An international team of scientists has sequenced mitochondrial genome of first New Zealand settlers, and revealed a surprising degree of genetic variation among these pioneering voyagers.
The breakthrough means that similar DNA detective work with samples from various modern and ancient Polynesian populations might now be able to clear up competing theories about the pathways of their great migration across the Pacific to New Zealand.
“Mitochondrial DNA 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,” explained Prof Lisa Matisoo-Smith of the University of Otago in Dunedin, New Zealand, senior author of a paper published in the Proceedings of the National Academy of Sciences.
The team mapped complete mitochondrial genomes of four of the Rangitane iwi tupuna who were buried at a large village on Marlborough’s Wairau Bar more than 700 years ago.
Prof Matisoo-Smith said: “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.”
The team found that the four genomes shared two unique genetic markers found in modern Maori while also featuring several previously unidentified Polynesian genetic markers. Intriguingly, they also discovered that at least one of the settlers carried a genetic mutation associated with insulin resistance, which leads to Type 2 diabetes.
“Overall, our results indicate that there is likely to be significant mitochondrial DNA variation among New Zealand’s first settlers. However, a lack of genetic diversity has previously been characterized in modern-day Maori and this was thought to reflect 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.”
“We are very excited to be the first researchers to successfully sequence complete mitochondrial genomes from ancient Polynesian samples. Until the advent of next generation sequencing techniques, the highly degraded state of DNA in human remains of this age has not allowed such genomes to be sequenced,” Prof Matisoo-Smith said.
Now that the researchers have identified several unique genetic markers in New Zealand’s founding population, work can begin to obtain and sequence other ancient and modern DNA samples from Pacific islands and search for these 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,” Prof Matisoo-Smith concluded.
Bibliographic information: Michael Knapp et al. Complete mitochondrial DNA genome sequences from the first New Zealanders. PNAS, published online before print October 22, 2012; doi: 10.1073/pnas.1209896109