How long has miso (soybean paste) been used in Japan?

The original form of miso, or soybean paste, is said to have existed in the Nara period (710-794).
In the Heian period (794-1185), there were already stores selling miso.
Miso is made from soybeans, which are steamed and mixed with salt and koji (fermented rice, barley or beans).
It was made at temples in the Kamakura period (1185-1333), and in the Age of Civil Wars in the 15th and 16th centuries, it was used in rations for soldiers.
It was in the Muromachi period (1333-1568) that miso, along with shoyu, became popular among the general public.