Noting differences in the feeding habits of the finches, Darwin wrote that cactus finches “may often be seen climbing about the flowers of the great cactus trees.” Seeing the diversity of beaks and other structures in the closely related finches, he wrote in his notebook, “one might really fancy that one species had been taken and modified for different ends.”ĭarwin elaborated on this idea when he published his intellectual bombshell, the “Origin of Species,” some 25 years later in 1859. “Some of the craters, surmounting the larger islands, are of immense size, and they rise to a height of between three and four thousand feet.” When Charles Darwin first saw the Galapagos Islands he described them as 10 islands “situated under the equator.” He noted that they originated as volcanoes and were pockmarked with craters. “This higher level is both biologically relevant and functionally important for shaping of elongated beaks, which are used in a specialized manner to probe cactus flowers and fruit for pollen, nectar, and seeds.” The same surge of calmodulin was not found in more blunt-beaked ground finches. “We found that calmodulin was indeed expressed at detectably higher levels in cactus finches compared to ground finches, and thus associated with their longer beaks,” says Clifford Tabin, professor of genetics. This protein had never before been implicated in the development of the skulls and faces of any birds. The investigation soon focused on calmodulin as the switch that can turn on genes involved in increasing beak length. This activity was then matched with the size and shapes of adult beaks. In the Department of Genetics at Harvard Medical School, 26 bird embryos were examined, using gene chips that reveal which genes are most active in the heads of the developing finches. To avoid disruption and abandonment of the nests, the researchers took only the third eggs laid. Female finches lay clutches of four to five eggs, one per day. ![]() Members of the research team received permission to collect finch eggs from the Galapagos National Park, a group of rocky islands in the Pacific Ocean, about 600 miles west of Ecuador. These signals alter the behavior of cells responsible for beak sculpturing. “Calmodulin is a protein that binds and activates certain enzymes, which triggers a signal that eventually turns specific genes on or off,” explains Arkhat Abzhanov, an evolutionary biologist at Harvard. Using modern genetic analyses, they found a molecule that regulates genes involved in shaping the beaks of Darwin finches. Researchers at Harvard Medical School have taken the story one step further. These adaptations make them more fit to survive on available food. Beaks of warbler finches are thinner and more pointed than both. So-called cactus finches boast longer, more pointed beaks than their relatives the ground finches. The birds he saw on the Galapagos Islands during his famous voyage around the world in 1831-1836 changed his thinking about the origin of new species and, eventually, that of the world’s biologists.ĭarwin wondered about the changes in shape of bird beaks from island to island. (Staff photo Kris Snibbe/Harvard News Office)ĭarwin’s finches are the emblems of evolution. He and his colleagues discovered a molecule that controls the length of the birds’ beaks, which enhance their ability to survive on available seeds and insects. Arkhat Abzhanov checks out a selection of Darwin’s finches preserved in the Harvard Museum of Natural History.
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