When Wellington researcher Paul Callister climbed Australia's tallest peak Mt Kosciusko recently, he met a young man at the top who was both a New Zealander and an Australian.
Although he was not noticeably Maori, one of his parents was Maori and he wore a bone carving around his neck.
His mother lived in Queensland, his father in Gisborne.
"The way he talked, he didn't really see the boundaries between the two countries," Dr Callister said. "So I think there will be that group between New Zealand and Australia who are neither here nor there, they are both here and there."
This phenomenon of transnationalism, having a foot in two or more parts of the world simultaneously, is already apparent not just between the two sides of the Tasman but on a global scale.
Twenty years from now, despite the likely rising costs of travel and other impacts from global warming, transnationalism is expected to be much stronger.
Dr Callister said he watched his 19-year-old daughter communicate on Facebook "all the time" with "some kid in New York and some friend in Berlin".
By 2030, when the Facebook generation begins to take positions of power in the world, global society will surely feel quite different from the narrow, inward-looking national societies that have characterised the era of the nation state over the past few hundred years.
New Zealand, with its long tradition of "overseas experience", is already at the forefront of whatever this change will mean.
Roughly one in five people born in New Zealand, or 800,000 people, now live overseas - a higher percentage than any other developed nation except Ireland, although a much smaller proportion than for even smaller and poorer island nations such as most South Pacific and Caribbean islands.
Conversely, 22.9 per cent of the people in New Zealand at the last census were born overseas, a higher share of immigrants than in any other developed nation except Australia and Switzerland (both 25 per cent).
Immigrants' share of our population increased by two-fifths, from 16.4 per cent, in the 20 years to 2006.
Although there are no official population projections by birthplace, the ethnic projections give us a clue. Statistics NZ's best guess is that ethnic Asians will rise from 11 per cent of our population in 2006 to 17 per cent in 2026.
The changes are even more spectacular for Auckland, where the bulk of new migrants settle. People born overseas rose from 22 per cent of Auckland's population in 1986 to 37 per cent in 2006, and Aucklanders of Asian ethnicity leapt from under 5 per cent to 19 per cent.
Massey University sociologist Paul Spoonley estimated that Asians would be a quarter of Auckland's population just six years from now, and that immigrants and their children probably already made up more than half of Auckland's people.
"In terms of the size of its immigrant population [in proportion to its total population], Auckland is now sixth-equal in the world with Vancouver. Sydney is 19th," Dr Spoonley said.
While migration to the United States and other developed nations has slowed since September 11, 2001, migration to New Zealand has held up relatively well.
"Since 2000, our immigration rate per head is the highest in the OECD," Dr Spoonley said.
"In the proportion of international students per head, we are top of the world. Since 2000 we have leapfrogged other countries that would have been ahead of us a decade ago."
Unlike earlier migrations, this one is extraordinarily fluid. Many come as students, temporary workers or on working holidays intending to go home again. A growing number have found ways to live in New Zealand and earn incomes from offshore, keeping in touch with employers or their own businesses by email.
"We had a lady in the other day who is Korean," said Dr Spoonley. "She lives in Auckland. Her children are being educated in English in Auckland. She earns her living by running a business in Korea, which she can do remotely."
They came, he said, almost universally for lifestyle reasons. Even if they come from poorer countries, they choose New Zealand rather than other, richer countries for our safety, stability and uncrowded environment.
They stay in touch with home.
"I'm staggered at the level of communication that occurs between home communities and immigrant communities," Dr Spoonley said. "If you look at any immigrant community in Auckland, the number of websites they access locally and home-based is huge."
He said communication on popular social networking sites "completely ignored boundaries", reinforcing the rootlessness that migration often brings.
Many migrants do go home eventually, but others stay, and many go home and later return to New Zealand.
"We've done a wee bit of work asking these kids whether they'd go back to Asia. They say, 'Yes, Auckland is boring'," he said.
"But they don't, because they establish families and start their careers in Auckland and so if they go, they tend to come back."