Tracing where the first Kiwis came from

DNA sequencing of the remains of some of the first New Zealanders has raised hopes of identifying the where the first canoes to arrive in this country travelled from.

University of Otago researchers have sequenced complete mitochondrial genomes for members of what is thought to have been one of the first groups of Polynesians to live here.

Mitochondrial DNA (mtDNA) is only inherited through the mother's side and can be used to trace maternal lineages and provide insights into ancient origins and migration routes, study director Professor Lisa Matisoo-Smith said.

The researchers mapped complete mitochondrial genomes of four of the Rangitane iwi tupuna (ancestors)  buried at a large village on Marlborough's Wairau Bar more than 700 years ago.

"We found that three of the four individuals had no recent maternal ancestor in common, indicating that these pioneers were not simply from one tight-knit kin group, but instead included families that were not directly maternally related.

"This gives a fascinating new glimpse into the social structure of the first New Zealanders and others taking part in the final phases of the great Polynesian migration across the Pacific," Matisoo-Smith said.

The researchers discovered the four genomes shared two unique genetic markers found in modern Maori while also featuring several previously unidentified Polynesian genetic markers. At least one of the settlers carried a genetic mutation associated with insulin resistance, which leads to Type 2 diabetes.

While the results indicated that there was likely to be significant mtDNA variation among New Zealand's first settlers, modern-day Maori had been characterised as having a lack of genetic diversity. It had been thought that reflected uniformity in the founding population.

"It may be rather that later decimation caused by European diseases was an important factor, or perhaps there is actually still much more genetic variation today that remains to be discovered. Possibly, it may have been missed due to most previous work only focusing on a small portion of the mitochondrial genome rather than complete analyses like ours," Matisoo-Smith said.

Now researchers had identified several unique genetic markers in New Zealand's founding population, work could begin to obtain and sequence other ancient and modern DNA samples from Pacific islands and search for those same markers.

"If such research is successful, this may help identify the specific island homelands of the initial canoes that arrived in Aotearoa/New Zealand 700 years ago," she said.

It was the first time mitochondrial genomes from ancient Polynesian samples had been successfully sequenced. Techniques used in the study were similar to those used by other scientists recently to sequence the Neanderthal genome.

The arrival of Polynesian colonists in this country about 750 years ago represented the end of the settlement of East Polynesia, the last major human migration event.

A report on the Otago University research, published in the Proceedings of the National Academy of Sciences, said a recent re-evaluation of the dates for the colonisation of East Polynesia suggested the settlement happened quickly in the period from around 1190 to 1290. That was different from earlier studies which had thought the settlement took much longer.