Papers by Steven Worthington
American Journal of Biological Anthropology, 2025
Objectives: Self-domestication theory and preliminary data suggest that western chimpanzees (Pan ... more Objectives: Self-domestication theory and preliminary data suggest that western chimpanzees (Pan troglodytes verus) could have smaller brains than eastern chimpanzees (P. t. schweinfurthii), but no large-scale studies of chimpanzee endocranial volume (ECV) have tested this. This study compares ECV of wild adult P. t. verus and P. t. schweinfurthii, along with femoral head diameter (FHD; an index of body size), bizygomatic breadth (BZB) and palate length (PAL). Materials and Methods: Adult crania of P. t. schweinfurthii (60 females, 90 males, from Uganda and Democratic Republic of Congo) and P. t. verus (43 females, 37 males, from Liberia and Ivory Coast) were sampled. ECV was measured using 3 mm diameter glass beads, and FHD, PAL, and BZB with digital calipers. Quantities of interest were estimated using Bayesian inference. Results: No meaningful differences were found between subspecies on average in ECV, FHD, or the relationship between ECV and FHD. Within countries and subspecies, ECV varied widely among individuals, partly because males had higher ECV on average than females. When sex was controlled for, ECV was unrelated to FHD. Within subspecies there was no evidence of meaningful differences in average ECV among countries. PAL was the only measure that differed between subspecies on average, being shorter in P. t. verus females. Discussion: Current data show that within sexes, mean ECV is similar between P. t. verus and P. t. schweinfurthii. This suggests that average brain size in chimpanzees has remained unchanged for ~0.7 million years, in contrast to orangutans (Pongo) and humans. Brain size differences among primate species are not well understood, but numerous explanations have been advanced at both the ultimate and proximate level (Dunbar and Shultz 2017). The overall evolutionary trend is for brains to enlarge . Major influences proposed to account for this tendency include increases in the ability to sustain the energetic costs of growing or maintaining the brain (Isler and van Schaik 2009; Fonseca-Azevedo and Herculano-Houzel 2012), to solve ecological problems , and to adapt to complex social problems . Brains also sometimes evolve to be smaller, as has happened in most domesticated mammals and bonobos Pan paniscus . In this paper we examine whether western chimpanzees (Pan troglodytes verus) have smaller brains than eastern chimpanzees (P. t. schweinfurthii). This possibility is stimulated by evidence of brain reduction being associated with reduced aggression, suggestions that western chimpanzees are less aggressive than eastern chimpanzees,
The American Journal of Clinical Nutrition, 2023
Background: Although human diets varied considerably before the spread of agriculture, public per... more Background: Although human diets varied considerably before the spread of agriculture, public perceptions of preagricultural diets have been strongly influenced by the Paleo Diet, which prescribes percentage calorie ranges of 19-35% protein, 22-40% carbohydrate, and 28-47% fat, and prohibits foods with added sugar, dairy, grains, most starchy tubers, and legumes. However, the empirical basis for Paleolithic nutrition remains unclear, with some of its assumptions challenged by the archaeological record and theoretical first principles. Objectives: We assessed the variation in diets among tropical hunter-gatherers, including the effect of collection methods on implied macronutrient percentages. Methods: We analyzed data on animal food, plant food, and honey consumption by weight and kcal from 15 high-quality published ethnographic studies representing 11 recent tropical hunter-gatherer groups. We used Bayesian analyses to perform inference and included data collection methods and environmental variables as predictors in our models. Results: Our analyses reveal high levels of variation in animal versus plant foods consumed and in corresponding percentages of protein, fat, and carbohydrates. In addition, studies that weighed food items consumed in and out of camp and across seasons and years reported higher consumption of animal foods, which varied with annual mean temperature. Conclusions: The ethnographic evidence from tropical foragers refutes the concept of circumscribed macronutrient ranges modeling preagricultural diets.
Social Science & Medicine, 2023
Pharmacovigilance databases contain larger numbers of adverse drug events (ADEs) that occurred in... more Pharmacovigilance databases contain larger numbers of adverse drug events (ADEs) that occurred in women compared to men. The cause of this disparity is frequently attributed to sex-linked biological factors. We offer an alternative Gender Hypothesis, positing that gendered social factors are central to the production of aggregate sex disparities in ADE reports. We describe four pathways through which gender may influence observed sex disparities in pharmacovigilance databases: healthcare utilization; bias and discrimination in the clinic; experience of a drug event as adverse; and pre-existing social and structural determinants of health. We then use data from the U.S. FDA Adverse Event Reporting System (FAERS) to explore how the Gender Hypothesis might generate novel predictions and explanations of sex disparities in ADEs in existing widely referenced datasets. Analyzing more than 37 million records of ADEs between 2014 and 2022, we find that patient-reported ADEs show a larger female skew than healthcare provider-reported ADEs and that the sex disparity is markedly smaller for outcomes involving death or hospitalization. We also find that the sex disparity varies greatly across types of ADEs, for example, cosmetically salient ADEs are skewed heavily female and sexual dysfunction ADEs are skewed male. Together, we interpret these findings as providing evidence of the promise of the Gender Hypothesis for identifying intervenable mechanisms and pathways contributing to sex disparities in ADEs. Rigorous application of the Gender Hypothesis to additional datasets and in future research studies could yield new insights into the causes of sex disparities in ADEs.
JAMA Network Open, 2023
Author Contributions: Ms Rushovich and Dr Worthington had full access to all of the data in the s... more Author Contributions: Ms Rushovich and Dr Worthington had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Ms Rushovich, Ms Gompers, and Dr Lockhart had equal contribution to the work.
Science Advances, 2023
Vestibular schwannoma (VS) is an intracranial tumor arising from neoplastic Schwann cells and typ... more Vestibular schwannoma (VS) is an intracranial tumor arising from neoplastic Schwann cells and typically presenting with hearing loss. The traditional belief that hearing deficit is caused by physical expansion of the VS, compressing the auditory nerve, does not explain the common clinical finding that patients with small tumors can have profound hearing loss, suggesting that tumor-secreted factors could influence hearing ability in VS patients. We conducted profiling of patients' plasma for 66 immune-related factors in patients with sporadic VS (N > 170) and identified and validated candidate biomarkers associated with tumor size (S100B) and hearing (MCP-3). We further identified a nine-biomarker panel (TNR-R2, MIF, CD30, MCP-3, IL-2R, BLC, TWEAK, eotaxin, and S100B) with outstanding discriminatory ability for VS. These findings revealed possible therapeutic targets for VS, providing a unique diagnostic tool that may predict hearing change and tumor growth in VS patients, and may inform the timing of tumor resection to preserve hearing.
Supplemental material, sj-pdf-1-cpx-10.1177_2167702621991804 for A Year in the Social Life of a T... more Supplemental material, sj-pdf-1-cpx-10.1177_2167702621991804 for A Year in the Social Life of a Teenager: Within-Persons Fluctuations in Stress, Phone Communication, and Anxiety and Depression by Alexandra M. Rodman, Constanza M. Vidal Bustamante, Meg J. Dennison, John C. Flournoy, Daniel D. L. Coppersmith, Erik C. Nook, Steven Worthington, Patrick Mair and Katie A. McLaughlin in Clinical Psychological Science
TNT_character_matrix_positions.csv: provides descriptions of the 115 characters and their positio... more TNT_character_matrix_positions.csv: provides descriptions of the 115 characters and their positions in the character matrices. TNT_95CI_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is a 95% confidence interval for the species mean. TNT_DVC_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is coded using divergence coding. TNT_GWC_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is coded using generalized gap weighting. TNT_HSC_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is coded using homogeneous subset coding. TNT_IDO_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is coded using identification of overlap coding. TNT_Mean_character_matrix.tnt: TNT format character matrix with 115 traits. Each trait value is a species mean.
Replication code and data for the paper: "Native plant phylogenetic diversity set to decline... more Replication code and data for the paper: "Native plant phylogenetic diversity set to decline in the United States over the next 50 years." The following files are included in this repository: 1) R scripts (numbered 0 through 9) include replication code for data analysis 2) Datasets (6 zip folders) contain the data analyzed in the R scripts
Table S1. Anthropoid (n=100) lower molar proportions, body mass, and diet summary data. Table S2.... more Table S1. Anthropoid (n=100) lower molar proportions, body mass, and diet summary data. Table S2. Molar area proportion pglmm posterior probabilities. Table S3. Relative M 2 area pglmm posterior probabilities. Table S4. Proportion mediated (p r m ) pglmm posterior probabilities. Table S5. Modern human (n=66) lower molar proportions data. Table S6. Strepsirrhine (n=1) lower molar proportions summary data. Table S7. Primate molar crown formation time data. Figure S1. Molar area correction coefficients method. Figure S2. Molar area correction coefficients test. Figure S3. Anthropoid lower molar proportions of individual specimens (n=2,895). Figure S4. Posterior density of molar proportion slope (interspecific). Figure S5. Posterior density of molar proportion intercept. Figure S6. Posterior density of relative M 2 area slope (interspecific). Figure S7. Posterior density of relative M 2 area intercept. Figure S8. Posterior density of proportion mediated (interspecific). Figure S9. Ln bo...
1 ) Code for simulating community phylogenies: community_simulations_creation.R [taxon].gene [tax... more 1 ) Code for simulating community phylogenies: community_simulations_creation.R [taxon].gene [taxon].phy [taxon].RAxML_bestTree.tre [taxon].Simulate.A.Community.pl [taxon].Simulate.B.Community.pl [taxon].Simulate.C.Community.pl [taxon].Simulate.D.Community.pl 2) R code for creating and comparing phylogenetic diversity metrics: simulated_metric_calculation_and_comparison.R empirical_metric_calculation_and_comparison.R 3) R code and data for statistical analyses: simulated_data_analysis.R empirical_data_analysis.R simulated_interval_individual_lme_data.csv simulated_summary_interval_individual_lme_data.csv empirical_interval_individual_lme_data.csv empirical_summary_interval_lme_data.csv
Data and R replication code for testing the Marginal Habitat Hypothesis. The R code files contain... more Data and R replication code for testing the Marginal Habitat Hypothesis. The R code files contain all models and are organized by the figures they generate for the associated paper. The data are sourced from: 1) the Standard Cross Cultural Sample (SCCS). 2) NASA Moderate Resolution Imaging Spectroradiometer (MODIS) NPP data (MOD17A3 algorithm) from Numerical Terra Dynamic Simulation Group at the University of Montana. 3) Marine Ecoregions Of the World (MEOW): http://maps.tnc.org/files/metadata/MEOW.xml 4) Terrestrial Ecoregions Of the World (TEOW): http://maps.tnc.org/files/metadata/TerrEcos.xml
BMC Evolutionary Biology, 2016
This repository contains four files: 1) a NEXUS phylogeny of 100 anthropoid primates; 2) a CSV te... more This repository contains four files: 1) a NEXUS phylogeny of 100 anthropoid primates; 2) a CSV text file of anthropoid primate lower molar areas, body mass, and primary dietary category; 3) a CSV text file of modern human lower molar area proportions; and, 4) an R script containing replication code for fitting Bayesian phylogenetic generalized linear mixed models to the morphometric data. These files are associated with the paper "The Evolution of Anthropoid Molar Proportions" in BMC Evolutionary Biology (2016).
Clinical Psychological Science, 2021
Stressful life events (SLEs) are strongly associated with the emergence of adolescent anxiety and... more Stressful life events (SLEs) are strongly associated with the emergence of adolescent anxiety and depression, but the underlying mechanisms remain poorly understood, especially at the within-persons level. We investigated how adolescent social communication (i.e., frequency of calls and texts) following SLEs relates to changes in internalizing symptoms in a multitimescale, intensive, year-long study ( N = 30; n = 355 monthly observations; n ≈ 5,000 experience-sampling observations). Within-persons increases in SLEs were associated with receiving more calls than usual at both the month and moment levels and making more calls at the month level. Increased calls were prospectively associated with worsening internalizing symptoms at the month level only, suggesting that SLEs rapidly influence phone communication patterns, but these communication changes may have a more protracted, cumulative influence on internalizing symptoms. Finally, increased incoming calls prospectively mediated th...
ACR Open Rheumatology, 2021
Previous studies have demonstrated that low physical activity levels during youth are associated ... more Previous studies have demonstrated that low physical activity levels during youth are associated with the development of thin knee cartilage, which may increase susceptibility to osteoarthritis later in life. Here, we propose and test the hypothesis that reductions in physical activity impair knee cartilage growth among people in developing countries experiencing urbanization and increased market integration.
Scientific Reports, 2021
To test the effects of domestication on craniofacial skeletal morphology, we used three-dimension... more To test the effects of domestication on craniofacial skeletal morphology, we used three-dimensional geometric morphometrics (GM) along with linear and endocranial measurements to compare selected (domesticated) and unselected foxes from the Russian Farm-Fox Experiment to wild foxes from the progenitor population from which the farmed foxes are derived. Contrary to previous findings, we find that domesticated and unselected foxes show minimal differences in craniofacial shape and size compared to the more substantial differences between the wild foxes and both populations of farmed foxes. GM analyses and linear measurements demonstrate that wild foxes differ from farmed foxes largely in terms of less cranial base flexion, relatively expanded cranial vaults, and increased endocranial volumes. These results challenge the assumption that the unselected population of foxes kept as part of the Russian Farm-Fox experiment are an appropriate proxy for ‘wild’ foxes in terms of craniofacial m...
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Papers by Steven Worthington