'We're human': Scientist urges caution over DNA tests that claim to 'prove' race

One of New Zealand's foremost DNA scientists is cautioning against accepting the word of DNA testing companies that claim they can pinpoint a person's racial background, after one told Native Affairs newsreader Oriini Kaipara she had "100 per cent Maori" DNA.

Professor Lisa Matisoo-Smith from the University of Otago is an expert in biological anthropology, specialising in the origins of Pacific peoples.

She told the Herald testing companies greatly overstate how much scientists know about the human genome. Their knowledge is nowhere near comprehensive enough to say a person has 100 per cent Polynesian ancestry.

But she was not surprised by the company's findings, based on the limited understanding scientists do have of Polynesian DNA.

Matisoo-Smith's lab at Otago has carried out full genome analyses of around 150 Maori people. Many of them had "minimal to zero European admixture".

DNA markers showing Polynesian ancestry are mostly found via a process of elimination, through looking for markers that are not found in the genetic makeup of European, Asian or African peoples.

But most of those markers, Polynesian or otherwise, haven't been identified.

"I'm always extremely concerned about those kinds of analyses that tell you you have 'x' percentage of ancestry from any particular place - because we know that's just not the case," Matisoo-Smith said.

"The human genome is variable across the world. It's not made up of discrete units that we see in particular populations as percentages."

Ultimately, all human populations came out of Africa - as Matisoo-Smith has previously pointed out, humans left Africa about 60,000 years ago, while Maori came to New Zealand at the last stage of that journey a mere 750 years ago.

The difference between the DNA of ethnic groups such as Maori or European was "infinitesimal" compared to the DNA all humans have in common, making race an "imaginary construct", at least when it came to genes.

"There is no such thing as a pure population - there has been a mixture throughout our entire human existence. When people define what is Maori or Polynesian or whatever - there is no such thing as a 'pure' anything - we're human. We carry DNA from Neanderthal, Denisovan and other ancient hominins."

Many online commenters took issue with using the outdated Western concept of "blood quantum" to define how Maori a person is - given that being Maori is defined by whakapapa. Matisoo-Smith agrees.

"Maori have whakapapa and they know they are Maori...they don't need the DNA to provide that evidence. DNA contributes to who you are but it does not make you who you are. Social context, whakapapa, makes much more of a contribution."

Racial purity and blood quotients have historically been used in New Zealand to denigrate Maori or deny them their rights.

In 2006, then-National Party leader Don Brash said there were no "full-blooded Maori" left in New Zealand, and that they should not receive what he called "special treatment" as a distinct ethnic group.