case of peppered moths in industrial England. The moth had its picture in all the textbooks, as a kind of special case.

Then, in 1973, a married pair of evolutionary biologists, Peter and Rosemary Grant, now at Princeton University, began a study of Darwin’s process in Darwin’s islands, the Galápagos, watching Darwin’s finches. At first, they assumed that they would have to infer the history of evolution in the islands from the distribution of the various finch species, varieties, and populations across the archipelago. That is pretty much what Darwin had done, in broad strokes, after the Beagle’s five-week survey of the islands in 1835. But the Grants soon discovered that at their main study site, a tiny desert island called Daphne Major, near the center of the archipelago, the finches were evolving rapidly. Conditions on the island swung wildly back and forth from wet years to dry years, and finches on Daphne adapted to each swing, from generation to generation. With the help of a series of graduate students, the Grants began to spend a good part of every year on Daphne, watching evolution in action as it shaped and reshaped the finches’ beaks.

At the same time, a few biologists began making similar discoveries elsewhere in the world. One of them was John A. Endler, an evolutionary biologist at the University of California, Santa Barbara, who studied Trinidadian guppies. In 1986 Endler published a little book called Natural Selection in the Wild, in which he collected and reviewed all of the studies of evolution in action that had been published to that date. Dozens of new field projects were in progress. Biologists finally began to realize that Darwin had been too modest. Evolution by natural selection can happen rapidly enough to watch.

Now the field is exploding. More than 250 people around the world are observing and documenting evolution, not only in finches and guppies, but also in aphids, flies, grayling, monkeyflowers, salmon, and sticklebacks. Some workers are even documenting pairs of species—symbiotic insects and plants—that have recently found each other, and observing the pairs as they drift off into their own world together like lovers in a novel by D.H. Lawrence.

To learn about some of these studies, see the rest of Jonathan Weiner’s article in the print issue of Natural History.

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Jonathon Weiner

Jonathon Weiner began writing about evolution in 1990, when he met Peter and Rosemary Grant, who observe evolution firsthand in finch populations in the Galápagos. Weiner’s book The Beak of the Finch (Alfred A. Knopf) won a Pulitzer Prize in 1994. He is a professor in the Graduate School of Journalism at Columbia University, in New York City. He is also working on a book about human longevity for Ecco Press.

The Illusion of DesignDarwin’s ShrinkEvolution in ActionThe Origins of FormUniverse

Copyright © Natural History Magazine, Inc., 2005

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