Trabecular Bone Orientation in Flexed Versus Extended Postures in Guinea Fowl: A Test of Wolff’s Law

Although bipedal locomotion is a hominin synapomorphy, disagreements persist about whether early hominin bipeds were capable of fully extended limb posture, or used a bent-knee, bent-hip gait. Several recent studies have used the orientation of trabecular bone in limb joints to infer posteral differences during bipedal locomotion between early bipeds and later Homo. There analyses depend on the assumption that the orientation of the trabeculae in joint corresponds to the orientation of compressive forces that are transmitted through the joints. However, the hypothesis that trabecular struts will differ in orientation because of differences in the orientation of loads they experience during growth have not been tested. This study experimentally tests the hypothesis that there is a quantifiable relationship between the orientations of trabeculae and joint posture. The experiment included 16 guinea fowl (Numida melegris): 6 extended-posture runners, 6 flexed-posture runners, and 4 sedentary controls. The exercised animals ran 6 days per week at 1.9 mph for 15 minutes, on either a flat treadmill or a treadmill inclined to 20°. Kinematic and ground reaction force data collected as the birds moved on horizontal and inclined substrates confirm that the degree of flexion at the knee at toe-off is 10° greater when moving up inclines relative to level running. Micro-CT scans were analyzed using image analysis software to relate this difference to trabecular and subchondral bone morphology within the distal femoral epiphysis, including subchondral bone thickness, and trabecular orientation, number, thickness, volume, and connectivity.AnthropologyHuman Evolutionary Biolog

Trabecular Bone in the Bird Knee Responds with High Sensitivity to Changes in Load Orientation

Wolff’s law of trajectorial orientation proposes that trabecular struts align with the orientation of dominant compressive loads within a joint. Although widely considered in skeletal biology, Wolff’s law has never been experimentally tested while controlling for ontogenetic stage, activity level, and species differences, all factors that may affect trabecular bone growth. Here we report an experimental test of Wolff’s law using a within-species design in age-matched subjects experiencing physiologically normal levels of bone strain. Two age-matched groups of juvenile guinea fowl Numida meleagris ran on a treadmill set at either 0° (Level group) or 20° (Incline group), for 10·min per day over a 45-day treatment period. Birds running on the 20° inclined treadmill used more-flexed knees than those in the Level group at midstance (the point of peak ground reaction force). This difference in joint posture enabled us to test the sensitivity of trabecular alignment to altered load orientation in the knee. Using a new radon transform-based method for measuring trabecular orientation, our analysis shows that the fine trabecular bone in the distal femur has a high degree of correspondence between changes in joint angle and trabecular orientation. The sensitivity of this response supports the prediction that trabecular bone adapts dynamically to the orientation of peak compressive forces.Anthropolog

The ecology of exercise: mechanisms underlying Individual variation in behavior, activity, and performance: an introduction to symposium

Wild animals often engage in intense physical activity while performing tasks vital for their survival and reproduction associated with foraging, avoiding predators, fighting, providing parental care, and migrating. In this theme issue we consider how viewing these tasks as “exercise”—analogous to that performed by human athletes—may help provide insight into the mechanisms underlying individual variation in these types of behaviors and the importance of physical activity in an ecological context. In this article and throughout this issue, we focus on four key questions relevant to the study of behavioral ecology that may be addressed by studying wild animal behavior from the perspective of exercise physiology: (1) How hard do individual animals work in response to ecological (or evolutionary) demands?; (2) Do lab-based studies of activity provide good models for understanding activity in free-living animals and individual variation in traits?; (3) Can animals work too hard during “routine” activities?; and (4) Can paradigms of “exercise” and “training” be applied to free-living animals? Attempts to address these issues are currently being facilitated by rapid technological developments associated with physiological measurements and the remote tracking of wild animals, to provide mechanistic insights into the behavior of free-ranging animals at spatial and temporal scales that were previously impossible. We further suggest that viewing the behaviors of non-human animals in terms of the physical exercise performed will allow us to fully take advantage of these technological advances, draw from knowledge and conceptual frameworks already in use by human exercise physiologists, and identify key traits that constrain performance and generate variation in performance among individuals. It is our hope that, by highlighting mechanisms of behavior and performance, the articles in this issue will spur on further synergies between physiologists and ecologists, to take advantage of emerging cross-disciplinary perspectives and technologies

Lifestyle and patterns of physical activity in Hadza foragers

Objectives: Physically active lifestyles are associated with several health benefits. Physical activity (PA) levels are low in post-industrial populations, but generally high throughout life in subsistence populations. The Hadza are a subsistence-oriented foraging population in Tanzania known for being physically active, but it is unknown how recent increases in market integration may have altered their PA patterns. In this study, we examine PA patterns for Hadza women and men who engage in different amounts of traditional foraging. Materials and Methods: One hundred and seventy seven Hadza participants (51% female, 19–87 years) wore an Axivity accelerometer (dominant wrist) for ~6 days during dry season months. We evaluated the effects of age, sex, and lifestyle measures on four PA measures that capture different aspects of the PA profile. Results: Participants engaged in high levels of both moderate-intensity PA and inactivity. Although PA levels were negatively associated with age, older participants were still highly active. We found no differences in PA between participants living in more traditional “bush” camps and those living in more settled “village” camps. Mobility was positively associated with step counts for female participants, and schooling was positively associated with inactive time for male participants. Conclusions: The similarity in PA patterns between Hadza participants in different camp types suggests that high PA levels characterize subsistence lifestyles generally. The sex-based difference in the effects of mobility and schooling on PA could be a reflection of the Hadza's gender-based division of labor, or indicate that changes to subsistence-oriented lifestyles impact women and men in different ways. © 2023 The Authors. American Journal of Biological Anthropology published by Wiley Periodicals LLC

The effects of lifestyle change on indicators of cardiometabolic health in semi-nomadic pastoralists

Background and objectives Non-communicable disease risk and the epidemic of cardiometabolic diseases continue to grow across the expanding industrialized world. Probing the relationships between evolved human physiology and modern socioecological conditions is central to understanding this health crisis. Therefore, we investigated the relationships between increased market access, shifting subsistence patterns and cardiometabolic health indicators within Daasanach semi-nomadic pastoralists who vary in their engagement in traditional lifestyle and emerging market behaviors.Methodology We conducted cross-sectional socioecological, demographic and lifestyle stressor surveys along with health, biomarker and nutrition examinations among 225 (51.6% female) Daasanach adults in 2019-2020. We used linear mixed-effects models to test how differing levels of engagement in market integration and traditional subsistence activities related to blood pressure (BP), body composition and blood chemistry.Results We found that systolic and diastolic BP, as well as the probability of having high BP (hypertension), were negatively associated with distance to market, a proxy for market integration. Additionally, body composition varied significantly by socioeconomic status (SES), with significant positive associations between BMI and body fat and higher SES among adults.Conclusions and implications While evidence for evolutionary mismatch and health variation have been found across a number of populations affected by an urban/rural divide, these results demonstrate the effects of market integration and sedentarization on cardiometabolic health associated with the early stages of lifestyle changes. Our findings provide evidence for the changes in health when small-scale populations begin the processes of sedentarization and market integration that result from myriad market pressures. Being settled is associated with poor cardiometabolic health indicators among Daasanach pastoralists in northern Kenya. This study demonstrates the effects of lifestyle change on health among adults in a population at the beginning stages of market integration and reduced reliance on traditional subsistence strategies, providing clinically and evolutionarily relevant insight for global health

Beyond the here and now: hunter–gatherer socio-spatial complexity and the evolution of language

Human evolutionary ecology stands to benefit by integrating theory and methods developed in movement ecology, and in turn, to make contributions to the broader field of movement ecology by leveraging our species’ distinct attributes. In this paper, we review data and evolutionary models suggesting that major changes in socio-spatial behaviour accompanied the evolution of language. To illustrate and explore these issues, we present a comparison of GPS measures of the socio-spatial behaviour of Hadza hunter–gatherers of northern Tanzania to those of olive baboons (Papio anubis), a comparatively small-brained primate that is also savanna-adapted. While standard spatial metrics show modest differences, measures of spatial diversity, landscape exploration and spatiotemporal displacement between individuals differ markedly. Groups of Hadza foragers rapidly accumulate a vast, diverse knowledge pool about places and things over the horizon, contrasting with the baboon’s narrower and more homogeneous pool of ecological information. The larger and more complex socio-spatial world illustrated by the Hadza is one where heightened cognitive abilities for spatial and episodic memory, navigation, perspective taking and communication about things beyond the here and now all have clear value.This article is part of the theme issue ‘The spatial–social interface: a theoretical and empirical integration’

Methodological Differences Cannot Explain Associations Between Health, Anthropometrics, and Excess Resting Metabolic Rate

We appreciate Ocobock\u27s interest in methodological rigor. We largely agree with her commentary, which suggests that departures from standard protocols might have contributed to the high resting metabolic rate (RMR) measured for Tsimane. Indeed, our paper acknowledges many of the key departures from gold-standard indirect calorimetry methods of RMR assessment and attempts to adjust for several of these (Gurven et al., 2016). Bringing standard clinical methods into remote field settings often involves certain compromises, especially in our case, where RMR measurement was just one component of a large-scale health and aging project (Gurven et al., 2017). RMR data collection was from 2012 to 2014, and where we to measure RMR again for focused follow up, we would consider new available technologies, improve our protocol to the extent possible, and compare against our published estimates

Total daily energy expenditure and elevated water turnover in a small-scale semi-nomadic pastoralist society from Northern Kenya

Background: Pastoralists live in challenging environments, which may be accompanied by unique activity, energy, and water requirements. Aim: Few studies have examined whether the demands of pastoralism contribute to differences in total energy expenditure (TEE) and water turnover (WT) compared to other lifestyles. Subjects and methods: Accelerometer-derived physical activity, doubly labelled water-derived TEE and WT, and anthropometric data were collected for 34 semi-nomadic Daasanach adults from three northern Kenyan communities with different levels of pastoralist activity. Daasanach TEEs and WTs were compared to those of other small-scale and industrialised populations. Results: When modelled as a function of fat-free-mass, fat-mass, age, and sex, TEE did not differ between Daasanach communities. Daasanach TEE (1564–4172 kcal/day) was not significantly correlated with activity and 91% of TEEs were within the range expected for individuals from comparison populations. Mean WT did not differ between Daasanach communities; Daasanach absolute (7.54 litres/day men; 7.46 litres/day women), mass-adjusted, and TEE-adjusted WT was higher than most populations worldwide. Conclusions: The similar mass-adjusted TEE of Daasanach and industrialised populations supports the hypothesis that habitual TEE is constrained, with physically demanding lifestyles necessitating trade-offs in energy allocation. Elevated WT in the absence of elevated TEE likely reflects a demanding active lifestyle in a hot, arid climate. © 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

Does Habitual Physical Activity Increase the Sensitivity of the Appetite Control System? A Systematic Review.

BACKGROUND: It has been proposed that habitual physical activity improves appetite control; however, the evidence has never been systematically reviewed. OBJECTIVE: To examine whether appetite control (e.g. subjective appetite, appetite-related peptides, food intake) differs according to levels of physical activity. DATA SOURCES: Medline, Embase and SPORTDiscus were searched for articles published between 1996 and 2015, using keywords pertaining to physical activity, appetite, food intake and appetite-related peptides. STUDY SELECTION: Articles were included if they involved healthy non-smoking adults (aged 18-64 years) participating in cross-sectional studies examining appetite control in active and inactive individuals; or before and after exercise training in previously inactive individuals. STUDY APPRAISAL AND SYNTHESIS: Of 77 full-text articles assessed, 28 studies (14 cross-sectional; 14 exercise training) met the inclusion criteria. RESULTS: Appetite sensations and absolute energy intake did not differ consistently across studies. Active individuals had a greater ability to compensate for high-energy preloads through reductions in energy intake, in comparison with inactive controls. When physical activity level was graded across cross-sectional studies (low, medium, high, very high), a significant curvilinear effect on energy intake (z-scores) was observed. LIMITATIONS: Methodological issues existed concerning the small number of studies, lack of objective quantification of food intake, and various definitions used to define active and inactive individuals. CONCLUSION: Habitually active individuals showed improved compensation for the energy density of foods, but no consistent differences in appetite or absolute energy intake, in comparison with inactive individuals. This review supports a J-shaped relationship between physical activity level and energy intake. Further studies are required to confirm these findings. PROSPERO REGISTRATION NUMBER: CRD42015019696