Stuck within notches: Direct evidence of plant processing during the last glacial maximum to Holocene in North Sulawesi

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The existence of an organic or plant-based technology during the Late Pleistocene and Early Holocene is an ongoing debate in Island Southeast Asia (ISEA). Evidence of plant-based technologies in the current archaeological record of ISEA is very limited. Nevertheless, excavations of prehistoric sites across the region have provided clues that plants played a key role in the subsistence and technology of early islanders. Our previous use-wear study on the assemblage from Leang Sarru, a rockshelter in the Talaud Islands, North Sulawesi with an occupation history of c. 35,000 years, indicated that plant remains were preserved on artefacts from 22,000 years ago. In this paper, we present the identification of these plant remains that include parenchyma, fibres, stomata, starch, phytoliths, and raphides. However, in the case of Leang Sarru, we observed that not only were those residues deposited on unretouched lithic flakes typical for the prehistoric sites in ISEA but were especially preserved on flakes with a distinctive notched retouch – a case which has never been documented in the region yet. We conducted experiments using replicas of notched tools to test our hypothesis that they were particularly designed and used for scraping and smoothing plant materials. Our results show that a variety of plants can be processed using these notched tools. The simple modification was observed to be efficient in scraping experiments, and plant residues were stuck within the notches – possibly a factor in their preservation. Overall, the current debate on the presence or absence of plant working revolves around the absence of formal tool types in ISEA. Other aspects of cultural and technological adaptations, such as tool retouching for particular functional purposes, might have been overlooked in favour of a justification that plant-based technologies were preferred.