Professor David Burley from Simon Fraser University in Vancouver, Canada says the technique could be used to retrace the steps of the ancient seafarers throughout Oceania with astonishing accuracy.
Dr Burley who has spent more than 20 years researching Lapita settlement in Tonga says Laptias took about 300 years to expand across the Pacific from Solomon Islands to Tonga.
He says a new research technique is at the heart of the findings.
Presenter: Geraldine Coutts
Speaker: Professor David Burley, Archaeology Department, Simon Fraser University, Vancouver
BURLEY: The technique is known as uranium florium dating or new series dating or U series dating and basically it's a radium metric dating technique, so it takes an unstable radioactive isotope in this case, uranium 234 which is decaying into thorium 230 and it has an approximate half life of 245,000 years so we know what the rate of change is and then it measures that it comes up and provides us with a date and it dates anything with calcium cabonate in it, such as coral.
COUTTS: So your confident that you can track it to within eight years of 826. There's been no depreciation of the conditions that you're looking at to trick you a little bit on this particular tracing method?
BURLEY: First of all, I should acknowledge that the dating itself was done in Australia. Two colleagues of mine, Marshall Weisler and Jin Jin Zhou whose at the University of Queensland and the dating was done in the Centre of Microscopy and Microanalysis. I want to make sure I give them credit for what they've done. But essentially in terms of the possibilites of contamination or error what this article has done, the dating technique itself is not new, but what we've done in this study is taken some very ancient material, it's almost 3,000 years old, and come up with protocols that are able to identify if the dates we have digenetical alteration, which is change in the mineral structure. And in doing that, we're able to get these very, very precise dates and they're replicable. So yeah, no it's a pretty good approach.
COUTTS: Well, now that we know this and we know when people first arrived in Tonga. What else could this possibly tell us or aid us in understanding?
BURLEY: Well, we have done a lot of archaeology on this people we refer to as the Lapita peoples and it's defined by a very distinctive type of ceramics and has quite a complex decorative motive on the ceramics and wherever we find them, we know we're dealing with the initial migration or very close to the initial migration in terms of dating and this type of ceramics occurs first in the Bismark Archipelago off the New Guinea Coast and it then it proceeds eastward so we find a beginning about 3300 years ago off the New Guinea Coast and then we can track it across the Pacific all the way out to Tonga, which is the end of sort of the line for this type of pottery, Tonga-Samoa. And we've been using radio carbon dating to predominantly date the different stages of progression. The problem with radio carbon dating is that when we use radio carbon dating, the answers we get are not in calendar years or in carbon years and there's other problems. And typically what happens when we do the conversion in the calendar years, we get a fair range of statistical probability gives us a fair range, so we don't get a very, very accurate date. It maybe within 150 years and this technique now allows us the possibility of looking at very precisely when early settlements occurred in pretty much all of the island nations from New Guinea all the way east as far as West Polynesia.
COUTTS: This method, is it going to be in any other areas, are you going use it more broadly? I mean you've sort of got down to the origins of Tonga, but what about right across Polynesia?
BURLEY: It has actually been used in archaeology in Hawaii and in Tahiti, but in the samples that have been used and dated have been very, very recent, so when in Hawaii, for example, there are these big temple sites called Ha'au and Professor Patrick Kircher at the University of California Burkley has been studying these and essentially every time when the temple was first built, the Hawaiians put in little sprigs of coral and as the temples get modified, they put in new offerings of corals. So he's been using these coral offerings to date different construction phases, but nothing earlier than 500 years ago. So what we've done is we've used a much more ancient material.
We're currently doing a number of different samples from Tonga, so what we're trying to do now is we have the earlier site in Tonga, the one in Tongatapua called Nukulapa and what we're trying to do is look at how in very precise detail how Tonga itself from South, on Tonga Tapua all the way up to Vavau in the north, how these islands were settled and exactly when they were settled, so we'll be able to get a very, very detailed historical picture on the settlement of Tonga. But there are plans to talk with other of our colleagues to try and do this additional broader picture of Oceania.
COUTTS: Has it changed the current story of the migration around the Pacific now that we've got this new knowledge of precisely when they arrived?
BURLEY: It hasn't changed the story, but it's resolved a lot of debate over exactly when this occurs. There's been, particularly of late, in the last five to seven years large concern about the accuracy of radio carbon dating and whether we're measuring, because we use charcoal, whether we're measuring ancient trees as opposed to short lived species, whether the dates themselves are because we're not dating artefacts like we are in this study that are made out of coral, when we use radio carbon dating , we're dating charcoal and we have to assume an association, so it's indirect. So it hasn't changed the big picture story, but it's providing some very specific details that we just didn't have. So it's fine grained data so to speak.