Evolution's Small Wonder

A three-foot-tall "hobbit" who lived in Indonesia up to 12,000 years ago is changing the way we think about the human family

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She was only three feet tall, and her brain was smaller than your average chimp's. Yet she and her relatives apparently lived fully human lives. They seem to have made sophisticated tools, cooperated to find food and cook it, and perhaps even buried their dead with ceremony. The startling discovery of bones from hobbit-size humans who lived on the Indonesian island of Flores as recently as 12,000 years ago--a time when our own species had already populated the Americas--has scientists revising their ideas about the skills of other humans in our growing family tree and about the importance of brain size.

Peter Brown of the University of New England in Australia, who leads the team that's examining the bones, says it was a major surprise to find tools, including points and hafted microblades, associated with homo floresiensis, as the new human family member has been named. The tools are like those previously seen only with European fossils from our own species, Homo sapiens, Brown notes, and the oldest of them were made 94,000 years ago. Homo sapiens is thought to have arrived in the region a mere 40,000 years ago, much too late to be responsible for the implements. If this tiny human made the tools, then the internal structure of its brain must have been more like our own than a chimp's, despite being just a third the size of ours. Of the six species of humans known, all extinct except ours, this is by far the smallest-brained human scientists have ever seen.

The researchers suspect that H. floresiensis is a dwarfed descendant of H. erectus, to which it is anatomically similar. This is not so strange as it might at first sound. When organisms are isolated in regions with scarce resources but few predators, being big is a disadvantage, and evolution tends to shrink them, a process known as island dwarfing. There are other examples on Flores, notably an extinct dwarf elephant, Stegodon.

Could strong selective pressures miniaturize a human while keeping--even expanding--intellectual capacity? Quite possibly, believes Christopher Wills of the University of California at San Diego, who studies the evolution of behavior. Was H. floresiensis even capable of language? "I find it difficult to imagine that people could make tools, use fire, and kill large animals without fairly sophisticated communication," Wills says. Did H. floresiensis possess the rudiments of human culture--such as the ritual burying of the dead? Emiliano Bruner of the Italian Institute of Anthropology points out that Indonesia's hot, wet environment is bad for fossilization. It is not absurd to hypothesize, he says, that the 18,000-year-old bones of the most complete Flores woman were well-preserved because she was buried with special care.

Answers to these questions may be clearer after Brown finishes studying a cast of the interior of the Flores skull. Brain structures are typically imprinted inside the braincase, so the cast should help determine how the small brain compares with those of other human species.