92
5 Transoceanic Trade and Migration (2)
rare or absent when the 28-chromosome form was introduced to Eastern Polynesia.
It is clear from the history of diffusion for the taro that the 42-chromosome form
could not have been brought to New Zealand from Eastern Polynesia by medieval
migrants.
Hendy’s analysis shows that 2,000–3,000 years ago a differentiating mutation
separated the New Zealand cultivar from the Japanese taro from which it derives.
The New Zealand variant does not exist in Japan. Hendy’s work has interesting
implications for early Spice Island contact with both Japan and New Zealand.
Transplanting a cultivar, especially to a significantly different environment, can
trigger mutation and differentiation, driven by selective pressures for adjustment
to a new latitude, a new climate and growing conditions. Whether the mutation
Hendy records came from a rare chance seedling or was a sport or somatic mutation is unclear but genetically it was probably a rare event. In Parts II and III we
argue for a Lapita-age first settlement of New Zealand and in Chapter 20 establish that it probably occurred close to 3,400 years ago. The descent of a global
cold period about 3,000 years ago would have brought additional selective pressures for the Japanese taro’s adaptation to the colder conditions and higher latitude
of New Zealand. That the differentiating mutation occurred in New Zealand seems
probable, given that the New Zealand cultivar is not found in Japan and given the
extreme selective pressures that the Japanese taro would have encountered especially during the global cold period in New Zealand (about 400 years after first
settlement by our calculations). In Chapter 7 we provide evidence of the sophisticated knowledge and awareness of early Spice Island horticulturalists and argue that
their horticultural expertise was vital to their success as colonists, enabling them to
establish horticultural systems on depauperate Pacific islands that made it possible for them to support significant human populations. That Spice Island colonists
brought a form of taro to New Zealand that was already adapted to the higher latitude
(34
◦ N–35 ◦ N) and colder climate of Japan increased its chances of being successfully acclimatized to the colder conditions and higher latitude (40.5 ◦ S–48 ◦ S) of
the South Island of New Zealand, which traditional accounts show was the first
part of New Zealand to be settled (see Chapter 16). Later introductions to Western
Polynesia and Eastern Polynesia of taro cultivars which were long acclimatized
to tropical conditions similarly reflect a persistent history of aware horticultural
practice.
Hendy suggests how studying the phylogenetic history of commensal plants
might cast new light on the migration history of humans responsible for their dispersal. He suggests that in the case of the taro the 10% variation in the nested tandem
repeat phylogenies of a New Zealand and a Japanese cultivar “suggests the rate of
duplication will be a marker sufficient to measure relative times of the introduction and trade of this crop across the world”. He notes that a project to do this
is underway and that it is also possible that ancient DNA may be extracted from
some archaeologically dated grinding tool to help calibrate this clock. Applying
this new approach for studying the path through the Pacific of plants such as the
sweet potato, cotton, plantain and gourd, which have all been foci in debates relating to transoceanic diffusion between Asia, Polynesia and America, may well be
5 Transoceanic Trade and Migration (2)
rare or absent when the 28-chromosome form was introduced to Eastern Polynesia.
It is clear from the history of diffusion for the taro that the 42-chromosome form
could not have been brought to New Zealand from Eastern Polynesia by medieval
migrants.
Hendy’s analysis shows that 2,000–3,000 years ago a differentiating mutation
separated the New Zealand cultivar from the Japanese taro from which it derives.
The New Zealand variant does not exist in Japan. Hendy’s work has interesting
implications for early Spice Island contact with both Japan and New Zealand.
Transplanting a cultivar, especially to a significantly different environment, can
trigger mutation and differentiation, driven by selective pressures for adjustment
to a new latitude, a new climate and growing conditions. Whether the mutation
Hendy records came from a rare chance seedling or was a sport or somatic mutation is unclear but genetically it was probably a rare event. In Parts II and III we
argue for a Lapita-age first settlement of New Zealand and in Chapter 20 establish that it probably occurred close to 3,400 years ago. The descent of a global
cold period about 3,000 years ago would have brought additional selective pressures for the Japanese taro’s adaptation to the colder conditions and higher latitude
of New Zealand. That the differentiating mutation occurred in New Zealand seems
probable, given that the New Zealand cultivar is not found in Japan and given the
extreme selective pressures that the Japanese taro would have encountered especially during the global cold period in New Zealand (about 400 years after first
settlement by our calculations). In Chapter 7 we provide evidence of the sophisticated knowledge and awareness of early Spice Island horticulturalists and argue that
their horticultural expertise was vital to their success as colonists, enabling them to
establish horticultural systems on depauperate Pacific islands that made it possible for them to support significant human populations. That Spice Island colonists
brought a form of taro to New Zealand that was already adapted to the higher latitude
(34
◦ N–35 ◦ N) and colder climate of Japan increased its chances of being successfully acclimatized to the colder conditions and higher latitude (40.5 ◦ S–48 ◦ S) of
the South Island of New Zealand, which traditional accounts show was the first
part of New Zealand to be settled (see Chapter 16). Later introductions to Western
Polynesia and Eastern Polynesia of taro cultivars which were long acclimatized
to tropical conditions similarly reflect a persistent history of aware horticultural
practice.
Hendy suggests how studying the phylogenetic history of commensal plants
might cast new light on the migration history of humans responsible for their dispersal. He suggests that in the case of the taro the 10% variation in the nested tandem
repeat phylogenies of a New Zealand and a Japanese cultivar “suggests the rate of
duplication will be a marker sufficient to measure relative times of the introduction and trade of this crop across the world”. He notes that a project to do this
is underway and that it is also possible that ancient DNA may be extracted from
some archaeologically dated grinding tool to help calibrate this clock. Applying
this new approach for studying the path through the Pacific of plants such as the
sweet potato, cotton, plantain and gourd, which have all been foci in debates relating to transoceanic diffusion between Asia, Polynesia and America, may well be