Hobbits are inexplicable to paleontologists. A tiny foot bone.

By JOHN NOBLE WILFORD


STONY BROOK, New York - Six years after their discovery, the extinct little people nicknamed hobbits who once occupied the Indonesian island of Flores remain mystifying anomalies in human evolution, out of place in time and geography, their ancestry unknown. Recent research has only widened their challenge to conventional thinking about the origins, transformations and migrations of the early human family.

Indeed, the more scientists study the specimens, the more they are drawn to heretical speculation.

Were these primitive survivors of even earlier hominid migrations out of Africa, before Homo erectus migrated about 1.8 million years ago? Could some of the earliest African toolmakers, around 2.5 million years ago, have made their way across Asia?

Did some of these migrants evolve into new species in Asia, which moved back to Africa? Two-way traffic is not unheard of in other mammals.

Or could the hobbits be an example of reverse evolution? That would seem even more bizarre; there are no known cases in primate evolution of a wholesale reversion to some ancestor in its lineage.

The possibilities grow more curious, said William L. Jungers of Stony Brook University on Long Island, making hobbits“the black swan of paleontology - totally unpredicted and inexplicable.”

Everything about them seems incredible. They were very small, barely a meter tall, yet do not resemble any modern pygmies. They walked upright on short legs, but might have had a peculiar gait obviating long-distance running. The single skull that has been found is no bigger than a grapefruit, suggesting a brain less than one-third the size of a human’s, yet they made stone tools similar to those produced by other hominids with larger brains. They appeared to live isolated on an island as recently as 17,000 years ago, well after humans had made it to Australia.

Although the immediate ancestor of modern humans, Homo erectus, lived in Asia and the islands for hundreds of thousands of years, the hobbits were not simply scaled-down erectus. In fact, erectus and Homo sapiens appear to be more closely related to each other than either is to the hobbit, scientists have determined.

It is no wonder, then, that the announcement describing the skull and the several skeletons as remains of a previously unknown hominid species, Homo floresiensis, prompted heated debate. Critics contended that these were merely modern human dwarfs afflicted with genetic or pathological disorders.

Scientists who reviewed hobbit research at a symposium here recently said that a consensus had emerged among experts in support of the initial interpretation that H. floresiensis is a distinct hominid species much more primitive than H. sapiens. On display for the first time at the meeting was a cast of the skull and bones of a H. floresiensis, probably an adult female.

Several researchers showed images of hobbit brain casts in comparison with those of deformed human brains. They said this refuted what they called the“sick hobbit hypothesis.”

Michael J. Morwood, an archaeologist at the University of Wollongong in Australia who was one of the discoverers, said that investigations of stone tools had determined that hominids arrived at Flores as early as 880,000 years ago and“it is reasonable to assume that those were ancestors of the hobbits.”But none of their bones have been uncovered, so they remain unidentified, and no modern human remains have been found there earlier than 11,000 years ago.

So if several lines of evidence now encourage agreement that H. floresiensis was a distinct and primitive hominid, the hobbit riddle can be compressed into a single question of far-reaching importance: where did these little people come from?

Scientists said in reports that they had only recently begun contemplating possible ancestries.

Still, some scientists believe the Flores skull is not a previously unrecognized species and is a modern human with microcephaly or a similar developmental disorder that shrinks the head and brain.