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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. Incisor tooth wear and age determination in mountain gorillas from Volcanoes National Park, Rwanda

   https://doi.org/10.1002/ajpa.23720  

   Galbany, Jordi ; Muhire, Thadée ; Vecellio, Veronica ; Mudakikwa, Antoine ; Nyiramana, Aisha ; Cranfield, Michael R. ; Stoinski, Tara S. ; McFarlin, Shannon C. ( October 2018 , American Journal of Physical Anthropology)

   Ecological factors, but also tooth‐to‐tooth contact over time, have a dramatic effect on tooth wear in primates. The aim of this study is to test whether incisor tooth wear changes predictably with age and can thus be used as an age estimation method in a wild population of mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda.

   In mountain gorillas of confidently known chronological age (N = 24), we measured the crown height of all permanent maxillary and mandibular incisors (I¹, I₁, I², I₂) as a proxy for incisal macrowear. Linear and quadratic regressions for each incisor were used to test whether age can be predicted by crown height. Using these models, we then predicted age at death of two individual mountain gorillas of probable identifications, based on their incisor crown height.

   Age decreased significantly with incisor height for all teeth, but the upper first incisors (I¹) provided the best results, with the lowest Akaike's Information Criterion corrected for small sample size (AICc) and lowest Standard Error of the Estimate (SEE). When the best age equations for each sex were applied to gorillas with probable identifications, the predicted ages differed 1.58 and 3.33 years from the probable ages of these individuals.

   Our findings corroborate that incisor crown height, a proxy for incisal wear, varies predictably with age. This relationship can be used to estimate age at death of unknown gorillas in the skeletal collection, and in some cases, to corroborate the identity of individual gorillas recovered from the forest postmortem at an advanced state of decomposition. Such identifications help fill gaps in the demographic database and support research that requires individual‐level data.

    

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3. Establishing a hemoglobin adjustment for 129Xe gas exchange MRI and MRS

   https://doi.org/10.1002/mrm.29712  

   Bechtel, Aryil ; Lu, Junlan ; Mummy, David ; Bier, Elianna ; Leewiwatwong, Suphachart ; Mugler, III, John ; Kabir, Sakib ; Church, Alex ; Driehuys, Bastiaan ( May 2023 , Magnetic Resonance in Medicine)

   ¹²⁹Xe MRI and MRS signals from airspaces, membrane tissues (M), and red blood cells (RBCs) provide measurements of pulmonary gas exchange. However,¹²⁹Xe MRI/MRS studies have yet to account for hemoglobin concentration (Hb), which is expected to affect the uptake of¹²⁹Xe in the membrane and RBC compartments. We propose a framework to adjust the membrane and RBC signals for Hb and use this to assess sex‐specific differences in RBC/M and establish a Hb‐adjusted healthy reference range for the RBC/M ratio.

   We combined the 1D model of xenon gas exchange (MOXE) with the principle of TR‐flip angle equivalence to establish scaling factors that normalize the dissolved‐phase signals with respect to a standard (14 g/dL).¹²⁹Xe MRI/MRS data from a healthy, young cohort (n = 18, age = 25.0 3.4 years) were used to validate this model and assess the impact of Hb adjustment on M/gas and RBC/gas images and RBC/M.

   Adjusting for Hb caused RBC/M to change by up to 20% in healthy individuals with normal Hb and had marked impacts on M/gas and RBC/gas distributions in 3D gas‐exchange maps. RBC/M was higher in males than females both before and after Hb adjustment (p < 0.001). After Hb adjustment, the healthy reference value for RBC/M for a consortium‐recommended acquisition of TR = 15 ms and flip = 20° was 0.589 0.083 (mean SD).

   MOXE provides a useful framework for evaluating the Hb dependence of the membrane and RBC signals. This work indicates that adjusting for Hb is essential for accurately assessing¹²⁹Xe gas‐exchange MRI/MRS metrics.

    

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4. Seasonal Patterns of Riverine Carbon Sources and Export in NW Greenland

   https://doi.org/10.1029/2018JG004895  

   Csank, Adam Z. ; Czimczik, Claudia I. ; Xu, Xiaomei ; Welker, Jeffrey M. ( April 2019 , Journal of Geophysical Research: Biogeosciences)

   Glacial runoff exports large amounts of carbon (C) to the oceans, but major uncertainty remains regarding sources, seasonality, and magnitude. We apportioned C exported by five rivers from glacial and periglacial sources in northwest Greenland by monitoring discharge, water sources (δ¹⁸O), concentration and composition of dissolved organic carbon (DOC), and ages (¹⁴C) of DOC and particulate organic C over three summers (2010–2012). We found that particulate organic C (F = 1.0366–0.2506) was generally older than DOC in glacial sourced rivers and likely sourced from the physical erosion of aged C pools. Most exported DOC showed strong seasonal variations in sources and discharge. In summer, mean DOC ages ranged from modern to 4,750 cal years BP (F = 1.0022–0.6291); however, the annual C flux from glacially sourced rivers was dominated by young, plant‐derived DOC (F = 0.9667–1.002) exported during the spring freshet. The most aged DOC (F = 0.6891–0.8297) was exported in middle to late summer at lower concentrations and was glacial in origin. Scaled to the whole of Greenland using model‐estimated runoff, we estimate a total riverine DOC flux of 0.29% to 0.45% ± 20% Tg C/year. Our flux results indicate that the highest C fluxes occur during the time of year when the majority of C is modern in age. However, higher melt rates from the Greenland ice sheet and longer growing seasons could result in increasing amounts of ancient C from the Greenland ice sheet and from the periglacial landscape to the ocean.

    

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5. Using a multimethod life history approach to navigate the osteological paradox: A case study from Prehispanic Nasca, Peru

   https://doi.org/10.1002/ajpa.24279  

   McCool, Weston C. ; Anderson, Amy S. ; Kennett, Douglas J. ( March 2021 , American Journal of Physical Anthropology)

   We leverage recent bioarchaeological approaches and life history theory to address the implications of the osteological paradox in a study population. The goal of this article is to evaluate morbidity and mortality patterns as well as variability in the risk of disease and death during the Late Intermediate period (LIP; 950–1450 C.E.) in the Nasca highlands of Peru. We demonstrate how the concurrent use of multiple analytical techniques and life history theory can engage the osteological paradox and provide salient insights into the study of stress, frailty, and resilience in past populations.

   Crania from LIP burial contexts in the Nasca highlands were examined for cribra orbitalia (n = 325) and porotic hyperostosis (n = 270). All age groups and both sexes are represented in the sample. Survivor/nonsurvivor analysis assessed demographic differences in lesion frequency and severity. Hazard models were generated to assess differences in survivorship. The relationship between dietary diversity and heterogeneity in morbidity was assessed using stable δ¹⁵N and δ¹³C isotope values for bone collagen and carbonate. One hundred and twenty‐four crania were directly AMS radiocarbon dated, allowing for a diachronic analysis of morbidity and mortality.

   The frequency and expression of both orbital and vault lesions increases significantly during the LIP. Survivor/nonsurvivor analysis indicates cranial lesions co‐vary with frailty rather than robusticity or longevity. Hazard models show (1) decreasing survivorship with the transition into the LIP, (2) significantly lower adult life expectancy for females compared to males, and (3) individuals with cranial lesions have lower survivorship across the life course. Stable isotope results show very little dietary diversity. Mortality risk and frequency of pathological skeletal lesions were highest during Phase III (1300–1450 C.E.) of the LIP.

   Results provide compelling evidence of increasing physiological stress and mortality in the Nasca highlands during the LIP, but also reveal substantial heterogeneity in frailty and the risk of death. Certain members of society experienced a heavier disease burden and higher mortality compared to their contemporaries. Elevated levels of disease and lethal trauma among females account for some of the sex differences in survivorship but cannot explain the large degree of female‐biased mortality. We hypothesize that parental investment in males or increased female fertility rates may explain these differences.

    

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