A Sydney-based university museum has repatriated 16 human skulls to six villages in Papua New Guinea.

The ancestral remains were returned back to villages in the country's north-eastern Madang province last week.

The skulls were taken from the Rai Coast in Madang by prominent Russian explorer Nickolai Miklouho-Maclay during an expedition in 1876.

The Russian anthropologist, who was reportedly the first "outsider" to make contact with people on the Rai Coast, was famous for also being one of the earliest Europeans to study the "Indigenous people of New Guinea".

He noted in his journal at the time that the Papuan skulls were not exhumed and were "freely given".

Miklouho-Maclay aimed to prove that people of different races, ethnicities and cultures were physiologically the same as Caucasians, which was not prominently believed in the 19th century, and wanted to study the skulls to prove that.

A friend of author Leo Tolstoy, he was also once an early follower of the evolution theories of Charles Darwin.

The skulls landed in Sydney in 1878 with Miklouho-Maclay, who would work alongside naturalist William John Macleay.

The remains were donated towards the establishment of Sydney University's Macleay Museum in 1887 from Miklouho-Maclay's Australian widow the following year, after his death.

The Macleay Museum recently became part of the Chau Chak Wing Museum in 2020.

Museum staff have been in contact with descendants of the skulls for more than 40 years, engaging with ancestors on items from its collections, including the skulls.

Miklouho-Maclay's great-great nephew, Nikolay Miklouho-Maclay junior, made the discovery of these remains when visiting the Rai Coast and, after contacting Madang locals, a request was made for the return of the skulls.

The repatriation of the head crania followed a formal request in April 2024.

"People are looking at (the repatriation) as a rebirth of their history in some ways and to think about those people and the wisdom of that time," Chau Chak Wing Museum's senior curator Jude Philp, who formally handed over the skulls, told the Art Newspaper.

The return was commemorated in local ceremonies of song and dance accompanied by the roasting of pigs for a feast.

Philp joined dignitaries in Papua New Guinea, arriving in ceremonial boats carrying the remains in special crates.

There was little resentment from authorities for the missing skulls at the commemoration.

"These ancestors were taken by Nickolai nearly 150 years ago to support his work promoting one shared humanity," PNG's Department for Community Development and Religion deputy secretary Jack Simbou said.

"They departed the Rai Coast aboard a Russian Corvette and returned on a Boeing jet.

"Their journey spans time and distance, and we extend gratitude to the Chau Chak Wing Museum for reuniting us."