Sites In Central California Research Articles

Compound marine cold spells and hypoxic events in a nearshore upwelling system

Prolonged periods of extreme warm and cold seawater temperature anomalies, known as marine heatwaves (MHWs) and marine cold spells (MCSs), respectively, can have significant impacts on coastal marine ecosystems. Prior research has examined the co-occurrence of multiple extremes [low dissolved oxygen (DO) and/or low pH] during MHWs, with the impact of these compound events potentially exceeding that of a single stressor due to synergistic effects. However, we are not aware of any studies that have examined compound extreme events during MCSs, despite the ecosystem implications. Along Eastern Boundary Current Upwelling Systems (EBUS), strong-wind driven upwelling has led to reduced warming trends and persistence of MCSs, as well as an increased seasonal risk for coastal hypoxia via the cross-shelf advection of cold, low DO subthermocline waters. In this short communication, we investigated for the first time compound MCS-hypoxic events at a nearshore site in central California using several decades of nearshore water temperature data, short-term nearshore DO data, and several decades of DO data from the California Cooperative Oceanic Fisheries Investigations program. From 1988 to 2020, we identified 55 MCS events, with 50 events (∼90.9%) initiated during anomalously strong upwelling. Using long-term temperature-DO relationships, we identified 20 of the 55 MCS events (∼34.6%) as potential compound MCS-hypoxic events, with an average duration of 11.7 days. These compound events occurred almost exclusively during the major upwelling season (March to June) when there is a high propensity for the advection of cold, low DO subthermocline waters from the adjacent shelf into the nearshore. This work provides the first known investigation into the co-occurrence of MCS and hypoxic events in a nearshore upwelling system and provides a baseline for assessing future changes to these compound events in a changing climate, with important implications for ecosystem health in EBUS globally.

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Comparison of Diets in the California Least Tern (Sternula antillarum browni) at Two Sites in Central California, U.S.A.

Sex-Biased Differences in Infant Mortality and Life Expectancy at Síi Túupentak , an Ancestral Ohlone Village in Central California (ca. 540–145 cal. BP)

ABSTRACT: Síi Túupentak (CA-SCA-565/H) is a late precontact ancestral Ohlone village and cemetery site in Central California (ca. 540–145 cal. BP). Integration of proteomic, genomic, and osteological analyses provided highly confident biological sex estimates for remains of most individuals at this site (65 of 76), spanning all age groups, from perinatal infants to aged adults. Based on these relatively comprehensive data, it was possible to generate sex-specific Kaplan-Meier survival curves for this burial population of sedentary hunter-gatherers. As was common among societies predating modern Western medicine and antibiotics, infant mortality was high for both males and females. However, male infants (from birth to 5 years of age) appear to have died at nearly twice the rate of female infants (10 of 33 males vs. 5 of 32 females) and had a mean age of survival at birth of only 19 years, compared to 30 years for females. The difference in male and female survival was statistically significant by log-rank test ( p = 0.005). Compared to survival curves for other societies predating modern Western medicine and antibiotics, including American-era historical deaths recorded for a cemetery in San Francisco, this bias is larger than might be expected. We suspect the pattern of sex-biased infant mortality at Síi Túupentak could relate to an intrinsic survival advantage for female infants, combined with extrinsic factors such as environmental pathogens, nutritional stress, and gendered differences in weaning patterns detected through stable isotope analyses. Using isotopic data on weaning ages and ethnographic accounts of gendered foraging activities, we focus on the potential role of sex-biased differences in weaning patterns and highlight potential demographic and social implications. Broader application of proteomic and genomic sex estimation would allow sex-biased differences in nutrition and health, as well as social and cultural aspects of male and female life histories, to be compared across a wide range of archaeologically known hunter-gatherer societies.

Evaluation of the Impact of Eustenopus villosus on Centaurea solstitialis Seed Production in California.

Simple SummaryThe exotic thistle, Centaurea solstitialis, has become overly abundant in the western USA. A seed weevil, Eustenopus villosus, was released in the early 1990s to reduce seed production and abundance of the thistle. A first step in evaluating success of the biological control program is to evaluate the amount of seed destroyed by the weevil in its new area of infestation. At two sites for two years, we found that adult weevils killed 60–70% of young flower buds, forcing plants to regrow new buds which delayed flowering by 9 days and extended flowering by 4 weeks at season end. Flower heads varied in size and seed production increased linearly by size of the flower head. The seed weevil attacked larger flower heads more frequently than smaller flower heads but the probability of a flower head being attacked did not vary with plant size. Weevil larvae occurred in 27% to 49% of seed heads and resulted in 34% to 47% of the annual seed crop being destroyed. We recommend that another survey be performed to see if the seed weevil has increased in abundance since its introduction.The impact of the capitulum weevil Eustenopus villosus on Centaurea solstitialis seed production was examined at two field sites in central California. The study occurred in 1993–1995 during the early phases of the biological control program on C. solstitialis and before the current guild of capitulum insects had become widespread. Results showed that adult feeding on early flower buds resulted in 60–70% of buds failing to develop. Regrowth delayed capitulum production by 9 days and extended production by 4 weeks at season end. Between 69% and 92% of capitula were punctured from feeding or oviposition but the occurrence of larvae in capitula ranged from 27% to 49%. Seed production in C. solstitialis capitula increased linearly with size. The occurrence of larvae was proportionally higher in larger capitula (>8 mm) but the probability of attack for individual capitula did not vary with plant size. Total seed loss from larval feeding ranged from 34 to 47%. It is recommended that another survey be performed to determine if the level of infestation of E. villosus has increased since its initial introduction.

A multimillennial snow water equivalent reconstruction from giant sequoia tree rings

The first dendroclimatic reconstruction of May 1 snow water equivalent (SWE) was developed from a Sequoiadendron giganteum regional tree-ring chronology network of 23 sites in central California for the period 90–2012 CE. The reconstruction is based on a significant relationship between May 1 SWE and tree-ring growth and shows climate variability from interannual to intercentennial time scales. A regression-based reconstruction equation explains up to 55% of the variance of SWE for 1940–2012. Split-sample validation supports our use of a reconstruction model based on the full period of reliable observational data (1940–2012). Thresholds for May 1 SWE low (15 percentile) and high (80 percentile) years were selected based on the exploratory scatterplots relationship between observed and reconstructed data for the period 1940–2012. The longest period of consecutive low-SWE years in the reconstruction is 2 years and the frequency of the lowest SWE years is highest during the period 710–809 CE. The longest high-SWE period, defined by consecutive wet years, is 3 years (558–560 CE). SWE and its reconstruction positively correlate with northeastern Pacific sea surface temperatures, the low-frequency variability of which may provide some predictive ability. Ultimately, the instrumental record and reconstruction suggest that unlike other sites in the region, twentieth century SWE variability in these Sequoia groves has remained within historical boundaries and relatively buffered from extremes and severe declines, though this is likely to change in coming decades with potentially negative effects on water availability for these trees.

A comparison of proteomic, genomic, and osteological methods of archaeological sex estimation

Sex estimation of skeletons is fundamental to many archaeological studies. Currently, three approaches are available to estimate sex–osteology, genomics, or proteomics, but little is known about the relative reliability of these methods in applied settings. We present matching osteological, shotgun-genomic, and proteomic data to estimate the sex of 55 individuals, each with an independent radiocarbon date between 2,440 and 100 cal BP, from two ancestral Ohlone sites in Central California. Sex estimation was possible in 100% of this burial sample using proteomics, in 91% using genomics, and in 51% using osteology. Agreement between the methods was high, however conflicts did occur. Genomic sex estimates were 100% consistent with proteomic and osteological estimates when DNA reads were above 100,000 total sequences. However, more than half the samples had DNA read numbers below this threshold, producing high rates of conflict with osteological and proteomic data where nine out of twenty conditional DNA sex estimates conflicted with proteomics. While the DNA signal decreased by an order of magnitude in the older burial samples, there was no decrease in proteomic signal. We conclude that proteomics provides an important complement to osteological and shotgun-genomic sex estimation.

Impact of Primary Care Worksite Health and Wellness Clinics on HbA1c Level Among Prediabetic or Diabetic Employees.

To determine whether the use of worksite health and wellness clinics reduced hemoglobin A1c (HbA1c) for prediabetic and diabetic employees. Hemoglobin A1c values were compared between clinic users and matched non-users. The Wonderful Company's (TWC's) agricultural and packaging sites in Central California. TWC's 2016 to 2017 employees who used clinics (n = 445, defined below) and clinic non-users (n = 217) who had HbA1c screening and worked at TWC for 3 or more months each year. A unique worksite health and wellness clinic that offers multidisciplinary primary medical care in synergy with TWC's overall wellness programs. Exposure was clinic use, defined by frequency and patterns of visits. Hemoglobin A1c was the outcome of interest. Users and non-users were propensity score matched using the 2016 employee data including HbA1c, and then 2017 HbA1c values were compared between the 2 groups. The 2017 HbA1c of diabetic employees was lower among clinic users compared to non-users (7.42 vs 8.53, P < .001). Differences in HbA1c among prediabetics or diabetics and prediabetics aggregated were not statistically significant, despite TWC's population-level data showing a reduction in prediabetes prevalence. The clinic impact results were robust to multivariate analyses and an alternative definition of utilization. The implementation of TWC's Health and Wellness clinics was associated with reductions in HbA1c among diabetics, but further research is needed on prediabetics.

Cobble community DNA as a tool to monitor patterns of biodiversity within kelp forest ecosystems.

Kelp forest ecosystems dominate 150,000km of global temperate coastline, rivalling the coastal occurrence of coral reefs. Despite the astounding biological diversity and productive ecological communities associated with kelp forests, patterns of species richness and composition are difficult to monitor and compare. Crustose coralline algae are a critically important substrate for propagule settlement for a range of kelp forest species. Coralline-covered cobbles are home to hundreds of species of benthic animals and algae and form a replicable unit for ecological assays. Here, we use DNA metabarcoding of bulk DNA extracts sampled from cobbles to explore patterns of species diversity in kelp forests of the central California coast. The data from 97 cobbles within kelp forest ecosystems at three sites in Central California show the presence of 752 molecular operational taxonomic units (MOTUs) and 53 MOTUs assigned up to the species level with >95% similarity to current databases. We are able to detect spatial patterns of important management targets such as abalone recruits, and localized abundance of sea stars in 2012. Comparison of classic ecological surveys of these sites reveals large differences in species targets for these two approaches. In order to make such comparisons more quantitative, we use Presence/Absence Metabarcoding, using the fraction of replicate cobbles showing a species as a measure of its local abundance. This approach provides a fast and repeatable survey method that can be applied for biodiversity assessments across systems to shed light on the impact of different ecological disturbances and the role played by marine protected areas.

Microbiological safety of popular recreation swimming sites in Central California.

The objective of the study was to assess the microbiological safety of popular recreational swimming sites in Central California. Water samples were collected from eleven monitoring sites across the lower reaches of two watersheds for two consecutive swimming seasons (2012-2013), and levels of indicator and pathogenic microorganisms were determined. Data on ambient weather and water chemistry were collected for analyzing their associations with microorganisms in water. All water samples were positive for indicator E. coli with mean concentrations per site ranging from 3.07 to 216.11 MPN/100ml in 2012 and 13.4 to 226.97 MPN/100ml in 2013. Mean E. coli concentrations in 27% and 36% samplings sites exceeded the EPA 2012 Recreational Water Quality Criteria recommended mean concentration of ≤ 126CFU/100ml of E. coli, in 2012 and 2013, respectively. Cryptosporidium spp. oocysts were detected in all water samples from all sampling sites, with an overall prevalence of 50% and mean concentrations of 0.08 oocysts/l in 2012 and 0.19 oocysts/l in 2013. Giardia spp. cysts were detected at eight sites, with an overall prevalence of 28.8% and mean concentration of 0.2 cysts/l in both years. The majority of the detected Cryptosporidium spp. oocysts and Giardia spp. cysts appeared damaged under microscopy. E. coli O157:H7 was detected in 9% of water samples, with positive samples limited to three sites. Salmonella spp. were detected in all but one site across the twoyears, with mean concentrations of 0.94 MPN/l in 2012 and 1.85 MPN/l in 2013. Cryptosporidium spp. oocyst concentrations were negatively associated with 30-day mean wind speed and cumulative precipitation and dissolved oxygen in water. Giardia spp. cyst concentrations were positively associated with turbidity and pH of water and negatively associated with E. coli concentrations and 24-h mean air temperature. Salmonella spp. concentrations were positively associated with 30-day mean air temperature. The occurrence of E. coli O157:H7 was positively associated with previous 30-day cumulative precipitation.

Atmospheric observation-based estimation of fossil fuel CO2 emissions from regions of central and southern California

Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (14CO2) measurements and atmospheric inverse modeling to estimate fossil fuel CO2 (ffCO2) emissions for 2009–2012 from a site in central California, and for June 2013–May 2014 from two sites in southern California. A priori predicted ffCO2 mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO2 prior emission map (Vulcan 2.2). Regional inversions using observations from the central California site suggest that emissions from the San Francisco Bay Area (SFBA) are higher in winter and lower in summer. Taking all years together, the average of a total of fifteen 3-month inversions from 2009 to 2012 suggests ffCO2 emissions from SFBA were within 6 ± 35% of the a priori estimate for that region, where posterior emission uncertainties are reported as 95% confidence intervals. Results for four 3-month inversions using measurements in Los Angeles South Coast Air Basin (SoCAB) during June 2013–May 2014 suggest that emissions in SoCAB are within 13 ± 28% of the a priori estimate for that region, with marginal detection of any seasonality. While emissions from the SFBA and SoCAB urban regions (containing ~50% of prior emissions from California) are constrained by the observations, emissions from the remaining regions are less constrained, suggesting that additional observations will be valuable to more accurately estimate total ffCO2 emissions from California as a whole.

New Radiocarbon Dates from CA-CCO-138 (Hotchkiss Mound) and CA-CCO-139 (Simone Mound) and Insights into Mounds, Settlement Patterns, and Culture History in the California Delta

ABSTRACTWe report 91 new AMS radiocarbon dates on human bone collagen from two important central California sites: CA-CCO-138 (Hotchkiss Mound; n = 46) and CA-CCO-139 (Simone Mound; n = 45). The sites lie within 500 m of one another in the California Delta and have figured prominently in the formulation of culture historical sequences in central California. The new AMS dates show that the two sites are nearly separate in their occupation sequences, with CA-CCO-139 interments dating between 1,190 and 790 cal BP and CA-CCO-138 between 810 and 150 cal BP (median date ranges). We compare the new dates to previous age assignments based on associated artifacts and depth, and discuss implications for understanding ancient settlement patterns, mound occupation sequences, and culture history in the region.

Evapotranspiration estimates derived using thermal-based satellite remote sensing and data fusion for irrigation management in California vineyards

Irrigation in the Central Valley of California is essential for successful wine grape production. With reductions in water availability in much of California due to drought and competing water-use interests, it is important to optimize irrigation management strategies. In the current study, we investigate the utility of satellite-derived maps of evapotranspiration (ET) and the ratio of actual-to-reference ET (fRET) based on remotely sensed land-surface temperature (LST) imagery for monitoring crop water use and stress in vineyards. The Disaggregated Atmosphere Land EXchange Inverse (ALEXI/DisALEXI) surface-energy balance model, a multi-scale ET remote-sensing framework with operational capabilities, is evaluated over two Pinot noir vineyard sites in central California that are being monitored as part of the Grape Remote-Sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX). A data fusion approach is employed to combine ET time-series retrievals from multiple satellite platforms to generate estimates at both the high spatial (30 m) and temporal (daily) resolution required for field-scale irrigation management. Comparisons with micrometeorological data indicate reasonable model performance, with mean absolute errors of 0.6 mm day−1 in ET at the daily time step and minimal bias. Values of fRET agree well with tower observations and reflect known irrigation. Spatiotemporal analyses illustrate the ability of ALEXI/DisALEXI/data fusion package to characterize heterogeneity in ET and fRET both within a vineyard and over the surrounding landscape. These findings will inform the development of strategies for integrating ET mapping time series into operational irrigation management framework, providing actionable information regarding vineyard water use and crop stress at the field and regional scale and at daily to multi-annual time scales.

Sources of pollution and interrelationships between aerosol and precipitation chemistry at a central California site

This study examines co-located aerosol and precipitation chemistry data between 2010 and 2016 at Pinnacles National Monument ~65 km east of the coastline in central California. Positive matrix factorization analysis of the aerosol composition data revealed seven distinct pollutant sources: aged sea salt (25.7% of PM2.5), biomass burning (24.2% of PM2.5), fresh sea salt (15.0% of PM2.5), secondary sulfate (11.7% of PM2.5), dust (10.0% of PM2.5), vehicle emissions (8.2% of PM2.5), and secondary nitrate (5.2% of PM2.5). The influence of meteorology and transport on monthly patterns of PM2.5 composition is discussed. Only secondary sulfate exhibited a statistically significant change (a reduction) over time among the PM2.5 source factors. In contrast, PMcoarse exhibited a significant increase most likely due to dust influence. Monthly profiles of precipitation chemistry are summarized showing that the most abundant species in each month was either SO42−, NO3−, or Cl−. Intercomparisons between the precipitation and aerosol data revealed several features: (i) precipitation pH was inversely related to factors associated with more acidic aerosol constituents such as secondary sulfate and aged sea salt, in addition to being reduced by uptake of HNO3 in the liquid phase; (ii) two aerosol source factors (dust and aged sea salt) and PMcoarse exhibited a positive association with Ca2+ in precipitation, suggestive of directly emitted aerosol types with larger sizes promoting precipitation; and (iii) sulfate levels in both the aerosol and precipitation samples analyzed were significantly correlated with dust and aged sea salt PMF factors, pointing to the partitioning of secondary sulfate to dust and sea salt particles. The results of this work have implications for the region's air quality and hydrological cycle, in addition to demonstrating that the use of co-located aerosol and precipitation chemistry data can provide insights relevant to aerosol-precipitation interactions.

Native acquisition of obsidian in colonial-era central California: Implications from Mission San José

In many regions, the mechanisms by which indigenous people acquired lithic materials during the colonial period are only poorly understood. We take on these issues through the examination of more than 1100 obsidian artifacts recovered from the Native American neighborhood at Mission San José (ca. CE 1797–1840) in central California. We conducted a multifaceted analysis of the assemblage, with an eye toward understanding how indigenous people in this region acquired obsidian after the onset of missionary colonialism. Our study included analysis of technological attributes, geological provenance via X-ray fluorescence spectrometry, and dating through obsidian hydration. Our results demonstrate that native people living at Mission San José acquired obsidian both through long-distance conveyance from source areas and through some recycling of archaeological artifacts. We compare our results to regional precontact patterns of obsidian acquisition and conveyance as well as obsidian assemblages from other colonial-era sites in central California. Taken together, our study indicates persistent yet modified pathways of obsidian acquisition in central California during the colonial period.

Habitat fragmentation provides a competitive advantage to an invasive tree squirrel, Sciurus carolinensis

Changes in the composition of biological communities can be elicited by competitive exclusion, wherein a species is excluded from viable habitat by a superior competitor. Yet less is known about the role of environmental change in facilitating or mitigating exclusion in the context of invasive species. In these situations, decline in a native species can be due to the effects of habitat change, or due to direct effects from invasive species themselves. This is summarized by the “driver-passenger” concept of native species loss. We present a multi-year study of tree squirrels that tested the hypothesis that tree canopy fragmentation, often a result of human development, influenced the replacement of native western gray tree squirrels (Sciurus griseus) by non-native eastern gray tree squirrels (Sciurus carolinensis). We tested this hypothesis along a continuum of invasion across three study sites in central California. We found that within the developed areas of the University of California at Santa Cruz campus and city of Santa Cruz, S. carolinensis excluded S. griseus from viable habitat. The competitive advantage of S. carolinensis may be due to morphological and/or behavioral adaptation to terrestrial life in fragmented hardwood forests. We classify S. carolinensis as a “driver” of the decline of native S. griseus in areas with high tree canopy fragmentation. Future habitat fragmentation in western North America may result in similar invasion dynamics between these species. Our study warrants consideration of existing and predicted interactions between potentially invasive species that co-occur with native species where land use change is proposed.

Heads or Tails? Modified Ceramic Gaming Pieces from Colonial California

Modified ceramic disks have been recovered from historic-era sites across the Americas. Small unperforated disks are commonly interpreted as gaming pieces and larger perforated disks are often classified as spindle whorls. Here, we examine these interpretations in light of collections from three colonial-era sites in central California: Mission San Antonio de Padua, Mission San Jose, and the Rancho San Andres Castro Adobe. We argue that the small unperforated disks from our study sites were two-sided dice. These gaming pieces facilitated the social cohesion of Native people living in the large, multiethnic Indigenous communities that formed around Spanish colonial missions and later Mexican-era ranchos.

Weaning and Early Childhood Diets at Two Early Period Sites: Implications for Parental Investment and Population Growth in Central California

Using stable isotope analysis of serial samples in permanent first molars, we reconstruct age of weaning and early childhood diets for eight individuals at CA-SJO-112, a 3,000–3,300 cal B.P. site in central California. We compare the results to previously published data from a nearby contemporary site, CA-CCO-548. Data show that, on average, children were weaned earlier at CA-SJO-112, but unlike at CA-CCO-548, boys and girls were eating similar types of foods and overall dietary composition was more homogenous among all children at CA-SJO-112. These differences suggest alternative parental investment strategies at the two sites, perhaps due to greater sharing and communal foraging at CA-SJO-112. Combined with low apparent infant mortality rates and similar rates of stress, as measured by rates of linear enamel hypoplasia, earlier weaning at CA-SJO-112 has important implications for population growth in the region.

Livestock grazing supports native plants and songbirds in a California annual grassland.

Over eight years we measured the effects of plant community composition, vegetation structure, and livestock grazing on occurrence of three grassland bird species—Western Meadowlark (Sturnella neglecta), Horned Lark (Eremophila alpestris), and Grasshopper Sparrow (Ammodramus savannarum)—at sites in central California during breeding season. In California’s Mediterranean-type climatic region, coastal and inland grassland vegetation is dominated by exotic annual grasses with occasional patches of native bunchgrass and forbs. Livestock grazing, primarily with beef cattle, is the most widely used management tool. Compared with ungrazed plots, grazed plots had higher bare ground, native plant cover, and vertically heterogeneous vegetation. Grazed plots also had less plant litter and shorter vegetation. Higher native plant cover, which is predominantly composed of bunchgrasses in our study area, was associated with livestock grazing and north-facing aspects. Using an information theoretic approach, we found that all three bird species had positive associations with native plant abundance and neutral (Western Meadowlark, Grasshopper Sparrow) or positive (Horned Lark) association with livestock grazing. All species favored flatter areas. Horned Larks and Western Meadowlark occurred more often where there were patches of bare ground. Western Meadowlarks and Grasshopper Sparrows were most common on north-facing slopes, suggesting that these species may be at risk from projected climate change. These findings demonstrate that livestock grazing is compatible with or supports grassland bird conservation in Mediterranean-type grasslands, including areas with high levels of exotic annual grass invasion, in part because grazing supports the persistence of native plants and heterogeneity in vegetation structure. However, conservation of low-lying grasslands with high native species presence, and active management to increase the abundance of native plant species are also likely to be important for sustaining grassland birds long-term.

Comparisons of statistical techniques to assess age-related skeletal markers in bioarchaeology.

Many authors argue that inconsistencies between studies of skeletal markers are based on different data collection protocols, especially when comparing age-related markers such as osteoarthritis. Less attention is given to the choice of statistical techniques that are used to test the hypotheses associated with the data. This paper addresses how different statistical techniques compare the prevalence of age-related skeletal indicators, specifically osteoarthritis. Osteoarthritis prevalence was scored in eight postcranial joints in 243 adult individuals from seven prehistoric archaeological sites in Central California, and data was compared between three time periods [Early (4800-2800 BP), Middle (2800-1200 BP), and Late (1200-250 BP)] using commonly used statistical tests: chi-square, Fisher's exact, and odds ratios. In addition, we analyzed the data with tests that are able to take into consideration the effect of age on osteoarthritis prevalence: ANCOVA and Factorial ANOVA. Finally, bootstraps were applied to the data to investigate how fluctuating frequencies, sample size, and age-at-death distributions affected the interpretations resulting from each test. The results demonstrate that the tests that consider age as a covariate (ANCOVA and Factorial ANOVA) are more efficient in rejecting the null hypothesis when smaller magnitudes of difference are observed between samples, irrespective of sample size, even though osteoarthritis prevalence fails to meet assumptions of normal distribution and homoscedasticity. ANCOVAs or Factorial ANOVAs that incorporate age as a covariate should be considered more often in studies that test different prevalences of age-related osteological markers among past populations.

Stable isotope evidence of juvenile foraging in prehistoric Central California

Ethnographic evidence demonstrates that hunter–gatherer children may forage effectively enough to supplement an adult provisioned diet, where ecology, subsistence strategies, and social organization are conducive to juvenile participation. We use stable isotope measures (δ15N and δ13C) from bone collagen and serial-samples of dentinal collagen extracted from first molars to examine childhood dietary patterns among 24 individuals from the Late Holocene Central California site CA-ALA-554. We identify weaning age and early childhood dietary patterns, and find evidence for independent child foraging among 25% of the sample population (n=6), the majority of whom lived during the high-stress Medieval Climatic Anomaly (1100–700 BP).