Bird’s-Eye View of Evolution : THE BEAK OF THE FINCH: A Story of Evolution In Our Time, <i> By Jonathan Weiner (Alfred A. Knopf: $25; 332 pp.)</i>
On the fourth floor of the American Museum of Natural History in New York City is an ancient world alive with oddities: a stalking Smilodon, the saber-toothed cat, Osteoborus, a prehistoric, bone-devouring dog and Syndyoceras cooki, an early deer that sported a sling-shot shaped antler on its snout. The museum’s new wing, devoted to mammals and their extinct relatives, is a vivid representation of current thinking about evolution and contains snapshots from hundreds of millions of years of evolutionary development. It represents one side in a debate over the nature of our kinship with the rest of creation that has remained vociferous and emotional ever since the appearance of Darwin’s “Origin of Species” 135 years ago. Despite the fact that we share some fundamental biological traits with these ancient creatures--or perhaps because we do--about half of the U.S. population still finds Darwin’s vision of life’s origins repellent and unbelievable.
Until very recently, the fossilized and skeletal remains of animals and plants, and the stories that we can reconstruct from the geological strata in which they were found, have been just about the only evidence to support evolution. The paucity of studies upholding one of its central tenets has been a continuing embarrassment to the scientific community. But recently, a group of scientists has found that by closely observing species over dozens of generations, and through the use of the relatively new tools of biotechnology to decode and compare DNA, it is possible to see evolution in action. Their work goes a long way toward upholding the mechanism by which a single, primordial ancestor branched out into the incredible diversity of life that now blankets the planet.
Jonathan Weiner’s engaging new volume, “The Beak of the Finch,” tells the story of one of these research teams, that of Peter and Rosemary Grant, both Princeton University ecologists. Their study of the resident finch population of a cindery, barnacle-shaped island in the Galapagos archipelago is a richly detailed documentation of evolution in the flesh, a landmark in evolutionary studies. In 1973, the Grants embarked on what they thought would be a yearlong sojourn on Daphne Major, among the smallest and least habitable of the islands in the Galapagos. Their curiosity was so piqued by the birds and their doings that they, or members of their research team, have returned to Daphne every year since. Throughout their almost constant watch, they have meticulously recorded the feeding and mating habits and the exact dimensions of the legs, beaks and wingspans of about 18,000 members of the ground and cactus finches that live on Daphne.
Weiner, a former editor at The Sciences magazine and author of two previous books, was persistent in his own pursuit of the apparently journalist-shy Grants. At first reluctant to talk to Weiner, they eventually warmed to him and brought him along to Daphne. He successfully knits together the tremendous amount of information he gathered there and in discussions with other researchers and conveys some difficult, abstract concepts in accessible terms. His fascination with the work of the Grants is apparent--and contagious. Weiner’s few lapses, such as his failure to define the key term species until well into the story, are bothersome but do not mar the overall fabric of the book.
“The Beak of the Finch” is as much about the scientific method and the inventiveness of the researchers in their pursuit of knowledge as it is about the information gathered. Weiner describes often tedious, and sometimes extraordinarily inventive, methods that the group uses to pin down the facts. One season was spent sifting through plots of volcanic dirt to get a precise handle on the kind, size and number of seeds available to the finches. The Grants then designed a unique nutcracker and came up with a “Struggle Index” to define how hard each of the kinds of seeds is for a bird to crack. The research team even undertook a ghoulish experiment in which they created strange hybrids from some of the island’s dead birds: female cactus finch heads attached to ground finch bodies. They floated these atop poles near male birds’ nests to determine what feature males use to find mates of their own species. (It was the beak.)
What the Grants learned through all this hard work--what makes their studies so important and what they themselves did not believe at the outset--is that evolution is not a glacially slow process, but one that is taking place all the time, all around us. “The closer you look at life, the more rapid and intense the rate of evolutionary change. The farther back in time you stand, the less you see,” Weiner writes. “The reasons for the discrepancy are not far to seek. If at any time in those millions of years a species changed swiftly, but the rest of the time it changed slowly, that start-and-stop motion would average out into a very sluggish movement.”
The speed at which evolutionary change can occur was brought home to the Grants when, over the course of a couple of years, the island experienced both drought and flood. Conditions reversed, no longer favoring finches with the largest beaks, which could crack open the largest seed pods, but rather selecting for those with the smallest beaks, when there was an abundance of smaller seeds. Minute variations in the dimensions of a bird’s main tool can mean life or death.
Weiner’s observations are not limited to the Galapagos. He introduces other scientists who are also working on the evolutionary frontier, several of them former graduate students of the Grants. Many are studying the effects of the evolutionary pressures humans are placing on the rest of the planet’s inhabitants. By applying billions of tons of pesticides to our agricultural lands, for example, we have created a population of insects that is utterly invulnerable to these poisons. Through our widespread deployment of antibiotics since the 1940s, we have pressured bacteria to evolve into increasingly resistant strains. The Grants themselves believe that global warming may already be having a profound effect on climactic conditions around the Equator--with unknown consequences for the life of the region and the earth.
Daphne Major’s residents include a group of finches, spoilers that inadvertently snap the stigma of cactus flowers as they feed on pollen. In their wake, they leave flowers that bear no fruit, and an island that is poorer for all its inhabitants, writes Weiner. Through the Grants’ and their followers’ work, Homo sapiens’ self-portrait becomes a little more complete. At the same time that we scrutinize the workings of the planet, we sweep away bits of the amazing vibrancy that nature has worked so furiously to evolve.
