Ancestors of the cactus finch colonized a new island. They did not have the beak type seen i?

Scientists have long believed that the 14 species of finches on the Galapagos Islands evolved from a single species of finch that migrated to the islands one to five million years ago (Lack, 1940). Recent research (Burns, et al. 2002) suggests that the original finches came from the Caribbean Islands. Different species live on different islands. For example, the medium ground finch and the cactus finch live on one island. The large cactus finch occupies another island. Among the major differences in finch species are their beak sizes and shapes as shown in Figure 1. Evolutionary changes occur by many processes, one of which is natural selection.