Galapagos Finches, the subfamily that more than any other inspired Darwin to discover natural selection, are evolving so fast biologists may have seen a new species appear in the time they have been studying them.
Unusually, the claim isn't being made by the scientists responsible. Princeton Professors Peter and Rosemary Grant have said in their new book 40 Years of Evolution “It is highly unlikely that we have witnessed the origin of a long-lasting species, but not impossible.” Other scientists, however, are more confident the Grants have documented the real thing.
Few arguments are more beloved of creationists than the claim that no new species has been observed appearing. Darwin, however, thought natural selection worked too slowly to observe, writing, “we see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages.”
We can trace evolution through the fossil record, and to some extent in short-lived species such as bacteria, but until the Grants visited the uninhabited volcanic cone of Daphne Major in 1973 it was thought that birds operated on a slower path.
The Grants, however, noticed that the finches on Daphne Major were changing faster than anyone expected. The island is small enough, and the Grants hardy enough, that they and their assistants have managed to tag and measure most of the local birds and trace their descendents. The Grants' work was celebrated in Jonathan Weiner's Pulitzer Prize winning book The Beak of the Finch: A Story of Evolution in Our Time.
The Grants' work observing the way finches' eyes, bodies and most of all, beaks changed with time is hugely exciting. In The New York Times Weiner notes, “The Grants have won just about every award in their field.” Still, the changes they observed were similar to the ones seen in dogs, albeit driven by natural, rather than artificial, selection. A pitbull and poodle differ greatly, but they are still both Canis familiaris, capable of interbreeding and producing fertile offspring.
The Grants were witnessing several species change with time, until in 1981 a hybrid finch turned up from a neighboring island. Hybrid finches happen now and then, just as ligers and tigons occasionally delight zookeepers, but this does not mean a new species has occurred. Usually enough of the offspring are sterile that a sustainable new species is impossible.
Peter and Rosemary Grant. This Galapagos finch appears to have founded an entire new species
However, the Grants' hybrid, named Big Bird, proved the exception. The result of a love match between a medium-beaked ground finch and a cactus finch, he was supremely well adapted to the environment. He could crack a wide array of Tribulus seeds, where many ground finches can only manage seeds whose size match their beaks, while also being able to feed on cactus nectar, pollen and seeds like a cactus finch.
Big bird was also exceptionally cute to human eyes, with a big head, extra-black feathers and a unique song. A medium-beak ground finch apparently agreed, and the pair started a clan. The offspring prefer to mate with each other than to interbreed with either of the species from which Big Bird sprung, and equipped to eat a variety of foods have thrived on Daphne Major's nearly barren slopes, even recovering from a terrible drought that reduced their numbers to two.
“Maybe in 2007, we really grasped what was going on,” Peter Grant told Weiner. Only the likelihood that Global Warming will deplete their food supply looks likely to prevent their long-term success. If the birds survive climate and taxonomy the Grants have chosen the name Geospiza strenuirostris in recognition of their strength.
