The fossils' wide age range makes that explanation seem less likelyit's improbable that all the specimens found would have had the conditions. It's more likely that small heads and bodies were normal for the hobbits, according to the new report.
Homo floresiensis had jaw, teeth, and skull features similar to those of humans. Other H. floresiensis proportions, such as their long arms and lack of a defined chin, are unlike those of any modern humans, including Pygmies. Pygmies are equatorial African people who rarely grow taller than 5 feet (1.5 meters).
This odd mix of features makes the hobbits' origins a mystery.
Where Did the Hobbits Come From?
Some scientists suggest that the unique species existed before its arrival on Flores. They hypothesize that a tiny species of human ancestors left Africa at the same time Homo erectus didabout 1.8 million years ago. (Named for its upright walk, H. erectus is thought by many scientists to be a direct ancestor of modern humans.)
The team of archaeologists that found the new remainsled by Mike Morwood, Bert Roberts, and Thomas Sutiknasuggests that the hobbits are the result of island dwarfing, an evolutionary procedure where species become smaller over many years to adapt to the limited resources of their environment. Smaller species, the thinking goes, can get by on less food.
If an isolated human species occupied Flores for the better part of a million years, it may have undergone dwarfing, the researchers say.
"We know that large mammals tend to shrink," Morwood explained. "The smallest stegodon species [a small elephant-like animal] in the world is from Flores. On Flores and adjacent islands there are some pretty weird things going on."
"There was probably in situ evolution of this quite unusual human species," he continued. Morwood speculates that H. floresiensis may have evolved from "a small-bodied [early human] species from earlier in human evolution."
"It's a totally unique situation, and the end result seems to be also totally unique."
The study, which will be published in tomorrow's issue of the journal Nature, also reports that, though H. floresiensis had chimpanzee-size brains, they used stone tools to butcher animals and had mastered the use of fire in cooking. (See "'Hobbit' Brains Were Small but Smart, Study Says.") Such behaviors raise interesting questions about prevailing evolutionary theories that suggest that big brains are better.
"Nobody knows what this thing is," Harvard's Lieberman said. "That's what's fun about this fossilall the questions that it raises. It should be terrific fun to try to figure it out."
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