WHEN the going gets tough, the tough evolve. A species of Darwin’s finch in the Galapagos has evolved a smaller beak to avoid competing with a larger-billed recent immigrant, possibly the clearest demonstration to date of competition driving evolution of a specific trait.
Peter and Rosemary Grant, evolutionary biologists at Princeton University, have been studying Darwin’s finches on the Galapagos Islands since the early 1970s. Until recently one small island, Daphne Major, was occupied only by a medium-sized species of ground finch, Geospiza fortis. During a drought in 1977, when the seeds they normally ate became scarce, the birds…
