Pacific Archaeology: Rock Chemistry Traces Ancient Traders
Robert F. Service
BOSTON--Archaeologists have long known that Captain James Cook was a Johnny-come-lately. By the time he ventured to the South Pacific in 1769, people of the region had been navigating--and trading--on the high seas for at least 3300 years. But now, Captain Cook may have fallen even farther behind. At a meeting of the Materials Research Society here earlier this month, a Malaysian and an American researcher presented a chemical analysis of flecks of volcanic glass that may push back the earliest dates for long-distance sea trading on the Pacific by another 2500 years, to 4000 B.C.
The analysis, by archaeologist Stephen Chia of the Universiti Sains Malaysia and chemist and archaeologist Robert Tykot of the University of South Florida, links volcanic glass found at a 6000-year-old archaeological site on Borneo to sources on islands 3500 kilometers to the east. It points to the longest sea trading network yet traced in the Stone Age. Other researchers are intrigued, although "there will be some skeptics about the dating," says Bennet Bronson, curator of Asian ethnology and archaeology at the Field Museum in Chicago. But if the claim holds up, Bronson says, it "is going to affect our whole understanding" of the migrations that peopled the islands of the western and central Pacific.
At the heart of the new findings are some 200 obsidian flecks, which Chia unearthed beginning in 1994 at the Borneo site, called Bukit Tengkorak. Because there are no obsidian sources nearby, Chia teamed up with Tykot to analyze the flecks and pinpoint their origin. At the meeting, Tykot reported that an analysis of the relative abundance of 11 different compounds, such as silicon dioxide and titanium oxide, in 30 of the flecks yielded several distinctive chemical fingerprints. For the majority of the flecks, these fingerprints matched well-known sources some 3500 kilometers away near New Guinea--on the island of New Britain and on one of the Admiralty Islands. A smaller percentage seemed to come from a source closer to the Philippines, Tykot reported.
Ancient mariners. Volcanic glass found at Bukit Tengkorak comes from sources on the Admiralty Islands and New Britain. It testifies to 3500-kilometer trade routes in 4000 B.C.
SOURCE: R. TYKOT/UNIVERSITY OF SOUTH FLORIDA
The tightness of the matches makes it "almost impossible" that the flecks came from some as yet undiscovered obsidian source closer to the excavation site, says Tykot. Ron Hancock, a chemist and archaeologist at the University of Toronto who saw Tykot's presentation, agrees, saying that the chemical evidence tying the obsidian to distant sources "looks real," which "gives good credibility to the story" of early sea trading. And because materials in the sediment layers from which some of the obsidian was taken have been carbon-dated to 4000 B.C., Tykot and Chia conclude that the trading network was in place by that time.
The new results are "a tremendous surprise," says Bronson, and not just because of the early date. Widespread long-distance sea trading in the southwestern Pacific, he explains, has long been thought to have arisen around 1600 B.C., when seafarers pioneered trade routes extending Melanesian islands near New Guinea to Polynesia in the Central Pacific, leaving behind a trail of distinctive pottery, obsidian, and other ornaments known as the Lapita culture. The new obsidian flecks not only show that traders took to the open ocean much earlier than the people who made Lapita wares, but that their trading network extended far to the west of New Guinea, nearly to Southeast Asia. "This is revolutionary, because it offers apparent proof for a routine trading system in [a westward] direction," says Bronson.
The evidence that skilled navigators were roaming the western Pacific at such an early date also supports a new picture of how the Pacific islands were settled in the first place, says Bronson's Field Museum colleague John Terrell. In the standard picture, the people who settled Polynesia reached the central Pacific by island-hopping from Southeast Asia 3600 years ago--perhaps picking up some fellow travelers from Melanesia along the way (Science, 7 January 1994, p. 32). The new work, however, supports the idea that instead of setting out on a one-way eastward migration, the ancestral Pacific islanders opened up a "voyaging corridor" between Southeast Asia, Melanesia, and Polynesia, "with people and ideas flowing back and forth," says Terrell. The obsidian at Bukit Tengkorak, adds Bronson, "suggests that the early migrations come out of an early commercial system at a surprisingly early date capable of sophisticated navigation."
Because this picture demands that archaeologists reconsider some long-held notions, says Bronson, Chia and Tykot's claims are likely to come under intense scrutiny, especially the radiocarbon dating. Bronson says, however, that there's no reason at this point to doubt the early dates. Captain Cook's demotion may turn out to be permanent.
