Geosciences researchers prove Micronesia’s coral pyramidal tombs much older than previous thoughts Monumental tombs within ancient civilizations worldwide hold precious clues for deciphering the architectural skill, acumen, and industry of prehistoric cultures. A recent study has found that the world’s only coral pyramidal tombs, which are located in Kosrae, Micronesia, dated back to 700 years ago by Prof. Chuan-Chou Shen of the High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences and his international collaborators. It is at least three centuries ahead of what was previously estimated. The findings, which were published in the journal Science Advances1, also reconstruct the fading prehistoric trans-oceanic culture. Pyramidal structures dating back to some 6000 years ago provide an important archive of the architectural styles and cultural practices of ancient civilizations. The pyramids often served as tombs for royalty and were built using locally and/or regionally available abiotic material, such as stone, soil, and clay. The ruins of the prehistoric capital city of Leluh (~AD 1250–1850) in Micronesia contain several royal tombs, the world-unique pyramids constructed using biotic coral. However, the construction date and means by which they were built had remained a myth since their discovery. In the study, Prof. Shen and his team utilized the high-precision radiometric uranium-thorium techniques to determine the dates of three selected sacred Leluh tombs. The team discovered that the tombs were created in the 14th century, around 600-700 years ago. Not only does the new discovery predate previous estimations by at least 300 to 500 years, the team also found that fossil corals with ages of 4,000 to 6,000 years in the tomb structure, refuting previous arguments that only live corals were used in these tombs. According to oral history, locals built the tombs by forming a queue between the tomb’s location and the coastal reef so that live coral material could be relayed to the construction site. This is why the tombs were made up of tens of thousands of coral stones measuring up to several decimals in centimeters. Unlike the pyramidal tombs from other parts of the world, the Leluh tombs are open and accessible from a truncated top that features an up to 2 by 4 meter crypt. The reason, as legend has it, is that the tomb was used only as a temporary burial site and the body was placed inside the crypt for praying and worshiping purposes during the king’s funeral. After a few months, the royal bones would be relocated and buried in a deep hole on a reef nearby. These tales, however, have never been validated with substantial scientific evidence until now. In a previous study, the remains of a 50-year-old male estimated to have lived between the 1800s was found in one of the tombs. Previous researchers subsequently concluded that the tombs were built around 200 years ago. As precise analysis of the coral has shown that the tombs were built in the 14th century, Prof. Shen’s team deduced that the 19th century body had belonged to the last king to have practiced the ancient burial ceremony. While the reason as to why the remains were not relocated is unknown, the findings validate previous tales that the tombs were reused as temporary burial sites. Reference 1. Richards, Z. T., Shen C.-C., Hobbs J.-P. A., Wu C.-C., Jiang X., and Beardsley F. (2015) New precise dates for the ancient and sacred coral pyramidal tombs of Leluh (Kosrae, Micronesia). Science Advances, 1, e1400060, doi: 10.1126/sciadv.1400060. Reference Zoe T. Richards, Chuan-Chou Shen, Jean-Paul A. Hobbs, Chung-Che Wu, Xiuyang Jiang, Felicia Beardsley (2015) New precise dates for the ancient and sacred coral pyramidal tombs of Leluh (Kosrae, Micronesia). Science Advances, 1, e1400060, DOI: 10.1126/sciadv.1400060. Professor Chuan-Chou Shen High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC) Department of Geosciences river@ntu.edu.tw