In their study of the evolutionary ladder, scientists have found that modern humans rubbed elbows with some colorful cousins. But few have been as puzzling as a purported cousin unearthed on the Indonesian island of Flores.
The partial skeleton, first reported last October, was stunning. Estimated to stand just over three feet tall, it offered the tantalizing possibility that a new species of mini-human lived 18,000 years ago. But some researchers dismissed the find as a pygmy or the result of a physical defect.
Now the research team that gave the world the hobbit-like Homo floresiensis has found what it sees as confirmation that the species did, in fact, exist. It reports that it has unearthed additional fossils at the site, representing at least nine similar individuals. They range in age from 12,000 years ago to perhaps 95,000 years old. If the team's conclusions hold up, the fossils throw into question key theories about the human family tree.
The fossils "are not only astonishing, but also exciting because of the questions they raise," according to Daniel Lieberman, a biological anthropologist at Harvard University.
Among the questions: Who were their ancestors? How did the diminutive creatures reach the island? And how did they survive so long after modern humans appeared in the Indonesian archipelago?
At the very least, the finds dramatically underscore how much anthropologists still have to learn about the diversity of species gathered under the umbrella designation of hominids, which gave rise to modern humans, researchers say.
The mineralized remains from the site at Liang Bua include arm and thigh bones, shoulder blades, fingers, toes, and jaws. The results appear in today's edition of the journal Nature.
These additional puzzle pieces suggest that H. floresiensis not only was short but built much like long-extinct primates called australopithecines, according to the Australian and Indonesian research team, led by Michael Morwood and Peter Brown at Australia's University of New England. Australopithecines lived in eastern Africa from 1 million to 4 million years ago.
Just as confounding, stone chips, anvils, and tools indicated that these Ice Age Lilliputians had mastered stone toolmaking, as well as the use of fire. And they had a penchant for hunting pygmy elephants and Komodo dragons for dinner. All these are feats that scientists usually attribute to hominids with far bigger brains and greater cognitive abilities.
"I really have to start rethinking the amount of variation you can have" and still wind up with a toolmaking hominid like H. floresiensis, says Dean Falk, a paleoanthropologist at Florida State University. This species had a brain smaller than a Florida grapefruit, she adds, yet it was capable of complex behaviors.
Given its oddities, H. floresiensis threatens to throw cold water on some long-held ideas about human cognitive evolution. It also suggests that modern humans coexisted with relatives who became evolutionary dead ends more recently than previously believed.
For that reason the team's initial results met with a lot of skepticism. Some argued that the team had uncovered nothing more than an Ice Age pygmy. Others held that the individual merely had an abnormally small brain induced by a physical defect. Indeed, research teams in the United States and Europe are independently trying to answer this question more thoroughly.
Bit by bit, however, the alternate explanations appear to be eroding in light of the new fossils and of studies of a skull that was part of the initial discovery reported last year.
One of many intriguing questions focuses on H. floresiensis' origins.
One possibility is that it is descended from Homo erectus, another hominid species that reached Flores some 800,000 years ago. Isolated on the island, the population - or some portion of it - might have given up some of its physical stature to survive in the face of limited resources. Such environmentally induced dwarfism has been documented in other mammals, researcher say.
Another intriguing possibility posited by Dr. Brown: H. floresiensis, as well as H. erectus, may have descended from a munchkin ancestor. This raises the possibility that australopithecine-like creatures may have migrated out of Africa, as well as more-modern hominids. It's a long shot, researchers say. But tentative evidence for other "little people" has cropped up in the former Soviet Republic of Georgia.
"Something came out of Africa around 2 million years ago," Dr. Falk says. "Until a few years ago, the answer was homo - something like Homo erectus, modern in body build."
But, she adds, H. floresiensis "makes me wonder: What about the little folks? Have they been lurking around and we just haven't been aware of them?"