Sometimes a burst of diversification is accompanied by dramatic morphologi - cal evolution—an event known as an adaptive radiation. When the ancestors of Darwin’s finches arrived on the Galápagos Islands a few million years ago, they did not simply evolve into 14 barely distinguishable species. They evolved dis- tinctive beaks and behaviors that allowed them to feed on cactuses, crack hard nuts, and even drink the blood of other birds. The Great Lakes of East Africa also saw an adaptive radiation of cichlid fishes. These enormous lakes are geologically very young, in many cases having formed in just the past few hundred thousand years. Once they formed,.
