Journal of California and Great Basin Anthropology

Mortar and pestle technology has long been considered prima facie evidence for the intensive use and storage of acorns in pre-contact California. The relatively late adoption of this technology has commonly been interpreted as a direct measure of population pressure and?due to the presumed low caloric return rate of acorns?declining foraging efficiency. Conversely, hand-stone and milling-slab technology was used throughout the Holocene, and was equated with the non-intensive processing of small seeds. Here we decouple these erroneous assumptions by demonstrating that acorns are among the most productive native plant foods widely available in California, and small seeds are among the least productive. Archaeobotanical data also show that the regular use of acorns in central California began early in the Holocene when hand-stones and milling-slabs were the only milling technology used. Bowl mortars and pestles first appear in some parts of central California by 7,000 years ago. Because they are highly efficient but costly to produce and transport, they are typically found in residentially stable contexts, characteristic of a transition to delayed-return, energy-maximizing economies. Hand-stone and milling-slab technology persists in residentially mobile situations well into the late Holocene and was used to process a variety of resources including acorns, reflecting time-minimizing, immediate-return economies. We conclude that milling tool form has as much to do with labor investment, processing efficiency, and settlement strategy as the types of resources processed.