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The first itinerant humans, Homo erectus, crossed land bridges from Asia to Indonesia. But their trail seemed to end at Java (above), the site of Homo erectus bones at least 1.5 million years old. No one believed these early humans could cross the ocean barrier called Wallace's line. Scientists thought it wasn't until 50,000 years ago that people—modern Homo sapiens—made the jump. But 840,000-year-old stone tools found in the Soa Basin on Flores are a sign that Homo erectus crossed Wallace's line much earlier. "How they managed to get there is still a real mystery," says Mike Morwood of the University of New England in Australia.

Looking for signs of early humans, archaeologists Wahyu Saptomo and Mike Morwood (below) examine stone artifacts found buried in a limestone cave that the local Manggarai people call Liang Bua. Above its massiveentrance (above right) gray stalactites hang like jagged fangs, but the grim exterior belies an inner beauty. "It's very much like a cathedral inside," says Morwood, who has excavated here since 2001. He says islanders have used the cave as a burial ground for millennia. The dirt below its clay floor is riddled with human bones from a range of eras. But Morwood is interested in the cave's first occupants, Homo floresiensis, who arrived at least 95,000 years ago. The search has involved hauling tons of dirt bucket by bucket to a washing station set up in a nearby rice field (above left), where researchers sifted artifacts and bones from the mud. The work paid off with the discovery of remains from at least seven tiny individuals. The team also found well-flaked stone points—possibly spearheads—that suggest Homo floresiensis, although much smaller than its Homo erectus ancestors, was also smarter.

For millennia the only land mammals on flores were rodents, stegodonts, and humans.

The Homo floresiensis skeleton stands roughly half as tall as a modern adult's. "I knew within about 60 seconds of seeing the jawbone that this was something entirely new," says paleoanthropologist Peter Brown, who examined the bones. The premolars are a giveaway, with a root much different from ours. The pelvis of this female is also wider than in Homo sapiens. Her arms hung almost to her knees, says Brown, but her delicate hand and wrist bones imply that "she wasn't doing a lot of climbing."

Why were the Flores humans so small? Biogeographer Mark Lomolino, who studies the phenomenon called island dwarfism, says, "We know that when evolutionary pressures change, some species respond by shrinking." Stegodonts—extinct elephant ancestors—were especially prone to dwarfing, because they often colonized islands. "Elephants are strong swimmers," he says. Once there, with limited food and fewer predators, they shrank. On Sicily, Crete, and Malta, scientists have unearthed bones from primitive elephants as little as a twentieth the size of mainland forms. But other species, such as rats, tend to grow larger in a place without competitors. Flores yielded remains of giant rats and lizards, as well as cow-size dwarf stegodonts and diminutive human bones (shown above with stone tools and stegodont teeth). Peter Brown says the tiny Homo floresiensis may have evolved from a population of Homo erectus that reached Flores some 800,000 years ago. "The problem is we haven't found Homo erectus bones," says Brown. "All we have is these small-bodied people."

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