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1. Comparative life history patterns of female gorillas

   https://doi.org/10.1002/ajpa.24792  

   Robbins, Martha M. ; Akantorana, Moses ; Arinaitwe, Joseph ; Breuer, Thomas ; Manguette, Marie ; McFarlin, Shannon ; Meder, Angela ; Parnell, Richard ; Richardson, Jack L. ; Stephan, Claudia ; et al ( June 2023 , American Journal of Biological Anthropology)

   Several theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population(Gorilla gorilla gorilla) and two mountain gorilla populations(Gorilla beringei beringei).

   We compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long‐term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas).

   The Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns.

   These patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolutionary mechanisms responsible for these differences, whether a consequence of genetic adaptation to fluctuating food supplies (“ecological risk aversion hypothesis”) or phenotypic plasticity in response to the abundance of food (“energy balance hypothesis”). Our results do not seem consistent with the extrinsic mortality risks at each site, but current conditions for mountain gorillas are unlikely to match their evolutionary history. Not all traits fell along the expected fast‐slow continuum, which illustrates that they can vary independently from each other (“modularity model”). Thus, the life history traits of each gorilla population may reflect a complex interplay of multiple ecological influences that are operating through both genetic adaptations and phenotypic plasticity.

    

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2. Phylogenetic and environmental effects on limb bone structure in gorillas

   https://doi.org/10.1002/ajpa.23437  

   Ruff, Christopher B. ; Burgess, M. Loring ; Junno, Juho‐Antti ; Mudakikwa, Antoine ; Zollikofer, Christophe P. E. ; Ponce de León, Marcia S. ; McFarlin, Shannon C. ( February 2018 , American Journal of Physical Anthropology)

   The effects of phylogeny and locomotor behavior on long bone structural proportions are assessed through comparisons between adult and ontogenetic samples of extant gorillas.

   A total of 281 wild‐collected individuals were included in the study, divided into four groups that vary taxonomically and ecologically: western lowland gorillas (G. g. gorilla), lowland and highland grauer gorillas(G. b. graueri), and Virunga mountain gorillas (G. b. beringei). Lengths and articular breadths of the major long bones (except the fibula) were measured, and diaphyseal cross‐sectional geometric properties determined using computed tomography. Ages of immature specimens (n = 145) were known or estimated from dental development. Differences between groups in hind limb to forelimb proportions were assessed in both adults and during development.

   Diaphyseal strength proportions among adults vary in parallel with behavioral/ecological differences, and not phylogeny. The more arboreal western lowland and lowland grauer gorillas have relatively stronger forelimbs than the more terrestrial Virunga mountain gorillas, while the behaviorally intermediate highland grauer gorillas have intermediate proportions. Diaphyseal strength proportions are similar in young infants but diverge after 2 years of age in western lowland and mountain gorillas, at the same time that changes in locomotor behavior occur. There are no differences between groups in length or articular proportions among either adults or immature individuals.

   Long bone diaphyseal strength proportions in gorillas are developmentally plastic, reflecting behavior, while length and articular proportions are much more genetically canalized. These findings have implications for interpreting morphological variation among fossil taxa.

    

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3. Ancient anomalies: Twinned and supernumerary incisors in a medieval Nubian

   https://doi.org/10.1002/oa.2954  

   Phillips, Emma L. W. ; Irish, Joel D. ; Antoine, Daniel ( January 2021 , International Journal of Osteoarchaeology)

   During the analysis of a skeletal assemblage from a medieval cemetery in Nubia (c. AD 500–1550), a young adult female with abnormally developed maxillary incisors was discovered. The possible causes of the two dental anomalies found in this individual and their archaeological context are discussed. The remains are from a medieval assemblage from the Fourth Cataract region of Nubia, which forms part of the Nubian collection curated at the British Museum. The left central incisor has a twinned crown with two root canals, and a supernumerary tooth is present on the right side between the central incisor and lateral incisors. Although two different dental anomalies are present, the bilateral expression suggests that the same biological mechanism could be responsible.

    

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4. Functional and phylogenetic variation in anthropoid incisor size

   https://doi.org/10.1002/ajpa.24375  

   Scott, Jeremiah E. ( July 2021 , American Journal of Physical Anthropology)

   Previous studies have shown that frugivorous anthropoids have wider incisors than folivores relative to body mass, and that catarrhines have relatively wider incisors than platyrrhines. This study reexamines these contrasts using mandibular length as a biomechanical standard to quantify relative incisor width.

   Dental, mandibular, and body‐mass data for 86 anthropoid species were taken from the literature. Incisor width was size‐adjusted using shape ratios, with mandibular length and body mass as the denominators. Dietary and phylogenetic effects were examined using phylogenetic generalized least squares.

   Mandible‐based ratios provide a signal that is very similar to the one derived from ratios computed using body mass. Frugivores have relatively wider incisors than folivores, as expected. There is limited support for a stronger dietary effect in platyrrhines when mandible‐based ratios are used, but neither type of ratio indicates an overall difference between platyrrhines and catarrhines.

   Although both ratios support a link between incisor size and diet, there is some evidence indicating that mandible‐based ratios are more sensitive to dietary variation at smaller phylogenetic scales. Understanding why the signals from the two ratios diverge at such scales may help clarify the functional significance of variation in incisor width. The results of this study undermine the view that platyrrhines, as a group, tend to have narrower incisors than catarrhines, regardless of diet. Instead, the difference between the two clades noted in previous studies can be explained by greater incisor functional diversity in platyrrhines.

    

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5. Dental enamel defects predict adolescent health indicators: A cohort study among the Tsimane’ of Bolivia

   https://doi.org/10.1002/ajhb.23107  

   Masterson, Erin E. ; Fitzpatrick, Annette L. ; Enquobahrie, Daniel A. ; Mancl, Lloyd A. ; Eisenberg, Dan T. A. ; Conde, Esther ; Hujoel, Philippe P. ( February 2018 , American Journal of Human Biology)

   Bioarchaeological findings have linked defective enamel formation in preadulthood with adult mortality. We investigated how defective enamel formation in infancy and childhood is associated with risk factors for adult morbidity and mortality in adolescents.

   This cohort study of 349 Amerindian adolescents (10‐17 years of age) related extent of enamel defects on the central maxillary incisors (none, less than 1/3, 1/3 to 2/3, more than 2/3) to adolescent anthropometrics (height, weight) and biomarkers (hemoglobin, glycated hemoglobin, white blood cell count, and blood pressure). Risk differences and 95% confidence intervals were estimated using multiple linear regression. Enamel defects and stunted growth were compared in their ability to predict adolescent health indicators using log‐binomial regression and receiver operating characteristics (ROCs).

   Greater extent of defective enamel formation on the tooth surface was associated with shorter height (–1.35 cm, 95% CI: −2.17, −0.53), lower weight (−0.98 kg, 95% CI: −1.70, −0.26), lower hemoglobin (−0.36 g/dL, 95% CI: −0.59, −0.13), lower glycated hemoglobin (−0.04 %A_1c, 95% CI: −0.08, −0.00008), and higher white blood cell count (0.74 10⁹/L, 95% CI: 0.35, 1.14) in adolescence. Extent of enamel defects and stunted growth independently performed similarly as risk factors for adverse adolescent outcomes, including anemia, prediabetes/type II diabetes, elevated WBC count, prehypertension/hypertension, and metabolic health.

   Defective enamel formation in infancy and childhood predicted adolescent health outcomes and may be primarily associated with infection. Extent of enamel defects and stunted growth may be equally predictive of adverse adolescent health outcomes.

    

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