Wide, slender, pointed, blunt: The many flavors of beak sported by the finches that flit about the remote Galápagos Islands were an important clue to Darwin that species might change their traits over time, adapting to new environments.

Now scientists peering into the DNA of these birds have found a piece of genetic code that contributes to the striking variation in beak shape. (Watch a video to learn more about the unique animals of the Galápagos.)

The discovery is described in a study published today in the journal Nature that also brings fresh insights into the forces that drive the formation of new species. The birds' past—and their current connections to one another—is more tangled than previously thought.

The Galápagos finches are ideal subjects for