Floodplain Dispersal of Domestic Cucurbit (C. pepo ssp. pepo) circa 1000 BP

Dispersal of squash and gourds has been attributed to multiple natural and cultural processes. Among these is the downstream dispersal of seeds and intact fruits into slack-water wetland environments, where stands are likely to become established. While this explanation has fundamental merit given the established buoyancy of these fruits (Hart et al. 2003), there are few if any empirical examples of the process from the precontact period. Recent deep testing at a project locale on the Detroit River in southeastern Michigan produced an uncarbonized seed of Cucurbita pepo ssp. pepo, a domesticated Mesoamerican variety of squash (aka pumpkin), although no evidence of in situ precontact occupation was identified. The specimen was recovered from a zone of saturated alluvium interbedded with wetland plant deposits. A direct AMS date on the seed produced an age of 974–1150 cal AD (p = 0.95). This age range coincides with the Medieval Climatic Optimum of 950–1250 AD and reduced elevations of Great Lakes water planes resulting in increased downcutting of rivers grading to lower elevations. Regardless of association with these macroscale events, this is the first evidence for cucurbit from southeastern Michigan and the first clear precontact evidence for floodplain dispersal and depositional processes of cucurbits. Additionally, it represents a relatively early occurrence of the Mesoamerican variety of squash, Cucurbita pepo ssp. pepo, in the Midwest, yet it is consistent with the overall chronology of the taxon (Simon 2011; Smith 2006).