Donax - Baja and California

The genus Donax, composed of small bean clams, is widely represented along the tropical and temperate shorelines of the Pacific, Atlantic, and Indian oceans. Donax spp. shells have been found in significant quantities within archaeological middens in several regions, including South Africa (Parkington et al. 1988), Greece (Shackleton 1988), the east coast of Florida (Larson 1980; Miller 1980), and northern San Diego County. Two species occur locally: D. gouldii, which appears to account for most of the archaeological specimens, and D. californica.

A review by Don Laylander and Dan Saunders (1993) suggested that the occurrence of Donax as a major constituent in shell middens on the Pacific coast of North America was primarily limited, in time, to the Late Prehistoric period, and in space, to the San Luis Rey River – Buena Vista Creek drainages and adjacent areas. Several cases of Late Prehistoric deposits in northern San Diego County with more than 10% Donax by count or weight were identified, both at locations near the coast (Cardenas and Robbins Wade 1985; Corum 1991; Corum and White 1982; Flower et al. 1977; Hector 1983) and farther inland (Cook 1978; Fulmer 1984; Quintero 1987). A cursory examination of shell speciation for middens elsewhere in southern California and Baja California and from earlier periods within San Diego County revealed no cases in which Donax was found to have been a major constituent.

Subsequent studies, for instance by Henry C. Koerper, Adella B. Schroth, and Paul E. Langenwalter (1992), Brian F. Byrd (1998), Patricia M. Masters (2003), and Don Laylander (2006; Laylander and Becker 2004) have somewhat expanded the geographical and chronological ranges of focused Donax exploitation in San Diego County, but the general pattern of a focus on northern San Diego County during the late period still seems to hold true.

Several possible explanations for the apparent limitations of Donax exploitation in space and time have been suggested:

Donax may not have been available in economically attractive quantities at other times and places. Changes in water temperature and the development of sandy-beach habitat only relatively late in the Holocene are possible factors (see Masters 1988:4-4).
Key elements of Donax procurement or processing technology may not have been available at other times and places. The availability of ceramic pots for cooking Donax as a broth is a plausible technological factor limited to the Late Prehistoric period.
Donax exploitation may have been limited by high procurement and processing costs. However, modern accounts seem to argue against the supposition that those costs were high (Flower et al. 1977).
Interest in Donax exploitation may have been limited by a low nutritional yield. The likelihood of this factor has also been called into question (Quintero 1987; Reddy 1996a, 1996b).
Donax exploitation may have been attractive only after the availability of preferred lagoonal shellfish genera, such as Chione and Argopecten, had declined either through overexploitation or through the loss of their natural habitat.
The erratic availability of large Donax populations may have made this resource attractive only within certain types of settlement system contexts (Coe 1953, 1955; Fulmer 1984; Reddy 1996a).
The value assigned to Donax may have been influenced by its compatibility or incompatibility with seasonal scheduling for the exploitation of other resources.

PROSPECTS

Future archaeological investigations may be able to clarify the geographical and chronological limits of focused Donax exploitation, the seasons during which it occurred, its settlement system contexts, and its associated processing technology. Additional replicative experiments may shed light on Donax‘s nutritional value, its procurement and processing costs, and the technological requirements for efficient procurement and processing.