Thursday, August 14, 2008

The Founding Mothers

If the first humans arrived in Aoteroa-New Zealand around 1280 – 1300 AD, how many of them were there and where did they come from?

One approach to answering this question has been to combine genetic analysis with population dynamics to work back to an origin and estimate of the numbers of women of child-bearing age to produce a Maori population estimated to number around 100,000 in the early years of European or Pakeha settlement in New Zealand in the late eighteenth century.

Whyte et al analyzed the mutational changes in mitochondrial DNA (mtDNA) samples, known as “the Polynesian motif”, of Maori and Polynesian individuals. The low rate of diversity between the two groups mtDNA suggests that they are close ancestrally and the time since they developed in two separate locations is relatively brief – if by brief, one means 7-8 centuries. Since the mutations studied are found generally across Polynesia, no precise island location could be pinpointed as the starting point for the migration to New Zealand.

Adopting a population growth model incorporating the sigmoid (or S curve) population growth curve, Whyte et al ran computer simulations that would result in the known estimate of a total Maori population by the time of European settlement.

From these simulations, it was estimated that approximately 190 women (within a range of 170-230) of child-bearing age were among those who were on the founding waka canoes that arrived in New Zealand around 1200 AD. These numbers may be conservative as it is likely that many of those on the first waka were related hence not potential breeding partners. Further studies are underway to adjust for these kinship factors.

Source: A Whyte, S Marshall, and G Chambers, “Human Evolution in Polynesia”, Human Biology, April 2005, vol 77 no 2, 157-177.

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