Charles Darwin spent only five weeks on the Galápagos Islands, and at first, the British biologists Peter and Rosemary Grant didn’t plan to stay very long either — a few years at most.
They landed in 1973 on the tiny uninhabited island of Daphne Major, the cinder cone of an extinct volcano. (Darwin himself never set foot there.) Daphne is as steep as a roof, with cliffs running all around the base, and just one small spot on the outer slope flat enough to pitch a tent.
Their goal, as they relate in their new book, “40 Years of Evolution,” was to study finches in the genus Geospiza — the birds that gave Darwin some of his first inklings of evolution by natural selection — and to try to reconstruct part of their evolutionary history. Instead, they made an amazing discovery.
After several years of meticulous measurements, the Grants and their students realized that the finches’ dimensions were changing before their eyes. Their beaks and bodies were evolving and adapting from year to year, sometimes slowly, sometimes strikingly, generation after generation. The researchers were watching evolution in real time, evolution in the flesh
Peter and Rosemary Grant on Daphne Major, capturing and measuring finches. Their work documented the evolution of finches in the genus Geospiza in real time.
Darwin never dreamed that was possible. In the first chapter of “On the Origin of Species,” he writes that while natural selection is at work everywhere and always, “we see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages.”
The Grants discovered that Darwin’s process was more powerful than he thought. So they stayed on, and on. Daphne Major turned out to be a perfect theater for watching evolution in action — big enough to support many hundreds of finches, but small enough that the Grants and their students and assistants could band and recognize and measure almost every bird.
In researching my own book, “The Beak of the Finch,” I came to know the Grants well. When I first met them, more than two decades ago, they were in their 50s, cheerfully focused, understated, competent. They were also very fit, to use Darwin’s word. They had to be, to carry all their food and water up the cliff of the desert island.
They kept up their watch during years of downpours and years of drought — seasons of feast and famine for the finches. And Darwin’s process unfolded before their eyes in intense episodes that illustrated better than anything in the Origin the struggle for existence, and the ways that life adapts and emerges fitter from the struggle.
When I read “40 Years of Evolution,” I started near the end. I wanted to know more about the Grants’ latest discovery, which I wish I could have witnessed in person.
Its own origins date to 1981, when a strange finch landed on the island. He was a hybrid of the medium-beaked ground finch and the cactus finch. He had the sort of proportions that touch our protective feelings: a big head on a stout body. In other words, he was cute. They called him Big Bird.
Hybrids are not unknown among Darwin’s 13 species of finches, but they are rare. Because they evolved so recently, birds of these different species can mate but ordinarily choose not to. (Our own ancestors seem to have felt the same way about Neanderthals.)
Big Bird had a strange song that none of the finch watchers had ever heard. His feathers were a rich, extra-glossy black. He had more tricks in his repertory than his neighbors: He could crack the spiky, troublesome seeds of the Tribulus plant, normally the specialty of the big-beaked ground finch, as well as small seeds favored by the small-beaked ground finch. He could dine on the nectar, pollen and seeds of the cactus, which belongs to the cactus finch.
Big Bird mated with a medium-beak on Daphne. Their offspring sang the new song of Big Bird. And slowly, Big Bird became a patriarch. He lived 13 years, a long time for one of Darwin’s finches. His children, grandchildren and great-grandchildren all sang his song, and they were clannish. They roosted in hearing distance of one another on the slopes of Daphne Major. What’s more, they bred only among their kind, generation after generation.
Big Bird’s lineage has now lasted for 30 years and seven generations. The Grants are cautious about its prospects — “It is highly unlikely that we have witnessed the origin of a long-lasting species, but not impossible,” they write — but other scientists are buzzing.
“I think it’s fantastic, the most exciting research finding I’ve read in the last decade,” said Jonathan B. Losos, an evolutionary biologist at Harvard.
The Grants say that if the Big Birds are, in fact, a species, they would call them Geospiza strenuirostris, from the Latin word meaning strong, exceptionally vigorous and active.
But alas, there are rough times ahead in the Galápagos, as in every other place affected by global warming. In the coming decades, as the climate of these islands grows warmer and wetter, Daphne may lose its cactus. And Big Bird can’t live without cactus.
Even in 40 years, of course, you can’t expect to witness the whole story of evolution, which has been going on for nearly four billion. Still, it turns out that if you know what to look for, put yourself in the right place and keep your eyes open, you can see a lot. The Grants have won just about every award in their field, including the prestigious 2009 Kyoto Prize in Basic Science. (The Nobel Prizes don’t have a category for evolution.)
“The Grants’ work is possibly the most important research program in evolutionary biology in the last half-century,” Dr. Losos told me in an email. “It has reshaped both how we understand evolution and how we study it. Before their work, no one was trying to study evolution in action — now it seems that everyone is.”
And life on Daphne was kind to the Grants. They never seemed to age, although Peter’s beard grew almost as long and white as the celebrated beard of Darwin, whom he resembles somewhat. When they weren’t camped on Daphne, they analyzed their data at Princeton in adjoining offices with the door open between them. They write books and papers together, give lectures together, finish each other’s sentences.
There’s an old proverb, “Just sink one well deep enough.” For the Grants, Daphne Major has been a magic well. With their four decades of work on the island, they’ve made it a magnificent microcosm, a model of life on Earth. And with their long collaboration on Daphne and at Princeton (where they’re now emeritus professors), they make a model for how to live a happy life.
A few nights ago, I called the Grants at home in Princeton to talk about Big Bird. They sounded the same as ever, still fascinated by the finches and still finishing each other’s sentences. I asked when the significance of the story had dawned on them.
“Maybe in 2007, we really grasped what was going on,” Peter said.
“But it was a very gradual process,” Rosemary added. “No eureka moment.”
If they hadn’t stayed on, hadn’t kept watching all those years, they would never have witnessed this surprise ending. “But then,” Rosemary said, “you could almost say that anything we would see on Daphne, we didn’t expect.”
Rosemary does most of the talking on the phone these days; Peter had warned me in an email, “I am acoustically challenged.” He recently had a hip replacement, from which he is recovering nicely. They’re both 77. They can’t keep going back to Daphne year after year.
“But we’d like to monitor and see how our Big Birds are doing,” Rosemary said with a small laugh.
At the end of the last chapter of “40 Years of Evolution,” there’s a page with two photographs. One shows the Grants at work in the island’s only cave, where they did their cooking and stored their supplies. “A cave for cool reflection,” the caption says.
Under that is a little photograph of two brown boots, battle-scarred from all that hiking up and down on lava.
“Boots,” the caption says. “Finis.”
