March 17, 2010 | 23
Predecessors of the controversial "hobbit" (Homo floresiensis) discovered on the Indonesian island of Flores might have had a longer history there than researchers previously thought.
Although early hominins were presumed to be living on Flores about 800,000 years ago—as evidenced by the discovery of stone tools dated to that time—new finds and analysis push their arrival back another 200,000 years, according to a study in the March 18 issue of Nature (Scientific American is part of Nature Publishing Group). If hominins were present on the island for one million years, as the new findings suggest, that would extend the window of time in which a small primitive human, such as H. floresiensis, which lived about 18,000 years ago, could have evolved.
The group, led by Adam Brumm of the Centre for Archaeological Science at the University of Wollongong in Australia, found some 45 stone artifacts, which the team was able to describe and date. The tools were likely made by early ancient hominin ancestors on the island; it remains unknown if the users of these tools were directly related to H. floresiensis.
Scientists had proposed that the arrival of hominins on Flores precipitated the vanishing of giant tortoise (Geochelone) and pygmy elephant species (Stegodon sondaari) from the area about 800,000 years ago. But an earlier arrival of these individuals now raises doubts about such a direct causation. "It now seems that this extirpation or possible extinction event…were the result of natural processes rather than the arrival of hominins," noted the researchers, who proposed that climate change, volcanoes or other force might have killed off these animals.
Tracing stone tool clues to discover the earliest date of hominins’ arrival on the island, however, might prove to be difficult, the researchers noted. The sediment at the popular Soa Basin site, which has long been exploited for ancient evidence, appears be too recently deposited to yield artifacts much older than those described in the study. Therefore, concluded the researchers, new clues should "be sought in other parts of the island."
Image of excavation site courtesy of Adam Brumm