A very small human ancestor made a very big splash back in 2004, when researchers discovered the remains of Homo floresiensis, a 3-ft., prehuman "hobbit," in a cave on the Indonesian island of Flores. The origin of the species and the route it took to Flores have been much discussed since then. Earlier this month, researchers presented work at the annual meeting of the American Association of Physical Anthropologists, in Chicago, suggesting that H. floresiensis may have left Africa a full million years earlier than any other hominids were thought to have ventured out from the home continent. (Read "The Riddle of the Hobbit.")
The new theory comes from recent analyses of the interior of the skull of Flo as some call the 18,000-year-old fossil remains. A young female, Flo exhibits features that bear an uncanny resemblance to skulls from the hominid genus Australopithecus, which lived in Africa from roughly 4 million to 1.5 million years ago. The best-known australopithecene fossils are the 3.2 millionyear-old A. afarensis Lucy, discovered in Ethiopia, and the 3 millionyear-old A. africanus Taung Child, unearthed in South Africa. (See pictures of South Africa, fifteen years on.)
The problem is, the only early hominids found outside Africa are Homo erectus, the earliest of which date to 1.9 million years ago about a million years after Lucy, Taung and their ilk. If Flo so closely resembles Lucy and Taung, her ancestors may have emigrated from Africa back when those famous kin were still around.
Florida State University skull-morphology specialist Dean Falk and an international team of researchers compared Flo's skull not only to skulls of other prehuman species, but also to those of modern humans, some with normal development and others with microcephaly, an abnormal smallness of the head. That last comparison was critical, since some researchers have suggested that H. floresiensis represents not a separate species but is instead a modern human stricken with microcephaly or similar illnesses. But the "sick hobbit" hypothesis has been unable to gain much traction.
Falk and the others identified seven specific features of Flo's brain that seem to be more-evolved versions of key characteristics of the much older A. africanus brain. "Over the entire cerebral cortex, there are advanced features that make it look like a very fancy brain," says Falk. "H. floresiensis was clearly there a long time, because it developed its own features."
Overall, Flo's brain shows the global neural reorganization that's a mark of advancing intelligence. What's striking about this relative sophistication is that it developed in such a small brain case. A prime indicator of increasing human intelligence has long been thought to be increasing brain size. However, Falk says, the hobbit's skull is a bit of a mishmash of characteristics in terms of who it resembles. "Its brain sorts with africanus, yet its outside skull features look like Homo erectus," she says.
But William Jungers, one of the primary hobbit researchers, says the similarities to erectus seem to end at the neck. Analysis of various anatomical features suggests that the new species has an overall body plan that looks more ancient than that. "It's not identical to Australopithecus," Jungers says, "but it resembles it in limb proportions, the shape of the bony pelvis, the hands." Adds paleoanthropologist Donald Johansen, who discovered the Australopithecus Lucy: "It is a possibility they got out of Africa earlier than we ever thought. If they were isolated on an island and didn't have gene flow from other populations, it would make sense that they retained ancient features like small stature and small heads."
Upcoming excavations of Flores spearheaded by Mike Morwood, the lead researcher of the Australian-Indonesian team that first unearthed the bones, may help answer the essential question, as Falk puts it, "When did the first [hobbit ancestors] get to the island, and what did they look like?"