DUMBING DARWIN DOWN:

"Shrunken" Boas Pose Question: Nature or Nurture? (Brian Handwerk, March 14, 2003, National Geographic News)

It's not the large size of boas that interests Auburn University herpetology graduate student Scott Boback. It's the smaller size of the boas found on certain Central American islands. In the Snake Cayes, a group of small islands just off the coast of Belize, boas grow to only a fraction of the size of their mainland relatives.

"You have snakes on the islands that are completely different in size," Boback told the National Geographic Channel. "The mainland snakes are at least twice as long and four or five times as heavy [as those on the islands]." The island snakes are no small fry, averaging some six feet (1.8 meters) in length, but their mainland relatives can grow up to 12 feet (3.6 meters) long or more. Why the discrepancy? No one knows, but Scott Boback hopes to find out. If he can, he might just shed some light on the evolution not only of reptiles-but many other island-dwelling animals as well.

Boback's plan requires research subjects, willing or otherwise. That means the arduous collection of a lot of boa constrictors-specifically females. With his professor, Craig Guyer, and several research assistants, Boback has already gathered 16 female boas from both the islands and the mainland and brought them back to his research lab in Auburn, Alabama, to carefully watch them give birth.

It's the lab-reared generation of snakes that may help Boback to solve this "nature versus nurture" dilemma. He plans to study the offspring carefully to determine whether varying diets or genetics lie behind the differences in island and mainland boa constrictors. By feeding snakes from both locations identical food, raising them in the same environment, and carefully charting their growth, Boback hopes to learn more about the factors determining their differing sizes.

"The questions that I'm asking are critically important to understanding snake biology and evolution in general," he explained.

The size of boa constrictors may be endlessly fascinating--for shut-ins who don't get Red Sox games on the radio--but to refer to the variations as revealing something about "evolution" is just inane. We've increased the average height of the Japenese by almost half a foot since WWII just by improving their diets--and the Chinese are following suit. Yet no one would claim we're evolving them. Call us when the boa constrictors' essential snakeness actually changes and we'll talk. Posted by Orrin Judd at March 15, 2003 12:18 PM