Morphometric Identification of Starch Granules From Archaeological Contexts: Diagnostic Characteristics of Seven Major North American Plant Families

Abstract

Starch-rich plants have played an important role in human evolution and societal development. Collected, grown, and consumed to support ever-increasing populations, such plants are integral to understanding past human diets. With the advent of starch granule analysis, plant resources that were invisible in the archaeological record can now be revealed in the cracks and crevices of artifacts. Widespread application of this technique, however, has stalled due to a lack of rigorous and standardized protocols. For example, taxonomic identification of starch granules using consistent diagnostic characteristics is still a challenge as there are no comprehensive surveys across important (i.e., dietary) plant taxa, especially at the levels of families, genera, and species. This study provides characteristics for identifying starch granules of seven major North American plant families (Amaranthaceae, Apiaceae, Fagaceae, Liliaceae, Pinaceae, Poaceae, and Solanaceae) based on systematic, morphometric studies of modern reference materials. A dichotomous key to starch granules of the seven families was also generated to aid in identification of those from archaeological contexts. Although we have focused on plants from western North America, these families occur across the globe and have had dietary significance throughout prehistory.

Fatty Acids and Starch Identification within Minute Archaeological Fragments: Qualitative Investigation for Assessing Feasibility

“…(10) Add distilled water to reach a total volume of 1.5 mL and centrifuge at 5000 rpm for 5 min. (11) Remove 1 mL of the floating fraction by decanting. ( 12) Perform a repetition of step 10.…”

“…Starch derived from various food sources tends to accumulate within surface irregularities on vessel walls, and this allows the material to maintain properties like a crystalline structure, and birefringence over time [10]. In addition, ceramics can absorb triglycerides (the main component of fat and vegetable oils), thus facilitating their preservation over extended durations [11,12]. Factors that could contribute to the preservation of biomolecules encompass the presence of conditions such as reduced water activity (which inhibits the enzymatic activity responsible for the degradation of starch and lipid compounds), close-to-neutral pH, and relatively lower ambient temperatures.…”

Identification of Neolithic diet by the morphology of the starch grains of dental calculus found in the Dehesilla Cave (Cadiz – South of the Iberian Peninsula)

“…Starch is a carbohydrate polymer, composed by two different molecules, both of them made of the monosacharide D-glucose: amylose (linear, constituting 5-35% of natural starches) and amylopectin (rami ed, forming 95 − 65% of this polysaccharide) (Lodish et al 2004;Seung 2020). It accumulates throughout the photosynthesis in the amyloplasts, and is commonly found, as energy storage granules, in various organs (e.g., tubers, rhizomes and seeds) of vascular plants (Chakraborty et al 2020;Louderback et al 2022), constituting the primary storage carbohydrate in the Plant Kingdom (Lodish et al 2004). The morphology of these granular structures (shape, size, internal and surface characteristics) varies signi cantly within the different taxa, providing data for their identi cation (…”