Origin of the species: where did Darwin’s finches come from?

The Guardian: When the first of the Galápagos Islands arose from the ocean floor around 3m years ago, they were naked, angry, lava-spewing cones devoid of life. Now, millions of years later, they are alive with some of the world’s most iconic animals. Giant tortoises. Sea iguanas. Flightless cormorants. And those finches equipped with Swiss army knife beaks.
The Galápagos finches are probably one of the most well-known examples of evolution and will forever be tightly linked to Charles Darwin’s voyage and his theory of natural selection (although you may be surprised to learn that the Galápagos finches were not as central to Darwin’s theory as we like to think). With their diversity of bill sizes and shapes, each species has adapted to a specific type of food; the ground-finch (Geospiza) has a thick beak adapted to feeding on a variety of crunchy seeds and arthropods, whereas the warbler finch (Certhidea olivacea) developed a slender, pointy bill to catch tasty insects hiding between the foliage. The woodpecker finch (Camarhynchus pallidus) even uses twigs or cactus spines to pry arthropods out of treeholes.
The Galápagos finches are seen as a classic example of an adaptive radiation, the rapid evolution of ecologically different species from a common ancestor. Comparisons of anatomical features of the Galápagos finches, as well as modern molecular techniques, show they are indeed more closely related to each other than to any other species. This means they form a monophyletic group, a group of organisms all descended from one ancestral species.