From Moriori: A People Rediscovered, by Michael King (Penguin, 2017), Kindle Loc. 192ff., 249ff.:
THE CHATHAMS — FOUR MAIN ISLANDS AND AN OUTLYING GROUP OF rocks and reefs — constitute the ridge of a submarine mountain known to geologists as the East Chatham Rise. They break the surface of the Pacific Ocean 870 kilometres east of New Zealand, bisected by the latitude 44° South. This location and the convergence there of warm currents from the north and cold water from the south produces the islands’ climate and weather: almost incessant wind (the ‘Roaring Forties’), near-constant cloud cover, low sunshine hours, wet winters and humid summers.
The Moriori had a variety of myths to account for their presence on these islands, the largest of which they referred to as Rekohu — ‘misty sky’ or ‘misty sun’. The most common recalled an ancestor named Kahu, who sailed the first canoe there from a homeland some remembered as Aotea. Kahu found the islands in an unsettled state. He joined up disparate fragments and anchored them in what became their permanent positions. He also planted fernroot and kumara. Then, in the East Polynesian tradition of the wide-ranging traveller, he returned to his homeland to report on what he had seen. Three further canoes are said to have followed: Rangihoua and Rangimata (together), and subsequently Oropuke.
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If there is any mystery, it revolves around the identity of the ancestors of the Moriori — and that is not impenetrable.
The ancestors of the Moriori were the same people as the ancestors of the New Zealand Maori: East Polynesians whose own ancestors had entered the Pacific from the region now called South-east Asia and the South China Sea. Having expanded throughout the Malaysian, Indonesian and Philippine archipelagoes, one group settled the coasts of the Melanesian islands, and had arrived in Fiji, Tonga and Samoa before 1000 B.C. From there, descendants moved into East Polynesia — especially the Cook, Society and Marquesas Islands — where many of the enduring features of their hierarchical and sea-based culture were further developed and refined. From East Polynesia, some of their descendants migrated north to Hawaii, others east to Easter Island, and still others south-west to New Zealand; and from New Zealand, sometime between the twelfth and the sixteenth centuries A.D., to the Chathams.
Evidence that the final migration was from New Zealand is explicit. Artifacts have been found on both Pitt and Chatham Islands — but more especially on Pitt — made from New Zealand materials (obsidian and argillite). Other Chathams artifacts — necklace units, bird spear points, quadrangular adzes — are shaped in styles known to archaeologists as New Zealand Archaic; and some of them have been found only in New Zealand and on the Chathams. Sections of Moriori vocabulary reveal inextricable links with New Zealand (kawhai [Moriori] and kahawai [Maori] for the fish caught off the Chathams and New Zealand, for example; and kopi, the Moriori name for the karaka tree is a Maori name for the tree and its fruit, and the tree is found nowhere else in Polynesia other than the Kermadecs). The Moriori language as a whole shows a far closer affinity to Maori than to any other Polynesian dialect, with shared innovations that set them apart from other Polynesian languages and reveal their common origin.
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Precisely which part of New Zealand the first people to settle the Chathams derived from, and when, is not known, and will not be until techniques of genetic analysis and radio carbon dating are further refined. There are signposts to answers, however.
Most early canoe voyages, particularly long ones for the trading of obsidian, greenstone or food, occurred down the east coast of New Zealand, the ‘sheltered’ side of the country. Like the winds, the convergence of currents from this coast tends to gather up and push flotsam eastwards towards the Chathams. Axed totara and kauri logs appeared there regularly during the height of mainland logging, and objects such as boxes and bottles from New Zealand still fetch up on Chathams beaches. This suggests that any canoe voyage to the Chathams — planned or accidental — is likely to have come from that part of the country.
The chances are probably highest in favour of an accidental journey: a double-hulled sailing canoe holding fewer than fifty people being forced eastwards by a storm. The fact that the founding group included men and women, and that they brought sufficient tools or tool-making expertise to reproduce their artifacts in local bone and stone, suggests a substantial trading party; or evidence of a planned migration, though not necessarily to the Chathams. Some writers have claimed that a study of the migratory paths of petrels and albatross would have signalled the existence of the islands to people who had never seen them. On the slender and hypothetical nature of evidence available, the verdict on deliberate or accidental colonisation has to remain open.
Linguistic and skeletal analysis show a closer affinity between Moriori and the Maori who lived in Murihiku (southern South Island) at the time of European contact than between Moriori and any other group (other than Taranaki Maori, whose invasion in 1835 had profound effects on Moriori language). This fact, combined with the probabilities of wind and current convergence, points to a likely voyage to the Chathams from some point south of Cook Strait.
