When archaeologists working on the Indonesian island of Flores announced a new species of human, Bob Eckhardt and colleagues set about debunking their claim.
—By Charles Fergus
In October 2004, while working in his lab, Bob Eckhardt heard a report on National Public Radio: A team of archaeologists had unearthed bones of a three-foot-tall humanlike creature on the island of Flores in Indonesia. Based on the shape and size of the skull and other skeletal remains, the archaeologists, led by Michael J. Morwood of the University of New England in Armidale, Australia, claimed they had discovered a new species of human.
The diminutive biped had a cranium no larger than a chimpanzee's, yet its bones had been found along with abundant stone tools. Radiocarbon dating of charcoal in the same stratum, along with luminescence dating of surrounding sediments, implied that the skeleton was only 18,000 years old. Considering other earlier archaeological finds on Flores, Morwood and his colleagues concluded that a new human species had evolved from a preceding population of Homo erectus that had been isolated for over 840,000 years on Flores, in the archipelago between Asia and Australia.
Eckhardt, a professor of developmental genetics and evolutionary morphology in Penn State's department of kinesiology, added it up. Three feet tall. A tiny brain. Complex stone tools. Evolved in complete isolation in 40,000 generations. He says: "It just didn't ring true."
Eckhardt read the scientific papers, published in the British journal Nature, setting forth the findings and conclusions of Morwood's group. "A lot of things didn't make sense," he says. "For instance, the overall height seemed to be off. I took the long-bone measurements from the paper and plugged them into standard regression formulas." Where Morwood and colleagues estimated an overall height of 1.06 meters for their specimen, Eckhardt came up with figures ranging from 1.15 to 1.33 meters, with an average of 1.25 meters—more than seven inches taller than Morwood's estimate. Eckhardt also wondered about the proximity of the small cranium to sophisticated stone tools, including points, perforators, blades, and microblades. Over a century of research by anthropologists has established a rough correlation between an increasing brain size and advances in stone-tool technology. The kinds of tools described in the Nature article matched those made elsewhere by Homo sapiens. Says Eckhardt, "It seemed very unlikely that a human with a chimp-sized brain would have invented such tools independently and in total isolation."
A "hobbit" is born
Front view of LB1 skull.Courtesy R.B. Eckhardt
That the Morwood find represented a new species also seemed doubtful to Maciej Henneberg. Henneberg works at the University of Adelaide in Australia, where he is the Wood Jones Chair of Anthropological and Comparative Anatomy and heads the division of Anatomical Sciences. The day the Morwood papers appeared in Nature, Henneberg announced during a radio interview that the most complete skeleton recovered by the Morwood group likely came from a developmentally abnormal individual, a member of Homo sapiens whose tiny head exhibited microcephaly, a condition in which a person's braincase remains very small because the brain fails to attain a normal adult size.
A flurry of e-mails passed between Eckhardt and Henneberg. (The two have known each other for years and currently are co-investigators on a project funded by the Australian Research Council.) Says Eckhardt, "Maciej's hunch complemented my own conviction that the 'new species' scenario didn't make sense. And it dovetailed with my belief that the Morwood group had exaggerated the size of their specimen downward." Eckhardt notes that the apparent novelty of the Flores skeleton was enhanced by comparisons with populations from Europe and other major continents where the "normal" stature approaches six feet.
Peter Brown, also of the University of New England, had worked with Morwood in analyzing the Flores remains. They named the purported new species Homo floresiensis, since it had been found on Flores. The nearly complete skeleton (the arms were missing, but they turned up in a later dig) was categorized as LB1, in reference to the expansive limestone cave, Liang Bua, where the bones had been unearthed about six meters below the cave floor. (Liang Bua means "cool cave" in the local language.) Less formally, members of Morwood's team dubbed the creature a "hobbit"—capitalizing, Eckhardt believes, on the popularity of the film adaptation of J. R. R. Tolkien's fictional trilogy The Lord of the Rings, in which small humans known as hobbits do heroic things.
The press, both popular and science-oriented, latched onto the name. And they embraced the new-species notion enthusiastically.
In February 2005, Scientific American ran an article accompanied by a color illustration of a band of pint-sized, spear-toting hunters overwhelming a Stegodon, an extinct dwarf elephant. (Stegodon bones had also been found in Liang Bua, bearing marks made by bladed tools.) The article, by Kate Wong, was entitled "The Littlest Human" and included as a subhead: "A spectacular find in Indonesia reveals that a strikingly different hominid shared the earth with our kind in the not so distant past." It continued: "Conventional wisdom holds that Homo sapiens has been the sole human species on the earth for the past 25,000 years," but the remains found on Flores "have upended that view."
The cover of the May 2005 National Geographic presented a mockup portrait of the hobbit—dark-skinned, big-eyed, startled-looking. Morwood, in a feature article inside, wrote: "We had discovered a new kind of human ... We had stumbled on a lost world: pygmy survivors from an earlier era, hanging on far from the main currents of human prehistory." Jared Diamond, a UCLA evolutionary biologist, stated in a Public Broadcasting System interview: "This is the most amazing discovery in any field of science in the last ten years." Others touted the find as the most important discovery in human evolution and paleoanthropology in half a century.
Alone on an island?
Those characterizations of the importance of the Flores skeletons only intensified Eckhardt's interest. In the kinesiology department he teaches a graduate course in Experimental Design and Methodology. "The course stresses a key principle articulated by Sir Peter Medawar, who shared a Nobel Prize for pioneering work in immunology," Eckhardt says. "Scientists, particularly those of us with decades of experience, are supposed to work on the most important problems that we have a reasonable chance of solving." To Eckhardt and his colleagues, the Flores find represented precisely such a problem. They would attack it, Medawar-style, not through armchair theorizing but by testing hypotheses.
Morwood and his colleagues speculated that a founding cohort of Homo erectus individuals had reached Flores from a nearby island, probably during a period of intense global glaciation, when huge volumes of water would have been tied up in the polar icecaps, lowering sea level and exposing a greater amount of land. It was unclear how the hominids had gotten to Flores, whether by using primitive rafts or clinging to flotsam. Stegodons had also colonized Flores at about the same time. (Elephants are known to be strong swimmers.) Once isolated on the island, both hominids and elephants shrank. The stegodons went from being slightly larger than modern African elephants to about the size of a water buffalo. The hominids supposedly dwindled as well from their more robust Homo erectus ancestors.
The so-called island rule is a widely accepted biological precept holding that mammals larger than approximately rabbit size tend to become smaller over millennia in an adaptive response to an island's limited food resources. Most paleoanthropologists, however, believe that our culture and behaviors buffer humans against some of the factors that cause other mammals to evolve rapidly; where another species might develop a thick pelt to ward off the cold, we make clothes and harness fire. In his National Geographic article, Morwood said that the small human skeletons provided "powerful evidence" for hominid evolution in isolation on Flores.
But had the island really been isolated? In the 1950s and 1960s, evidence of an early human presence had been found on Flores. Theodor Verhoeven, a Dutch priest and amateur archaeologist, had excavated crude stone artifacts near the fossilized bones of stegodons thought to be around 750,000 years old. On nearby Java, others had found 1.5-million-year old Homo erectus remains, which led Verhoeven to conclude that erectus had somehow made the crossing to Flores.
Morwood and his colleagues had unearthed a number of hominid bones in Liang Bua, although only the one complete cranium. They noted the sloping forehead, arched brow ridges, large jawbones, and receding chin on LB1, which, they said, mirrored Homo erectus traits. However, as Morwood wrote in National Geographic, "The tiny skull is most reminiscent not of the hefty Homo erectus from elsewhere in East Asia but of older, smaller erectus fossils." The Morwood team stated in their Nature article that a CT scan demonstrated a congenital absence of a third molar, and they noted a unique positioning of other teeth. They also pointed to an unusual robustness of the leg bones and a low degree of humeral torsion, the twisting of the upper arm bone between the shoulder and the elbow. All of these characteristics were advanced as proof of a new species.