Evidence from an ancient graveyard has begun to illuminate one of the great mysteries of the human journey: the peopling of the Pacific. A study in the Proceedings of the National Academy of Sciences reports that the shape and contours of the earliest skull in a 3,000-year-old burial ground in Vanuatu, a group of islands once known as the New Hebrides,suggests a starting point for the great Polynesian migration.

This enduring question was directly framed by Captain Cook, the great 18th century navigator, on his third voyage, when he stopped at the Hawaiian islands. He wrote in his journal: “How shall we account for this Nation spreading itself so far over this Vast ocean? We find them from New Zealand to the South, to these islands to the North, and from Easter Island to the Hebrides.”

Anthropologists, archaeologists, oceanographers and geneticists have been trying to answer his question ever since. The great adventurer Thor Heyerdahl, who in 1947 sailed the balsa wood raft Kon-Tiki more than 4,000 miles from Peru to the Tuamotu islands, did so to prove that the Pacific must have been settled from the Americas. But linguistic and genetic evidence continued to point to a settlement originally spreading eastwards from Asia.

The latest study, led by Frederique Valentin, an archaeologist and ethnologist from Nanterre in France, reports that although most of the skulls from other later Lapita sites in Vanuatu and elsewhere are linked to the western Pacific’s Melanesian ethnic group, the oldest ones, dated 3,000 years ago from the graveyard on Efate Island in Vanuatu, seemed more aligned with “present-day Polynesian and Asian populations.” The archaeological evidence identifies these as from the ancient Lapita culture, already linked to modern Polynesian settlers.

If so, the research does not explain how one group of oceanic navigators took their language, traditions and canoes to tens of thousands of islands scattered across almost one third of the world’s biggest ocean. But it does suggest Vanuatu may have been the springboard for the great leap into the Pacific.

• This article was amended on 30 December 2015 to correct a misunderstanding about the number of skulls included in the study.