Why do finches on one island have long and thin beaks while finches on another island have short and thick beaks?

Read Leban chapter 2 HERE

 

What is the three part method for explaining the difference in beaks?

What are cooperation problems?  How can we solve them?

What is the general cooperation problem humans have faced since our earliest evolutionary history?

What trait/behavior does Leban think we evolved to solve this problem?