During his voyage on the HMS Beagle, Darwin observed the beaks and behavior of finches. These finches were similar
in some ways to the single finch species that existed on
the mainland of South America. On the Galápagos Islands,
however, there were 13 different species, each with
different beaks and different diets. Later, Darwin
hypothesized that natural selection could explain the
differences in the finch species. Many years later,
Rosemary and Peter Grant of Princeton University began to
test Darwin's hypothesis.
Scientists have recently developed a hypothesis based on
evolutionary concepts and the Grants' work. First, finches
from South America arrived on one of the islands. Then,
the finches that arrived on the island had to survive in a
new environment. The plants on the island were different
from the plants on the mainland. As a result, the
population on the island evolved differently from the
population on the mainland.
Later, a few finches from the island may have flown to
another island and begun the speciation process again.
This process may have been repeated many times. Now
there are 13 distinct species.