Study shows kūmara stored in Otago coast pits in 15th century, may even have been grown there

Saturday, 24 April 2021

The Southern Pacific Archaeological Research (SPAR) unit form The University of Otago has uncovered a Māori Village in Gisborne that is believed to have been from the 14th century. (report from 2018)

Radiocarbon dating shows kūmara were being stored in pits on the Otago coast in the 15th century, seemingly overturning assumptions the area was too cold to store live Polynesian crops.

Confirmation the pits were used for kūmara storage also ties in with local Māori oral history and tradition. While some of those traditions refer to southern kūmara loss or failure, some reference kūmara memories, atua (deities), stores and cultivation.

In particular, those traditions refer to the Huriawa Peninsula headland and pā, at the Waikouaiti River mouth – referred to historically as Waikouaiti pā. That site is less than 30km north of Pūrākaunui, which is the location of the pits in the new study.

A close-up from a section of the main pit. Closed pipi shells in the centre were radiocarbon-dated to between 1430 and 1460.

Research into the pits was led by Associate Professor Ian Barber of the University of Otago’s archaeology programme. He said questions remained about whether the stored kūmara roots were imported from further north or grown in local microclimates.

A dark, sandy archaeological soil found in the same area as the pits may have been used for ancient cultivation, although that had not been confirmed, Barber said.

In any case, the pits in sand dunes at Pūrākaunui, less than 30km north of Dunedin, were the earliest dated rua kūmara (covered semi-subterranean stores) in Aotearoa.

Secure pit deposits that incorporated starch granules with kūmara characteristics were dated to between 1430 and 1460 – some of the most accurate carbon dating in New Zealand, due to the advanced technology used.

The view looking towards the Otago coast.

A paper on the research said the pits were dated to about the same time moa went extinct, and breeding seal colonies in Otago were reduced. The paper, published in Plos One, suggested kūmara may have been introduced because of the loss of megafauna in the area.

The researchers also proposed the pits may have been abandoned due to the impacts of a Southern Hemisphere Little Ice Age after 1450, along with migration and enhanced competition.

The pits, in the traditional southern South Island region known as Murihiku, were more than 200km south of the previously considered limit for premodern kūmara production at Taumutu, south of Christchurch, the paper said.

The Māori archaeological site at Pūrākaunui was a former open settlement on sand dunes generally more than four metres above the channel of a solid tidal inlet. The pits were found, unexpectedly, in 2001, and have since been studied to get an idea of their age, purpose and context.

The discovery of kūmara pits at such an “unlikely latitude” was unprecedented but not inexplicable, the paper said.

Live kūmara roots became highly susceptible to fungal rot when average daily temperatures dropped below 10 degrees Celsius, as was typical of Otago’s earlier 20th-century winters.

But use of regular internal fires and heated rocks in a covered pit might keep the internal temperature above 10C. Evidence for that suggestion was provided by large rocks and indication of fires at the base of several archaeological rua kūmara in the South Island.

The source of the kūmara kept in the Otago pits was “more puzzling”, the paper said.

A 19th century account talked of how short exposure to damp, or even cold air, could quickly spoil kūmara. The sustained supply of live kūmara root from the north over hundreds of kilometres of sea, would have been “a remarkable accomplishment”.

Discarded bone, shellfish and charcoal in a pit.

For now, the possibility of 15th century microclimate kūmara production in the relatively warm dune sands of Pūrākaunui was intriguing but unconfirmed, the paper said.

Sustained pit construction at Pūrākaunui, possibly beyond the 15th century, suggested some measure of success in the supply, if not local production, of acclimatised kūmara.

Along with the suggestion that the importation of kūmara into Otago in the 15th century may have been a response to the decline of megafauna, the researchers also proposed a sociopolitical thesis.

They suggested the rua kūmara may have been under elite management, to reinforce social differentiation.

It was possible management of the pits contributed to the origins or maintenance of Polynesia’s southernmost residential chiefdom, the paper said.

The Little Ice Age – from about 1450 to 1850 in Aotearoa – may have led to kūmara production failures, and could have affected bulk kūmara root transfer to Otago by waka, the paper said.

Pūrākaunui Block Incorporation chairperson Nicola Taylor said there was significant excitement around the research.

“These findings reinforce our very long association with the land and contribute to our own compilation of stories designed to capture the history for future generations,” Taylor said.

Kāti Huirapa Rūnaka ki Puketeraki manager Suzanne Ellison said confirmation and dating of the kūmara pit at Pūrākaunui was affirming of the traditions and mātauraka (knowledge) relating to Huriawa Peninsula.