Galapagos Finches and Evolution

• The Galapagos Islands have a unique variety of species, with over 300,000 beetles, 17,000 butterflies, and thousands of mammals, fish, and birds, all astonishingly different.

• Biologists Peter and Rosemary Grant have been studying the Galapagos finches for 40 years to understand how species arise, focusing on the island of Daphne Major.

• The Galapagos Islands are geologically young, beginning to rise from the ocean floor less than 5 million years ago, and initially devoid of life, but now support a modest number of species.

• There are 13 species of finches found in various combinations on the different islands, with diverse habitats, including larger trees at higher elevations and low islands with mostly cactus, grasses, and shrubs.

• The finches have evolved many ways to survive, with different beak shapes and sizes adapted to specific food sources, such as insects, beetle larvae, termite larvae, and cactus flowers.

• The Grants' research revealed that the finches are more related to each other than any one is to a species on the mainland, indicating that all 13 species came from a single common ancestor.

• The Grants' study focused on one species on the island of Daphne Major, where they measured the size and shape of each bird's beak, weight, and tagged them for identification, tracking over 1,000 finches.

• In 1977, a severe drought led to a scarcity of food, and the medium ground finches had to compete for scarce resources, with birds having smaller beaks having the most trouble surviving.

• The Grants discovered that the larger the beak, the better the bird's chances of survival, with natural selection changing the average beak size in just one generation.

• Five years later, in 1983, an unusually strong El Nino brought heavy rainfall, changing the vegetation on the island, and the selection pressure swung in the opposite direction, with smaller beaks becoming more advantageous.

• The Grants demonstrated that evolution of beak size can occur in an amazingly short period of time, not once, but twice, in response to changing environmental conditions.

• The Grants also investigated how finches with different beaks become distinct species, and found that song and appearance play a crucial role in keeping different species from mating.

• The males only responded to songs of their own species and only courted females with a similar size and beak shape, demonstrating that geography and ecology are keys to the evolution of the Galapagos finches.

• Two million years ago, a single finch population arrived from the mainland to the Galapagos Islands.
• The descendants of this population adapted to their new surroundings, resulting in changes to their traits.
• If the trait changes involved mating, the isolated populations became distinct species when they came into contact again.
• The unique history of the Galapagos finches provides insight into the diversity of species in the world.
• The diversity of the environment provides opportunities for evolutionary change, leading to the production of new species.
• The Galapagos finches were first recognized as significant by Darwin over 150 years ago.
• The finches continue to illustrate how the diversity of life arose and continues to evolve.