Resource intensification in pre-contact central California: a bioarchaeological perspective on diet and health patterns among hunter-gatherers from the lower Sacramento Valley and San Francisco Bay

Abstract

In this study, I use bioarchaeological data derived from human burials to evaluate
\nsubsistence change in mid-to-late Holocene central California (circa 4950-200 B.P.).
\nPrevious investigations in the region have proposed two competing models to account
\nfor changes in subsistence patterns. The seasonal stress hypothesis argues that the
\nincreased reliance on acorns and small seeds during the late Holocene led to improved
\nhealth status, since these resources could be stored and used as a “buffer” against
\nseasonal food shortages. In contrast, resource intensification models predict temporal
\ndeclines in health during the late Holocene, as measured by a decline in dietary quality
\nand health status, increased population crowding, and greater levels of sedentism. I test
\nthe hypothesis that health status, as measured by childhood stress and disease indicators,
\ndeclined during the late Holocene in central California.
\nI analyzed 511 human skeletons from ten archaeological sites in the Sacramento
\nValley and San Francisco Bay area to investigate temporal and spatial variability in diet
\nand health. I analyzed a subset (n = 111) of this sample to evaluate prehistoric dietary patterns using carbon and nitrogen stable isotope ratios. Indicators of health status show
\nsignificant temporal and regional variation. In the Valley, tibial periosteal reactions,
\nporotic hyperostosis, and enamel hypoplasias significantly increased through time,
\nimplying a decline in health status. In the Bay, health indicators show little temporal
\nvariability. However, inter-regional comparisons indicate a higher prevalence of stress
\nand disease indicators among Bay Area skeletons than in the Valley skeletal series. The
\nstable isotope data from human bone collagen and apatite also indicate significant interregional
\ndifferences in prehistoric diets between the Bay and the Valley. In the Bay,
\ndiets shifted from high trophic level marine foods to a more terrestrially focused diet
\nover time. In the Valley, there are no significant dietary trends observed in the data.
\nDental caries and antemortem tooth loss are significantly more prevalent in the Valley
\nthan in the Bay, and closely match the isotopic findings. The paleopathological findings
\nprovide support for late Holocene resource intensification models posited for the Valley,
\nbut not for the Bay Area.