Correction: Recombinant Lloviu virus as a tool to study viral replication and host responses.

[This corrects the article DOI: 10.1371/journal.ppat.1010268.].

Recombinant Lloviu virus as a tool to study viral replication and host responses.

Next generation sequencing has revealed the presence of numerous RNA viruses in animal reservoir hosts, including many closely related to known human pathogens. Despite their zoonotic potential, most of these viruses remain understudied due to not yet being cultured. While reverse genetic systems can facilitate virus rescue, this is often hindered by missing viral genome ends. A prime example is Lloviu virus (LLOV), an uncultured filovirus that is closely related to the highly pathogenic Ebola virus. Using minigenome systems, we complemented the missing LLOV genomic ends and identified cis-acting elements required for LLOV replication that were lacking in the published sequence. We leveraged these data to generate recombinant full-length LLOV clones and rescue infectious virus. Similar to other filoviruses, recombinant LLOV (rLLOV) forms filamentous virions and induces the formation of characteristic inclusions in the cytoplasm of the infected cells, as shown by electron microscopy. Known target cells of Ebola virus, including macrophages and hepatocytes, are permissive to rLLOV infection, suggesting that humans could be potential hosts. However, inflammatory responses in human macrophages, a hallmark of Ebola virus disease, are not induced by rLLOV. Additional tropism testing identified pneumocytes as capable of robust rLLOV and Ebola virus infection. We also used rLLOV to test antivirals targeting multiple facets of the replication cycle. Rescue of uncultured viruses of pathogenic concern represents a valuable tool in our arsenal for pandemic preparedness.

The 3' Untranslated Regions of Ebola Virus mRNAs Contain AU-Rich Elements Involved in Posttranscriptional Stabilization and Decay.

The 3' untranslated regions (UTRs) of Ebola virus (EBOV) mRNAs are enriched in their AU content and therefore represent potential targets for RNA binding proteins targeting AU-rich elements (ARE-BPs). ARE-BPs are known to fine-tune RNA turnover and translational activity. We identified putative AREs within EBOV mRNA 3' UTRs and assessed whether they might modulate mRNA stability. Using mammalian and zebrafish embryo reporter assays, we show a conserved, ARE-BP-mediated stabilizing effect and increased reporter activity with the tested EBOV 3' UTRs. When coexpressed with the prototypic ARE-BP tristetraprolin (TTP, ZFP36) that mainly destabilizes its target mRNAs, the EBOV nucleoprotein (NP) 3' UTR resulted in decreased reporter gene activity. Coexpression of NP with TTP led to reduced NP protein expression and diminished EBOV minigenome activity. In conclusion, the enrichment of AU residues in EBOV 3' UTRs makes them possible targets for cellular ARE-BPs, leading to modulation of RNA stability and translational activity.

Quantum monodromy in NCNCS - direct experimental confirmation.

Since the first confirmation of quantum monodromy in NCNCS (B. P. Winnewisser et al., Report No. TH07 in 60th International Symposium on Molecular Spectroscopy, Columbus, OH, (2005) and B. P. Winnewisser et al., Phys. Rev. Lett., 2005, 95, 243002) we have continued to explore its implications for the quantum structure of molecules. To confirm quantum monodromy bending-vibrational + axial-rotational quantum energy level information is needed. This was not directly available from the pure a-type rotational transitions available in 2005. The confirmation of quantum monodromy therefore had to be based on the fitting of the Generalised SemiRigid Bender (GSRB) model to the experimental rotational data. The GSRB is a physically motivated model and was able to extract the required information based on the changes of the rotational energy level structure upon excitation of the bending vibration and of the axial rotation. These results were, in some sense, predictions. Our goal here was to obtain a fully experimental and unambigous confirmation of quantum monodromy in NCNCS. This involved a series of experimental campaigns at the Canadian Light Source (CLS) synchrotron. To coax the required information out of the masses of spectral data that had been obtained a variety of techniques had to be used. The result is that we can now confirm, without recourse to a theoretical model, the existence of quantum monodromy in the ν7 bending mode of NCNCS. As a side benefit we also confirm the power of the GSRB model to extract the required information from the previously available data. The predictions previously provided by the GSRB were surprisingly accurate. Only a slight augmentation of the model was required to allow us to refit it including the new data, while maintaining the quality of the fitting for that data previously available. We also present a very basic introduction to the idea of monodromy and to how the GSRB was used.

Single-Dose Psilocybin Treatment for Major Depressive Disorder: A Randomized Clinical Trial.

Importance: Psilocybin shows promise as a treatment for major depressive disorder (MDD). Objective: To evaluate the magnitude, timing, and durability of antidepressant effects and safety of a single dose of psilocybin in patients with MDD. Design, Setting, and Participants: In this phase 2 trial conducted between December 2019 and June 2022 at 11 research sites in the US, participants were randomized in a 1:1 ratio to receive a single dose of psilocybin vs niacin placebo administered with psychological support. Participants were adults aged 21 to 65 years with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of MDD of at least 60 days' duration and moderate or greater symptom severity. Exclusion criteria included history of psychosis or mania, active substance use disorder, and active suicidal ideation with intent. Participants taking psychotropic agents who otherwise met inclusion/exclusion criteria were eligible following medication taper. Primary and secondary outcomes and adverse events (AEs) were assessed at baseline (conducted within 7 days before dosing) and at 2, 8, 15, 29, and 43 days after dosing. Interventions: Interventions were a 25-mg dose of synthetic psilocybin or a 100-mg dose of niacin in identical-appearing capsules, each administered with psychological support. Main Outcomes and Measures: The primary outcome was change in central rater-assessed Montgomery-Asberg Depression Rating Scale (MADRS) score (range, 0-60; higher scores indicate more severe depression) from baseline to day 43. The key secondary outcome measure was change in MADRS score from baseline to day 8. Other secondary outcomes were change in Sheehan Disability Scale score from baseline to day 43 and MADRS-defined sustained response and remission. Participants, study site personnel, study sponsor, outcome assessors (raters), and statisticians were blinded to treatment assignment. Results: A total of 104 participants (mean [SD] age, 41.1 [11.3] years; 52 [50%] women) were randomized (51 to the psilocybin group and 53 to the niacin group). Psilocybin treatment was associated with significantly reduced MADRS scores compared with niacin from baseline to day 43 (mean difference,-12.3 [95% CI, -17.5 to -7.2]; P <.001) and from baseline to day 8 (mean difference, -12.0 [95% CI, -16.6 to -7.4]; P < .001). Psilocybin treatment was also associated with significantly reduced Sheehan Disability Scale scores compared with niacin (mean difference, -2.31 [95% CI, 3.50-1.11]; P < .001) from baseline to day 43. More participants receiving psilocybin had sustained response (but not remission) than those receiving niacin. There were no serious treatment-emergent AEs; however, psilocybin treatment was associated with a higher rate of overall AEs and a higher rate of severe AEs. Conclusions and Relevance: Psilocybin treatment was associated with a clinically significant sustained reduction in depressive symptoms and functional disability, without serious adverse events. These findings add to increasing evidence that psilocybin-when administered with psychological support-may hold promise as a novel intervention for MDD. Trial Registration: ClinicalTrials.gov Identifier: NCT03866174.

Familiarity mediates apes' attentional biases toward human faces.

In zoos, primates experience markedly different interactions with familiar humans, such as the zookeepers who care for them, compared with those with unfamiliar humans, such as the large volume of zoo visitors to whom they are regularly exposed. While the behaviour of zoo-housed primates in the presence of unfamiliar, and to a lesser extent familiar, humans has received considerable attention, if and how they spontaneously distinguish familiar from unfamiliar people, and the cognitive mechanisms underlying the relationships they form with familiar and unfamiliar humans, remain poorly understood. Using a dot-probe paradigm, we assessed whether primates (chimpanzees and gorillas) show an attentional bias toward the faces of familiar humans, with whom the apes presumably had a positive relationship. Contrary to our predictions, all subjects showed a significant attentional bias toward unfamiliar people's faces compared with familiar people's faces when the faces showed a neutral expression, both with and without a surgical face mask on, but no significant attentional bias when the faces showed a surprised expression. These results demonstrate that apes can spontaneously categorize humans based on familiarity and we argue that the attentional biases the apes showed for unfamiliar human faces reflect a novelty effect.

Metabolic acceleration and the evolution of human brain size and life history.

Humans are distinguished from the other living apes in having larger brains and an unusual life history that combines high reproductive output with slow childhood growth and exceptional longevity. This suite of derived traits suggests major changes in energy expenditure and allocation in the human lineage, but direct measures of human and ape metabolism are needed to compare evolved energy strategies among hominoids. Here we used doubly labelled water measurements of total energy expenditure (TEE; kcal day(-1)) in humans, chimpanzees, bonobos, gorillas and orangutans to test the hypothesis that the human lineage has experienced an acceleration in metabolic rate, providing energy for larger brains and faster reproduction without sacrificing maintenance and longevity. In multivariate regressions including body size and physical activity, human TEE exceeded that of chimpanzees and bonobos, gorillas and orangutans by approximately 400, 635 and 820 kcal day(-1), respectively, readily accommodating the cost of humans' greater brain size and reproductive output. Much of the increase in TEE is attributable to humans' greater basal metabolic rate (kcal day(-1)), indicating increased organ metabolic activity. Humans also had the greatest body fat percentage. An increased metabolic rate, along with changes in energy allocation, was crucial in the evolution of human brain size and life history.

Do zoo visitors induce attentional bias effects in primates completing cognitive tasks?

While previous research has focused on the impact of visitors on zoo-housed animals' behavior, here, we evaluated the impact of visitors on the performance of four zoo-housed Japanese macaques (Macaca fuscata) in a cognitive task. The macaques completed a touchscreen-based match-to-sample task in glass-sided booths at the perimeter of their enclosure, adjacent to a visitor viewing area. The task was novel to all macaques at the start of this study but over the 6-month testing period the macaques showed increased accuracy on the task, suggestive of learning. We recorded the number of visitors within the viewing area roughly every 12 trials each macaque completed. We categorized visitor counts as small (0-20), medium (21-40), and large (41-60) crowds and we considered the macaques' response latencies and accuracy by crowd size and study period (first 3 months versus second 3 months). If visitor presence negatively influenced performance, we predicted that macaques' accuracy would decrease but response times would increase with crowd size. We found effects of crowd size and study period on the macaques' accuracy. In the first period, the macaques performed at chance and accuracy did not differ across crowd categories. In the second period, the macaques' accuracy improved as compared to the first period, but their accuracy was mediated by crowd size: the macaques were significantly more accurate in the presence of small crowds than medium or large crowds. The macaques' response latencies also varied by study period and crowd size, but we found no evidence of a response-slowing effect.

The relationship between personality, season, and wounding receipt in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study.

It is important to those managing Japanese macaques (Macaca fuscata) in captive settings to understand predictors of wounding. While studies have demonstrated that season (breeding or nonbreeding) and sex predict rates of wounding received by zoo-housed Japanese macaques, we investigated whether individual differences in personality ratings also might explain some of the observed interindividual variance in wounding. Such patterns were previously observed in rhesus macaques (M. mulatta), such that individuals rated higher on Anxiety and Confidence received greater wounding. Here, we collected wounding data over 24 months on 48 Japanese macaques from eight AZA-accredited zoos. Each macaque was also rated by keepers using a 26-item personality questionnaire. Principle components analysis of these ratings revealed four personality components: Openness, Friendliness, Dominance, and Anxiety/Reactivity. The model with the best fit revealed an interaction effect between season (breeding vs. nonbreeding) and the personality component Friendliness, such that individuals rated higher on Friendliness incurred fewer wounds in the nonbreeding season. The second-best model revealed both a main effect of the season as well as an interaction effect between season and Openness, such that macaques rated higher in Openness received more wounds in the nonbreeding season than those rated lower in Openness. Thus, as with rhesus macaques, personality mediated wounding receipt rate in Japanese macaques, although different personality components explained interindividual variance in wounding for these two species. These differences likely reflect species differences in behavior and personality structure, as well as the influence of differing management practices, highlighting the importance of species-specific approaches for captive primate care and welfare. This study provides further support for understanding primate personality to create individualized strategies for their care.

Hip extensor mechanics and the evolution of walking and climbing capabilities in humans, apes, and fossil hominins.

The evolutionary emergence of humans' remarkably economical walking gait remains a focus of research and debate, but experimentally validated approaches linking locomotor capability to postcranial anatomy are limited. In this study, we integrated 3D morphometrics of hominoid pelvic shape with experimental measurements of hip kinematics and kinetics during walking and climbing, hamstring activity, and passive range of hip extension in humans, apes, and other primates to assess arboreal-terrestrial trade-offs in ischium morphology among living taxa. We show that hamstring-powered hip extension during habitual walking and climbing in living apes and humans is strongly predicted, and likely constrained, by the relative length and orientation of the ischium. Ape pelves permit greater extensor moments at the hip, enhancing climbing capability, but limit their range of hip extension, resulting in a crouched gait. Human pelves reduce hip extensor moments but permit a greater degree of hip extension, which greatly improves walking economy (i.e., distance traveled/energy consumed). Applying these results to fossil pelves suggests that early hominins differed from both humans and extant apes in having an economical walking gait without sacrificing climbing capability. Ardipithecus was capable of nearly human-like hip extension during bipedal walking, but retained the capacity for powerful, ape-like hip extension during vertical climbing. Hip extension capability was essentially human-like in Australopithecus afarensis and Australopithecus africanus, suggesting an economical walking gait but reduced mechanical advantage for powered hip extension during climbing.

A review of research in primate sanctuaries.

While non-human primate studies have long been conducted in laboratories, and more recently at zoological parks, sanctuaries are increasingly considered a viable setting for research. Accredited sanctuaries in non-range countries house thousands of primates formerly used as subjects of medical research, trained performers or personal pets. In range countries, however, sanctuaries typically house orphaned primates confiscated from illegal poaching and the bushmeat and pet trafficking trades. Although the primary mission of these sanctuaries is to rescue and rehabilitate residents, many of these organizations are increasingly willing to participate in non-invasive research. Notably, from a scientific standpoint, most sanctuaries provide potential advantages over traditional settings, such as large, naturalistic physical and social environments which may result in more relevant models of primates' free-ranging wild counterparts than other captive settings. As a result, an impressive scope of research in the fields of primate behaviour, cognition, veterinary science, genetics and physiology have been studied in sanctuaries. In this review, we examine the range and form of research that has been conducted at accredited sanctuaries around the world. We also describe the potential challenges of sanctuary-based work and the considerations that external researchers may face when deciding to collaborate with primate sanctuaries on their research projects.

Reducing the primate pet trade: Actions for primatologists.

This commentary emerged from a panel presentation at the International Primatological Society Congress in Nairobi, Kenya, 2018. The goal was to provide regional updates on the status of primate removal from habitat countries, especially for the pet trade, and develop guidelines that could help primatologists address this critical problem. The trade in live primates includes those used as pets, in entertainment, and as subjects of biomedical experimentation, but here we focus on those primates destined for the pet trade. Such transactions are a hugely lucrative business, impacting hundreds of thousands of individuals annually and affecting the survival of wild populations. Being intimately familiar with primate social behavior, life history and biology, primatologists, whether they work with captive or wild primates, are in a unique position to understand the nature of the trade and attempt to counter its effects. In addition to updating the status of the primate pet trade, we provide recommendations that may help primatologists formulate a plan to deal, locally and regionally, with illegal trafficking in live primates. General guidelines include increasing awareness of local customs, policies and laws; developing collaborative research opportunities for local people; engaging in training/informational opportunities; and instructing on how to take action when encountering illegally-trafficked primates.

Food Cleaning by Japanese Macaques: Innate, Innovative or Cultural?

Japanese macaques (Macaca fuscata) display a number of cultural behaviours including food washing, stone handling and certain grooming techniques. These are deemed cultural behaviours because it is presumed that they are socially learned and, importantly, that social learning is essential for their emergence. Recently, however, research has revealed that culturally naïve primates can re-innovate presumed cultural behaviours. These behaviours are said to fall within that species' "zone of latent solutions" (ZLS). A notable cultural behaviour of Japanese macaques is food washing, first reported by Japanese researchers studying wild Japanese macaques in the 1950s. To test whether culturally naïve Japanese macaques would spontaneously wash food and also, therefore, whether food-washing behaviour is within their ZLS, we presented 12 zoo-housed macaques with sweet potato covered in sand near a pool in their exhibit. Over 11 days we recorded the macaques' behaviour. While 11 of the 12 macaques ate the potato pieces, none washed them. However, 4 macaques cleaned their food, brushing off the sand using their hand or rubbing the potato against their body or another food item, using three distinct techniques. We found no change over time in the rate at which monkeys cleaned or consumed potato, but there was a significant positive correlation between the number of potato pieces a monkey ate and the number of cleaning behaviours performed. We conclude that, minimally, food-cleaning behaviour is within macaques' ZLS.

Sex and season predict wounds in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study.

Japanese macaque societies are characterized by frequent intragroup conflict both in free-ranging and zoo-housed conditions. In zoos, understanding the factors that contribute to wounding is of interest because this knowledge can aid in proactive husbandry and management planning that can minimize the negative impacts wounding can have on individual welfare. This study sought to determine whether the variables sex, season and age predicted wounding rates. Data were collected for 24 months on 119 Japanese macaques living in 10 zoos, and we analyzed the contribution of variables using generalized linear mixed models. A total of 1,007 wounds were reported, and the best model included the interaction between sex and season. Follow-up analyses revealed that females incurred more wounds than males, and this sex difference was more pronounced during the breeding compared to the nonbreeding season. On average, individuals received 4.67 (±SEM: 0.55) wounds per year and 77.31% of the population incurred at least one wound in the study period. The majority of wounds were superficial and did not require veterinary intervention. Wound locations were not randomly distributed across body regions and were most often reported on the face. Finally, macaques living in larger social groups experienced more wounds, on average. This study represents the first quantification of wounding in this species and may provide insight to help inform husbandry and management strategies in zoos.

Comparative effectiveness of extended-release naltrexone versus buprenorphine-naloxone for opioid relapse prevention (X:BOT): a multicentre, open-label, randomised controlled trial.

BACKGROUND: Extended-release naltrexone (XR-NTX), an opioid antagonist, and sublingual buprenorphine-naloxone (BUP-NX), a partial opioid agonist, are pharmacologically and conceptually distinct interventions to prevent opioid relapse. We aimed to estimate the difference in opioid relapse-free survival between XR-NTX and BUP-NX. METHODS: We initiated this 24 week, open-label, randomised controlled, comparative effectiveness trial at eight US community-based inpatient services and followed up participants as outpatients. Participants were 18 years or older, had Diagnostic and Statistical Manual of Mental Disorders-5 opioid use disorder, and had used non-prescribed opioids in the past 30 days. We stratified participants by treatment site and opioid use severity and used a web-based permuted block design with random equally weighted block sizes of four and six for randomisation (1:1) to receive XR-NTX or BUP-NX. XR-NTX was monthly intramuscular injections (Vivitrol; Alkermes) and BUP-NX was daily self-administered buprenorphine-naloxone sublingual film (Suboxone; Indivior). The primary outcome was opioid relapse-free survival during 24 weeks of outpatient treatment. Relapse was 4 consecutive weeks of any non-study opioid use by urine toxicology or self-report, or 7 consecutive days of self-reported use. This trial is registered with ClinicalTrials.gov, NCT02032433. FINDINGS: Between Jan 30, 2014, and May 25, 2016, we randomly assigned 570 participants to receive XR-NTX (n=283) or BUP-NX (n=287). The last follow-up visit was Jan 31, 2017. As expected, XR-NTX had a substantial induction hurdle: fewer participants successfully initiated XR-NTX (204 [72%] of 283) than BUP-NX (270 [94%] of 287; p<0·0001). Among all participants who were randomly assigned (intention-to-treat population, n=570) 24 week relapse events were greater for XR-NTX (185 [65%] of 283) than for BUP-NX (163 [57%] of 287; hazard ratio [HR] 1·36, 95% CI 1·10-1·68), most or all of this difference accounted for by early relapse in nearly all (70 [89%] of 79) XR-NTX induction failures. Among participants successfully inducted (per-protocol population, n=474), 24 week relapse events were similar across study groups (p=0·44). Opioid-negative urine samples (p<0·0001) and opioid-abstinent days (p<0·0001) favoured BUP-NX compared with XR-NTX among the intention-to-treat population, but were similar across study groups among the per-protocol population. Self-reported opioid craving was initially less with XR-NTX than with BUP-NX (p=0·0012), then converged by week 24 (p=0·20). With the exception of mild-to-moderate XR-NTX injection site reactions, treatment-emergent adverse events including overdose did not differ between treatment groups. Five fatal overdoses occurred (two in the XR-NTX group and three in the BUP-NX group). INTERPRETATION: In this population it is more difficult to initiate patients to XR-NTX than BUP-NX, and this negatively affected overall relapse. However, once initiated, both medications were equally safe and effective. Future work should focus on facilitating induction to XR-NTX and on improving treatment retention for both medications. FUNDING: NIDA Clinical Trials Network.

The effect of captivity on the primate gut microbiome varies with host dietary niche.

Despite careful attention to animal nutrition and wellbeing, gastrointestinal distress remains relatively common in captive non-human primates (NHPs), particularly dietary specialists such as folivores. These patterns may be a result of marked dietary differences between captive and wild settings and associated impacts on the gut microbiome. However, given that most existing studies target NHP dietary specialists, it is unclear if captive environments have distinct impacts on the gut microbiome of NHPs with different dietary niches. To begin to examine this question, we used 16S ribosomal RNA gene amplicon sequences to compare the gut microbiomes of five NHP genera categorized either as folivores (Alouatta, Colobus) or non-folivores (Cercopithecus, Gorilla, Pan) sampled both in captivity and in the wild. Though captivity affected the gut microbiomes of all NHPs in this study, the effects were largest in folivorous NHPs. Shifts in gut microbial diversity and in the relative abundances of fiber-degrading microbial taxa suggest that these findings are driven by marked dietary shifts for folivorous NHPs in captive settings. We propose that zoos and other captive care institutions consider including more natural browse in folivorous NHP diets and regularly bank fecal samples to further explore the relationship between NHP diet, the gut microbiome, and health outcomes.

An assessment of touchscreens for testing primate food preferences and valuations.

Typically, animals' food preferences are tested manually, which can be both time-consuming and vulnerable to experimenter biases. Given the utility of ascertaining animals' food preferences for research and husbandry protocols, developing a quick, reliable, and flexible paradigm would be valuable for expediting many research protocols. Therefore, we evaluated the efficacy of using a touchscreen interface to test nonhuman primates' food preferences and valuations, adapting previously validated manual methods. We tested a nonhuman primate subject with four foods (carrot, cucumber, grape, and turnip). Preference testing followed a pairwise forced choice protocol with pairs of food images presented on a touchscreen: The subject was rewarded with whichever food was selected. All six possible pairwise combinations were presented, with 90 trials per pairing. Second, we measured how hard the subject was willing to work to obtain each of the four foods, allowing us to generate demand curves. For this phase, a single image of a food item was presented on the touchscreen that the subject had to select in order to receive the food, and the number of selections required increased following a quarter-log scale, with ten trials per cost level (1, 2, 3, 6, 10, and 18). These methods allowed us to ascertain the subject's relative preferences and valuations of the four foods. The success of this touchscreen protocol for testing the subject's food preferences, from both a practical and a theoretical standpoint, suggests that the protocol should be further validated with other foods with this subject, with other subjects, and with other test items.

A review of zoo-based cognitive research using touchscreen interfaces.

In the past few decades, there has been an increase in the number of zoo-based touchscreen studies of animal cognition around the world. Such studies have contributed to the field of comparative cognition despite the fact research has only been performed at a relatively small number of institutions and with a narrow range of species. Nonetheless, zoo-based touchscreen studies are increasingly recognized as both having the potential to be enriching for captive animals by providing them with opportunities for choice, as well as potentially being a tool with which to measure changes in welfare. Zoo-based touchscreen research on public display also has the potential to impact zoo visitors; encouraging them not only learn more about the cognitive abilities of animals, but also potentially promoting increased respect for these species. Given the lack of a comprehensive review of this scope of specialized research, and the broad potential impacts on animals and programs, here we discuss the history, implementation, and potential outcomes of touchscreen research in zoo settings.

Estimating the effects of friends on health behaviors of adolescents.

This paper estimates the effects of friends' smoking and drinking on own behavior while controlling for correlated unobservables between friends. The effect of friends' behaviors is identified by comparing similar individuals who have similar friendship opportunities and make similar friendship choices, exploiting the idea that friendship choice reveals information about unobservables. We combine this identification strategy with an across-cohort within school design so that identification arises in our reduced form estimates from across-grade differences in the clustering of health behaviors. Finally, we use estimated information on correlated unobservables to examine longitudinal data on the onset of health behaviors, where the likelihood of reverse causality should be minimal. We find evidence that this strategy produces somewhat smaller (no more than 16% smaller) friendship effect estimates than the more standard school fixed effect models consistent with at most modest bias from correlated unobservables.

Great ape walking kinematics: Implications for hominoid evolution.

OBJECTIVES: Great apes provide a point of reference for understanding the evolution of locomotion in hominoids and early hominins. We assessed (1) the extent to which great apes use diagonal sequence, diagonal couplet gaits, like other primates, (2) the extent to which gait and posture vary across great apes, and (3) the role of body mass and limb proportions on ape quadrupedal kinematics. METHODS: High-speed digital video of zoo-housed bonobos (Pan paniscus, N = 8), chimpanzees (Pan troglodytes, N = 13), lowland gorillas (Gorilla gorilla, N = 13), and orangutans (Pongo spp. N = 6) walking over-ground at self-selected speeds were used to determine the timing of limb touch-down, take-off, and to measure joint and segment angles at touch-down, midstance, and take-off. RESULTS: The great apes in our study showed broad kinematic and spatiotemporal similarity in quadrupedal walking. Size-adjusted walking speed was the strongest predictor of gait variables. Body mass had a negligible effect on variation in joint and segment angles, but stride frequency did trend higher among larger apes in analyses including size-adjusted speed. In contrast to most other primates, great apes did not favor diagonal sequence footfall patterns, but exhibited variable gait patterns that frequently shifted between diagonal and lateral sequences. CONCLUSION: Similarities in the terrestrial walking kinematics of extant great apes likely reflect their similar post-cranial anatomy and proportions. Our results suggest that the walking kinematics of orthograde, suspensory Miocene ape species were likely similar to living great apes, and highlight the utility of videographic and behavioral data in interpreting primate skeletal morphology.