Since 1973, Peter Grant, Rosemary Grant, and their colleagues have studied natural selection in finches found on the Galápagos Islands. For over 30 years, the Grants have focused much of their work on one of the Galápagos Islands known as Daphne Major (Figure 1). This small island (0.34 km2) has a moderate degree of isolation (it is 8 km from the nearest island), an undisturbed habitat, and a resident population of Geospiza fortis, the medium ground finch (Figure 2).