Making the cut: experimental bamboo processing using chert tools from Island Southeast Asia

The absence of formal stone tool types in Island Southeast Asia (ISEA) is often viewed as a result of the replacement of lithic tools with implements made from bamboo, the so-called bamboo hypothesis. While tools from Pleistocene sites do display traces that indicate plant processing, it remains an issue whether such plant-based technology was the main reason for the trajectory of tool technology in the region. One distinct trace that has been identified on flaked lithic tools from the region is polish produced through contact with plant materials, a microscopic trace that can be formed through prolonged contact with phytolith-rich grassy plants like reed, cereal crops, or bamboo. It remains an open question whether bamboo tools were indeed used as complement or replacement of stone tools, or whether the plant polishes were due to other activities involving plants such as fibre extraction. However, current techniques of characterising these polishes remain qualitative in nature and have limitations. To address this, we conducted controlled experiments using chert flakes to process bamboo. Combining wide-field and laser-scanning confocal microscopy, we were able to create an experimental protocol for the identification of bamboo processing. Our results indicate that chert type and the original surface topography of the tool influence polish formation. This may be useful as additional diagnostic features that would permit a clearer differentiation of microwear traces from the processing of different bamboo species. We recommend further developing experimental protocols for tool use in ISEA, and assessing the mechanics of use-wear formation in controlled experiments relating to plant processing. Overall, the identification and quantification of plant polishes in relation to intensity of activity, contact material geometry, and stone tool raw material type should be incorporated in tool interpretation for both archaeological and experimental tools.