Miniature People Add Extra Pieces to Evolutionary PuzzleBy NICHOLAS WADE
The miniature people found to have lived on the Indonesian island of Flores until 13,000 years ago may well appeal to the imagination. Even their Australian discoverers refer to them with fanciful names. But the little Floresians have created something of a headache for paleoanthropologists.
The Floresians, whose existence was reported late last month, have shaken up existing views of the human past for three reasons: they are so recent, so small and apparently so smart. None of these findings fits easily into current accounts of human evolution.
The textbooks describe an increase in human brain size that parallels an increasing sophistication in stone tools. Our close cousins the chimpanzees have brains one third the size of ours, as do the Australopithecines, the apelike human ancestors who evolved after the split from the joint human-chimp ancestor six or seven million years ago. But the Australopithecines left no stone tools, and chimps, though they use natural stones to smash things, have no comprehension of fashioning a stone for a specific task.
The little Floresians seem to have made sophisticated stone tools yet did so with brains of 380 cubic centimeters, about the same size as the chimp and Australopithecine brains. This is a thumb in the eye for the tidy textbook explanations that link sophisticated technology with increasing human brain size.
The Australian and Indonesian researchers who found the Floresian bones have an explanation that raises almost as many questions as it resolves. They say the Floresians, who stood three and a half feet high, are downsized versions of Homo erectus, the archaic humans who left Africa 1.5 million years before modern humans. But some critics think the small people may have descended from modern humans - Homo sapiens.
Homo erectus had arrived on the remote island of Flores by 840,000 years ago, according to earlier findings by Dr. Mike Morwood, the Australian archaeologist on the team. The species then became subject to the strange evolutionary pressures that affect island species. If there are no predators and little food, large animals are better off being small. Homo erectus was sharply downsized, as was the pygmy elephant the little Floresians hunted.
But the Morwood theory is not universally accepted. Homo erectus is known to have made crude stone tools but is not generally thought to have spoken or been able to build boats.
Maybe Dr. Morwood's alleged stone tools were just natural pieces of rock. "Many researchers (myself included) doubted these claims," writes Chris Stringer, a paleoanthropologist at the Natural History Museum in London, adding that "nothing could have prepared me" for the surprise of the little Floresians. It is surprising enough that Homo erectus managed to reach Flores. But not only have the Floresians evolved to be much more advanced than their ancestors ever were, as judged by the stone tools, but they did so at the same time that their brain was being reduced to one-third human size. Getting smaller brained and smarter at the same time is the exact reverse of the textbook progression.
The Floresians' other surprise lies in the time of their flourishing. The skeleton described in Nature lived as recently as 18,000 years ago, but Dr. Morwood said that in the most recent digging season he found six other individuals whose dates range from 95,000 to 13,000 years ago. Modern humans from Africa arrived in the Far East some time after 50,000 years ago and had reached Australia by at least 40,000 years ago.
There has been little evidence until now that Homo erectus long survived its younger cousins' arrival in the region. Modern humans probably exterminated the world's other archaic humans, the Neanderthals in Europe. Yet the little Floresians survived some 30,000 years into modern times, the only archaic human species known to have done so.
All these surprises raise an alternative explanation. What if the Floresians are descended from modern humans, not from Homo erectus?
"I think the issue of whether it derives from H. erectus or H. sapiens is difficult or impossible to answer on the morphology," says Dr. Richard Klein, an archaeologist at Stanford. And if the individual described in the Nature articles indeed made the sophisticated tools found in the same cave, "then it is more likely to be H. sapiens," he says.
The same possibility has been raised by two anthropologists at the University of Cambridge, Dr. Marta Mirazón Lahr and Dr. Robert Foley. Commenting on the sophisticated stone implements found in the cave with the Floresians, they write that "their contrast with tools found anywhere with H. erectus is very striking."
There is the basis here for a fierce dispute. Given what is on the record so far, the argument that the Floresians are descended from Homo sapiens, not erectus, has a certain parsimony. Moderns are known to have been around in the general area, and no Homo erectus is known to have made such sophisticated tools.
Dr. Morwood counters this thesis with data that he has not yet published, and which therefore does not strictly count in scientific arguments. The 95,000-year-old Floresians far antedate the arrival of modern humans in the area. There are modern human remains on Flores, Dr. Morwood says, but the earliest is 11,000 years old, suggesting there was not necessarily any overlap between the two human species.
His view is supported by Dr. G. Philip Rightmire, a paleoanthropologist at Binghamton University in New York and an expert on Homo erectus. "There is no ambiguity about the morphological pattern, and it is erectus-like," Dr. Rightmire says of the Floresian skeleton. "I'm not sure why it should be difficult to accept the reasoning that the little Floresians made progress with stone working and honed their hunting-butchering skills" during their long co-existence on Flores with the pygmy elephants, he said.
Dr. Morwood believes the little Floresians must have had language to cooperate in elephant hunts. Others are not willing to follow him so far, especially given Homo erectus's apparent lack of achievement. Even chimps can hunt cooperatively, Dr. Foley says.
Whether the Floresians' line of descent runs through Homo erectus or through Homo sapiens, a whole new line of human evolution has opened up, even though one that is now all but certainly extinct. The Floresians are not like human pygmies, which have almost normal-size brains but smaller bodies because their growth is retarded during puberty. Nor are they dwarves. The skeleton described last month could be a called a midget, in the sense of a tiny person with the head and body proportions of a full-size person, Dr. Klein said.
"I always tell my students that I've taught for 30 years and I've never given the same lecture twice. Hardly a year goes by when something new isn't found," says Dr. Leslie Aiello, a paleoanthropologist at University College London. Of the Floresian discovery she says, "It's a total knockout."
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