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.
