Until quite recently, archaeological researchers developed culture-histories for the Sierran foothill region based on the more studied areas of the western Great Basin and California Central Valley. Temporal divisions reflecting culture change in the foothills, therefore, hinged on data from bordering regions. A recent study for the East Sonora Bypass Project 1, however, has developed an entirely new chronology focusing on a synthesis of local data from more than 100 excavated sites in the watersheds of the Mokelumne, Calaveras, Stanislaus, and Tuolumne rivers. Based on spatial and stratigraphic analyses of more than 200 radiocarbon dates, more than 4,000 source-specific obsidian hydration readings, slightly more than 875 projectile points, and close to 600 shell beads, five major time periods are defined—Early Archaic, Middle Archaic, Late Archaic, Recent Prehistoric I, and Recent Prehistoric II. Each period has one or more relevant change that distinguishes it from what came before, such as subsistence (a new food sources, a change in preparation techniques), land-use (seasonal camps, long-term villages), or technological (e.g., a dominant projectile point style is identified for each period). Obsidian hydration brackets for the Bodie Hills obsidian source (located east of the Sierran crest) are associated with each time period, and are useful for interpreting the age of this obsidian when found on the west slope of the Sierra below snow level 2; Table 1).
Table 1. Chronology of the Sierra Nevada.
ARCHAEOLOGICAL PERIOD GEOLOGICAL PERIOD AGE RANGE (CAL BP) BODIE HILLS OBSIDIAN HYDRATION RANGE (MICRONS)a
Early Archaic Early Holocene 11,500-7000 8.6-6.9
Middle Archaic Middle Holocene 7000-3000 6.8-4.8
Late Archaic Late Holocene 3000-1100 4.7-3.2
Recent Prehistoric I 1100-610 3.1-2.5
Recent Prehistoric II 610-100 2.4-0.9
Notes: - cal BP – calibrated Before Present ; a - Applicable only below snow level (4,000 feet).
Early Archaic deposits are quite rare in the Sierra Nevada foothills, identified locally at two sites, both discovered in buried stratigraphic contexts. They include abundant Wide-Stem and Large Stemmed Dart points, hundreds of handstones and millingstones, as well as a variety of cobble-core tools, large percussion-flaked “greenstone” bifaces, and comparatively high frequencies of obsidian from the Bodie Hills source. Plant macrofossil assemblages are dominated by grey pine and acorn nutshell, but include few if any small seeds or other spring- and summer-ripening plant foods (e.g., manzanita). This indicates a pattern of repeated occupation, suggesting that land use in the western Sierra was seasonally structured. This is supported by an almost exclusive use of local toolstone for the manufacture of bifaces and projectile points.
Middle Archaic sites, also often buried, are primarily distinguished by Corner-notched Dart points, an occasional mortar and pestle, and the earliest house structures in association with large subterranean storage pits. Fall and winter occupation is evident where large quantities of nuts were stored in underground granaries. In contrast, summer-ripening berries and other fruits are dominant in sites from higher elevations in the lower forests. These differences reveal a pattern of seasonal movement, with fall and winter villages placed below the snowline in the blue oak-grey pine woodland, and summer camps situated in the conifer forest zone where annual roots, bulbs, seeds, and fruits are common during warmer months. Faunal assemblages from Middle Archaic sites are dominated by large mammal remains (e.g., deer), a pattern that continues throughout the region’s occupation. Soapstone “frying pans” and other vessels first appear in the local record during the Middle Archaic, along with various stone pendants, incised slate, and stone beads. The presence of atlatl weights and spurs in these deposits confirms that the dart and atlatl were the primary hunting implements.
Late Archaic sites are among the most common on the western slope, again with many occurring in buried stratigraphic contexts. Late Archaic lifeways, technologies, and subsistence patterns were quite similar to those of the previous time period, with the primary difference being an increase in the use of obsidian between about 3000 and 1100 BP. Chert, only available in the foothills of the western Sierra below about 3,000 feet, is common at Archaic sites in the lower Montane Forest up to about 6,000 feet. However, flaked stone assemblages on the western slope found above 6,000 feet are composed almost entirely of obsidian (>80%), suggesting that groups who utilized upper elevations of the western Sierra arrived from the east side where obsidian was the primary toolstone.
The beginning of the Prehistoric Period coincides with a region-wide interval of reduced precipitation known as the Medieval Climatic Anomaly. Among the most important changes in the archaeological record of the western slope at this time was the introduction of the bow and arrow (about 1100 cal BP), an innovation apparently borrowed from neighboring groups to the north or east. This shift in technology is clearly reflected by the dominance of small stemmed and corner-notched arrow points in Recent Prehistoric I sites. The common occurrence of bedrock mortars at Recent Prehistoric II sites suggests that they became an important milling technology by 610 cal BP.
Unfortunately, too few single-component Recent Prehistoric I assemblages exist to characterize basic lifeways and subsistence patterns during this interval. However, by the Recent Prehistoric II Period, numerous well-dated sites and site components (including the current project sites) provide substantial evidence for changes in the nature of local subsistence economies. The dominance of acorn nutshell in these sites is among the most compelling evidence for acorn intensification in central California. Bedrock milling fixtures are established across the landscape, near well-developed residential middens and as isolated features. The occurrence of these facilities above and below the oak zone suggests that a variety of foods, in addition to acorns, was processed in these features. Subsistence remains in foothill sites include many more spring and summer grasses, fruits, and berries than were present in Archaic deposits, indicating that occupation occurred for a longer part of the year, or that sites below the snow-line were more regularly used to store warm-season resources for winter use.
There also appears to have been greater settlement differentiation during the Recent Prehistoric II Period, with clear residential sites, often including house-depressions and other structural remains, but also special-use localities consisting simply of bedrock milling features. Summer use of higher elevations is also apparent, as many sites from this time period are found in the Lower Montane Forest, always dominated by summer-ripening plant foods. Like the Archaic, large mammal remains continue to make up a substantial portion of faunal assemblages from both high- and low-elevation sites. Many more specialized technologies are associated with the Recent Prehistoric II Period than were evident during the Archaic, including stone drills and the common occurrence of bone awls, suggesting that basketry and other composite implements may have taken on a new importance. The Desert Side-notched arrow point is first introduced on the western slope at about 610 cal BP, clearly adopted from Great Basin people to the east. Circular stone shaft-straighteners are also common in these sites, consistent with the use of the bow and arrow. Imported shell beads from coastal California first appear in appreciable amounts in Recent Prehistoric II village sites, as do other rare items such as shell ornaments and bone whistles.