Could three rocks found in the lower South Island prove to be the Holy Grail of New Zealand archaeology? A retired Kerikeri geologist has been leading a study of the scoria blocks thought to have been carried 4000km across the Pacific Ocean by ancient sea voyagers from Tahiti. Heritage Northland shares the story which could change an earlier version of history.
The geochemical signatures of three shaped scoria blocks found in three early Māori occupation sites in the South Island challenge the understanding of early human settlement in New Zealand.
Retired geologist Dr Ross Ramsay, who lives in Kerikeri, and his research colleagues Graeme Collett of Dunedin; Georgia Kerby of Kiwi North, Whangārei; and consultant Gael Ramsay have recently completed geochemical testing of what are likely to be three marae stones brought to New Zealand by some of the earliest east Polynesian settlers from their ancestral home in the ''Hawaiki zone''.
It appears these early navigators placed scoria blocks or marae stones at different points of their arrival in the southern South Island.
The petrographical and geochemical signature of the three blocks compare closely with each other and to a similar stone brought back from Tahiti by the former director of Otago Museum, HD Skinner, in the 1930s.
"The three South Island blocks were found at different times over a period of close to 50 years – two of them excavated from archaeological sites that also contained east Polynesian-style artefacts and the remains of the extinct moa. The third one was found on a sand dune in Stewart Island with eroding Māori cultural material very close by," says Ramsay.
The first block was discovered in January 1939 by archaeologists David Teviotdale and Les Lockerbie at King's Rock in the Catlins, and the second by Lockerbie and Bill Knox in the early 1960s in an excavation at Tautuku in South Otago.
"Given the archaeological context in which these scoria blocks were found – and the distinctive nature of their geological composition exotic to New Zealand – it now appears likely that all three blocks were brought here hundreds of years ago by the first Polynesian settlers," Ramsay says.
The block found at Tautuku in the early 1960s is on permanent display at the Owaka Museum near Balclutha, while the King's Rock block is in the collection of the Otago Museum. The third block from Stewart Island is in private ownership.
Ramsay sampled minute fragments of a number of scoria blocks – including one collected by Skinner from Mehetia in the Society Islands. These were analysed at the University of Otago and the University of Melbourne.
The results were staggering.
"The three blocks found in New Zealand and the one collected on Mehetia have virtually the same chemical and mineral signature; effectively the same DNA," says Ramsay.
All four blocks reflect the characteristic features of the Tahiti "mantle plume" and, coupled with the very youthful aspects of the scoria petrography lacking any distinctive weathering, strongly indicates a young volcanically active island in the Society Islands.
According to Ramsay, based on mineralogy, major, minor and trace elements, at face value the scoria blocks are very similar to the young alkaline basaltic scoria of South Auckland, Auckland and Northland. Their isotopic signature, however, demonstrates they are not from New Zealand or the sub-Antarctic islands.
Even more intriguingly, the youthful nature and mineral and chemical composition strongly suggests they come from one island in the Society Islands – Mehetia Island, a small volcanically active island about 100km southeast of the main island of Tahiti-Nui.
According to Ramsay, the scoria block brought to New Zealand by Skinner - which was collected on Mehetia Island - has very similar petrographical and chemical features.
"This is further reinforced by the common chemical and mineral content of all the blocks that we analysed, and the fact that Mehetia was volcanically active very recently – probably in the past thousand years or so; the only active subaerial volcano in this part of the Pacific at that time.''
Tahitians also have an oral history that navigators sailing to New Zealand stopped off at the sacred island of Mehetia before embarking on the long journey.
"The weight of scientific evidence and cultural knowledge highlights the fact that these rather lifeless, uninteresting-looking rocks found in South Otago and Stewart Island/Rakiura are in fact an important ancestral link to Polynesia.
"That makes these scoria blocks some of the most significant artefacts associated with the voyaging heritage of Māori in New Zealand. They are both identifiable and diagnostic in the sense that we can say with reasonable certainty where they came from.
''I cannot think of another pre-European artefact in New Zealand that we can make that claim with the same level of archaeological and science-backed certainty."
The results of Ramsay and colleagues' research are more than interesting according to Heritage New Zealand Pouhere Taonga Northland Manager, Bill Edwards, who is also an archaeologist.
''What's really exciting, from my perspective, is that two of these rocks were found in a very clear, well-recorded archaeological context.
"The stones were found among moa bone and cultural material such as an early triangular adze and early bone fish hooks, which links them to an early site. This also supports the idea that these objects were brought here from Polynesia by people many hundreds of years ago.''
Ramsey says the find supports the theory the people who brought the rocks sailed direct from Tahiti over 4000km of open water following the patterns of migratory birds rather than "island hopping" through the Tonga-Kermadec arc and then fanning out around the North Island as other waka did.
The fact they left their homeland with scoria blocks also indicates they expected to arrive at a destination, he says.
''You also have to wonder whether there was one waka carrying three stones, or perhaps three waka carrying one stone each – which then raises questions about planned migration and settlement.
"Whatever conclusions are drawn or questions asked about the blocks, they are likely to become an important reference point in discussions around Polynesian navigation and the earliest settlement of New Zealand."