A new archaeobotanical proxy for plant food processing: Archaeological starch spherulites at the submerged 23,000-year-old site of Ohalo II

Archaeological starch spherulites discovered at the submerged 23,000-year-old site of Ohalo II, Sea of Galilee, Israel, provide a new line of archaeobotanical evidence for plant food processing. Six-hundred and thirty-two (632) starch spherulites were recovered from four stone implements. The analysis of starch spherulites from reliable archaeological contexts is a breakthrough that will potentially allow the identification of a range of plant processing and wet cooking activities. Our work provides a baseline for starch spherulite extraction and identification protocols. They were confirmed as spherulites using Lugol's iodine confirmation and the optical properties of the polarisation cross when rotated on a microscope stage under cross-polarised light. Their identification as starch spherulites was based on their archaeological context, size range and optical (polarized light and SEM) characteristics (including partial iodine uptake). Following our promising results, we encourage researchers to describe archaeological starch spherulite morphology and elemental characteristics in as much detail as possible. Future experimental archaeology work may find that these details provide evidence for how starch spherulites were formed through plant processing and cooking techniques.