Starch granule analysis of bedrock metates in Warner Valley, Oregon

Starch-rich geophytes are a highly-valued food among many human societies.
For example, Indigenous people in the northern Great Basin plan social
activities around the seasonal foraging of bulbs, roots, and tubers.
Despite such obvious dietary and cultural importance, the antiquity of
geophyte use in the Great Basin remains difficult to establish. Herbaceous
underground storage organs do not preserve well in the archaeological
record. Therefore, most studies rely on indirect evidence to infer
geophyte consumption by hunter-gatherers during the late Pleistocene/early
Holocene.  It has been suggested that bedrock metates found among
upland rock art sites in the northern Great Basin reflect seasonal
geophyte exploitation over 14,000 years. Our study tests this hypothesis
by analyzing starch residue extracted from bedrock metates at three
archaeological sites in the uplands of Warner Valley, Oregon. Species of
biscuit root (Lomatium) were collected in the field and sampled for
starch. Systematic studies conducted on granules defined morphological
characteristics were then applied to the identification of archaeological
granules. Starch granules from geophytes, specifically Lomatium spp., were
identified on metate surfaces at all sites, thereby providing direct
evidence for the collection and processing of geophytes. These results
support previous hypotheses regarding Paleoindian foraging strategies in
the northern Great Basin.