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1. 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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2. Allometric scaling and growth: Evaluation and applications in subadult body mass estimation

   https://doi.org/10.1002/ajpa.24329  

   Yim, An‐Di ; Konigsberg, Lyle W. ; Hwa, Hsiao‐Lin ; Chang, Chin‐Chen ; Chen, Jo‐Yu ; Liu, Hon‐Man ( May 2021 , American Journal of Physical Anthropology)

   Previously developed methods in subadult body mass estimation have not been tested in populations other than European–American or African–American. This study uses a contemporary Taiwanese sample to test these methods. Through evaluating their accuracy and bias, we addressed whether the allometric relationships between body mass and skeletal traits commonly used in subadult body mass estimation are conserved among different populations.

   Computed tomography scans of lower limbs from individuals aged 0–17 years old of both sexes were collected from National Taiwan University Hospital along with documented body weight. Polar second moment of area, distal femoral metaphyseal breadth, and maximum superior/inferior femoral head diameter were collected either directly from the scans or from reconstructed 3D models. Estimated body mass was compared with documented body mass to assess the performance of the equations.

   Current methods provided good body mass estimates in Taiwanese individuals, with accuracy and bias similar to those reported in other validation studies. A tendency for increasing error with increasing age was observed for all methods. Reduced major axis regression showed the allometric relationships between different skeletal traits and body mass across different age categories can all be summarized using a common fitted line. A revised, maximum likelihood‐based approach was proposed for all skeletal traits.

   The results suggested that the allometric relationships between body mass and different skeletal traits are largely conserved among populations. The revised method provided improved applicability with strong underlying theoretical justifications, and potential for future improvements.

    

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3. Morphometric panel regression equations for predicting body mass in immature humans

   https://doi.org/10.1002/ajpa.23422  

   Yapuncich, Gabriel S. ; Churchill, Steven E. ; Cameron, Noël ; Walker, Christopher S. ( January 2018 , American Journal of Physical Anthropology)

   Predicting body mass is a frequent objective of several anthropological subdisciplines, but there are few published methods for predicting body mass in immature humans. Because most reference samples are composed of adults, predicting body mass outside the range of adults requires extrapolation, which may reduce the accuracy of predictions. Prediction equations developed from a sample of immature humans would reduce extrapolation for application to small‐bodied target individuals, and should have utility in multiple predictive contexts.

   Here, we present two novel body mass prediction equations derived from 3468 observations of stature and bi‐iliac breadth from a large sample of immature humans (n = 173) collected in the Harpenden Growth Study. Prediction equations were generated using raw and natural log‐transformed data and modeled using panel regression, which accounts for serial autocorrelation of longitudinal observations. Predictive accuracy was gauged with a global sample of human juveniles (n = 530 age‐ and sex‐specific annual means) and compared to the performance of the adult morphometric prediction equation previously identified as most accurate for human juveniles.

   While the raw data panel equation is only slightly more accurate than the adult equation, the logged data panel equation generates very accurate body mass predictions across both sexes and all age classes of the test sample (mean absolute percentage prediction error = 2.47).

   The logged data panel equation should prove useful in archaeological, forensic, and paleontological contexts when predictor variables can be measured with confidence and are outside the range of modern adult humans.

    

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4. Relative tooth size, Bayesian inference, and Homo naledi

   https://doi.org/10.1002/ajpa.24353  

   Irish, Joel_D ; Grabowski, Mark ( June 2021 , American Journal of Physical Anthropology)

   Size‐corrected tooth crown measurements were used to estimate phenetic affinities amongHomo naledi(~335–236 ka) and 11 other Plio‐Pleistocene and recent species. To assess further their efficacy, and identify dental evolutionary trends, the data were then quantitatively coded for phylogenetic analyses. Results from both methods contribute additional characterization ofH. naledirelative to other hominins.

   After division by their geometric mean, scaled mesiodistal and buccolingual dimensions were used in tooth size apportionment analysis to compareH. nalediwithAustralopithecus africanus,A. afarensis,Paranthropus robustus,P. boisei,H. habilis,H. ergaster,H. erectus,H. heidelbergensis,H. neanderthalensis,H. sapiens, andPan troglodytes. These data produce equivalently scaled samples unaffected by interspecific size differences. The data were then gap‐weighted for Bayesian inference.

   Congruence in interspecific relationships is evident between methods, and with many inferred from earlier systematic studies. However, the present results placeH. naledias a sister taxon toH. habilis,based on a symplesiomorphic pattern of relative tooth size. In the preferred Bayesian phylogram,H. nalediis nested within a clade comprising allHomospecies, but it shares some characteristics with australopiths and, particularly, earlyHomo.

   Phylogenetic analyses of relative tooth size yield information about evolutionary dental trends not previously reported inH. nalediand the other hominins. Moreover, with an appropriate model these data recovered plausible evolutionary relationships. Together, the findings support recent study suggestingH. naledioriginated long before the geological date of the Dinaledi Chamber, from which the specimens under study were recovered.

    

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5. Bone density and frame size in adult women: Effects of body size, habitual use, and life history

   https://doi.org/10.1002/ajhb.23502  

   Lee, Katharine M. N. ; Rogers‐LaVanne, Mary P. ; Galbarczyk, Andrzej ; Jasienska, Grazyna ; Clancy, Kathryn B. H. ( September 2020 , American Journal of Human Biology)

   Bone mineral density (BMD) and frame size are important predictors of future bone health, with smaller frame size and lower BMD associated with higher risk of later fragility fractures. We test the effects of body size, habitual use, and life history on frame size and cortical BMD of the radius and tibia in sample of healthy adult premenopausal women.

   We used anthropometry and life history data from 123 women (age 18‐46) from rural Poland. Standard techniques were used to measure height, weight, and body fat. Life history factors were recorded using surveys. Grip strength was measured as a proxy for habitual activity, wrist breadth for skeletal frame size. Cortical BMD was measured at the one‐third distal point of the radius and mid‐point of the tibia using quantitative ultrasound (reported as speed of sound, SoS).

   Radial SoS was high (meant‐score 3.2 ± 1.6), but tibia SoS was average (meant‐score 0.35 ± 1.17). SoS was not associated with age, although wrist breadth was positively associated with age after adjusting for height. Radius SoS was not associated with measures of body size, habitual use, or life history factors. Wrist breadth was associated with body size (p < .05 for all), lean mass, and grip strength. Tibia SoS was associated with height. Life history factors were not associated with frame size or cortical SoS.

   Habitual use and overall body size are more strongly associated with frame size and cortical SoS than life history factors in this sample of healthy adult women.

    

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