Researchers at The Australian National University (ANU) identified the earliest known evidence of rice in the Pacific Islands at an ancient cave site on Guam in the Mariana Islands of western Micronesia. The discovery pushes back the timeline of rice's arrival in the Pacific Islands, settling long-standing academic debates and satisfying decades of curiosity about the origins and lifestyles of early Pacific peoples.
At the Ritidian Beach Cave in northern Guam, researchers used phytolith analysis of microscopic plant debris found on ancient earthenware pottery, which revealed traces of rice husks preserved on the pottery. These findings indicate that rice arrived there at least 3,500 years ago, transported by the first islanders who sailed 2,300 kilometers (1,400 miles) of open ocean from the Philippines, demonstrating the navigation skills of ancient Pacific islanders.
Experts believe that because rice would have been such a precious commodity at that time, it was not consumed daily but instead reserved for special ritual use, and that rice played a role in rituals performed in the cave, which also included fine pottery, shell pendants, and ornaments.
"Early seafarers brought with them not only the tools of survival but also their symbolic and culturally meaningful plants, such as rice. It highlights how important rice must have been," said researcher Hsiao-chun Hung, according to Live Science.
The setting of the discovery—a beach cave—provides another interpretive perspective on its highly specialized cultural role, as no other cave has the same evidence of rice. "This direct association is extra confident because the phytoliths were 100% absent on other artifacts such as stone and shell tools, as well as 100% absent within the surrounding sedimentary matrix," said Michael T. Carson, an archaeology professor at the University of Guam in Mangilao, according to Fox News.
"Phytoliths are like fossils of ancient plant parts," Carson explained. He also noted that the rice was exclusively found on ancient pottery made from earthenware. "The rice husks came from a separate, deliberate activity using the finished pottery bowls," he said.
"The ancient rice remains were found only on the surfaces of the pottery, ruling out ordinary food storage," said Hung. She added, "A damp environment like the cave would have been unsuitable for storing unprocessed rice in pots," according to Fox News.
"These people traveled across 2,300 km of open ocean, setting a world record for long-distance ocean migration at the time," Carson said. "Among their accomplishments, they managed to transport and maintain the rice until they planted and produced successful crops in their new remote-distance island home," he added.
The Mariana Islands, located more than 2,000 kilometers (1,240 miles) east of the Philippines and northeast of Indonesia, were the first places in Remote Oceania reached by anyone, inhabited for the first time by Malayo-Polynesian-speaking populations from islands in Southeast Asia. This migration laid the foundations of the Austronesian world, which today comprises nearly 400 million individuals dispersed across an expansive area stretching from Taiwan to New Zealand and from Madagascar to Easter Island.
For nearly two decades, scholars debated the timing and the overseas source of the first islanders, the ancestors of today's Chamorro people. The study provides strong evidence that the first long-distance ocean crossings into the Pacific were not accidental. "People carefully planned the voyages," the researchers said, according to Live Science.
For more than a decade, researchers searched for evidence of early rice in open archaeological sites across the Mariana Islands but found nothing conclusive. The researchers used detailed microscopic analysis to determine whether the rice husks had been mixed into the clay to keep it from cracking when it dried or had arrived by other means. The findings showed the rice husks were not used for manufacturing the pottery.
Archaeological research confirmed settlement in the Mariana Islands 3,500 years ago at several sites in Guam, Tinian, and Saipan, but there are no traces of rice fields, irrigation systems, or harvesting tools at the Ritidian Beach Cave site in Guam. The discarded shell remains in the cave included different kinds of shellfish than otherwise made up the majority of the daily shellfish diet. The cave also included rare rock art and formal burial pits, indicating its significance.
According to records from 1521 through 1602, the Chamorro people in the Marianas grew rice in limited amounts and consumed it sparingly, reserving it for special occasions and critical life events, such as the impending death of a loved one. Today, Pacific islanders rely mostly on breadfruit, banana, coconut, taro, and yams. Rice cultivation faced challenges in the Pacific due to environmental constraints, including soil type, rainfall, and terrain.
In 2020, the first ancient DNA analysis from Guam confirmed that the early settlers came from central or northern Philippines, with further ancestral links tracing them back to Taiwan, the homeland of both their language and their genetics. The early seafarers were equipped, prepared, and resolute, completing one of the most extraordinary voyages in the history of humanity.
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