Victoria University Professor of New Zealand studies Richard Hill said theories about people arriving pre-Maori resurfaced from time to time.
"Not one of them has ever passed any remote academic scrutiny."
He said normally those types of theories were considered in the academic world to be "colonisation justification myths".
Independent Wellington historian Vincent O'Malley said the works Mr Rankin referred to were not considered to be scholarly or credible.
"It's not something I'd take seriously."
He said theories of Greek, Egyptian and other pre-Maori voyages were not based on scientific evidence - "it's all a joke".
Dr O'Malley said people who published notions that Maori were not the country's first residents often had a political agenda.
"That whole idea of de-legitimising Maori as tangata whenua or having any rights under the Treaty (of Waitangi)."
Mr Rankin is involved with treaty negotiations at the moment, but he said if the theories had any merit, that would not put discussions in peril.
"It will actually just start opening up new chapters in history. It's about finding out about the truth.
"It could open a Pandora's box."
He pointed to Maori oral histories which referred to people being here when the first Maori arrived, including fair-skinned people.
"If we believe our histories, then we as Maori are not the indigenous people of New Zealand."
Mr Rankin wanted debate around the issue in an attempt to uncover the truth behind the country's colonisation history.
"To work out whether they're crack-pots or whether they do have some standing in what they have to say."
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Current accepted theory on New Zealand settlement:
* initial settlement occurred about 1280 CE (common era) at the end of the medieval warm period;
* according to Maori oral history, Kupe was the first to reach New Zealand, by using stars and ocean currents from his Polynesian homeland of Hawaiki, in a large waka;
* more waka followed over the next few hundred years;
* there is limited evidence of return, or attempted return voyages, from archaeological evidence in the Kermadec Islands; and
* evidence from archaeology, linguistics, and physical anthropology indicated that the first settlers came from east Polynesia and became the Maori.
Alternative theories:
* a book, To the Ends of the Earth, written by Maxwell C Hill and Gary Cook, with shipwreck explorer Noel Hilliam, detailed evidence the authors said convinced them that Greek-Egyptians and others sailed to and settled New Zealand long before the arrival of Maori;
* it showed ancient maps detailing the coastlines of Australia and New Zealand and first drawn before the birth of Christ. Skeletons, rock carvings, stone buildings and monuments and oral tradition all attest to people of European origin living here for centuries before the arrival of Polynesians;
* another book, The Great Divide, by investigative journalist Ian Wishart, said New Zealand may have been settled by humans between 2000 and 14,000 years ago;
* but a massive comet strike that left a 20km wide crater with walls 150m high in the seabed near Stewart Island in the mid 1400s created a 220 metre high tsunami which swept up the coast, wiping out evidence of early human settlement, and was the most likely culprit in mass species extinction of moa, eagles and other animals around the same time;
* it said the early humans left South Island cave paintings featuring what scientists described as "crocodiles and pythons" - animals not known in Polynesia.
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