Published: April 2005
The People Time Forgot
Diminutive hominins make a big evolutionary point: Humans aren't exempt from natural selection.
By Mike Morwood, Thomas Sutikna,

At first we thought it was a child, perhaps three years old. But a closer look showed that the tiny, fragile bones we had just laid bare in a spacious cave on the Indonesian island of Flores belonged to a full-grown adult just over three feet tall.

Had we simply found a modern human stunted by disease or malnutrition? No. The bones looked primitive, and other remains from Liang Bua, which means "cool cave" in the local Manggarai language, showed that this skeleton wasn't unique. It was typical of a whole population of tiny beings who once lived on this remote island. We had discovered a new kind of human.

Back in the lab, where we analyzed the bones and other artifacts, the full dimensions of what we had discovered began to emerge. This tiny human relative, whom we nicknamed Hobbit, lived just 18,000 years ago, a time when modern humans—people like us—were on the march around the globe. Yet it looked more like a diminutive version of human ancestors a hundred times older, from the other end of Asia.

We had stumbled on a lost world: pygmy survivors from an earlier era, hanging on far from the main currents of human prehistory. Who were they? And what does this lost relative tell us about our evolutionary past?

A 220-mile-long (354 kilometer) island between mainland Asia and Australia, Flores was never connected by land bridges to either continent. Even at times of low sea level, island-hopping to Flores from mainland Asia involved sea crossings of up to 15 miles (24 kilometer). Before modern humans began ferrying animals such as monkeys, pigs, and dogs to the island about 4,000 years ago, the only land mammals to reach it were stegodonts (extinct elephant ancestors) and rodents—the former by swimming and the latter by hitching a ride on flotsam. No people could have reached Flores until modern humans came along, with the brainpower needed to build boats. Or so most scientists believed.

Yet in the 1950s and '60s Theodor Verhoeven, a priest and part-time archaeologist, had found signs of an early human presence. In the Soa Basin of Flores he found stone artifacts near stegodont fossils, thought to be around 750,000 years old. Homo erectus, an archaic hominin (a term for humans and their relatives), was known to have lived on nearby Java at least 1.5 million years ago, so Verhoeven concluded that erectus somehow crossed the sea to Flores.

As an amateur making extraordinary claims, Verhoeven failed to persuade the archaeological establishment. In the 1990s, however, other researchers used modern techniques to date tools from the Soa Basin to about 840,000 years ago. Verhoeven was right: Human ancestors had reached Flores long before modern humans landed. But no actual remains of Flores's earlier inhabitants had ever turned up.

So we went looking, focusing on Liang Bua, in the uplands of western Flores. By September 2003 our team of Indonesian and Australian researchers, assisted by 35 Manggarai workers, had dug 20 feet into the cave floor. Younger layers were rich in stone artifacts and animal bones, but by this point the dig seemed played out.

Then, a few days before the three-month excavation was due to end, our luck changed. A slice of bone was the first hint. The top of a skull appeared next, followed by the jaw, pelvis, and a set of leg bones still joined together—almost the entire skeleton of Hobbit.

We knew we had made a stunning discovery, but we didn't dare remove the bones for a closer look. The waterlogged skeleton was as fragile as wet blotting paper, so we left it in place for three days to dry, applied a hardener, then excavated the remains in whole blocks of deposit.

Cradled in our laps, the skeleton accompanied us on the flight back to Jakarta, Indonesia's capital. There Peter Brown, a paleoanthropologist from the University of New England in Australia, supervised cleaning, conservation, and analysis. The pelvic structure told him Hobbit was a female, and her tooth wear confirmed that she was an adult. Her sloping forehead, arched browridges, and nutcracker jaw resembled those of Homo erectus, but her size was unique.

It wasn't just her small stature and estimated weight—about 55 pounds (25 kilograms)—but a startlingly small brain as well. Brown calculated its volume at less than a third of a modern human's. Hobbit had by far the smallest brain of any member of the genus Homo. It was small even for a chimpanzee.

The tiny skull is most reminiscent not of the hefty Homo erectus from elsewhere in East Asia but of older, smaller erectus fossils. Viewed from above, the skull is pinched in at the temples, a feature also seen in the 1.77-million-year-old Dmanisi people from Georgia, in western Asia. And in some respects, such as the shape of her lower jaw, the Liang Bua hominin harks back to even earlier fossils such as Lucy, the 3.2-million-year-old Australopithecus from Ethiopia.

And yet—strangest of all—she lived practically yesterday. Radiocarbon dating of charcoal pieces found next to the skeleton, together with luminescence dating that indicated when the surrounding sediments were last exposed to the sun, revealed her 18,000-year age. By mid-2004 our excavation at Liang Bua had yielded bones and teeth from at least six other individuals, from about 95,000 until as recently as 13,000 years ago.

For a few skeptics, all this is too much to swallow. They argue that the one complete skull must have come from a modern human with a rare condition called microcephaly, in which the brain is shrunken and the body dwarfed. The other small bones, they say, might be the remains of children. But last year's discoveries include part of a second adult skull—a lower jaw—that is just as small as the first. It simply strains credibility to invoke a rare disease a second time.

Instead, Hobbit is our first glimpse of an entirely new human species: Homo floresiensis. Her kind probably evolved from an earlier Homo erectus population, likely the makers of the tools Verhoeven found. Her ancestors may have stood several feet taller at first. But over hundreds of thousands of years of isolation on Flores, they dwindled in size.

Such dwarfing is often the fate of large mammals marooned on islands. There they generally face fewer predators—on Flores, Komodo dragons were the only threat—which makes size and strength less important. And the scarce food resources on a small island turn a large, calorie-hungry body into a liability. On mainland Asia, stegodonts sometimes grew bigger than African elephants; at Liang Bua they were only a bit bigger than present-day water buffalo.

In the past some anthropologists have argued that even in prehistory humans could adapt to new environments by inventing new tools or behaviors rather than by physically evolving, like other creatures. The dwarfing seen on Flores is powerful evidence that humans aren't exempt from natural selection. The discovery of Hobbit is also a hint that still other human variants may once have inhabited remote corners of the world.

In spite of their downsized brains, the little people apparently had sophisticated technology. The fireplaces, charred bones, and thousands of stone tools we found among their remains must have been their handiwork, for we found no sign of modern humans. Stone points, probably once hafted onto spears, turned up among stegodont bones, some of which bore cut marks. The little hominins were apparently hunting the biggest animals around. It was surely a group activity—adult stegodonts, although dwarfed, still weighed more than 800 pounds (363 kilograms), formidable prey for hunters the size of preschool children.

The discovery underscores a puzzle going back to Theodor Verhoeven: How could ancient hominins ever have reached Flores? Was Homo erectus a better mariner than anyone suspected, able to build rafts and plan voyages? And it raises a new and haunting question. Modern humans colonized Australia from mainland Asia about 50,000 years ago, populating Indonesia on their way. Did they and the hobbits ever meet?

There's no sign of modern humans at Liang Bua before 11,000 years ago, following a large volcanic eruption that would have wiped out any Homo floresiensis in the region. But other bands may have hung on elsewhere in Flores. Perhaps modern humans did meet their ancient neighbors before something—maybe a changing environment, maybe competition or conflict with modern humans themselves—spelled the end for the little people. Further excavations on Flores, and on nearby islands that might have had their own hobbits, may settle the question.

In the meantime a clue may come from local folktales about half-size, hairy people with flat foreheads—stories the islanders tell even today. It's breathtaking to think that modern humans may still have a folk memory of sharing the planet with another species of human, like us but unfathomably different.

The Australian Research Council supported this work; your Society will help sponsor future study.