The Chumash, complex marine hunter-gathers of the Santa Barbara Channel region, have occupied both the northern Channel Islands and parts of the California mainland for around 13,000 years (Johnson et al. 2000). On the islands, where there are no terrestrial game animals, there is a dichotomy of marine faunal and terrestrial floral resources. Whereas fish, shellfish, and marine mammals are abundant in the waters surrounding the islands, terrestrial plants are less abundant and diverse than on the mainland. Nonetheless, dense shell middens throughout the northern Channel Islands attest to the fact that islanders regularly transported marine resources to interior and high elevation locations. The use of interior sites as residences (rather than logistical encampments) is most pronounced during the Middle Holocene (5500-1500 BC), after which there is a shift to permanent, coastal settlements (Kennett 2005). Scholars have hypothesized that this interior settlement pattern could be motivated by access to freshwater, toolstone, plants, travel routes, defensive locations, or locations used for community aggregation (Glassow 2014; Kennett 2005; Orr 1968; Perry and Delaney-Rivera 2011; Perry and Glassow 2015).
There are several lines of indirect evidence suggesting that plant resources were important during the Middle Holocene, including the development of the mortar and pestle circa 3850-3050 BC (Glassow 1997a), higher frequencies of plant processing tools deposited as grave goods (Hollimon 1990, 2001), and higher rates of dental caries (associated with carbohydrate rich plant foods) in burial populations (Walker and Erlandson 1986). Recent macrobotanical studies on the northern Channel Islands (e.g., Gill 2015; Martin 2010; Martin and Popper 2001; Reddy and Erlandson 2012; Thakar 2014) provide direct evidence that many ethnographically important plant resources were locally available, and were used throughout prehistoric occupation; however, none of these studies explicitly address the role of terrestrial resources in Middle Holocene settlement patterns.
The current study combines faunal and macrobotanical data from three interior Middle Holocene sites with starch granule residue analysis of groundstone artifacts from these and other interior Middle Holocene sites. The low densities of macrobotanical remains recovered do not support the long-held belief that interior sites were used to exploit terrestrial plant resources; indeed, the minimal seeds identified are largely from plants with ethnographic uses as medicine, rather than food. However, starch granules, including acorn (Quercus spp.), pine (Pinus muricata) and cherry (Prunus illicifolia), indicate that ethnographically important food resources were being processed at interior sites, but are not preserving in the macrobotanical record. Starch granules identified in this study provide the first direct evidence of what plants different types of groundstone were used to process on the northern Channel Islands. Moreover, this study demonstrates the value of integrating multiple lines of evidence to provide a more holistic understanding of prehistoric foodways, and sets baseline expectations for future paleoethnobotanical research in this region.
