TOKYO, Oct. 11 — A professor of Shizuoka University is advocating a theory that the population on the Japanese archipelago grew during the Jomon Period, spanning from approximately 13,000 B.C. to 400 B.C., before the introduction of rice farming, because people at the time — mainly hunter-gatherers — were eating nutritious taro.
Reiko Motohashi, a professor at Shizuoka University’s faculty of agriculture, came to the conclusion after closely investigating the historic roots of wild taro growing across the country and believing that it had been brought in to Japan earlier than other taro plant varieties currently cultivated and had been consumed by the Jomon people.
Taro, which is easily degradable, has not been discovered at the Jomon archaeological sites, but Motohashi continues to look for even a slight trace.
Population growth was significant in the early and mid-Jomon Period. This was before the spread of rice cultivation, and Motohashi assumes taro provided a rich source of nutrients that could not have been gained only through hunting and gathering.
Motohashi compared the genomes of wild taro found in various parts of Japan — such as the Kutsukake hot springs in the village of Aoki in Nagano Prefecture, the Ryugenji Temple in the city of Kofu in Yamanashi Prefecture and a valley called Imonotani in the city of Matsue, Shimane Prefecture — with several taro varieties in and out of the country.
She found that wild taro plants, although scattered over different locations, are of the same group, and were genetically closer to the one in India, which is believed to be the country of origin for wild taro, rather than to other taro plants cultivated in Japan. Wild taro was identified as a Japanese taro cultivar Eguimo, which is eatable.
Motohashi got permission to replant a taro plant of the Kutsukake hot springs to a farm held by the university.
The plant grew well, and while raw Eguimo contains quite a bit of oxalic acid, a bittering agent, the amount was reduced to roughly the same as that for cultivated taro varieties when boiled. Motohashi says it “is eatable although not outstandingly delicious.”
There are many archaeological Jomon sites in Nagano Prefecture and dogu clay figurines have been excavated there.
“This shows that (the Jomon people) had emotional leeway and were living in an environment where they didn’t have to worry about food all the time,” Motohashi said. “I believe one of the factors for that was taro.”
It is believed that the climate had been warmer than today up to the mid-Jomon Period, making it possible to grow taro in wide areas of the archipelago including the current Tohoku northeastern region.
The climate turned cooler after that, and since small corms had not been stored, the crops got frozen and were almost entirely destroyed, except for plants still growing wild in some places near springs and hot springs.
However, unlike shells and nuts that have been found from archaeological sites and pottery unearthed in Japan, no traces of taro have been discovered so far.
Motohashi is analyzing excavated carbide materials believed to be cooked food from the Jomon Period, looking for remains of taro-derived protein.
There are folk tales associated with wild taro handed down in various parts of Japan, but currently, the plant can be found growing wild only at a few locations including the Kutsukake hot springs.
Motohashi is asking for information on places where wild taro can be seen in order to conduct more in-depth analysis.
Taro plants growing wild in the Kutsukake hot springs in Nagano Prefecture PHOTO COURTESY OF REIKO MOTOHASHI