The Galapagos Archipelago consists of a dozen islands, all within 64 km of their nearest neighbor. From 1 to 11 of the 13 species of Darwin's finches live on each island. Many evolutionary biologists believe that if there had been only one island, there would be only one species of finch. This view is supported by the fact that Cocos Island is isolated (by several hundred kilometers of open ocean) from the other islands in the archipelago and only one species of finch is found there. How does the existence of an archipelago promote speciation?