Our not so distant relative

Scientists have discovered a new species of human in remotest Indonesia. Henry Gee reports on the Hobbit-like creature which questions our unique heritage.

W hen Indonesian and Australian archaeologists started to excavate a limestone cave on the Indonesian island of Flores, they weren't prepared for what they found, the skeleton of an entirely new species of human, Homo floresiensis, that lived as recently as 18,000 years ago.

"When we first unearthed the skeleton, I was simultaneously gobsmacked, puzzled and amused," says geochronologist Bert Roberts of the University of Wollongong.

"We had been looking for the remains of the earliest modern humans in Indonesia, so when we found the skeleton of a completely new species of human, with so many primitive traits and that survived until so recently, it really opened up a whole can of prehistoric worms. The discovery of Homo floresiensis was sweet serendipity."

Peter Brown, an anthropologist from the University of New England in Armidale, New South Wales, says: "I would have been less surprised if someone had uncovered an alien." The discovery at Liang Bua cave, described in Nature this week, could alter our outlook on our own place in nature.

The discovery raises obvious questions about the diversity of the human family, such as whether undiscovered human-like species might survive today. Are we really the sole human custodians of our planet? Could the existence of Homo floresiensis rehabilitate persistent rumours of undiscovered human-like species elsewhere, notably the orang pendek of Malay folklore? Could cryptozoology come in from the cold?

Unlike parts of Indonesia closer to the Asian mainland, far-flung Flores has been an island for at least a million years. As is the case with islands elsewhere, the fauna of Flores evolved in its own way, producing creatures larger or smaller than their mainland relatives: a looking-glass lost world of tiny elephants, giant rats, Komodo dragons and even larger, extinct lizards.

This isolation had its effects on the human inhabitants. One of the most surprising things about the skeleton is its size: in life, no more than a metre tall, about the same size as one of the giant rats. Living in a hole in the ground and chased by lizards of mythical proportions, the creature has, perhaps inevitably, been nicknamed "hobbit" by some of the researchers - a reference to the tiny hole-dwelling heroes of The Lord of the Rings.

For Brown, it was the smallness of the skull that showed that Homo floresiensis was truly different. When he measured the skull volume and found it a chimp-sized 380cc, he says his jaw "dropped to my knees. Small stature is easy to accommodate, but small brain size is a bigger problem - it still is." And yet these tiny-brained creatures were skilled enough to make finely crafted stone tools.

The clue to the origin of Homo floresiensis comes from earlier work sug gestive of the presence on Flores of earlier, full-sized prehumans. Michael Morwood, of the University of New England, New South Wales, co-director of the excavation, working closely with his Indonesian counterpart, RP Soejono, of the Indonesian Centre for Archaeology in Jakarta, whose team discovered the skeleton.

In the mid-1990s, Morwood and his colleagues unearthed stone tools on the island dating back 800,000 years. The implication was that the toolmakers, presumably Homo erectus, were capable of navigating the open sea. It is possible that once marooned on Flores, a population of Homo erectus set its own evolutionary course, morphing into Homo floresiensis.

When a small population of animals is cut off from a parent population for an extended period, it follows its own evolutionary course. Size change is a typical response. Small size is an ad vantage on isolated islands, where resources are scarce, so this might have been what predisposed the inhabitants of Flores towards smallness.

It is hard to comprehend the significance of the survival of such a strange species of human until what is, in geological terms, a very recent date. To put this in context, by 18,000 years ago, modern Homo sapiens had been in Indonesia for at least 20,000 years.

Chris Stringer, of the Natural History Museum in London, says: "One of the first things I thought of, on learning about the Flores skeleton, was a possible parallel with the orang pendek [found in Sumatra]." Bert Roberts offers hints of new discoveries just below the research horizon: "When I was back in Flores just three weeks ago, Gert van den Bergh [from the Royal Netherlands Institute for Sea Research at Texel, and the team's expert on the fossil elephants] and I headed off to a village in central Flores where we heard the most amazing tales of little hairy people whom they called ebu gogo: ebu meaning "grandmother" and gogo "he who eats anything".

"The ebu gogo were short - about a metre tall - long-haired, pot-bellied, with ears that stuck out, walking with a slightly awkward gait, and had longish arms and fingers. They murmured at each other and could repeat words parrot-fashion. They could climb slender trees but were never seen holding stone tools, whereas we have lots of sophisticated artefacts associated with Homo floresiensis. That's the only inconsistency with the archaeological evidence. Gert had heard of these stories 10 years ago and he thought them no better than leprechaun stories - until we unearthed the hobbit."

Could the ebu gogo still be alive? Roberts thinks it is possible. "The villagers said that the last hobbit was seen just before Dutch colonists settled that part of Flores in the 19th century," he said, adding that searches of the remaining rainforest on Flores, and the caves specifically associated with the ebu gogo stories, could turn up samples of hair or other material, if not living, breathing specimens.

The possibility of finding ebu gogo alive should not be dismissed as fantasy, because mammals unknown to science do still turn up - and South-East Asia is a particular hotspot for such finds. An antelope, Pseudoryx nghetinhensis, from the Lao-Vietnamese border, was described as recently as 1993. An ox-like creature, the kouprey, was discovered in Cambodia in the 1940s.

Morwood and Roberts have targets already in their sights. Many Indonesian islands contain peculiar faunas and have deep, barely explored limestone caves. "Sumba and Sulawesi are high on our hitlist," says Roberts. Morwood starts work on Sulawesi next year.

A larger theme raised by the discovery concerns the uniqueness of our human heritage, something which, in hindsight, has been in question for decades. Back in the 1960s, the great anthropologist Louis Leakey speculated that the human lineage had been distinct from that of the apes for 20m years or so. In the 1970s, extinct ape-like primates such as Ramapithecus, living around 10-20m years ago, were presumed to lie on the human lineage. But this consensus swept into reverse with the discovery that Ramapithecus was more akin to orang-utans - and molecular evidence showing that the DNA of humans and chimpanzees were so similar that a separation of more than 3-5m years was ruled out.

But opinions have, slowly, been changing back. The force has come from the discoveries of extinct members of the human lineage of ever greater antiquity. Ardipithecus ramidus, discovered in Ethiopia in the mid-1990s by Tim White of the University of California, Berkeley, and colleagues, put back the human-chimp divergence to at least 4.4m years ago. If this put the molecular evidence under strain, it was snapped by the discovery in Chad by Michel Brunet of the University of Poitiers, France, and colleagues of "Toumaï" - Sahelanthropus tchadensis, a member of the human lineage that could be as old as 7m years. Louis Leakey has been partially vindicated, with the effect that our own complacency at our distinctiveness with respect to the animal world has been reinforced.

By the same token, evidence for the diversity of human species through time has been downplayed, first by the cultural inertia of stories of an upwards progression towards the human state; second, by the curious chance that Homo sapiens happens to be the only species of human around today - a situation probably unprecedented in 7m years. The evidence for the coexistence of humans and Neanderthals in Europe for at least 10,000 years until Neanderthals disappeared around 30,000 years ago, and the fact that anthropologists have known for years of the multiple lineages of prehumans living in Africa between 4-2m years -has done little to dent the robust idea that humans are so distinct from the rest of the animal world that they rule the earth by virtue of inherent perfection, or divine fiat.

The Flores finds could change all that with a single stroke.

For one thing, they underscore the fact of human diversity until very recent times. "Maybe little folk from Flores will hammer the point home more effectively because they are so different in anatomy but so close in time," says Tim White. "How will the creationists cope?"

For another, the evidence challenges the human-centric idea that humans characteristically modify their surroundings to suit themselves, rather than allowing natural selection to adapt them to their environment. If the Flores skeleton is evidence of the kind of evolutionary size change more associated with animals such as rats and elephants, this, says Brown "is a clear indicator" of human-like creatures "behaving like all other mammals in terms of their interactions with the environment".

"Darwin and Wallace would be pleased," adds Tim White. "What better demonstration that humans play by the same evolutionary rules as other mammals?"

Of perhaps more current concern to anthropologists is the degree to which Homo floresiensis, with its small stature and - especially - tiny brain, will force a redefinition of humanity, at least in terms of anatomy. "I think the discovery challenges the very notion of what it is to be human," says Stringer.

"Here is a creature with a brain the size of a chimpanzee's, but apparently a tool-maker and hunter, and perhaps descended from the world's first mariners. Its very existence shows how little we know about human evolution. I could never have imagined a creature like this, living as recently as this."

Russell Ciochon, a paleoanthropologist from the University of Iowa, says: "I suspect that creationists will act very negatively toward this discovery.

"It shows that humans were not alone. There may be other dwarfed species lurking in the caves of other isolated islands. Each new discovery will subtract some essence from the uniqueness of humans. I wonder if this discovery might even be discussed in our current political campaign? It is no secret that Bush is anti-evolution. If he is smart, he will not touch this one."

Further reading:

Fission-track ages of stone tools and fossils on the east Indonesian island of Flores by MJ Morwood, PB O'Sullivan and A Raza, Nature vol 392, pp173-176 (1998) Earlier evidence that Homo erectus crossed open sea to reach the remote island of Flores

New ages for human occupation and climatic change at Lake Mungo, Australia by James M Bowler and colleagues, Nature vol. 421, pp837-840 (2003)

A new hominid from the Upper Miocene of Chad, Central Africa by Michel Brunet and colleagues, Nature vol 418, 145-151 (2002)