1378. Ocean Routes (“Kaijo no Michi”) and Technology Dissemination (Takaragawa’s Newsletter vol. 10)

YANAGITA Kunio, often called the father of Japanese folklore studies, proposed the “Kaijo no Michi (Ocean Route)” theory suggesting that the Japanese migrated across the sea, drawing on references such as Okinawa's cowries and the coconut palms at Cape Irako in Aichi Prefecture. His analysis that rice seeds and cultivation techniques spread together may offer insights into efficiently disseminating developed technologies like crop varieties and cultivation methods.

Yanagita, who established Japanese folklore studies, travelled throughout Japan—including the Nansei Islands—from the Meiji to the Showa eras. Focusing on the themes of what it means to be Japanese and where the Japanese people came from, he collected and recorded folklore. It is well known that his observations of a palm fruit floating ashore at Cape Irako, at the tip of Aichi Prefecture's Atsumi Peninsula, led him to contemplate human migration via wind and ocean currents. This story inspired the poet SHIMAZAKI Toson's famous poem “The Palm Fruit.”

Traces of Yanagita also remain on Ishigaki Island, home to the Tropical Agriculture Research Front  (※Photo shows a commemorative monument for the arrival. The coconut was just picked up and placed there by the author). The Yaeyama Islands and Nansei Islands, including Ishigaki Island, were the main settings for Yanagita's works “Kainan Shoki” and “Kaijo no Michi.” The relatively untouched farming, mountain, and fishing villages of the time provided a valuable research field (he focused not only on their role as Japan's ancestral homeland but also on their unique characteristics).

He particularly noted the value of cowrie shells found in the Nansei Islands, like Ishigaki, and theorized that people crossed the sea seeking these shells. Furthermore, while investigating rice cultivation culture, he noted that the mere distribution of rice grains was insufficient to establish a culture; it required the transmission of cultivation techniques alongside ceremonial practices and religious beliefs. This led him to conclude that Japanese people crossed the sea.

Although many of Yanagita's hypotheses have since been scientifically verified and some disproved, his enduring contribution lies in demonstrating the narrative power of field research and the importance of hypotheses grounded in fieldwork. Furthermore, his examination of the spread of rice seeds and cultivation techniques may offer insights for research aimed at technological development and its dissemination (social implementation).

The reason Japanese varieties like Muscat grapes and strawberries taste different overseas is likely due to inadequate cultivation techniques and a lack of locally adapted improvements (※It seems many cases involve illegal exports or merely borrowing the name). This might also explain why Okinawa's mango cultivation techniques differ from those in Miyazaki.

Japanese grains, tubers, and fruit trees often seem well-branded, with clear differentiation from other varieties. Cultivation techniques for each variety are frequently packaged and disseminated. In contrast, for sugarcane, the packaging of varieties and cultivation techniques has not yet advanced sufficiently, posing challenges for seedling propagation and dissemination.

The sugarcane variety “Haruno-ogi,” jointly developed by JIRCAS, has rapidly expanded its cultivation area after registration. This may be due not only to the variety's inherent capabilities but also to its catchy name and the strong message conveyed through its promotion, essentially saying, “Use it this way.”

To achieve efficient dissemination, I aim to deepen our understanding of post-breeding aspects—such as variety utilization patterns and seedling propagation—by drawing not only on natural science approaches focused on plants but also on social science approaches and insights, like folklore studies, that focus on people.

Contributor: TAKARAGAWA Hiroo, Tropical Agriculture Research Front