The old wood effect revisited: a comparison of radiocarbon dates of wood charcoal and short-lived taxa from Korea

Due to the “old wood effect,” wood is not an ideal material for radiocarbon dating if there are other options available. However, in regions where short-lived taxa are not well preserved, archeologists face a dilemma whether to use wood dates to construct archeological interpretations, often leading to controversies over validity of their chronologies. To systematically access this problem, this paper evaluates the intensity of the old wood effect in Korea. First we compared radiocarbon dates assayed from five wood and 32 soybean (Glycine max) samples obtained from a prehistoric pithouse in central-western Korea. Statistical analysis shows that there is no significant disparity in the ages between the materials in this case. To further assess the issue, we compared 24 cases from the Korean Radiocarbon Database in which both wood and short-lived taxa were found and dated from the same house feature. The results demonstrate that, in general, the old wood effect is not substantial in Korea. However, further analysis of these results suggests that the potential for an old wood effect increases slightly over time in Korea, despite the fact that there was no significant climatic change. We interpret the adoption of iron for woodcutting around the first century BCE as a catalyst for a noted increase in the thickness of wood timbers of houses, which consequently produced conditions more opportune for the occurrence of an old wood effect. It suggests that the variability of an old wood effect can be the result of technological factors even within the same general physical environment.