@article{decasien_chiou_testard_mercer_negron-del valle_surratt_gonzalez_stock_ruiz-lambides_martinez_et al._2024, title={Evolutionary and biomedical implications of sex differences in the primate brain transcriptome}, volume={4}, ISSN={["2666-979X"]}, DOI={10.1016/j.xgen.2024.100589}, abstractNote={Humans exhibit sex differences in the prevalence of many neurodevelopmental disorders and neurodegenerative diseases. Here, we generated one of the largest multi-brain-region bulk transcriptional datasets for the rhesus macaque and characterized sex-biased gene expression patterns to investigate the translatability of this species for sex-biased neurological conditions. We identify patterns similar to those in humans, which are associated with overlapping regulatory mechanisms, biological processes, and genes implicated in sex-biased human disorders, including autism. We also show that sex-biased genes exhibit greater genetic variance for expression and more tissue-specific expression patterns, which may facilitate rapid evolution of sex-biased genes. Our findings provide insights into the biological mechanisms underlying sex-biased disease and support the rhesus macaque model for the translational study of these conditions.}, number={7}, journal={CELL GENOMICS}, author={DeCasien, Alex R. and Chiou, Kenneth L. and Testard, Camille and Mercer, Arianne and Negron-Del Valle, Josue E. and Surratt, Samuel E. Bauman and Gonzalez, Olga and Stock, Michala K. and Ruiz-Lambides, Angelina V. and Martinez, Melween I. and et al.}, year={2024}, month={Jul} }
 @article{chiou_decasien_rees_testard_spurrell_gogate_pliner_tremblay_mercer_whalen_et al._2022, title={Multiregion transcriptomic profiling of the primate brain reveals signatures of aging and the social environment}, ISSN={["1546-1726"]}, DOI={10.1038/s41593-022-01197-0}, abstractNote={Aging is accompanied by a host of social and biological changes that correlate with behavior, cognitive health and susceptibility to neurodegenerative disease. To understand trajectories of brain aging in a primate, we generated a multiregion bulk (N = 527 samples) and single-nucleus (N = 24 samples) brain transcriptional dataset encompassing 15 brain regions and both sexes in a unique population of free-ranging, behaviorally phenotyped rhesus macaques. We demonstrate that age-related changes in the level and variance of gene expression occur in genes associated with neural functions and neurological diseases, including Alzheimer's disease. Further, we show that higher social status in females is associated with younger relative transcriptional ages, providing a link between the social environment and aging in the brain. Our findings lend insight into biological mechanisms underlying brain aging in a nonhuman primate model of human behavior, cognition and health.}, journal={NATURE NEUROSCIENCE}, author={Chiou, Kenneth L. and DeCasien, Alex R. and Rees, Katherina P. and Testard, Camille and Spurrell, Cailyn H. and Gogate, Aishwarya A. and Pliner, Hannah A. and Tremblay, Sebastien and Mercer, Arianne and Whalen, Connor J. and et al.}, year={2022}, month={Nov} }
 @article{testard_brent_andersson_chiou_negron-del valle_decasien_acevedo-ithier_stock_anton_gonzalez_et al._2022, title={Social connections predict brain structure in a multidimensional free-ranging primate society}, volume={8}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.abl5794}, abstractNote={Reproduction and survival in most primate species reflects management of both competitive and cooperative relationships. Here, we investigated the links between neuroanatomy and sociality in free-ranging rhesus macaques. In adults, the number of social partners predicted the volume of the mid–superior temporal sulcus and ventral-dysgranular insula, implicated in social decision-making and empathy, respectively. We found no link between brain structure and other key social variables such as social status or indirect connectedness in adults, nor between maternal social networks or status and dependent infant brain structure. Our findings demonstrate that the size of specific brain structures varies with the number of direct affiliative social connections and suggest that this relationship may arise during development. These results reinforce proposed links between social network size, biological success, and the expansion of specific brain circuits.}, number={15}, journal={SCIENCE ADVANCES}, author={Testard, Camille and Brent, Lauren J. N. and Andersson, Jesper and Chiou, Kenneth L. and Negron-Del Valle, Josue E. and DeCasien, Alex R. and Acevedo-Ithier, Arianna and Stock, Michala K. and Anton, Susan C. and Gonzalez, Olga and et al.}, year={2022}, month={Apr} }
 @article{cofran_vansickle_valenzuela_garcia-martinez_walker_hawks_zipfel_williams_berger_2022, title={The immature Homo naledi ilium from the Lesedi Chamber, Rising Star Cave, South Africa}, ISSN={["2692-7691"]}, DOI={10.1002/ajpa.24522}, abstractNote={AbstractObjectivesHomo naledi is represented by abundant remains from the Dinaledi Chamber of the Rising Star Cave system in South Africa. While pelvic elements from the Dinaledi Chamber of the cave are fragmentary, a relatively complete ilium (U.W. 102a–138) was recovered from the Lesedi Chamber. We reconstructed and analyzed the Lesedi ilium, providing qualitative descriptions and quantitative assessment of its morphology and developmental state.Materials and MethodsWe compared the Lesedi ilium to remains from the Dinaledi Chamber, other South African hominin fossils, and an ontogenetic series of human ilia. We used the Dinaledi adults as a guide for reconstructing the Lesedi ilium. To assess development of the Lesedi ilium, we compared immature/mature proportional ilium height for fossils and humans. We used 3D geometric morphometrics (GMs) to examine size and shape variation among this sample.ResultsThe Lesedi ilium showed incipient development of features expressed in adult H. naledi ilia. The proportional height of the Lesedi ilium was within the range of human juveniles between 4–11 years of age. GM analyses showed that the Lesedi ilium had an iliac blade shape similar to those of australopiths and an expanded auricular surface more similar to humans.ConclusionsThe reconstructed Lesedi specimen represents the best preserved ilium of H. naledi, confirming the australopith‐like iliac blade morphology first hypothesized in adult specimens, and establishing that this anatomy was present early in this species' ontogeny. In contrast to australopiths, the Lesedi ilium displays an enlarged sacroiliac joint, the significance of which requires further investigation.}, journal={AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY}, author={Cofran, Zachary and VanSickle, Caroline and Valenzuela, Reynaldo and Garcia-Martinez, Daniel and Walker, Christopher S. and Hawks, John and Zipfel, Bernhard and Williams, Scott A. and Berger, Lee R.}, year={2022}, month={Apr} }
 @article{dickinson_davis_deutsch_patel_nijhawan_patel_blume_gannon_turcotte_walker_et al._2021, title={Evaluating bony predictors of bite force across the order Carnivora}, volume={8}, ISSN={["1097-4687"]}, DOI={10.1002/jmor.21400}, abstractNote={AbstractIn carnivorans, bite force is a critical and ecologically informative variable that has been correlated with multiple morphological, behavioral, and environmental attributes. Whereas in vivo measures of biting performance are difficult to obtain in many taxa—and impossible in extinct species—numerous osteological proxies exist for estimating masticatory muscle size and force. These proxies include both volumetric approximations of muscle dimensions and direct measurements of muscular attachment sites. In this study, we compare three cranial osteological techniques for estimating muscle size (including 2D‐photographic and 3D‐surface data approaches) against dissection‐derived muscle weights and physiological cross‐sectional area (PCSA) within the jaw adductor musculature of 40 carnivoran taxa spanning eight families, four orders of magnitude in body size, and the full dietary spectrum of the order. Our results indicate that 3D‐approaches provide more accurate estimates of muscle size than do surfaces measured from 2D‐lateral photographs. However, estimates of a muscle's maximum cross‐sectional area are more closely correlated with muscle mass and PCSA than any estimates derived from muscle attachment areas. These findings highlight the importance of accounting for muscle thickness in osteological estimations of the masticatory musculature; as muscles become volumetrically larger, their larger cross‐sectional area does not appear to be associated with a proportional increase in the attachment site area. Though volumetric approaches approximate muscle dimensions well across the order as a whole, caution should be exercised when applying any single method as a predictor across diverse phylogenies.}, journal={JOURNAL OF MORPHOLOGY}, author={Dickinson, Edwin and Davis, Jillian S. and Deutsch, Ashley R. and Patel, Dhuru and Nijhawan, Akash and Patel, Meet and Blume, Abby and Gannon, Jordan L. and Turcotte, Cassandra M. and Walker, Christopher S. and et al.}, year={2021}, month={Aug} }
 @article{wei_zhao_walker_he_lu_hui_shui_jin_liu_2021, title={Internal structural properties of the humeral diaphyses in an early modern human from Tianyuan Cave, China}, volume={591}, ISSN={["1873-4553"]}, DOI={10.1016/j.quaint.2021.04.012}, abstractNote={Since the cross-sectional geometries of long bone diaphyses preserve evidence of a bone's mechanical loading history, examination of a bones' cross-sectional properties can be used to inform its loading history. Here, we use a novel colormap method to quantitatively visualize the topography of cortical bone, second moment of areas, and polar moment of areas along the humeral diaphyses to shed light on the potential manipulative behaviors of the Tianyuan 1 fossil human (Homo sapiens). We compare both humeri of Tianyuan 1 to two Holocene Chinese populations. Our results show that the standardized cortical bone thickness, standardized second moment of areas, and standardized polar moment of areas of Tianyuan 1's right humeral diaphysis are greater than those of the left diaphysis. This evidence supports the hypothesis that the individual was right-handed. The greater medial and lateral cortical reinforcement in the right midshaft humerus, relative to that of the left humerus, may be related to increased unilateral physical activity of the right arm. Unlike the lower humeral asymmetry of recent human agriculturalists, the relatively higher bilateral asymmetry, combined with the relatively larger femoral robusticity, indicate that Tianyuan 1 lived an activity lifestyle compared to the agriculturalists investigated in this study. The bilateral asymmetry of the right and left humeri may be more informative for discriminating between fossil and recent modern human samples than cortical thickness or rigidity values in only one side. This study also indicates that upper limb internal structures can provide important information for inferring the behavior of ancient hominins.}, journal={QUATERNARY INTERNATIONAL}, author={Wei, Pianpian and Zhao, Yuhao and Walker, Christopher S. and He, Jianing and Lu, Xiaoyu and Hui, Jiaming and Shui, Wuyang and Jin, Li and Liu, Wu}, year={2021}, month={Jul}, pages={107–118} }
 @article{pavez-fox_negron-del valle_thompson_walker_bauman_gonzalez_compo_ruiz-lambides_martinez_platt_et al._2021, title={Sociality predicts individual variation in the immunity of free-ranging rhesus macaques}, volume={241}, ISSN={["1873-507X"]}, DOI={10.1016/j.physbeh.2021.113560}, abstractNote={Social integration and social status can substantially affect an individual's health and survival. One route through which this occurs is by altering immune function, which can be highly sensitive to changes in the social environment. However, we currently have limited understanding of how sociality influences markers of immunity in naturalistic populations where social dynamics can be fully realized. To address this gap, we asked if social integration and social status in free-ranging rhesus macaques (Macaca mulatta) predict anatomical and physiological markers of immunity. We used data on agonistic interactions to determine social status, and social network analysis of grooming interactions to generate measures of individual variation in social integration. As measures of immunity, we included the size of two of the major organs involved in the immune response, the spleen and liver, and counts of three types of blood cells (red blood cells, platelets, and white blood cells). Controlling for body mass and age, we found that neither social status nor social integration predicted the size of anatomical markers of immunity. However, individuals that were more socially connected, i.e., with more grooming partners, had lower numbers of white blood cells than their socially isolated counterparts, indicating lower levels of inflammation with increasing levels of integration. These results build upon and extend our knowledge of the relationship between sociality and the immune system in humans and captive animals to free-ranging primates, demonstrating generalizability of the beneficial role of social integration on health.}, journal={PHYSIOLOGY & BEHAVIOR}, author={Pavez-Fox, Melissa A. and Negron-Del Valle, Josue E. and Thompson, Indya J. and Walker, Christopher S. and Bauman, Samuel E. and Gonzalez, Olga and Compo, Nicole and Ruiz-Lambides, Angelina and Martinez, Melween I. and Platt, Michael L. and et al.}, year={2021}, month={Nov} }
 @article{walker_genzer_santiso_2020, title={Effect of Poly(vinyl butyral) Comonomer Sequence on Adhesion to Amorphous Silica: A Coarse-Grained Molecular Dynamics Study}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c10747}, abstractNote={Modulating a comonomer sequence, in addition to overall chemical composition, is the key to unlocking the true potential of many existing commercial copolymers. We employ coarse-grained molecular dynamics (MD) simulations to study the behavior of random-blocky poly(vinyl butyral-co-vinyl alcohol) (PVB) melts in contact with an amorphous silica surface, representing the interface found in laminated safety glass. Our two-pronged coarse-graining approach utilizes both macroscopic thermophysical data and all-atom molecular dynamics simulation data. Polymer-polymer nonbonded interactions are described by the fused-sphere SAFT-γ Mie equation of state, while bonded interactions are derived using Boltzmann inversion to match bond and angle distributions from all-atom PVB chains. Spatially-dependent polymer-surface interactions are mapped from a hydroxylated all-atom amorphous silica slab model and all-atom monomers to an external potential acting on the coarse-grained sites. We ran a series of interfacial coarse-grained MD simulations for PVB melts, systematically varying overall chemical composition and block length distribution. We discovered an unexpectedly complex relationship between blockiness parameter and adhesion energy. For intermediate vinyl alcohol (VA) content, adhesion strength to the silica slab was found to be maximal not for diblock copolymers, but rather random-blocky copolymers with a moderately high degree of blockiness. We attribute this to two main factors: (1) changes in morphology, which dramatically alter the number of VA beads interacting with the surface, and (2) a non-negligible contribution of vinyl butyral (VB) monomers to adhesion energy, due to their preference to adsorb to zones with low hydroxyl density on the silica surface.}, number={42}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2020}, month={Oct}, pages={47879–47890} }
 @article{walker_genzer_santiso_2020, title={Extending the fused-sphere SAFT-gamma Mie force field parameterization approach to poly(vinyl butyral) copolymers}, volume={152}, ISSN={["1089-7690"]}, DOI={10.1063/1.5126213}, abstractNote={SAFT-γ Mie, a molecular group-contribution equation of state with foundations in the statistical associating fluid theory framework, is a promising means for developing accurate and transferable coarse-grained force fields for complex polymer systems. We recently presented a new approach for incorporating bonded potentials derived from all-atom molecular dynamics simulations into fused-sphere SAFT-γ Mie homopolymer chains by means of a shape factor parameter, which allows for bond distances less than the tangent-sphere value required in conventional SAFT-γ Mie force fields. In this study, we explore the application of the fused-sphere SAFT-γ Mie approach to copolymers. In particular, we demonstrate its capabilities at modeling poly(vinyl alcohol-co-vinyl butyral) (PVB), an important commercial copolymer widely used as an interlayer in laminated safety glass applications. We found that shape factors determined from poly(vinyl alcohol) and poly(vinyl butyral) homopolymers do not in general correctly reproduce random copolymer densities when standard SAFT-γ Mie mixing rules are applied. However, shape factors optimized to reproduce the density of a random copolymer of intermediate composition resulted in a model that accurately represents density across a wide range of chemical compositions. Our PVB model reproduced copolymer glass transition temperature in agreement with experimental data, but heat capacity was underpredicted. Finally, we demonstrate that atomistic details may be inserted into equilibrated fused-sphere SAFT-γ Mie copolymer melts through a geometric reverse-mapping algorithm.}, number={4}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2020}, month={Jan} }
 @article{yapuncich_bowie_belais_churchill_walker_2020, title={Predicting body mass of bonobos (Pan paniscus) with human-based morphometric equations}, volume={82}, ISSN={["1098-2345"]}, DOI={10.1002/ajp.23088}, abstractNote={AbstractA primate's body mass covaries with numerous ecological, physiological, and behavioral characteristics. This versatility and potential to provide insight into an animal's life has made body mass prediction a frequent and important objective in paleoanthropology. In hominin paleontology, the most commonly employed body mass prediction equations (BMPEs) are “mechanical” and “morphometric”: uni‐ or multivariate linear regressions incorporating dimensions of load‐bearing skeletal elements and stature and living bi‐iliac breadth as predictor variables, respectively. The precision and accuracy of BMPEs are contingent on multiple factors, however, one of the most notable and pervasive potential sources of error is extrapolation beyond the limits of the reference sample. In this study, we use a test sample requiring extrapolation—56 bonobos (Pan paniscus) from the Lola ya Bonobo sanctuary in Kinshasa, Democratic Republic of the Congo—to evaluate the predictive accuracy of human‐based morphometric BMPEs. We first assess systemic differences in stature and bi‐iliac breadth between humans and bonobos. Due to significant differences in the scaling relationships of body mass and stature between bonobos and humans, we use panel regression to generate a novel BMPE based on living bi‐iliac breadth. We then compare the predictive accuracy of two previously published morphometric equations with the novel equation and find that the novel equation predicts bonobo body mass most accurately overall (41 of 56 bonobos predicted within 20% of their observed body mass). The novel BMPE is particularly accurate between 25 and 45 kg. Given differences in limb proportions, pelvic morphology, and body tissue composition between the human reference and bonobo test samples, we find these results promising and evaluate the novel BMPE's potential application to fossil hominins.}, number={2}, journal={AMERICAN JOURNAL OF PRIMATOLOGY}, author={Yapuncich, Gabriel S. and Bowie, Aleah and Belais, Raphael and Churchill, Steven E. and Walker, Christopher S.}, year={2020}, month={Feb} }
 @article{walker_genzer_santiso_2019, title={Development of a fused-sphere SAFT-gamma Mie force field for poly(vinyl alcohol) and poly(ethylene)}, volume={150}, ISSN={["1089-7690"]}, DOI={10.1063/1.5078742}, abstractNote={SAFT-γ Mie, a group-contribution equation of state rooted in Statistical Associating Fluid Theory, provides an efficient framework for developing accurate, transferable coarse-grained force fields for molecular simulation. Building on the success of SAFT-γ Mie force fields for small molecules, we address two key issues in extending the SAFT-γ Mie coarse-graining methodology to polymers: (1) the treatment of polymer chain rigidity and (2) the disparity between the structure of linear chains of tangent spheres and the structure of the real polymers. We use Boltzmann inversion to derive effective bond-stretching and angle-bending potentials mapped from all-atom oligomer molecular dynamics (MD) simulations to the coarse-grained sites and a fused-sphere version of SAFT-γ Mie as the basis for non-bonded interactions. The introduction of an overlap parameter between Mie spheres leads to a degeneracy when fitting to monomer vapor-liquid equilibria (VLE) data, which we resolve by matching polymer density from coarse-grained MD simulation with that from all-atom simulation. The result is a chain of monomers rigorously parameterized to experimental VLE data and with structural detail consistent with all-atom simulations. We test our approach on atactic poly(vinyl alcohol) and polyethylene and compare the results for SAFT-γ Mie models with structural detail mapped from the Optimized Potentials for Liquid Simulations (OPLS) and Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) all-atom force fields.}, number={3}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Walker, Christopher C. and Genzer, Jan and Santiso, Erik E.}, year={2019}, month={Jan} }
 @article{friedl_claxton_walker_churchill_holliday_hawks_berger_desilva_marchi_2019, title={Femoral neck and shaft structure in Homo naledi from the Dinaledi Chamber (Rising Star System, South Africa)}, volume={133}, ISSN={["0047-2484"]}, DOI={10.1016/j.jhevol.2019.06.002}, abstractNote={The abundant femoral assemblage of Homo naledi found in the Dinaledi Chamber provides a unique opportunity to test hypotheses regarding the taxonomy, locomotion, and loading patterns of this species. Here we describe neck and shaft cross-sectional structure of all the femoral fossils recovered in the Dinaledi Chamber and compare them to a broad sample of fossil hominins, recent humans, and extant apes. Cross-sectional geometric (CSG) properties from the femoral neck (base of neck and midneck) and diaphysis (subtrochanteric region and midshaft) were obtained through CT scans for H. naledi and through CT scans or from the literature for the comparative sample. The comparison of CSG properties of H. naledi and the comparative samples shows that H. naledi femoral neck is quite derived with low superoinferior cortical thickness ratio and high relative cortical area. The neck appears superoinferiorly elongated because of two bony pilasters on its superior surface. Homo naledi femoral shaft shows a relatively thick cortex compared to the other hominins. The subtrochanteric region of the diaphysis is mediolaterally elongated resembling early hominins while the midshaft is anteroposteriorly elongated, indicating high mobility levels. In term of diaphyseal robusticity, the H. naledi femur is more gracile that other hominins and most apes. Homo naledi shows a unique combination of characteristics in its femur that undoubtedly indicate a species committed to terrestrial bipedalism but with a unique loading pattern of the femur possibly consequence of the unique postcranial anatomy of the species.}, journal={JOURNAL OF HUMAN EVOLUTION}, author={Friedl, Lukas and Claxton, Alex G. and Walker, Christopher S. and Churchill, Steven E. and Holliday, Trenton W. and Hawks, John and Berger, Lee R. and DeSilva, Jeremy M. and Marchi, Damiano}, year={2019}, month={Aug}, pages={61–77} }
 @article{pervaje_walker_santiso_2019, title={Molecular simulation of polymers with a SAFT-gamma Mie approach}, volume={45}, ISSN={["1029-0435"]}, DOI={10.1080/08927022.2019.1645331}, abstractNote={ABSTRACT We review the group contribution Statistical Associating Fluid Theory with Mie interaction potentials (SAFT-γ Mie) approach for building coarse-grained models for molecular simulation of polymeric systems. In this top-down method, force field parameters for coarse-grained polymer models can be derived from thermodynamic information on constituent monomer units using the SAFT-γ Mie equation of state (EoS). This strategy can facilitate high-throughput computational screening of polymeric materials, with a corresponding states correlation expediting the force field fitting. Accurate and transferable non-bonded parameters linked to macroscopic thermodynamic data allow for calculation of properties beyond those obtainable from the EoS alone. To overcome limitations of SAFT-γ Mie regarding polymer chain stiffness and branching, hybrid top-down/bottom-up approaches have combined non-bonded parameters from SAFT-γ Mie with bond-stretching and angle-bending potentials from higher-resolution force fields. Our review critically evaluates the performance of recent SAFT-γ Mie polymer models, highlighting the strengths and weaknesses in the context of other equation of state and coarse-graining methods.}, number={14-15}, journal={MOLECULAR SIMULATION}, author={Pervaje, Amulya K. and Walker, Christopher C. and Santiso, Erik E.}, year={2019}, month={Oct}, pages={1223–1241} }
 @article{walker_cofran_grabowski_marchi_cook_churchill_tommy_throckmorton_ross_hawks_et al._2019, title={Morphology of the Homo naledi femora from Lesedi}, volume={170}, ISSN={["1096-8644"]}, DOI={10.1002/ajpa.23877}, abstractNote={AbstractObjectivesThe femoral remains recovered from the Lesedi Chamber are among the most complete South African fossil hominin femora discovered to date and offer new and valuable insights into the anatomy and variation of the bone in Homo naledi. While the femur is one of the best represented postcranial elements in the H. naledi assemblage from the Dinaledi Chamber, the fragmentary and commingled nature of the Dinaledi femoral remains has impeded the assessment of this element in its complete state.Materials and methodsHere we analyze and provide descriptions of three new relatively well‐preserved femoral specimens of H. naledi from the Lesedi Chamber: U.W. 102a‐001, U.W. 102a‐003, and U.W. 102a‐004. These femora are quantitatively and qualitatively compared to multiple extinct hominin femoral specimens, extant hominid taxa, and, where possible, each other.ResultsThe Lesedi femora are morphologically similar to the Dinaledi femora for all overlapping regions, with differences limited to few traits of presently unknown significance. The Lesedi distal femur and mid‐diaphysis preserve anatomy previously unidentified or unconfirmed in the species, including an anteroposteriorly expanded midshaft and anteriorly expanded patellar surface. The hypothesis that the Lesedi femoral sample may represent two individuals is supported.DiscussionThe Lesedi femora increase the range of variation of femoral morphology in H. naledi. Newly described features of the diaphysis and distal femur are either taxonomically uninformative or Homo‐like. Overall, these three new femora are consistent with previous functional interpretations of the H. naledi lower limb as belonging to a species adapted for long distance walking and, possibly, running.}, number={1}, journal={AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY}, author={Walker, Christopher S. and Cofran, Zachary D. and Grabowski, Mark and Marchi, Damiano and Cook, Rebecca W. and Churchill, Steven E. and Tommy, Kimberleigh A. and Throckmorton, Zachary and Ross, Ann H. and Hawks, John and et al.}, year={2019}, month={Sep}, pages={5–23} }
 @article{walker_walker_paulo_pusey_2018, title={Morphological Identification of Hair Recovered from Feces for Detection of Cannibalism in Eastern Chimpanzees}, volume={89}, ISSN={["1421-9980"]}, DOI={10.1159/000488509}, abstractNote={Chimpanzees (Pan troglodytes) are primarily frugivorous but consume a variable amount of meat from a variety of organisms, including other chimpanzees. Cannibalism is rare, usually follows lethal aggression, and does not occur following natural deaths. While chimpanzee cannibalism has been documented at multiple sites, many instances of this behavior go unrecorded. Identification of chimpanzee remains in feces, however, can provide indirect evidence of cannibalism. Hair, in particular, typically passes through the gastrointestinal tract undamaged and is commonly used for purposes of identification in wildlife forensics. Here we test the hypothesis that eastern chimpanzee (Pan troglodytes schweinfurthii) guard hair morphology can be reliably distinguished from the hairs of their most common prey species. Methods and results are presented in the context of a case study involving a suspected chimpanzee infanticide from Gombe, Tanzania. We find that chimpanzee guard hair morphology is unique among tested mammals and that the presence of abundant chimpanzee hair in feces is likely the result of cannibalism and not incidental ingestion from grooming or other means. Accordingly, morphological analysis of guard hairs from feces is a promising, cost-effective tool for the determination of cannibalistic acts in chimpanzees.}, number={3-4}, journal={FOLIA PRIMATOLOGICA}, author={Walker, Christopher S. and Walker, Kara K. and Paulo, Gabo and Pusey, Anne E.}, year={2018}, pages={240–250} }
 @article{yapuncich_churchill_cameron_walker_2018, title={Morphometric panel regression equations for predicting body mass in immature humans}, volume={166}, ISSN={["1096-8644"]}, DOI={10.1002/ajpa.23422}, abstractNote={AbstractObjectivesPredicting 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.Materials and MethodsHere, 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.ResultsWhile 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).DiscussionThe 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.}, number={1}, journal={AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY}, author={Yapuncich, Gabriel S. and Churchill, Steven E. and Cameron, Noel and Walker, Christopher S.}, year={2018}, month={May}, pages={179–195} }
 @article{cofran_walker_2017, title={Dental development in Homo naledi}, volume={13}, ISSN={["1744-957X"]}, DOI={10.1098/rsbl.2017.0339}, abstractNote={
            Humans’ prolonged somatic development and life history are unique among primates, yet their evolutionary origins remain unclear. Dental development has been used as a proxy to reconstruct life history evolution in the hominin clade and indicates a recent emergence of the human developmental pattern. Here, we analyse tooth formation and eruption in two developing dentitions of
            Homo naledi
            , a late-surviving, morphologically mosaic hominin species. Deciduous dental development is more similar to humans than to chimpanzees, probably reflecting hominin symplesiomorphy rather than bearing life history significance. The later stages of permanent tooth development present a mix of human- and chimpanzee-like patterns. Surprisingly, the M
            2
            of
            H. naledi
            emerges late in the eruption sequence, a pattern previously unknown in fossil hominins and common in modern humans. This pattern has been argued to reflect a slow life history and is unexpected in a small-brained hominin. The geological age of
            H. naledi
            (approx. 300 kya), coupled with its small brain size and the dental development data presented here, raise questions about the relationship between dental development and other variables associated with life history.
          }, number={8}, journal={BIOLOGY LETTERS}, author={Cofran, Zachary and Walker, Christopher S.}, year={2017}, month={Aug} }
 @article{walker_yapuncich_sridhar_cameron_churchill_2017, title={Evaluating morphometric body mass prediction equations with a juvenile human test sample: accuracy and applicability to small-bodied hominins}, volume={115}, ISSN={["0047-2484"]}, DOI={10.1016/j.jhevol.2017.03.009}, abstractNote={Body mass is an ecologically and biomechanically important variable in the study of hominin biology. Regression equations derived from recent human samples allow for the reasonable prediction of body mass of later, more human-like, and generally larger hominins from hip joint dimensions, but potential differences in hip biomechanics across hominin taxa render their use questionable with some earlier taxa (i.e., Australopithecus spp.). Morphometric prediction equations using stature and bi-iliac breadth avoid this problem, but their applicability to early hominins, some of which differ in both size and proportions from modern adult humans, has not been demonstrated. Here we use mean stature, bi-iliac breadth, and body mass from a global sample of human juveniles ranging in age from 6 to 12 years (n = 530 age- and sex-specific group annual means from 33 countries/regions) to evaluate the accuracy of several published morphometric prediction equations when applied to small humans. Though the body proportions of modern human juveniles likely differ from those of small-bodied early hominins, human juveniles (like fossil hominins) often differ in size and proportions from adult human reference samples and, accordingly, serve as a useful model for assessing the robustness of morphometric prediction equations. Morphometric equations based on adults systematically underpredict body mass in the youngest age groups and moderately overpredict body mass in the older groups, which fall in the body size range of adult Australopithecus (∼26-46 kg). Differences in body proportions, notably the ratio of lower limb length to stature, influence predictive accuracy. Ontogenetic changes in these body proportions likely influence the shift in prediction error (from under- to overprediction). However, because morphometric equations are reasonably accurate when applied to this juvenile test sample, we argue these equations may be used to predict body mass in small-bodied hominins, despite the potential for some error induced by differing body proportions and/or extrapolation beyond the original reference sample range.}, journal={Journal of Human Evolution}, author={Walker, C.S. and Yapuncich, G.S. and Sridhar, S. and Cameron, N. and Churchill, S.E.}, year={2017}, pages={65–77} }
 @article{walker_walker_goodall_pusey_2018, title={Maturation is prolonged and variable in female chimpanzees}, volume={114}, ISSN={["0047-2484"]}, DOI={10.1016/j.jhevol.2017.10.010}, abstractNote={Chimpanzees are important referential models for the study of life history in hominin evolution. Age at sexual maturity and first reproduction are key life history milestones that mark the diversion of energy from growth to reproduction and are essential in comparing life history trajectories between chimpanzees and humans. Yet, accurate information on ages at these milestones in wild chimpanzees is difficult to obtain because most females transfer before breeding. Precise age at first birth is only known from a relatively small number of non-dispersing individuals. Moreover, due to small sample sizes, the degree to which age at maturation milestones varies is unknown. Here we report maturation milestones and explore sources of variance for 36 wild female chimpanzees of known age, including eight dispersing females born in Gombe National Park, Tanzania. Using Kaplan-Meier survival analysis, including censored intervals, we find an average age of 11.5 years (range 8.5-13.9) at sexual maturity and 14.9 years (range 11.1-22.1) at first birth. These values exceed previously published averages for wild chimpanzees by one or more years. Even in this larger sample, age at first birth is likely underestimated due to the disproportionate number of non-dispersing females, which, on average, give birth two years earlier than dispersing females. Model selection using Cox Proportional Hazards models shows that age at sexual maturity is delayed in females orphaned before age eight years and those born to low-ranking mothers. Age at first birth is most delayed in dispersing females and those orphaned before age eight years. These data provide improved estimates of maturation milestones in a population of wild female chimpanzees and indicate the importance of maternal factors in development.}, journal={JOURNAL OF HUMAN EVOLUTION}, author={Walker, Kara K. and Walker, Christopher S. and Goodall, Jane and Pusey, Anne E.}, year={2018}, month={Jan}, pages={131–140} }
 @article{hawks_elliott_schmid_churchill_ruiter_roberts_hilbert-wolf_garvin_williams_delezene_et al._2017, title={New fossil remains of Homo naledi from the Lesedi Chamber, South Africa}, volume={6}, DOI={10.7554/elife.24232}, abstractNote={The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.}, journal={Elife}, author={Hawks, J. and Elliott, M. and Schmid, P. and Churchill, S. E. and Ruiter, D. J. and Roberts, E. M. and Hilbert-Wolf, H. and Garvin, H. M. and Williams, S. A. and Delezene, L. K. and et al.}, year={2017} }
 @article{churchill_walker_schwartz_2016, title={Home-Range Size in Large-Bodied Carnivores as a Model for Predicting Neandertal Territory Size}, volume={25}, ISSN={["1520-6505"]}, DOI={10.1002/evan.21483}, abstractNote={Adult human foragers expend roughly 30–60 kcal per km in unburdened walking at optimal speeds.1,2 In the context of foraging rounds and residential moves, they may routinely travel distances of 50–70 km per week, often while carrying loads.3 Movement on the landscape, then, is arguably the single most expensive item in the activity budgets of hunter‐gatherers. Mobility costs may have been greater still for Neandertals. They had stocky, short‐limbed physiques that were energetically costly to move4 and lived in relatively unproductive Pleistocene environments5 that may have required greater movement to deal with problems of biodepletion and resource patchiness.6 But just how mobile were the Neandertals?}, number={3}, journal={EVOLUTIONARY ANTHROPOLOGY}, author={Churchill, Steven Emilio and Walker, Christopher Scott and Schwartz, Adam Michael}, year={2016}, pages={117–123} }
 @article{marchi_walker_wei_holliday_churchill_berger_desilva_2017, title={The thigh and leg of Homo naledi}, volume={104}, ISSN={["0047-2484"]}, DOI={10.1016/j.jhevol.2016.09.005}, abstractNote={This paper describes the 108 femoral, patellar, tibial, and fibular elements of a new species of Homo (Homo naledi) discovered in the Dinaledi chamber of the Rising Star cave system in South Africa. Homo naledi possesses a mosaic of primitive, derived, and unique traits functionally indicative of a bipedal hominin adapted for long distance walking and possibly running. Traits shared with australopiths include an anteroposteriorly compressed femoral neck, a mediolaterally compressed tibia, and a relatively circular fibular neck. Traits shared with Homo include a well-marked linea aspera, anteroposteriorly thick patellae, relatively long tibiae, and gracile fibulae with laterally oriented lateral malleoli. Unique features include the presence of two pillars on the superior aspect of the femoral neck and a tubercular distal insertion of the pes anserinus on the tibia. The mosaic morphology of the H. naledi thigh and leg appears most consistent with a species intermediate between Australopithecus spp. and Homo erectus and, accordingly, may offer insight into the nature of the earliest members of genus Homo. These fossils also expand the morphological diversity of the Homo lower limb, perhaps indicative of locomotor diversity in our genus.}, journal={JOURNAL OF HUMAN EVOLUTION}, author={Marchi, Damiano and Walker, Christopher S. and Wei, Pianpian and Holliday, Trenton W. and Churchill, Steven E. and Berger, Lee R. and DeSilva, Jeremy M.}, year={2017}, month={Mar}, pages={174–204} }
 @article{feuerriegel_green_walker_schmid_hawks_berger_churchill_2017, title={The upper limb of Homo naledi}, volume={104}, ISSN={["0047-2484"]}, DOI={10.1016/j.jhevol.2016.09.013}, abstractNote={The evolutionary transition from an ape-like to human-like upper extremity occurred in the context of a behavioral shift from an upper limb predominantly involved in locomotion to one adapted for manipulation. Selection for overarm throwing and endurance running is thought to have further shaped modern human shoulder girdle morphology and its position about the thorax. Homo naledi (Dinaledi Chamber, Rising Star Cave, Cradle of Humankind, South Africa) combines an australopith-like cranial capacity with dental characteristics akin to early Homo. Although the hand, foot, and lower limb display many derived morphologies, the upper limb retains many primitive traits. Here, we describe the H. naledi upper extremity (excluding the hand) in detail and in a comparative context to evaluate the diversity of clavicular, scapular, humeral, radial, and ulnar morphology among early hominins and later Homo. Homo naledi had a scapula with a markedly cranially-oriented glenoid, a humerus with extremely low torsion, and an australopith-like clavicle. These traits indicate that the H. naledi scapula was situated superiorly and laterally on the thorax. This shoulder girdle configuration is more similar to that of Australopithecus and distinct from that of modern humans, whose scapulae are positioned low and dorsally about the thorax. Although early Homo erectus maintains many primitive clavicular and humeral features, its derived scapular morphology suggests a loss of climbing adaptations. In contrast, the H. naledi upper limb is markedly primitive, retaining morphology conducive to climbing while lacking many of the derived features related to effective throwing or running purported to characterize other members of early Homo.}, journal={JOURNAL OF HUMAN EVOLUTION}, author={Feuerriegel, Elen M. and Green, David J. and Walker, Christopher S. and Schmid, Peter and Hawks, John and Berger, Lee R. and Churchill, Steven E.}, year={2017}, month={Mar}, pages={155–173} }
 @article{berger_hawks_de ruiter_churchill_schmid_delezene_kivell_garvin_williams_desilva_et al._2015, title={Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa}, volume={4}, ISSN={2050-084X}, url={http://dx.doi.org/10.7554/elife.09560}, DOI={10.7554/elife.09560}, abstractNote={Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.}, journal={eLife}, publisher={eLife Sciences Publications, Ltd}, author={Berger, Lee R and Hawks, John and de Ruiter, Darryl J and Churchill, Steven E and Schmid, Peter and Delezene, Lucas K and Kivell, Tracy L and Garvin, Heather M and Williams, Scott A and DeSilva, Jeremy M and et al.}, year={2015}, month={Sep} }
 @inbook{walker_churchill_2014, place={New York}, title={Territory size in Canis lupus: implications for Neandertal mobility}, booktitle={Reconstructing mobility: environmental, behavioral, and morphological determinants.}, publisher={Springer}, author={Walker, C.S. and Churchill, S.E.}, editor={Carlson, K. and Marchi, D.Editors}, year={2014} }
 @article{desilva_holt_churchill_carlson_walker_zipfel_berger_2013, title={The Lower Limb and Mechanics of Walking in Australopithecus sediba}, volume={340}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.1232999}, DOI={10.1126/science.1232999}, abstractNote={
            The discovery of a relatively complete
            Australopithecus sediba
            adult female skeleton permits a detailed locomotor analysis in which joint systems can be integrated to form a comprehensive picture of gait kinematics in this late australopith. Here we describe the lower limb anatomy of
            Au. sediba
            and hypothesize that this species walked with a fully extended leg and with an inverted foot during the swing phase of bipedal walking. Initial contact of the lateral foot with the ground resulted in a large pronatory torque around the joints of the foot that caused extreme medial weight transfer (hyperpronation) into the toe-off phase of the gait cycle (late pronation). These bipedal mechanics are different from those often reconstructed for other australopiths and suggest that there may have been several forms of bipedalism during the Plio-Pleistocene.
          }, number={6129}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={DeSilva, J. M. and Holt, K. G. and Churchill, S. E. and Carlson, K. J. and Walker, C. S. and Zipfel, B. and Berger, L. R.}, year={2013}, month={Apr}, pages={1232999–1232999} }