Ancient starch and usewear analyses of an excavated pestle fragment from the Upper Kaironk Valley, Madang Province, Papua New Guinea

Abstract

During archaeological survey and excavation along the Kaironk and Simbai Valleys of the New Guinea Highlands in 2016, a ground and pecked tool fragment was recovered from a subsurface context immediately adjacent to the Imbiben (JRQ) open area excavations where a well-preserved cultural deposit including hearth stones and a flaking floor has been dated to the mid-Holocene (4.4-4.3 cal. ka (ka: thousands of years ago). Technological and usewear analyses of the fragment identified a formally manufactured surface shaped by pecking, with minimal traces of use but consistent with the side of a pestle, on which starch residues were preserved. Ancient starch analysis identified Castanopsis acuminatissima as the primary contributing species in the residue sample. C. acuminatissima is an upper canopy tree found in primary forest across the highlands. It belongs to the acorn family (Fagaceae) and produces an edible starchy nut that can be eaten raw or roasted. The Imbiben pestle fragment is the fourth formally manufactured artefact with pecked and/or ground surfaces recovered from subsurface sediments during the current project, all of which date to the mid-Holocene. The other artefacts include two pestle fragments and a fragment of a carved face excavated at the Waim site. Pestles, mortars and carved stones are widely known from unprovenanced contexts across the Kaironk/Simbai Valleys, New Guinea and the Bismarck Archipelago. The functional study of the Imbiben pestle fragment described here aids in our understanding of the range, antiquity and use of these formally manufactured stone tools to process starchy plant foods.