May 1, 1997
Evolution, Thought Slow, Moves Fast
NEW YORK - A recent study shows that evolution, commonly thought of as operating over eons, can happen over just a few years.
That's nothing new to biologists, who have witnessed remarkably rapid evolution in bacteria, snails, moths and a host of other creatures since Charles Darwin first documented the process in finches.
But nobody had ever demonstrated rapid evolution in an actual experiment before researchers took lizards from the Bahamian island of Staniel Cay and introduced them to 14 even-smaller islands nearby.
The smaller islands had sparser, shorter vegetation than Staniel Cay. And since these particular lizards, of the species Anolis sagrei, spend a lot of time sitting on branches, the biologists predicted that the smaller vegetation would lead to correspondingly shorter hind limbs in the lizard.
Which is exactly what happened. Generally, the smaller the island, the smaller the vegetation, the smaller the hind limbs on the lizards, Jonathan Losos of Washington University in St. Louis, Kenneth Warheit of the University of Washington in Seattle and Thomas Schoenert of the University of California at Davis report in today's issue of the British journal Nature.
After introducing lizards to 11 islands in 1977 and to three others in 1981, the researchers returned in 1991 to find exactly what they expected.
``Although rates of evolution as rapid as observed in this study are not uncommon in introduced populations, rarely has the adaptive nature of this change been so clear-cut,'' the researchers wrote.