By OLIVIA JUDSON - THE NEW YORK TIMES
Added: Thu, 04 Feb 2010 00:00:00 UTC

http://opinionator.blogs.nytimes.com/2010/02/02/fearless/


Among biologists, the Galápagos Islands — an archipelago of volcanic islands that straddle the equator about 600 miles from the coast of mainland Ecuador — are legendary. For when the young Charles Darwin sailed around the world in the 1830s, he visited these islands, and was struck by five things.

First, he observed that many of the animals and plants living in the Galápagos are found nowhere else in the world. Examples? Marine iguanas, which swim, eat algae and spend hours basking on the rocks. Darwin, uncharitably, described them as “hideous” and “stupid.” Then there are the giant tortoises (“antediluvian,” said Darwin), the largest of which can weigh as much as 250kg, or 550 pounds. Among the birds, there are flightless cormorants, which have stumpy little wings; and, famously, there are several unique species of finch.

Darwin’s second observation was that certain sorts of animals are missing. The islands have no frogs, for example, and until humans came, there were no land-lubbing mammals like rats or cats. Third, he noted that many of the creatures living in the Galápagos resemble, but differ from, those of the nearest continent — South America. Fourth, the inhabitants of one island often differ from those of another.

These four observations formed an essential piece of Darwin’s evidence that evolution takes place. Remote volcanic islands can only be reached by certain sorts of life forms — those that can cross hundreds of miles of ocean without perishing. So: birds and bats can fly there. Reptiles, many of which can go for months without eating or drinking, can float there on driftwood. Frogs, in contrast, are killed by salt water, and have no way to travel across the sea. Once the organisms arrive in the new place, they begin to evolve to better cope with their new environment; over time, they start to diverge from their cousins on the mainland (and, in some cases, from their cousins on the other islands), producing the patterns that Darwin observed.
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http://opinionator.blogs.nytimes.com/2010/02/02/fearless/

TAGGED: BIOLOGY, COMMENTARY, EVOLUTION