Publications
Ancient Ryukyu Jomon contributed to past and current genetic structure of Japanese populations
A genetic divergence between the Ryukyu Jomon population and the Hondo (Japanese mainland) Jomon was identified, dating back approximately 6,900 years before present (YBP). This study, which sequenced 273 modern and 25 ancient whole genomes from the Ryukyu Archipelago, revealed that the Ryukyu Jomon experienced severe population bottlenecks with an effective size of around 2,000 individuals. Admixture between the Ryukyu Jomon and historic Hondo migrants occurred roughly 1,000 YBP, coinciding with the introduction of iron tools and agriculture in the Central Ryukyus. The findings highlight distinct demographic histories between modern Hondo and Ryukyu populations, contributing to our understanding of cultural transitions in the region.
Beyond Infrastructure: The Naha Port Freeway Airport Route Ventilation Towers as Landmarks of Continuous History and Collective Memory
Modern infrastructure often prioritizes functionality over cultural resonance, leading to urban 'non-places.' However, the Naha Port Ventilation Towers (2012) challenge this norm by integrating historical and cultural significance into a contemporary logistics hub. Located at Naha's historic gateway, these towers draw inspiration from Ryukyu Kingdom fortresses, Miegusuku and Yarazamori-gusuku, using Gusuku-inspired circular plinths and Ryukyuan limestone textures to create spatial continuity. This study demonstrates that large-scale civil engineering projects can transcend utilitarianism by embedding vernacular symbols into public landscapes, thereby revitalizing collective memory and fostering urban identity. The research employs a qualitative case study approach, analyzing historical iconography, architectural design, and media discourse, while tracing the towers' 15-year conceptual evolution through interviews with lead architects. It critiques the 'Architecture of the Fitting,' arguing that activating a site's stratified vitality rather than mere formal replication is key to maintaining continuous history.
Kastil Shuri di Prefektur Okinawa: Pelestarian Identitas Budaya Ryukyu dan Destinasi Wisata
Shuri Castle serves as a pivotal symbol of Ryukyuan cultural identity and a key tourism destination in Okinawa. The study reveals that the castle's strategic role in representing Ryukyu's political history, architecture, and symbolic meanings is crucial for preserving its cultural heritage. Through qualitative analysis using Stuart Hall’s theory of cultural identity, the research highlights how Shuri Castle's management as both a historical park and tourist site enhances public understanding of Okinawan history and culture. This dual function supports broader efforts in cultural preservation while fostering tourism.
The Diffusion of Sugar-Making Knowledge in the East China Sea: Japan, Amami, and Ryukyu, 1609–1868
Japan's early modern sugar industry, from the late 17th to mid-19th century, developed through two distinct yet interconnected pathways: a colonial monoculture in the Amami Islands under Satsuma Domain control and a decentralized household economy in eastern Shikoku. This study reveals that sugar-making knowledge entered Japan primarily via Ryukyuan intermediaries rather than directly from China, challenging conventional narratives of technological diffusion. Analyzing domain administrative records, sugar-making manuals, household documents, and the journal of a samurai exile, researchers demonstrate how Japanese producers adapted and hybridized imported technologies—such as three-cylinder mills, waterwheel-powered crushers, and refining methods—to local conditions, labor regimes, and market demands. The findings highlight significant environmental and social transformations in Amami, including deforestation, food insecurity, and debt bondage, while contrasting this with the more integrated development of sugar production in Shikoku. This work situates Japan's modest yet innovative sugar industry within broader global histories, suggesting possible connections to Latin American and Jesuit networks.
Application and Challenges of Chinese Lacquer Identification Techniques in the Conservation of Cultural Relics
Integrated analytical techniques combining microscopy, spectroscopy, chromatography, and biochemical methods have proven highly effective in characterizing complex lacquer–metal interfaces and layered structures in cultural relics. This approach provides critical insights into composition, degradation patterns, and conservation strategies for Chinese lacquer, a durable natural polymer with significant cultural heritage value. The study highlights the importance of standardized authentication protocols and shared databases to address regional and chronological variations in lacquer formulations. While non-destructive technologies show promise in reducing sampling needs and improving aging simulations, challenges such as ethical constraints on sampling and long-term degradation mechanisms persist. Future advancements in hyperspectral imaging, bioinspired consolidants, and computational modeling could further enhance non-invasive diagnostics and sustainable conservation efforts for global heritage protection.
Place-based science from Okinawa: 18th-century climate and geology recorded in Ryukyuan classical music
Ryukyuan classical music from the 18th century contains detailed observations of climate and geological phenomena, including surface winds, ocean currents, typhoons, and volcanism, that align with modern scientific records. This study demonstrates how indigenous knowledge embedded in art can serve as a historical record of environmental conditions, offering a novel perspective for understanding past climate and natural hazards. By comparing lyrics from Ryukyuan music with 20th–21st-century scientific data, researchers highlight the potential of this approach to engage contemporary audiences—particularly Okinawans and their diaspora—in discussions about climate change and natural disasters. The findings suggest that integrating indigenous knowledge into science education could foster greater public engagement with pressing environmental issues.
The Appearance and Disappearance of Ryukyu: The Historical Views of Tō Teikan, Motoori Norinaga, and Ueda Akinari
Edo-era Japanese intellectuals viewed the Ryukyu Kingdom (now Okinawa Prefecture) as occupying an ambiguous geopolitical space, neither fully foreign nor entirely native. This perspective emerged from debates between Motoori Norinaga and Ueda Akinari, who both engaged with Tō Teikan's controversial claims in Shōkōhatsu (1781), which suggested continental influences on ancient Japan and proposed that Emperor Jimmu had Ryukyuan origins. While Norinaga opposed the latter idea but acknowledged possible ties between Ryukyu and Japan, Akinari remained agnostic about Jimmu's origins while supporting continental influence. Their debate influenced 19th-century depictions of Ryukyu’s historical and cultural connections to Japan, notably in Kyokutei Bakin’s Chinsetsu yumiharizuki (1811). The study reconstructs these intellectual tensions using historiographical analysis.
Ugui Royal Portraits not seen since Battle of Okinawa, Recovered and Returned
Four ugui royal portraits of the Ryukyu Kingdom, previously believed lost since the 1945 Battle of Okinawa, were recovered and returned to Okinawa in March 2024. This marks the first confirmed recovery of such royal treasures since 1953, representing a significant cultural and historical milestone for Okinawa. The portraits, along with sixteen other artifacts looted by American soldiers, hold deep emotional and heritage value for the Okinawan people, who suffered extensive loss during World War II. The essay details the repatriation process, the significance of these artifacts, and their role in preserving Okinawan identity and history.
Biocultural Diversity of the Ryukyu Archipelago based on the Plant Diversity used as Fish Poison
Research on the Gusuku Sites and Related Properties of the Kingdom of Ryukyu reveals significant biocultural diversity in the Ryukyu Archipelago, particularly through the use of fish poison plants. The study identified 41 species from 24 families, with notable differences between high and low islands. This diversity reflects the varying 'island’s satoyama' landscapes shaped by human livelihoods and inter-island connections. The findings highlight how traditional practices, such as fishing techniques, have influenced plant diversity and ecosystem interactions in this UNESCO World Heritage Site.
Incorporating Biocultural Values in Biodiversity Conservation Policies: A Case Study of the Regional Strategy for Biodiversity in Okinawa
A key insight from this study is that integrating local biocultural values into biodiversity conservation policies can effectively bridge global policy imperatives and regional uniqueness, as demonstrated by Okinawa Prefecture's Regional Strategy for Biodiversity. The research employs a biocultural approach to analyze how traditional knowledge and cultural practices rooted in the Ryukyu Arc were adopted as indicators for evaluating biodiversity strategies. By examining the interaction between biocultural diversity and policy frameworks, the study highlights the potential of such an approach to foster sustainable development and enrich human-nature interactions. This work underscores the importance of comparative studies across the Pacific and Southeast Asia to deepen our understanding and implementation of biocultural conservation strategies.
A new perspective on the evolution of “Kawara” roof tiles in Ryukyu: A multidisciplinary non-destructive analysis of roof tile transition at Shuri Castle, Ryukyu Islands, Japan
A groundbreaking study reveals that the evolution of Ryukyuan 'Kawara' roof tiles, unique to Shuri Castle and other sites in the Ryukyu Islands, involved both changing and unchanged internal features over centuries. Despite external variations in form, pattern, and color—shifting from diverse origins in the 13th–15th centuries to a standardized red tone by the 16th–19th centuries—the elemental composition and paste density of these tiles remained consistent. This suggests that different material properties responded variably to social and environmental stressors, challenging traditional archaeological narratives that focus solely on external changes. The research employed non-destructive, multidisciplinary techniques—including quantitative analysis—to track transitions in firing conditions and surface color, offering a novel framework for studying the chronological evolution of material culture.
Distribution and utilization of homestead windbreak Fukugi (Garcinia subelliptica Merr.) trees: an ethnobotanical approach
Fukugi (Garcinia subelliptica) trees, native to the Ryukyu Archipelago, serve as cultural keystone species, shaping island landscapes and community identity while providing critical ecosystem services. These evergreen windbreaks, traditionally planted for coastal protection, also hold deep spiritual significance in sacred sites. Field surveys and interviews revealed their multifaceted roles—from timber during hardships to symbolic representations in cities—and highlighted a generational shift in cultural appreciation. The study underscores Fukugi's ecological and socio-cultural importance, advocating for conservation strategies that balance restoration with the preservation of old-growth trees to sustain Ryukyu's unique heritage.
Fine-Scale Genetic Structure and Demographic History in the Miyako Islands of the Ryukyu Archipelago
A fine-scale genetic analysis of the Miyako Islands, part of the UNESCO-listed Ryukyu Archipelago, reveals distinct subpopulations with divergent demographic histories. Using genome-wide single-nucleotide polymorphisms (SNPs) from 1,240 individuals, researchers identified three subpopulations—Miyakojima northeast, Miyakojima southwest, and Irabu/Ikema—with the latter showing unique gene flow patterns linked to historical immigration during the Gusuku period (900–500 BP). Haplotype-based analyses and coalescent demographic inference suggest that the Irabu/Ikema population split from the ancestral Ryukyu group around 41 generations ago, followed by further divergences. These findings provide critical insights into the genetic structure of modern Miyako populations, with implications for disease association studies.
Study on the Transition of Traditional Wooden Houses in Okinawa
Traditional Ryukyu wooden houses underwent significant structural and material changes from the pre-war to post-war periods, with key shifts observed in construction systems, wood materials, and roof characteristics. This study analyzed 122 houses—eight designated as important cultural properties (ICPs) and 114 ordinary—to identify patterns in their evolution. Findings revealed a decline in the use of high-quality timber and traditional joinery techniques post-war, alongside alterations in wall types and floor layouts. The research highlights how historical, political, and economic factors influenced architectural transitions, providing insights into the preservation challenges faced by UNESCO-listed sites like the Gusuku Sites of Okinawa.
Urbanization and Decline of Old Growth Windbreak Trees on Private Homesteads: A Case Study in Ryukyu Island Villages, Japan
High urbanization is significantly threatening the survival of old-growth windbreak trees on private homesteads in Ryukyu Island villages, Japan. A study analyzing 1659 Fukugi trees found that while these trees have historically provided resilience against typhoons and tsunamis, their density, height, and age are declining due to urban sprawl. Trees older than 200 years are particularly rare, suggesting that rapid population growth and reduced household sizes are exacerbating land pressure. The research combined field surveys with aerial photo analysis to track changes in tree distribution from 1945 to the present, revealing fragmentation and shorter tree heights in urbanized areas compared to rural ones. Conservation efforts involving multiple stakeholders are proposed to protect these ecologically and culturally valuable trees.
Ryukyu Trade in the Gusuku and Early Ryukyu Kingdom Periods
Archaeological evidence from the Gusuku Sites and Related Properties of the Kingdom of Ryukyu reveals a sophisticated maritime trade network centered on the Ryukyu Islands during the early kingdom period. This trade involved two primary categories of goods: locally produced items such as sulfur, mother-of-pearl, textiles, and red dye from the akagi tree (Bischoffia javanica), alongside transshipped commodities including Japanese swords, Chinese ceramics, silver, and iron tools. Ceramic artifacts, particularly serving vessels like plates, bowls, and processing tools such as suribachi, dominate the surviving trade-related materials, highlighting both domestic production and regional exchange. The study underscores Ryukyu's role as a critical maritime entrepō, facilitating the movement of goods and provisions across East Asia.
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