Gauge the Galapagos with a younger age.Gauge the Galapagos with a younger age It's been 150 years since Darwin first set foot on the Galapagos Islands and encountered the great variety of animals that helped transform his thinking about the origin of the species. One important question for the evolution biologists who followed has been how fast the species diverged from one another. On the Galapagos the answer rests in part on the age of the volcanic islands: The islands' rise above sea level marks the time available for animals to colonize col·o·nize v. col·o·nized, col·o·niz·ing, col·o·niz·es v.tr. 1. To form or establish a colony or colonies in. 2. To migrate to and settle in; occupy as a colony. 3. them and "radiate' into new species. Potassium-argon dating potassium-argon dating Method for determining the age of igneous rocks based on the amount of argon-40 in the rock. Radioactive potassium-40 decays to argon-40 with a half-life of about 1. of the volcanic rocks rocks which have been produced from the discharges of volcanic matter, as the various kinds of basalt, trachyte, scoria, obsidian, etc., whether compact, scoriaceous, or vitreous. See also: Volcanic puts the islands' ages between about 1 million (western islands) and 4 million (eastern islands) years. Past paleontology paleontology (pā'lēəntŏl`əjē) [Gr.,= study of early beings], science of the life of past geologic periods based on fossil remains. studies, however, suggested a much older age of 10 to 14 million years--a suggestion that caught on in the biological community, says Carole S. Hickman, a paleontologist at the University of California at Berkeley (body, education) University of California at Berkeley - (UCB) See also Berzerkley, BSD. http://berkeley.edu/. Note to British and Commonwealth readers: that's /berk'lee/, not /bark'lee/ as in British Received Pronunciation. . Now Hickman and geologist Jere H. Lipps Dr. Jere Henry Lipps (August 28, 1939) is a professor at the University of California at Berkeley in the Department of Integrated Biology since 1988 and Curator of Paleontology at the UC Museum of Paleontology. at U.C. Davis have reconciled the paleontologic age with the geologic evidence. In the March 29 SCIENCE, the researchers conclude that the western islands emerged from the sea less than 2 million years ago and that the eastern islands rose at least 3 million years ago. They base their conclusions on the first complete survey of marine fossils found in six different settings. The researchers arrived at relatively young dates, they say, because they paid more attention to how the settings formed than did previous workers. "We found we were dealing primarily with species that are still alive today,' says Hickman. A 4-million-year divergence time agrees with most biochemical studies, which indicate, for example, that the 13 finch species on the islands could have come from one species in 1 million years. The one exception is the iguana iguana (ĭgwä`nə), name for several large lizards of the family Iguanidae, found in tropical America and the Galapagos. The common iguana (Iguana iguana . Biochemical evidence says that the land and aquatic forms of the iguana diverged in 15 to 20 million years. The new findings suggest that these two species had diverged before they arrived at the islands. |
|
||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion