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1. Sex‐biased parental investment and female wealth accumulation in ancient California

   https://doi.org/10.1002/ajpa.24806  

   Greenwald, Alexandra M. ; Burns, Gregory R. ; Eerkens, Jelmer W. ; Bartelink, Eric J. ; Leventhal, Alan ; Arellano, Monica V. ( July 2023 , American Journal of Biological Anthropology)

   The mortuary record at Middle Period siteKalawwasa Rummeytak(CA‐SCL‐134) (2600‐1225 cal BP) in California's southern Santa Clara Valley shows pronounced wealth inequality;Olivellashell bead wealth, as well as other grave goods, are concentrated in the burials of several older adult females. The concentration of wealth among women, along with regional strontium isotopic evidence of male‐biased residential shifts in early adulthood, suggests a matrilineal kinship system that practiced matrilocal post‐marital residence patterns. We suggest local resource enhancement effects incentivized keeping women in their natal communities and investing more in female offspring.

   With the consent of, and in collaboration with, the Muwekma Ohlone Tribe of the San Francisco Bay Area, this paper employs isotopic analysis (δ¹⁵N andδ¹³C,⁸⁶Sr/⁸⁷Sr) to examine duration of exclusive breastfeeding, weaning age (complete cessation of breastmilk consumption), early childhood diet, and lifetime residential mobility of individuals interred atKalawwasa Rummeytakto test the assumption that the site inhabitants favored matrilocality and that female offspring received greater levels of investment in groups with female wealth/status attainment. First molars, third molars, and bone was sampled from 22 individuals.

   The average weaning age for females atKalawwasa Rummeytakis 36.3 months ± 9.7 (1 SD), or just over 3 years. The average weaning age for males is 31.2 ± 7.9 months (1 SD), or about 2.6 years. Infants at the site were provisioned with supplemental foods dominated by C₃plants and terrestrial herbivores, as well as anadromous fish. After weaning, individuals consumed a diet dominated by acorns, C₃plants, and terrestrial herbivores, with periodic inclusion of anadromous fish. 30% of the sampled population of females exhibit local first molar⁸⁷Sr/⁸⁶Sr values, suggesting thatKalawwasa Rummeytakis their natal community. None of the males interred at the site are locals.

   Despite the small sample size often unavoidable in archaeological contexts, we find possible female‐biased parental investment strategies. Cessation of breastfeeding (weaning) was, on average, 5 months earlier for males compared to females. There are no differences between females and males in the consumption of supplemental or post‐weaning foods. Strontium data suggest a flexible postmarital residence system that favored matrilocality. This may have incentivized greater investment in female offspring.

    

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2. Assessment of nutritional stress in famine burials using stable isotope analysis

   https://doi.org/10.1002/ajpa.24054  

   Walter, Brittany S. ; DeWitte, Sharon N. ; Dupras, Tosha ; Beaumont, Julia ( April 2020 , American Journal of Physical Anthropology)

   We compared δ¹⁵N and δ¹³C values from bone and dentine collagen profiles of individuals interred in famine‐related and attritional burials to evaluate whether individuals in medieval London who experienced nutritional stress exhibit enriched nitrogen in bone and tooth tissue. Dentine profiles were evaluated to identify patterns that may be indicative of famine during childhood and were compared with the age of enamel hypoplasia (EH) formation to assess whether isotopic patterns of undernutrition coincide with the timing of physiological stress.

   δ¹⁵N and δ¹³C isotope ratios of bone collagen were obtained from individuals (n= 128) interred in attritional and famine burials from a medieval London cemetery (c. 1120–1539). Temporal sequences of δ¹⁵N and δ¹³C isotope profiles for incrementally forming dentine collagen were obtained from a subset of these individuals (n= 21).

   Results indicate that individuals from attritional graves exhibit significantly higher δ¹⁵N values but no significant differences were found between burial types for the sexes. Analyses of dentine profiles reveal that a lower proportion of famine burials exhibit stable dentine profiles and that several exhibit a pattern of opposing covariance between δ¹⁵N and δ¹³C. EH were also observed to have formed during or after the opposing covariance pattern for some individuals.

   The results of this study may reflect differences in diet between burial types rather than nutritional stress. Though nutritional stress could not be definitively identified using bone and dentine collagen, the results from dentine analysis support previous observations of biochemical patterns associated with nutritional stress during childhood.

    

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3. An archaeological strontium isoscape for the prehistoric Andes: Understanding population mobility through a geostatistical meta-analysis of archaeological 87Sr/86Sr values from humans, animals, and artifacts

   https://doi.org/10.1016/j.jas.2020.105121  

   Scaffidi, Beth ; Knudson, Kelly ( January 2020 , Journal of archaeological science)

   Biogeographical studies of migration and mobility in archaeology and bioarchaeology rely on accurately characterizing local 87Sr/86Sr ranges, either through baseline studies or by statistically parsing archaeological results at a given site. However, when baseline materials are difficult to obtain or suspected to deviate from prehistoric isotopic catchments, archaeological data may provide an accurate characterization of local ranges. Through a spatial meta-analysis of 87Sr/86Sr values from archaeological human, faunal, and artifact samples (n = 1658) from 45 publications, this study aims to quantify and compare variation in bioavailable strontium and create the first predictive isotope model (or isoscape) for 87Sr/86Sr values in the prehistoric Andes. Descriptive statistics, including the coefficient of variation, are compared between sites from different temporal categories, and between coastal, yungas, and highland sites. Regional differences in the 87Sr/86Sr values of male and female biological sex categories are compared for human enamel and bone samples, and between sequentially-forming enamel and bone samples. The study finds that the archaeological dataset trimmed of outliers provides a reliable model of local ranges. However, we caution that when migration and trade networks being investigated are within homogeneous isoscape regions, or between contiguous neighbors, multiple isotopic signatures should be incorporated into provenience estimations. 

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4. Comparison of powdered enamel sample pretreatment methods for strontium isotope analysis

   https://doi.org/10.3389/fenvc.2023.1114807  

   Crowley, Brooke Erin ; Bruff Simpson, Emily Michelle ; Hammer, Sarah Jayne ; Smith, Joshua Michael ; Johnson, Thomas Martin ( March 2023 , Frontiers in Environmental Chemistry)

   Most researchers assume minimal impact of pretreatment on strontium isotope ratios ( 87 Sr/ 86 Sr) for bones and teeth, and methods vary tremendously. We compared 14 pretreatment methods, including no prep other than powdering enamel, ashing, soaking in water, an oxidizing agent (bleach or hydrogen peroxide) or acetic acid (0.1 M, 1.0 M, and 1.0 M buffered with calcium acetate), and a combination of these steps. We prepared and analyzed aliquots of powdered molar enamel from three proboscideans (one modern captive Indian elephant, Elephas maximus indicus ; one Pleistocene mastodon, Mammut americanum ; and one Miocene gomphothere, Afrochoerodon kisumuensis ). Each pretreatment was performed in triplicate and we measured 87 Sr/ 86 Sr, Sr concentration, and uranium (U) concentration, using the same lab space and instrumentation for all samples. Variability in 87 Sr/ 86 Sr and Sr and U concentrations was considerable across pretreatments. Mean 87 Sr/ 86 Sr across methods ranged from 0.70999 to 0.71029 for the modern tooth, 0.71458 to 0.71502 for the Pleistocene tooth, and 0.70804 to 0.70817 for the Miocene tooth. The modern tooth contained the least Sr and negligible U. The Pleistocene tooth contained slightly more Sr and measurable amounts of U, and the Miocene tooth had approximately 5x more Sr and U than the Pleistocene tooth. For all three teeth, variance in 87 Sr/ 86 Sr, Sr concentrations, and U concentrations among replicates was statistically indistinguishable across pretreatments, but there were apparent differences among pretreatments for the modern and Pleistocene teeth. Both contained relatively little Sr, and it is possible that small amounts of exogenous Sr from reagents, building materials or dust affected some replicates for some pretreatments. For the modern tooth, median 87 Sr/ 86 Sr varied considerably (but statistically insignificantly) across pretreatments. For the Pleistocene tooth, variability in median 87 Sr/ 86 Sr was also considerable; some pretreatments were statistically distinct but there were no obvious patterns among methods. For the Miocene tooth, variability in median 87 Sr/ 86 Sr was much smaller, but there were significant differences among pretreatments. Most pretreatments yielded 87 Sr/ 86 Sr and Sr concentrations comparable to, or lower than, untreated powder, suggesting selective removal of exogenous material with high 87 Sr/ 86 Sr. Further evaluation of the mechanisms driving isotopic variability both within and among pretreatment methods is warranted. Researchers should clearly report their methods and avoid combining data obtained using different methods. Small differences in 87 Sr/ 86 Sr could impact data interpretations, especially in areas where isotopic variability is low. 

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5. Trace element concentrations as proxies for diagenetic alteration in the African archaeofaunal record: Implications for isotope analysis

   https://doi.org/10.1016/j.jasrep.2024.104403  

   Bertacchi, Alex ; Zipkin, Andrew M. ; Giblin, Julia ; Gordon, Gwyneth ; Goepfert, Tyler ; Asael, Dan ; Knudson, Kelly J. ( February 2024 , Journal of Archaeological Science: Reports)

   Isotope ratio analyses of trace elements are applied to tooth enamel, ostrich eggshell, and other archaeological hard tissues to infer mobility and other aspects of hominin and animal paleoecology. It has been assumed that these highly mineralized tissues are resistant to diagenetic alteration, but this is seldom tested and some studies document diagenetic alteration over brief time spans. Here, we build on existing research on Maximum Threshold Concentrations (MTCs) to develop screening tools for diagenesis that can inform heavy isotopic analyses. The premise of the MTC approach is that archaeological tissues are likely contaminated and unsuitable for isotope ratio analysis when they exceed characteristic modern concentration ranges of trace elements. Furthermore, we propose a new metric called the Maximum Threshold Ratio (MTR) of 85Rb/88Sr or whole element Rb/Sr, which can be measured simultaneously with 87Sr/86Sr during laser ablation (LA) MC-ICP-MS or applied during post hoc screening of specimens. We analyzed 56 enamel samples from modern Kenyan mammals and 34 modern ostrich eggshells from South Africa, Namibia, and the United States by solution ICP-MS, as well as a subset of shells using LA-MC-ICP-MS. Our results indicate that thresholds are consistent across taxa at a single location, but likely vary across locations. Therefore, MTCs and MTRs need to be tissue and locality specific, but not necessarily taxon-specific. Other important differences are observed between the inner and outer surfaces of the eggshells and between LA and solution ICP-MS. This exploratory study provides guidelines for building reference thresholds to screen enamel and eggshell for diagenesis potentially impacting biogenic isotope ratios. 

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