‘The Real Moana’: what drove the Polynesians out into the open ocean

This story is reminiscent of the plot of *Moana*: a home island faces a threat, and its inhabitants resolve to venture beyond the reef.

New research has shown that these real-life voyages may well have had a climatic cause. Before the great migration began, Samoa and Tonga experienced a prolonged drought, whilst the islands further to the east were becoming wetter.

But the ‘real Moana’ is merely a figure of speech. Scientists have not found a real-life counterpart to the heroine, nor do they claim that the drought was the sole reason for the migration. The climate may have provided a strong impetus, but the voyages were made possible by navigational knowledge, ocean-going canoes and the decisions of the Polynesian communities themselves.

A mysterious hiatus lasting around 1,700 years

The ancestors of modern Polynesians reached Samoa and Tonga around 3,000 years ago. After that, further settlement eastwards slowed down considerably for a long time.

Around 1,700 years elapsed between the settlement of Western Polynesia and the active expansion towards the eastern islands. Researchers refer to this period as the ‘long pause’. Why these experienced seafarers remained in one part of the Pacific for so long, only to resume their journey relatively quickly afterwards, remains one of the key questions in the archaeology of the region.

A new wave of settlement began around the first millennium AD. Over the course of several centuries, Polynesian seafarers reached the numerous islands of Eastern Polynesia, traversing thousands of kilometres of open ocean.

What was discovered in ancient mud

To understand what the climate was like during these voyages, scientists studied sediment deposits from swamps and lakes in Samoa, Tonga, the Cook Islands and French Polynesia.

These layers contain chemical traces of ancient algae and terrestrial plants. The researchers analysed the ratio of heavy to light hydrogen isotopes: this ratio depends on the amount of tropical rainfall and allows us to estimate, to some extent, how wet or dry the climate was thousands of years ago.

Different natural archives painted a similar picture. Immediately prior to active settlement, the south-western Pacific, where Samoa and Tonga are located, experienced a prolonged period of drying. The eastern islands, by contrast, gradually became wetter, and climatic upheavals occurred less frequently there.

Drought has changed the cost of risk

For island communities, a reduction in rainfall means much more than just dry weather.

On small islands, fresh water supplies are limited. Prolonged drought could have reduced crop yields, restricted access to drinking water and made communities more vulnerable to subsequent years of poor harvests.

Population growth could have exacerbated the situation. The more people depended on limited land and erratic rainfall, the greater the pressure on local resources became. Socio-hydrological modelling has shown that growing island communities are particularly sensitive to recurring droughts against a backdrop of a generally drier climate.

Under such conditions, the perilous voyage eastwards might have begun to seem less reckless. The cost of inaction was rising, whilst reports of wetter islands made the journey more appealing.

Rain awaited them in the east

Climate models have helped explain why some islands were drying out whilst others were receiving more rainfall.

According to the researchers’ findings, long-term changes in the surface temperature of the Pacific Ocean shifted the vast tropical rain belt eastwards. As a result, Samoa and Tonga became drier, whilst some of the islands of Eastern Polynesia became wetter.

This created a kind of climatic trap and, at the same time, an opportunity: the familiar islands were less able to provide people with water and food, whilst the lands beyond the horizon were becoming more suitable for long-term settlement.

The authors suggest that some seafarers may already have known of the so-called ‘gateway islands’ further to the east. The drought did not necessarily force them to set out into completely unknown territory — it may have prompted them to make use of routes and knowledge that had existed previously.

How the Polynesians crossed the vast ocean

Climatic pressure alone was not enough. Crossing the Pacific Ocean required sophisticated technology and knowledge accumulated over generations.

Polynesian navigators relied on the stars, waves, winds, clouds, the behaviour of birds and other natural signs. Journeys were undertaken in large ocean-going canoes capable of carrying people, water, food, plants and animals to establish new settlements.

The authors of the study also link the start of active eastward expansion to developments in canoe design and sail rigging, which allowed for more efficient travel against prevailing winds.

Therefore, the great migration was not a flight of helpless people from drought, but the result of a combination of environmental pressures and outstanding seafaring skills.

Drought was not the only cause

The study shows that climate change coincided with the period of migration, but cannot reconstruct the decisions of individual people.

The exodus may have been influenced simultaneously by:

• population growth and competition for land;
• water scarcity and crop instability;
• social conflicts or the desire to establish new settlements;
• information about previously discovered islands;
• advances in canoe-building and navigation;
• changes in wind patterns and sailing conditions.

It is therefore more accurate to say that the drought contributed to the great migration or made it more likely, rather than that it single-handedly ‘forced’ the Polynesians to cross the ocean.

Why this is important

This research helps to explain one of the most remarkable episodes in human history. Polynesian seafarers settled islands scattered across a vast expanse of the Pacific Ocean without compasses, modern maps or engines.

New research shows that climate may have shifted the balance between safety and risk. As life on their familiar islands became increasingly precarious, a perilous voyage ceased to be unthinkable.

It also serves as a reminder that climate change does not affect societies in a mechanical way. Drought may create pressure, but the response depends on technology, knowledge, culture and people’s ability to make collective decisions.

Background

The history of Polynesian settlement is being reconstructed using archaeological finds, genetic data, changes in vegetation, traces of human activity in lake sediments and computer modelling of sea routes.

The dates of individual stages remain a matter of debate. Researchers suggest that some of the eastern islands may have been discovered before permanent settlements were established there. This suggests that the ‘long pause’ may not have been a period of complete absence of voyages, but rather a time of exploration and limited contact without large-scale migration.

Source

David Sear et al.,“How Did Changing Climate in the Tropical South Pacific Contribute to the Eastward Migration and Settlement of Polynesia?”, Journal of Pacific Archaeology, 2026.