Humans transported rice thousands of miles across the sea over 3,500 years ago

About 3,500 years ago, a small crew sailed roughly 1,430 miles (2,157 kilometers) from the Philippines to Guam with rice on board.

A new archaeological study has examined microscopic plant traces on pottery from a cave on Guam. It shows that the rice was used in special rituals and gives the earliest clear evidence of the grain anywhere in the Pacific Islands.

Guam seafarers and rice harvest

The story centers on the ancestors of the Chamorro people, the first known humans to settle the Mariana Islands. These early islanders reached Remote Oceania, long before nearby archipelagos saw human settlement.

The work was led by Dr. Mike Carson, an archaeologist at the University of Guam. His research focuses on uncovering the earliest settlements and ritual landscapes of the Mariana Islands.

These voyagers spoke Austronesian languages from a large family of languages spread across islands and coasts from Madagascar to Hawaii. Ancient DNA from skeletons on Guam points to origins in the central or northern Philippines and Taiwan.

Rice was already familiar to these travelers and tied to older farming traditions. Archaeologists studying plant remains in central China found domesticated grains at Baligang, dated to about 8.000 years ago.

Rice was rare in the Pacific

Rice might sound like an obvious crop to bring on a long voyage. However, it is hard to grow on many Pacific islands. Thin soils, steep limestone hills, and irregular rainfall make wet fields unreliable. Island communities relied more on breadfruit, taro, yams, bananas, and coconut.

Records from the 1500s and 1600s describe rice in the Marianas as rare. It was kept for ceremonies and for people close to death.

This status makes the cave evidence important because it shows the grain was present from the first settlement rather than being introduced much later.

Across the wider Pacific, archaeologists have found no ancient rice fields or rice harvesting tools. The Marianas stand out as the only remote island group where rice appears in both historical accounts and deep cultural layers.

That pattern suggests that rice in Guam was not simply a convenient food. It was something worth protecting, carrying, and using very carefully in a new homeland.

Studying rice in Guam’s clay

The key discovery comes from Ritidian Beach Cave, a shallow rock shelter at the northern tip of Guam. Archaeologists excavated layers of soil and found fragments of red pottery with smooth surfaces, some dating back thousands of years.

The team used phytoliths, tiny silica particles that preserve plant shapes for thousands of years, to figure out what had been in the pots.

Under the microscope, they saw clusters of double-peaked shapes that matched rice husks. They also identified distinctive forms from rice leaves and tiny flower parts.

In the cave, these rice signals were abundant on pottery fragments and even on one stone tool, yet completely absent from the surrounding sediments.

That sharp contrast makes it very unlikely that the rice came from later contamination or from random plant material blowing into the cave.

High resolution X-ray scans and thin sections of the pots showed that the clay did not contain plant temper such as chopped husks.

The rice fragments sat only on vessel surfaces, meaning the grain was used with finished bowls and jars rather than mixed into the clay.

Sacred cave and a careful ritual

The find location matters as much as the tiny plant fossils. Ritidian Beach Cave lies just above an ancient shoreline and sits among caves, burials, carvings, and ornaments that mark a ceremonial landscape.

In Chamorro tradition, caves are places where people connect with spirits and ancestors. Early historical accounts describe gatherings, offerings, and important life events focused in these shadowed spaces rather than in ordinary houses.

Only one part of the cave complex has strong traces of rice. Other nearby sites from the same period, including open shoreline camps and a second cave, show almost no sign of the crop.

Planned voyages, not accidental drifts

The new results settle an old question about how the first people reached the Marianas. Some had wondered whether they might have drifted there by accident, carried by winds and currents, with whatever food happened to be on board.

Taken together, the sailing skills, chosen crops, and ritual spaces point to careful planning rather than chance. These early navigators did not just survive an ocean trip, they carried traditions, including rice that tied them back to their Asian homelands.

Rice shows up in the oldest cultural layer of the cave, tied closely to the first generations of island life. Its ritual uses hint that the grain was not only used to feed people. It also helped these voyagers remember who they were and where they came from.

The study is published in Science.

Photographs are courtesy of  Hsiao-chun Hung.

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