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In 1968, a Dutch missionary living on the Indonesian island of Flores found stone tools alongside the bones of an extinct type of elephant called a Stegodon, known to have lived at least 750,000 years ago. If the tools were as old as the Stegodon, this was a spectacular discovery, for Flores lies beyond a deep-water strait that separates most Asian and Australian faunas. The tools meant that the only human species then living in Southeast Asia, Homo erectus, must have been able to cross this biological barrier, called Wallace's line.
But when the missionary, Theodor Verhoeven, reported his findings in the journal Anthropos, his claim was roundly dismissed. Although trained in classical archaeology, Verhoeven was an amateur, so researchers discounted his field work. And the accepted idea was that deep waters blocked human exploration until about 50,000 years ago. Although H. erectus was known from just 600 kilometers away on Java, most researchers were convinced that this early human lacked the social and linguistic skills needed to cross Wallace's line by piloting a raft over deep, fast-moving waters. Even after Dutch and Indonesian paleontologists backed Verhoeven's findings with new excavations and paleomagnetic dating in 1994, the claim was still considered dubious.
In this week's issue of Nature, however, an international team presents new dates for stone tools from Flores, based on a different and more reliable technique called fissiontrack dating, that confirm H. erectus's presence there 800,000 years ago. The authors propose that the early humans who left behind these simple flakes and cobbles were "capable of repeated water crossings using watercraft" and may even have had language, needed to cooperate to build rafts. The "cognitive capabilities of H. erectus may be due for reappraisal," says archaeologist Mike Morwood of the University of New England in Armidale, Australia, lead author of the paper.
Most researchers accept the new dates for the artifacts, but they are sharply divided over what the findings reveal about the toolmaker. A few questions linger about whether the artifacts are really tools-and no H. erectus bones have been found on Flores to dispel these questions. Some researchers add that H. erectus might have accidentally drifted over to Flores on a raft or even walked on some previously unknown land bridge,...