Mystery and intrigue surrounds the life and times of people who created the famous Moai statues on Rapa Nui off the coast of Chile — and a new study suggests they were more isolated than previously thought.

Key points: Scientists have long debated whether ancient Rapanui and native South Americans came in contact with each other

Scientists have long debated whether ancient Rapanui and native South Americans came in contact with each other Researchers analysed DNA from five ancient Easter Islanders and found no evidence the two groups intermingled.

Researchers analysed DNA from five ancient Easter Islanders and found no evidence the two groups intermingled. Findings contradict earlier studies

While it is widely accepted that the remote island, dubbed Easter Island by Dutch explorers, was first settled by Polynesians before 1200 AD, scientists have long debated about what happened next.

One of the big questions is whether or not the early islanders had any contact with Indigenous South Americans.

A 2014 DNA study of present-day Rapa Nui and archaeological evidence from sweet potato crops suggested the islanders mixed with native Americans before Europeans arrived in 1722 AD.

But now a new study of ancient DNA, published in the journal Current Biology, indicates the two groups did not intermingle at all before European settlement.

The research looked at the genomes of five early Rapa Nui islanders using samples taken from the Ahu Nau Nau site close to five of the famous moai statues.

Dating suggested three of these individuals lived between 1445 and 1624 AD — before European contact — while the other two were dated between 1815 and 1945; well after European arrival on the island.

But to the researchers' surprise, they found no evidence of native American genes in the three individuals from pre-European times.

"Our finding is that, at least in those individuals that we analysed, there is not native American ancestry," said Professor Lars Fehren-Schmitz, a co-author and professor of biological anthropology at the University of California, Santa Cruz.

"The first reaction to our findings was that we were pretty surprised ... because the [earlier] paper is very compelling and makes a very good case."

While the older individuals contained no native American DNA, there were traces of European genetic influence in the two post-European individuals.

What could have happened?

So why did the previous study find such compelling evidence of a genetic influence from South America when this study could find no trace?

Professor Fehren-Schmitz said there were a number of possible explanations for the conflicting findings between the two studies.

He said there was a possibility that the three ancient individuals without native American DNA studied just happened to be Rapa Nui who did not intermingle.

But, he said, the previous study suggested that native American ancestry was fairly evenly distributed across the population, which would imply it would be unlikely early individuals would have no trace of ancestry.

DNA samples were taken from this site at Ahu Nau Nau, Anakena ( Supplied: Terry Hunt )

Another explanation for the earlier study's finding of native American ancestry may relate to the mixed European and South American ethnicity of the crews that visited the island.

"Based on the historical sources, that is actually quite likely, because the crews that were on the ships that landed on Rapa Nui over and over and over again, mostly had crews from South America, from Peru and so on."

Professor Fehren-Schmitz said although the findings cast doubt on the idea that the two groups intermingled, it doesn't mean there wasn't contact between the two groups before the Europeans arrived.

The other possibility is that native Americans had contact with other Polynesian groups that travelled to Rapa Nui, rather than direct contact with the islanders themselves.

"So the genetic signature never made its way to Rapa Nui but there were other things, like the sweet potatoes, did."

Evidence for contact is contentious

Professor Alan Cooper, director of the Australian Centre for Ancient DNA, said the original claim of native American ancestry on Rapa Nui had always been contentious, especially given the only archaeological evidence was the sweet potato crop.

"The sweet potato has been held up as the golden standard of contact, but there was paper recently showing just how far those buggers can float," said Professor Cooper, who was not involved in the study.

Professor Cooper and colleagues have also been examining whether chickens were transported from South America to Polynesia in this pre-European period.

But despite the Polynesian fondness for chicken, no such evidence was found.

He said there's also no evidence of the transport of rats from South America to Polynesia.

"You'd figure that both of those two would be pretty good markers if there had been contact between Polynesia and South America."

Professor Fehren-Schmitz said their study was not the last word on the issue, but rather opened the door to further investigations.

"What our study tells us is that we have to dig deeper and we have to do that jointly as geneticists and archaeologists and anthropologists, to see if there is any other kind of traces that we can work with that give us a better idea of what might have happened."