The rocky islet of Daphne Major juts above the Pacific as seen from North Seymour Island. In 1973, Peter and Rosemary Grant of Princeton University began a decades-long study of the finches living on Daphne Major. They banded and measured every finch on this island laboratory every year, measuring traits that can be passed down, such as beak size. Through time and generations of finches, they documented how seasonal variation rolled the dice in a game of life or death for its feathered inhabitants. Drought years caused a shift in beak sizes among finches as the larger beaks were better adapted to open the harder, armed seeds that were the only food left on this desert island. Surviving birds had larger beaks, they reproduced, and the next generation had larger beaks. Evidence of evolution by natural selection, measured over decades one beak at a time.