After Hours

Geek Trivia: Creatures great and small

Who first theorized the "island rule" governing the development of dwarf and giant island species?

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If the collective film credits of Godzilla (now age 50—expect your AARP card any day now, 'Zilla) have taught us anything, it's that if you're looking for an obscenely oversized version of a particular creature, you should start your search on a remote island.

Not just an artifact of B-grade, Cold War-era monster movies, this concept is also a recurring subject of interest for biologists, who have spent decades studying the peculiar incidence of insular gigantism. For those of us not up to date on our bio vocabulary, insular gigantism is the official term for the development of giant-sized versions of plant and animal species on islands.

While this phenomenon has yet to produce any real-life examples of 30-story-tall, fire-breathing, radioactive, mutant reptiles, the inspiration for such model-stomping, rubber-suited movie stars is a prime example of insular gigantism. We speak, of course, of the Komodo dragon, the world's largest living lizard, which (outside of zoos) exists exclusively on four Indonesian islands.

Many scientists consider the Komodo dragon to be a classic example of island gigantism, claiming this 10-foot-long, 500-pound relative of the monitor lizard has bulked up over the centuries to prey on the local populations of deer. Some scientists, however, have a different take, suggesting that the Komodo dragon is an example of the flipside of island adaptation, insular dwarfism.

Apparently, Australia was home to a twice-as-large monitor lizard during the Pleistocene Era: Megalania, which was about 20 feet long and weighed in at 1,000 pounds plus. So Komodo could actually be an island pygmy version of that prehistoric dragon.

Thus, we come to the central issue of insular adaptation: Why do some species grow larger when adapting to island life, while others grow smaller?

The first cohesive attempt to answer that question came in a two-page paper published in the Nature journal in 1964, titled "Evolution of Mammals on Islands." This paper charted the size shift of 116 mammal species adapted to island living.

The paper found that larger mammals tend to shrink, and smaller mammals tend to enlarge, as if progressing toward some idealized island mean. Dubbed the "island rule," this rudimentary principle has had a profound impact on comparative biology over the last 40 years.


Who first theorized the so-called "island rule" regarding the development of giant or dwarf island cousins to mainland plant and animal species—a rudimentary guideline that has spawned 40 years of increasingly complex biodiversity research?

The biologist in question is one J. Bristol Foster, who wrote a mere two-page paper intended to clear up "much confusion and contradiction" on the subject of insular adaptation leading to gigantism and dwarfism in mammals. Foster's observation that big mammals get smaller and small mammals get bigger as they adapt to island environments helped shape a subset of biological research that wouldn't even earn a name until 1967, three years after Foster published his island rule.

That name, biogeography, came from a book titled The Theory of Island Biogeography, written by Robert MacArthur and Edward O. Wilson. Biogeography explicitly deals with the evolution of insular animal populations, a field of study that never loses sight of the dwarfism vs. gigantism issue.

Over the last four decades, the field of study that Foster helped start has both contradicted and elaborated on his island rule, agreeing only on two general principles. First, adaptation to an island environment will likely lead to a change in a species' size, but a wide variety of factors, many of which are too subtle or capricious for quantification, dictates the direction of the change. Second, insular size shifts can occur extremely quickly, scientifically speaking, with as little as five to six millennia separating mainland and giant/dwarf island species.

Thus, we come to the most recent example of the island rule: Homo floresiensis, an island-dwelling relative of Homo sapiens that lived as recently as 18,000 years ago—but matured to a mere three-foot adult height.

October's announcement of the discovery of these nicknamed "hobbits" on the Indonesian island of Flores (one of the four islands where one can still find Komodo dragons, I might add) spurred a fresh round of human evolutionary debate and brought the concept of insular dwarfism to the anthropological forefront. Not bad for a biological concept that's younger than the Godzilla film franchise, but it has just as much potential for great Geek Trivia.

The Quibble of the Week

If you uncover a questionable fact or debatable aspect of this week's Geek Trivia, just post it in the discussion area of the article. Every week, yours truly will choose the best post from the assembled masses and discuss it in the next edition of Geek Trivia.

This week's quibble comes from the Nov. 24 edition of Geek Trivia, "A Rosie by any other name," in which TechRepublic member Tlccomputers pointed out that I should have had my eyes checked before discussing symbolism in Norman Rockwell's "Rosie the Riveter" painting.

"You state, 'The most obvious example is the fact that Rosie is standing on a side-turned copy of Adolf Hitler's Mein Kampf.' Anyone who takes even a casual glance at the painting can plainly see that Rosie is sitting down rather than standing, with her feet propped up on the book, using it as a footstool, a symbol [that] at one time would have been considered even more degrading than standing on it."

Great point there, reader. Thanks for keeping me honest—and offering up another chance to take a pot shot at Nazism. Now that's a great quibble.

The Trivia Geek, also known as Jay Garmon, is a former advertising copywriter and Web developer who's duped TechRepublic into underwriting his affinity for movies, sci-fi, comic books, technology, and all things geekish or subcultural.

About Jay Garmon

Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger — amusing and abusing IT pros. Read his full profile. You can a...

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