Starch grains are microscopic plant remains that can be recovered from archaeological contexts to understand which plant foods ancient peoples were eating and how they were processed. From 2017-2018 I analyzed samples recovered during the Izapa Household Archaeology Project at the Smithsonian Tropical Research Institute (STRI) in Panama, where specialized facilities exist to extract and identify starch grains. In the field, residues were recovered from domestic artifacts like ceramic vessels and grinding stones. At STRI the samples were then processed in the lab with a heavy liquid (in this case, Cesium chloride) to cause these microscopic particles to float. After a series of runs through the centrifuge, a pipette is used to collect any starch grains present in the sample and place them on a slide. The slide is analyzed under a polarizing microscope, where features such as size and shape are used to identify the family or even species of plant present on the tool.

Sample tubes during processing

Yam starch grain (Dioscorea spp.) recovered from an IHAP grinding stone