Selections from the special section on
harles Darwins 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 Darwins view of life. And today, those of us who live in the United States, by many measures the worlds leading scientific nation, find ourselves in a house divided. Half of us accept Darwins theory, half of us reject it, and many people are convinced that Darwin burns in hell. I find that old debate particularly strange, because Ive spent some of the best years of my life as a science writer peering over the shoulders of biologists who actually watch Darwins process in action. What they can see casts the whole debate in a new lightor 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, Its 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 Darwins 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 Darwins process in Darwins islands, the Galápagos, watching Darwins 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 Beagles 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 speciessymbiotic insects and plantsthat 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.