The cord-marking question
The Jomon period of Japanese prehistory, which began around 15,000 years ago, gets its name from the distinctive "cord-marked" (jōmon) patterns on its pottery—some of the oldest in the world. For decades, researchers assumed these complex impressions were made by rolling cords made from plant fibers over the wet clay. This was a logical inference, as textiles from grasses and other herbaceous plants were common in many Neolithic cultures. The assumption placed Jomon textile technology firmly in the field of weaving and basketry, similar to other early societies.
This understanding of Jomon material culture persisted until experimental archaeology challenged the foundational evidence. Archaeologists began to notice a discrepancy: the impressions left on thousands of Jomon potsherds did not quite match the patterns created by typical plant-fiber cordage. The texture was different, the twists more defined. This observation opened up a new line of inquiry into the true nature of the cords used by Jomon potters and, by extension, their entire fiber technology.
Bark, twists, and new histories
Archaeological experiments provided a compelling answer. Researchers, including specialists like Hirofumi Ochiai, began to replicate the cord-making process using alternative materials available to the Jomon people. Instead of grasses, they turned to the inner bark (phloem) of trees such as the Japanese linden (Tilia japonica) and Japanese elm (Ulmus davidiana). They processed the bark and twisted it into cordage. When this newly created bark cord was rolled onto wet clay, it produced impressions that were a near-perfect match for the ancient pottery marks.
The experiments demonstrated that the direction of the twist was a critical detail. Cords could be made with a right-hand twist (S-twist) or a left-hand twist (Z-twist), and rolling these different cords produced distinct oblique patterns that matched the variations seen on artifacts. Further analysis using silicone casting and high-resolution CT scans on pottery fragments has allowed for the three-dimensional reconstruction of these ancient textiles. This confirmed that the impressions were made by twisted cords, not woven textiles, and revealed specific knot types, like the reef knot. This evidence effectively rewrites a chapter of Jomon history, showing a sophisticated woodworking and fiber technology based on trees and herbaceous plants. It suggests a deep ecological knowledge of the forest and its resources that went far beyond what was previously understood.