The break of the finch: A remarkable study of birds in the Galapagos Islands shows Darwin was not only right about evolution, but he underestimated the strength of his own theory, says Jonathan Weiner

A t a party a few years ago, I told some friends I had found a new subject to write about. Afterwards, a woman came up to me.

'Did I hear you say you're writing about evolution?' she asked.

'Yes.'

'Are you for it, or against it?'

A week later I was sitting in the dentist's chair, and the nurse asked me what I was working on.

'Evolution,' I said. She brought her eyes down closer to mine and said through her mask: 'Well, I'm born-again, so you know what I think about that.' I was in no position to argue.

Late last year, my Macintosh computer bombed, with the final draft of the final chapter of my book trapped inside it. I called our local computer store. It was almost closing time, but the manager let me bring in the machine. After almost an hour with his hands deep in my Mac, like a surgeon in an emergency room, he looked up to ask what the book was about. I told him.

'I have a PhD in engineering,' he said, 'and I can tell you that this world was made by God within the last 10,000 years.' Again, I was not in a position to argue.

According to polls, nearly half the population of the United States believes that Charles Darwin was wrong. I always assumed it was the polls that were wrong. But now I keep bumping into that other half of the nation at the post office, at the photocopying shop - wherever my book errands take me. Fundamentalists are still a power in this country, and some of them are still fighting evolution in the classrooms. The religious right claims to have helped to elect more than 12,000 of its members to school boards across the nation within the last five years.

For any student of evolution, this would be a strange phenomenon. To me it seems particularly strange because of the band of biologists I have been following, here and in the Galapagos Islands.

Darwin himself never saw evolution happen, either in the Galapagos (where he spent only five weeks) or anywhere else. In The Origin of Species he wrote: 'We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages.'

That is how most of us think of evolution today. We hear the word and we picture fossils: the cryptic skulls of Neanderthals and Cro-Magnons; the wings of archaeopteryx, a bird flying in a stone. We try to imagine a process so slow it is visible only in successive layers of condensed geological time.

I still remember my surprise when I first heard about the work of Peter and Rosemary Grant of Princeton University. They study the most celebrated place in the science of evolution: the Galapagos archipelago, which is in the Pacific about 650 miles west of Ecuador. 'Origin of all my views,' Darwin called it once.

The Grants camp on a tiny desert island in the centre of the archipelago, an extinct volcano called Daphne Major. There, they observe Darwin's finches, the birds whose beaks inspired Darwin's first veiled hints about his revolutionary theory. 'What a shame he couldn't stay longer,' a creationist once wrote, a bit sarcastically, of Darwin and the Galapagos. No one will ever say that about the Grants. They and their daughters and a long line of assistants have been staying on Daphne, like sentries on a revolving watch, since 1973.

Each year they get to know every finch on the island, the way shepherds can tell every sheep in their flocks. They band the bird in the nest when it is eight days old. Then, when it grows a bit older, they measure its legs, its wingspan and its beak - especially its beak. They take a mug-shot of the beak of the finch in profile, from a distance of 27 centimetres. They also take a single drop of blood from its wing top. Finally they track its fate as it learns to hunt and peck for seeds on the lava rubble, and they watch as the bird mates and nests in the cactus - if it lives that long.

So far the Grants and their team have banded about two dozen generations of finches in the Galapagos - almost 20,000 birds. They are doing what Darwin could not do, going back to the islands again and again; and they are seeing there what Darwin did not imagine could be seen at all.

Back in 1977, for instance, they and their team witnessed a terrible drought. It was a year that highlighted Darwin's 'struggle for existence'. Flocks of Geospiza fortis, the most common finch on Daphne, were reduced from more than 1,000 that January to fewer than 200 by December. And the birds evolved. The beaks of the next generation were bigger, and proportionately narrower and deeper, which made them better instruments for opening the last tough seeds on the desert island.

No one had ever seen Darwin's process work that fast. And this was not evolution in a test-tube, or in a lab cage full of fruit flies, or in the moths of a polluted city. The Grants were watching natural selection in nature, in an environment as pristine as you can find on Earth.

In 1983, the Grants witnessed a flood: the wettest year of the century in the Galapagos. Thunderstorms turned Daphne from desert to jungle almost overnight. In the upheaval, many finches died, while others multiplied. This time the beaks of the next generation of fortis were smaller, which made them better adapted to the wealth of tiny seeds that covered their new green island. Again the birds had evolved, and again the Grants had seen their evolution and recorded it.

Grand patterns are beginning to emerge in the Grants' two decades of data, patterns that illuminate what Darwin called 'that mystery of mysteries', the origin of species. The drought, for instance, pushed fortis a quarter of the way in the direction of another species of finch, magnirostris. One quarter of the way toward the origin of a species, in a single year.

The Grants' team is also beginning to decode the messages in every drop of bird blood. Between the measurements of the birds' DNA, the Grants are reading the story of life from the outside in and from the inside out. They can see evolution in the flesh, and evolution in the blood. The DNA shows that these species are extremely young, still in their infancy. The Grants are present at the creation.

The burden of the creationists' cry is 'only a theory'. A little paperback entitled Handy Dandy Evolution Refuter states: 'Neither evolution nor creation can be tested as a scientific theory so believers in evolution or creation must accept either view by faith.'

In his book Evolution? The Fossils Say No], Duane Gish, a prominent creationist, declares: 'We do not know how the Creator created, what processes He used, for He used processes which are not now operating anywhere in the natural universe.' (The italics are his.)

Creationists have been making these sorts of claims, with very little change, since before 1859, when Darwin published The Origin. But today evolutionists are watching the evolution of guppies, grass, flies, moths, mice and elephants; of the cosmopolitan bacteria that live in the human gut, and of the human beings, too.

Taken together, these new studies suggest that Darwin did not know the strength of his own theory. He vastly underestimated the power of natural selection.

Debating the reality of the process feels as absurd as debating the existence of gravity. The Grants' work will be remembered as one of the great close-up case studies of science, rather like the classic stop-action runners and jumpers in the photographs of Eadweard Muybridge, or the fall of a drop of water in the photographs of A M Worthington, in which the viewer marvels at how a single droplet pulled by gravity can make such an elaborate splash, raising a liquid coronet.

In the same way, one line of finches landed in the Galapagos a few million years ago, and now there are 13 species of finches, and the Grants are watching the action that may be raising more on the islands before their very eyes.

Creation is not confined to a moment in the distant past. Creation continues. The roots of the tree of life are fixed deep in the earth, but the twigs shake in the slightest breeze. The action is as beautiful as anything we can see, and as real as anything we can measure. We can only be for it.

Jonathan Weiner's new book, 'The Beak of the Finch', is published by Jonathan Cape (pounds 18.99 hardback) on 21 July.

(Photographs omitted)