A skull, found on the banks of a river near Wellington, has turned out to be that of a European woman who died more than 260 years back -- a finding that has raised serious doubt whether Captain James Cook was the first Westerner to step foot on the shores of New Zealand in 1769.

The discovery was made by a boy walking his dog four years back on the banks of a river in Wairarapa region of the North Island, an area settled by Europeans only after the establishment of a colony by the New Zealand Company in 1840.

"It's a real mystery, it really is.

"We have got the problem of how did this woman get here?

"Who was she? I recommended they do carbon date on it and of course they came up with that amazing result," Robin Watt, a Forensic Anthropologist who was called in by police who probed the discovery, said.

John Kershaw, the local Coroner, was told that police at first thought they had a murder inquiry on their hands.

"One of the reasons some work was done on the skull was because it had a number of puncture wounds.

"We don't know how this lady met her death, although the historian we used indicated drowning was a reasonable guess," Kershaw said.