I have an encyclopedia from the 1930s called The Wonderland of Knowledge which states:
It was a race not purely of Polynesian blood which first settled in New Zealand. These ancient settlers were part Polynesian and part Melanesian. The Polynesians...are supposed to be related to our own ancestors, although so far back in time that the time is lost in mists of uncertainty, for they came originally from India, thousands of years ago, and originally belonged to the Indo-European race...The Melanesians, on the other hand...came from Lower Asia and Africa...But it was not this mixed race that the white man found in New Zealand...
Obviously, given that it is an encyclopedia from the 1930s, I'm willing to take the idea of pre-Maori New Zealanders with a pinch of salt. But Gavin Menzies also talks about it in his book 1421, which I know is a work of pseudohistory. All I'm saying is, the concept of pre-Maori settlement seems to be a common theme, whether debunked or not. So do historians now believe that there were people living in NZ before the Maori, and if not, how did this theory come about?
Also, follow-up question: In the above extract, it states that the Maori were related to the Indo-European race. But in almost everything else I've seen, even from that period, Polynesians were counted as an Austronesian subbranch of the Mongoloid race, similar to Malays. Was the theory of Maoris being Indo-Europeans also widely held at the time?
No; its the result of Europeans thinking Polynesians were just distant cousins and finding ways to prove it.
The theory of Maoris (and all Polynesian peoples) being of Indo-European origin is part of a long tradition beginning really with European exploration in the 18th century. Polynesian peoples appeared to them, to be basically like Europeans. Here is a fabulous extract from the published account of Labillardière, who was one of many naturalists who transited the Pacific at the time. Labillardière was in Tonga at the time, part of Dentrecastaux's voyage in search of the missing La Pérouse:
This young person soon left us; but, before she went away, she kissed Toobou's daughters after the manner of the inhabitants of the Friendly Islands, which is by touching with the tip of the nose the nose of the person you sale. It is remarkable, that these islanders, who pretty much resemble Europeans, have, notwithstanding, the extremity of the nose a little flattened: this slight deformity may very probably be owing to the custom, of which I have just spoken.
Labillardière is not the only one to say somewhat bizarre things like this- its pretty common in fact. The problem for later writers was to figure how how these seemingly Indo-European peoples arrived in the Pacific- when they were otherwise surrounded by 'racially' different peoples. [I have written] (https://www.reddit.com/r/AskHistorians/comments/2l8g06/why_did_thor_heyerdahl_but_not_todays/clsh7o2) a few times about some of these theories- that link takes you to the only one I could find off hand. Basically a lot of pseudo-science/new age type thinkers have, since the turn of the last century, proposed lost continents, mass migrations, lost colonies, etc etc to explain the origins of the Polynesians (including the Maori). Some of these theories were far more accepted a hundred years ago; Sir Peter Buck (aka, Te Rangi Hiroa, who was half Maori) was a strong proponent of the Grand Migration theories that said Polynesians essentially travelled through Asia- sailed around the Pacific, and then settled islands coming down and out from North America. One thing all these theories have in common, is racial politics that want to make Maori and Polynesians in general more white- and effectively separate them from all other Pacific peoples. The theories that separated out Polynesians from other Pacific peoples were very much in vogue in the 1920's, 30's, and 40's when racial and colonial politics were especially strong and paternalistic- claiming Indo-European heritage was a way for Polynesians to be elevated in the colonial order.
Are these theories still accepted? By and large no. They do however retain a surprising amount of currency among the general public. And is it not hard to find website dedicated to explain the link between Polynesians and Egyptians or that cite stones or geographical features as proof of pre-Polynesian peoples, or believe that Melanesians are just Africans brought out into the Pacific as slaves thousands of years ago.
One of the best- and frankly only- counters specifically to these ideas comes from Kerry Howe. Most historians just don't have to time or inclination to try and tear down a theory piece by piece when they just don't even know where to begin.
Howe in fact addresses the question and purported evidence for pre-Maori people and does a pretty good job of deconstructing it. These theories are common on a few other Pacific Islands as well; perhaps not so coincidentally all islands with significant settler populations, some of whom perhaps feel more comfortable with their position by imagining that they are but one in a long line of colonizing peoples and that the Polynesians (or Melanesians in New Caledonia, or Aboriginals in Australia) are themselves, in fact, a colonizing people that ejected or displaced a prior civilization.
Given that the encyclopedia dates from the 1930s, it may well have been influenced by Stephenson Percy Smith's Great Fleet hypothesis which suggested that the Moriori (now found on the Chatham Islands) were a separate race, possibly of Melanesian origin, that settled New Zealand before Polynesian Māori. More recent works suggest that the Moriori were Māori that settled the Chatham Islands from New Zealand and that any subsequent linguistic and cultural changes were due to time and isolation. Consider reading Michael King, Moriori: A People Rediscovered, 2000.
The notion that "the Māori ate the Moriori" was still quite prominent when I was at school in the 1990s and early 2000s (I realise personal anecdotes aren't evidence, and that this is skirting the 20 year rule).