ABSTRACT
A cooperation problem is a situation where selfish actions lead to outcomes where all players would have preferred a different result. Situations like this are common in trade, production of food, mating, and war. More food per person can be produced by agriculture than by hunting and gathering, but agriculture requires cooperation and storage which can be taken advantage of by thieves. On the island with seeds as the most obvious source of food, the finches have strong beaks that seem tailor-made for crushing shells. There is always some degree of random variation in the sizes of beaks, and on the island with plenty of seeds, the birds with beaks better at crushing shells get more food, leading them to reproduce more. To show that foraging behavior is an evolutionary adaptation, John Krebs and his colleagues first identified the goal of the behavior: gathering as much food as possible while spending as little energy as possible.
