366
20 Dating the First Migration to New Zealand
the catastrophe, with the most common haplotypes multiplying more quickly
thereafter.
Such an event occurring just over 300 years after first settlement would have
had a controlling effect on the ultimate genetic outcome. As coalescence proceeded,
there would be a continual lessening of genetic diversity, especially when for 600
years climate isolated the peoples in New Zealand, preventing the possibility of new
genes arriving with new migrants or visitors.
Here we can contrast the pattern in New Zealand with that in tropical Polynesia,
which had a far shorter history and so a shorter time for coalescence to occur.
In Eastern Polynesia, given shorter distances between archipelagoes, warmer sea
surface temperatures, El Niño westerlies and seasonal westerlies to aid voyaging,
greater genetic diversity can be seen as a product of greater general voyaging activity, easier accessibility to other archipelagoes, greater trading opportunities and
cultural co-operation (as seen, for example, in the practice of seeking distant wives
for chiefs’ sons). Kin-based migrations within Polynesia would have limited initial genetic diversity but over time the tropical Polynesian islands would have been
exposed to continual infusion of new genetic material from migrants and visitors.
In New Zealand we have a very different pattern. The consequences of an initial
genetic bottleneck in limiting genetic diversity would have been compounded by
catastrophic loss of population in an early near-extinction event. The long period of
isolation that followed would have excluded the descendants of the original Spice
Island colonists from any infusion of new genes.
As we have seen, tradition reports a large population in the North Island in about
AD 841 at the time of Rakaihautu. Our demographic estimate of a population just
under 400,000 confirms this. Because of the size of the population in 841, later infusions of genes through sporadic migrations would have contributed little, percentage
wise, to the Lapita base: in other words, as descendants of the Lapita-age original
settlement increased in numbers, additional migrations would take appreciable time
to increase genetic diversity.
Earlier migrations would have been more significant. The visit in 360 BC of
Tu-te-rangi-marama and his and his crew’s contribution to the gene pool both in
New Zealand and in the Chatham Islands must have been welcome. Over 450 years
later the canoes led by Maui reached New Zealand, as did the canoes of Maui’s
defeated enemy and of his friend Tiwakawaka, who followed Maui to New Zealand.
The crews of all of these canoes probably contributed to the genetic diversity of
the tangata whenua. The people of Kui whom Maui left in New Zealand to defend
his land rights, the migrations led by Maui’s son Wi-Wi and Wi-Wi’s great-grandson
Tutumaiao will also have added diversity to the gene pool. In AD 1180, at the beginning of the Medieval Climatic Optimum, through coalescence, nearly all Maori who
had at least one ancestor in New Zealand at the time of Maui would have had a
common set of ancestors who were part of the first settlement.
While we think the later migrations led by the Tiwakawaka who may have
arrived in about AD 850, Kiwa, and the immigrants left by Kupe to have been
early, none of these were early enough for coalescence to have occurred by the
beginning of the Medieval Climatic Optimum or indeed for them to have made
20 Dating the First Migration to New Zealand
the catastrophe, with the most common haplotypes multiplying more quickly
thereafter.
Such an event occurring just over 300 years after first settlement would have
had a controlling effect on the ultimate genetic outcome. As coalescence proceeded,
there would be a continual lessening of genetic diversity, especially when for 600
years climate isolated the peoples in New Zealand, preventing the possibility of new
genes arriving with new migrants or visitors.
Here we can contrast the pattern in New Zealand with that in tropical Polynesia,
which had a far shorter history and so a shorter time for coalescence to occur.
In Eastern Polynesia, given shorter distances between archipelagoes, warmer sea
surface temperatures, El Niño westerlies and seasonal westerlies to aid voyaging,
greater genetic diversity can be seen as a product of greater general voyaging activity, easier accessibility to other archipelagoes, greater trading opportunities and
cultural co-operation (as seen, for example, in the practice of seeking distant wives
for chiefs’ sons). Kin-based migrations within Polynesia would have limited initial genetic diversity but over time the tropical Polynesian islands would have been
exposed to continual infusion of new genetic material from migrants and visitors.
In New Zealand we have a very different pattern. The consequences of an initial
genetic bottleneck in limiting genetic diversity would have been compounded by
catastrophic loss of population in an early near-extinction event. The long period of
isolation that followed would have excluded the descendants of the original Spice
Island colonists from any infusion of new genes.
As we have seen, tradition reports a large population in the North Island in about
AD 841 at the time of Rakaihautu. Our demographic estimate of a population just
under 400,000 confirms this. Because of the size of the population in 841, later infusions of genes through sporadic migrations would have contributed little, percentage
wise, to the Lapita base: in other words, as descendants of the Lapita-age original
settlement increased in numbers, additional migrations would take appreciable time
to increase genetic diversity.
Earlier migrations would have been more significant. The visit in 360 BC of
Tu-te-rangi-marama and his and his crew’s contribution to the gene pool both in
New Zealand and in the Chatham Islands must have been welcome. Over 450 years
later the canoes led by Maui reached New Zealand, as did the canoes of Maui’s
defeated enemy and of his friend Tiwakawaka, who followed Maui to New Zealand.
The crews of all of these canoes probably contributed to the genetic diversity of
the tangata whenua. The people of Kui whom Maui left in New Zealand to defend
his land rights, the migrations led by Maui’s son Wi-Wi and Wi-Wi’s great-grandson
Tutumaiao will also have added diversity to the gene pool. In AD 1180, at the beginning of the Medieval Climatic Optimum, through coalescence, nearly all Maori who
had at least one ancestor in New Zealand at the time of Maui would have had a
common set of ancestors who were part of the first settlement.
While we think the later migrations led by the Tiwakawaka who may have
arrived in about AD 850, Kiwa, and the immigrants left by Kupe to have been
early, none of these were early enough for coalescence to have occurred by the
beginning of the Medieval Climatic Optimum or indeed for them to have made