Posted on: Saturday, January 8, 2005

Coral dating tells story of Maui kingdom's rise

By Jan TenBruggencate
Advertiser Science Writer

Scientists have used coral dating, a technique new to archaeology, to determine than many major Hawaiian temples on Maui were built within a 30-year span.

The period, from the late 1500s to early 1600s, appears to coincide with the rule of Pi'ilani, the first chief to bring Maui under unified rule. Archaeologist Patrick Kirch said it suggests that Pi'ilani may have promoted temple construction as a way of solidifying his authority.

He said he now hopes to expand the coral dating technique to other islands and to the South Pacific.

"I think you could use it ... to solve numerous chronology problems" in archaeology, he said.

Kirch is an anthropology professor at the University of California at Berkeley who has worked extensively in Hawai'i, notably in the Kahikinui region of Maui.

He said he had noted that many Hawaiian stone temples, or heiau, had pieces of coral inside their walls. And the corals were unworn, suggesting they had been collected live and perhaps used as offerings.

A traditional tool used in archaeological dating is carbon-14 analysis of pieces of wood found at dig sites. But Kirch said the carbon-14 technique for dating wood is unreliable for dates within the past few hundred years. He sought out fellow scientist Warren Sharp of the Berkeley Geochronology Center, who has been using radioactivity dating techniques on fossil coral reefs.

The system, briefly, is this: Corals take up uranium from ocean water. Uranium degrades at a known rate into thorium, and the ratio of isotopes of uranium to isotopes of thorium provides a means for determining the age of the coral.

Few archaeologists have experience with the technique, but they are hopeful about it.

"If the uranium-thorium thing does work out, it could be very useful," said Tom Dye, of the archaeology firm T.S. Dye and Colleagues. "I have been experimenting with other techniques using carbon-14 dating that may be able to bring the range of variability way down, but they are very expensive."

When corals from seven heiau at Kahikinui on Maui and one heiau at Kawela on Moloka'i were dated, the youngest lobes of the corals turned out to have remarkably similar ages.

The temples included upland agricultural heiau, coastal fishing shrines and other forms. But another clue to consistent origin is that the architecture of all the temples was very similar, he said — "not as if they were built by one family here and another family there," but as if a consistent design had been dictated by an overall authority.

Kirch said the Big Island chief Umi-a-Liloa had islandwide control of Hawai'i island about the same time, and he would like to expand the coral dating to temples there, to see if there are similar findings. He said that corals are also found in Tahitian temples, called marae, and could be useful for dating them.

In an article in the journal Science, Kirch and Sharp said that temples functioned as mechanisms for the control of the production of food, and that they may provide clues to the transition of early Hawaiian culture from a decentralized series of chiefdoms to large-scale governments with central control.

"The rate at which these changes took place has been uncertain," the scientists wrote.

Their work suggests that it happened very quickly.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.