Answer:
He developed the theory of evolution.
Step-by-step explanation:
While Darwin was on the island, he saw how there was a variety finches varying from each island to the next. He determined that each species of finches had gone through natural selection to best adapt to their surroundings. Their beaks and behaviors changed depedning on what island they inhabited. Therefore, he determined that they had adapted to the opportunities presented to them on their respective islands. During his time there, he took numerous notes and created various drawings. They, in turn, helped prove how the creation of species occured through a long process of chang, as they developed into more evolved versions that could better adapt to their surroundings.