In February 1840 New Zealand was a bicultural nation. There was one European for every 39 Maori, but both races, if they weren't already, were about to become as important as each other to the country's history.

Despite barely registering a speck on the cultural horizon, the relative handful of British settlers ensured their presence was felt well before 1840. They had brought guns and germs - two of the biggest engines of colonial upheaval - and the impact was almost immediate. Maori killed about 20,000 of each other in the tribal Musket Wars of the 1820s and 30s.

The weapons of choice, of course, having come from the settlers. Diseases, particularly measles, killed countless thousands more. Ngai Tahu's pre-European population was almost halved by 1830.

So it was that by the day the Treaty of Waitangi was first signed in 1840, the estimated 2050 non-Maori people in New Zealand had done a good job of making their presence known to the 80,000 native forebears.

They then set about keeping that disproportionate level of influence up. Few settlers learned the local language, instead, in an unlikely role reversal, teaching English to the Maori.

"Imagine an immigrant group in New Zealand now that makes up 2 or 3 per cent of the population," historian Paul Moon said, for perspective.

"Imagine a large number of New Zealanders learning their language and them refusing to learn English. It's almost inconceivable."

It went from there. Colonial records don't record any population in the South Island until 1848 (Otago, European population: 620). Canterbury's first was in 1849 when the European headcount was just 301. Three years later it was nearly 4000.

Ngai Tahu first had contact with Pakeha whalers and sealers around 1795, and the two peoples co-operated to build a thriving trade with one another. After such an amicable arrangement, the Treaty of Waitangi seemed a mere continuation of relations already established.

But within 10 years of seven of the most high-ranking southern chiefs signing the document, the Crown began to default on major land agreements. The suspicions of chiefs who chose not to sign came to fruition, and so began Te Kereme: Ngai Tahu's Treaty of Waitangi claim. It would be 149 years before that claim, and others, were settled.

The 1960-70s brought the first resurgence of a collective Maori protest movement, the establishment of the Waitangi Tribunal and the recognition of Te Reo Maori as a national language. For rural Maori such as Christchurch kaumatua Peter Mason, it also signalled a heightened awareness of the Treaty, and it became a touchstone for the anger and bitter loss felt by iwi across New Zealand.

Mason, from Whakatane, was born into the Ngati Awa iwi, which was impoverished by land confiscation. The Treaty had little standing with him and his people. It was a dishonoured contract.

"It was actually the army that made me see what the Treaty was all about, and it was then I wanted to do something about it," he said.

That knowledge became a building block for Mason to aid Ngati Awa in pursuing a treaty claim. They settled with the Crown in 2005.

"We were very proud of the Treaty for the first time," he said.

"It brought a lot of the iwi together, and it also allowed us to celebrate and commemorate the signing of the Treaty of Waitangi."

Waitangi Tribunal member and Maori historian Aroha Harris said perceptions of the Treaty had changed markedly. She believes New Zealanders have gone from knowing almost nothing about it to knowing key parts.

More and better teaching of New Zealand history in schools has helped attitudinal changes, Harris said, and seen Waitangi Day become more widely commemorated today.

"It didn't look like that 20 years ago. But there is a question about consistency of Treaty education across schools, and there's a question about the quality of that education."

Mason said the Treaty would need to be upheld by - and for - Maori and Pakeha in the future, as the nation became more cosmopolitan.

"The Treaty ensures that we have mana whenua status. And now, Maoridom is strong enough to say, 'no, we are not going to do that', if something is not right."

Moon believes the traditional view of biculturalism in New Zealand will be difficult to hold onto.

"European identity seems to be reasonably well fixed in the sense that it's a biological or ethnic or racial group. Maori identity is getting to the point in a few cases where it's less obvious biologically or ethnically.

Maori self-identification would become more cultural, he said.

By the next census, there is a chance, for the first time in 175 years, Europeans will be a minority population in Auckland. Compare that with Canterbury, which may fall slightly from the 87 per cent of people in the province who identified with European ethnicity in 2013.

Whatever the shortcomings of the Treaty, New Zealand as we know it started on February 6, 1840. What we look like today is a direct result of that.