Journal of California and Great Basin Anthropology

In California archaeology, and in many contexts world-wide, few data exist to compare functional differences among traditional ground-stone mortar designs. Here, experimental small-seed and acorn/nut processing rates are reported for three mortar designs (deep bowl, deep conical, and shallow cup) and two grinding slab designs (flat unshaped, and shallow basin). These designs, in various combinations, are common in many plant-based hunting and gathering societies. Results of the grinding experiments are considered in reference to manufacturing costs, mobility, and resource use. Unexpected relationships are demonstrated for bowl and conical mortar shapes and seed processing. In particular, large mortars with deep, broad interiors are highly effective tools for producing flour from both small wild seeds and acorns. Conical mortar shapes are good for acorn processing, but perform poorly for processing small seeds into flour. As expected, shallow mortars are the least productive, but least expensive, tools. Large mortars with broad, bowl-shaped interiors would have been excellent tools for long-term use in settings where multiple types of plant resources were processed into finer particles. Despite their superior performance, steep costs of manufacturing, including the transport of suitable raw materials, may have limited the use and ownership of these mortars.