Archaeologists Find 3,500-Year-Old Traces of Rice in Guam

Rice was a basic harvest in the ancestral Austronesian regions of Taiwan and Southeast Asia of the island, but it was unknown in any of the Pacific islands at the time of European meetings, with the exception of the unique case of Guam and the Mariana islands. New research by scientists from Guam, China and Australia confirm the presence of an envelope of abundant rice and leaf phytoliths adhering to the red slide pottery found in the cave of the Ridiane beach in Guam, dated from the radiocarbon to 3,500 to 3,100 years.

Ritidian Beach Cave, Guam. Image credit: hsiao-chun hung.

The question of early rice in the colony of the Pacific islands is linked to the broader context of rice as a basic food among the ancient peoples of the Austronesian language, responsible for the most widespread language in the world before the superposition of the world colonial extensions.

Although the Austronesian people have cultivated rice for at least 4,800 years in Taiwan, culture has apparently decreased among communities beyond eastern Indonesia in the distant islands of the Pacific.
Ancestral Austronesian populations have migrated Taiwan in the Asia-Pacific region, from 4,200 years of age.

These first islanders brought back domestic rice from Taiwan, traced to a source in the average Yangtze basin in continental China.

In this context, the role of rice in Guam and the Mariana islands in Western microneia drew intense attention, because the Mariannes were the only islands of the distant Pacific Oceania where people cultivated rice, attesting at least from the documentary recordings of the 1500s to the 1600s.

“The results offer new indices on old migration and culture,” said Dr. Hsiao-Chun Hung, archaeologist at the Australian National University.

“Until now, archaeological evidence has only revealed rare traces of rice in the distant Pacific dating back may 1,000 to 700 years ago – so the evidence that we found reject this calendar significantly.”

Rice phytoliths of the excavations at Ritidian Beach Cave, Guam. Scale bars – 10 μm. Image credit: Carson and al., DOI: 10.1126 / SCIADV.ADW3591.

Dr. Hung and his colleagues found the ancient vestiges of rice in the cave of the Ridiane beach in northern Guam, a site that still has a cultural meaning today.

“While rice was a daily basic food in many ancient Asian societies, this discovery indicates that in the distant Pacific, it was treated as a precious goods, reserved for ritual use rather than being consumed daily,” said Dr. Hung.

“We have found no proof of ancient rice, irrigation systems or harvesting tools in Guam.”

“Our results support the idea that the first Pacific Icelanders transported rice with them from the Philippines on 2,300 km of free water – the longest trip to the ocean known at the time.”

“This shows not only their advanced navigation skills, but also their foresight in preserving and transporting valuable resources over large distances. This underlines the importance of rice. “

“The Ritidian beach cave offers a unique overview of the life of the first inhabitants of the region, because most of the other Guam caves sites were disrupted during and after the Second World War.”

“Despite many years of work on outdoor sites, we have found no evidence of early use of rice so far.”

“This discovery indicates a deep and lasting link with ancestral traditions and an Asian homeland.”

“The rice envelopes were found in the oldest cultural layer of the site and were dated using a series of advanced techniques, including the radiocarbon dating of surrounding human mounds – called Middens.”

“People have probably cooked rice elsewhere, far from the cave, because the treatment of cereals and cooking would undoubtedly have left other traces behind.”

“A wet cave environment would not have been suitable for storing non -transformed rice in the pots.”

“The old remains of rice have been found only on pottery surfaces, excluding ordinary food storage.”

The discovery is reported in an article in the review Scientific advances.

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Mike T. Carson and al. 2025. The earliest proof of rice culture in distant oceania: ritual use by the first islanders of the Mariannes 3500 years ago. Scientific advances 11 (26); DOI: 10.1126 / SCIADV.ADW3591