Estimated Body Mass Research Articles

Simplified estimates of soil nematode body mass using maximum diameter: Insights from large-scale grasslands across China

Soil nematode biomass is of growing importance in elucidating soil food web structure, ecosystem functioning, and global biogeographical cycling. However, a significant challenge exists in quickly obtaining body mass data for a large number of nematode specimens without compromising measurement quality. Recently, a simplified method has been proposed, utilizing only the maximum diameter of nematodes to evaluate their fresh weight (W) as a substitute for Andrássy's formula. This approach is based on strong linear correlations between nematode body length (L) and maximum diameter (D). Despite its effectiveness, further testing is needed in extensive regions with numerous specimens. For this purpose, we conducted a study comprising 24,465 nematode specimens obtained from 222 soil samples in five types of grasslands across China. Our findings provided a robust support for the wide use of this simplified method. Furthermore, we proposed new weight formulas for total nematodes, morphological groups, and trophic groups, which were all well fitted to power models as W = aDb/(1.6 × 106), with various values of a for different aggregations and approximately constant b ≈ 3. Based on additional comparative analyses of the formulas used to assess the mean weight of functional groups, community-weighted mean body size, and community metabolic functional footprints, we firstly recommend using trophic group-specific formulas to minimize weight deviations from Andrássy's formula. Our new simplified power-law formulas enable reliable estimates of nematode body mass and are therefore promising for future applications. Moreover, our findings suggest that the classical Euclidean scaling theory significantly contributes to precisely estimating the body mass of small-sized soil fauna using only maximum diameter. In a global approach with a large number of individuals, for functional biogeography studies for instance, measuring the maximum diameter of animals to calculate their biomass is intriguing and compelling to motivate scientists to embrace functional approaches.

Insights on the oldest terror bird (Aves, Phorusrhacidae) from the Eocene of Argentina

ABSTRACT Phorusrhacidae, commonly known as terror birds, constitutes a group of Cariamiformes that lived mainly in South America during the Cenozoic. The oldest record is represented by an isolated distal end of tibiotarsus (MLP-PV 75-II-3-22) discovered in the Lutetian (middle Eocene) levels of the Sarmiento Formation exposed in the Cañadón Vaca locality (Chubut Province, Argentina). Despite being frequently cited as the oldest specimen of Phorusrhacidae, this specimen has never been figured or comprehensively described. Motivated by this gap and recognising the significance of this finding, we conducted a detailed comparison of the tibiotarsus MLP-PV 75-II-3-22 with those of other species, assigning it to an indeterminate species of Psilopterinae with an estimated body mass of approximately 5 kg. Furthermore, following the identification of numerous tooth marks on the distal surface, we hypothesised that this small phorusrhacid may have been subjected to an attack or scavenging event by a small-to-medium predator, such as Nemolestes spalacotherinus, a hypercarnivorous marsupial previously recorded in the Cañadón Vaca assemblage.

Weighing in on miniaturization: New body mass estimates for Triassic eucynodonts and analyses of body size evolution during the cynodont-mammal transition.

Body size influences most aspects of an animal's biology, consequently, evolutionary diversification is often accompanied by differentiation of body sizes within a lineage. It is accepted that miniaturization, or the evolution of extremely small body sizes, played a key role in the origin and early evolution of different mammalian characters in non-mammaliaform cynodonts. However, while there are multiple studies on the biomechanical, behavioral, and physiological consequences of smaller sizes, few explore the evolutionary processes that lead to them. Here, we use body mass as a universal size measurement in phylogenetic comparative analyses to explore aspects of body size evolution in Cynodontia, focusing on the cynodont-mammal transition, and test the miniaturization hypothesis for the origin of Mammaliaformes. We estimated the body masses of 29 species, ranging from Theriocephalia to Mammaliaformes, providing the largest collection of Triassic cynodont body mass estimates that we know of, and used these estimates in analyses of disparity through time and RRphylo . Unexpectedly, our results did not support the miniaturization hypothesis. Even though cynodont body size disparity fell during the Late Triassic, and remained lower than expected under a purely Brownian motion model of evolution up until the Early Jurassic, we found that rates of body size evolution were significantly lower in prozostrodontians leading to the first Mammaliaformes than in other lineages. Evolution rates were higher in medium and large-sized taxa, indicating that size was changing more rapidly in those lineages and that small sizes were probably a persistent plesiomorphic character-state in Cynodontia.

Prominent Methods and Theories in the Estimation of Body Mass from Skeletal Remains

Estimating body mass from skeletal remains is considered a gap in the creation of a biological profile. Over the last few decades, there have been attempts to fill this gap using different elements from the skeleton. Using various academic databases, a study was done to investigate the prominent methods and theories in body mass estimation. These methods include the use of the femur, the articular surfaces, and the interpretation of musculoskeletal stress markers at the entheses. Calculations using the femur found success in adults most prominently when the cortical area is used. The cortical area provided a percent error margin of 14–22%, with the error decreasing when sex and ancestry-specific equations were used. Musculoskeletal stress markers correlated with heavier body mass in various regions when looking at robusticity. However, these results could not be distinguished between higher body mass individuals and athletic individuals. The articular surface area exhibited no change when body mass is considered, although other features such as osteoarthritis can potentially provide insight into body mass. In addition, subadult femurs were investigated and provided error percentages of 5–7% for juveniles 7 years and younger, and the bi-iliac breadth with long bones can be used for those 15–17 years old with an error margin of 5–8%. These methods exhibit limitations in the demographics of the study, the lack of weight extremely investigated, and various confounding factors. However, these methods and theories in body mass estimations from skeletal remains provide a promising start.

Lost in the collections. A critical re-appraisal on Equus major provides a new perspective on the paleobiogeography of the Plio-Pleistocene European equids and on the Equus Datum

Despite its description at the end of the XIX Century, the alpha-taxonomy, paleobiogeography and biochronology of Equus major remains obscure and ill-defined, leaving a gap of knowledge in the evolutionary history of the Eurasian Palearctic Early Pleistocene Equus species. In this contribution, we describe the Early Pleistocene E. major samples from Pardines and Senèze, providing a comparison by multivariate and statistical analyses with the Early and Middle Pleistocene European stenonid fossil Equus species. Moreover, we explore the paleoecology of E. major by mesowear and body mass estimates, comparing its palaeobiogeographic distribution with European paleoclimatic conditions during the Early Pleistocene. Our outcomes help to clarify the fossil record of E. major, leading to our interpretation that it was the largest Early Pleistocene Equus in Europe, it had a browse-dominated to mixed-feeding diet and was well adapted to humid and forested parts of Europe during the earliest Pleistocene. Eventually, the comparison of our paleoclimatic map with the European fossil record provides new insights in understanding their distribution in time and space during the Early Pleistocene, allowing to clarify details surrounding the Equus Datum in Western Eurasia.

Abstract 18797: Use of Convolutional Neural Networks to Detect Overweight and Obesity and Estimate Body Mass Index

Background: Our team has previously developed convolutional neural networks (CNNs) to estimate age and sex from a 10-second, 12-lead ECG as indicators of patient wellness. Here, we develop an additional wellness network to estimate body mass index (BMI) from the ECG input signal. Aims: To evaluate the performance of neural networks trained to classify and directly estimate BMI. Methods: We identified all adult patients in the Mayo Clinic system who had a 10-second, 12-lead ECG within 15 days of a BMI measurement. Of the 174,863 patients in the cohort, 2,895 were underweight (BMI < 18.5), 42,387 were of normal weight (BMI 18.5-24.9), and 57,939 were overweight only (BMI 25.0-29.9). Among patients categorized as obese, 39,788 had class I obesity (BMI 30.0-34.9), 18,978 had class II obesity (BMI 35.0-39.9), and 12,876 had class III obesity (BMI ≥ 40.0). The cohort was split into training, validation, and testing datasets in an 8:1:1 ratio to develop networks for BMI classification and a direct estimation of BMI. Results: In detecting overweight in the testing set, the model achieved an AUC of 0.86 (95% CI 0.85, 0.87). In detecting class I, class II, and class III obesity, the model yielded AUCs of 0.84 (95% CI 0.83, 0.85), 0.84 (95% CI 0.83, 0.85), and 0.85 (95% CI 0.85, 0.86), respectively. The model to estimate BMI achieved a mean absolute error of 3.70. Conclusions: AI-enabled ECGs demonstrate efficient detection of overweight patients and all classes of obesity. Further research is needed to determine if discrepancies between the traditionally measured BMI and the AI-ECG BMI reflect the presence or lack of metabolic abnormalities.

The conversion of native savannah into pasturelands does not affect exclusively species diversity: Effects on physiological condition of a highly abundant dung beetle species.

Dung beetles are efficient indicators to obtain responses regarding the effects of land use change on biodiversity. Although the biological consequences of Cerrado conversion into pasture have been observed at the assemblage scale, there are no cues regarding the effects of tropical savanna conversion into pasture on physiological condition of dung beetle individuals. In this study, we evaluated whether native and non-native habitats in Cerrado affect the physiological condition and body traits of males and females of Phanaeus palaeno. The individuals were collected from a Cerrado fragment (sensu stricto) and an exotic pasture (Urochloa spp.). Physiological condition was assessed through the estimation of individuals' dry body mass, fat mass, and muscle mass. Body traits were estimated through individual body size and males' horn length. We did not find differences between dung beetle morphological traits between Cerrado and pastures. However, individuals collected in exotic pastures had lower dry mass and fat mass, but higher muscle mass, than in conserved Cerrado. Understanding how the land use change affects individuals' body condition is essential to maintain abundant and healthy populations of dung beetles in human-modified landscapes. Although the estimation of physiological condition is logistically more complex than species body traits, future studies aiming to present complex and finer ecological responses of dung beetles should incorporate physiological data to their approaches.

An unusually robust specimen attributed to Buriolestes schultzi (Dinosauria: Sauropodomorpha) from the Late Triassic of southern Brazil.

Buriolestes schultzi is a small sauropodomorph dinosaur from Carnian beds (ca., 233 Ma) of southern Brazil. It is one of the earliest members of that lineage and is a key taxon to investigate the initial evolution of Sauropodomorpha. Here, we attribute a new specimen to B. schultzi from Late Triassic of southern Brazil, which represents the first occurrence of the taxon outside the type locality. The new specimen comprises a disarticulated and partial skeleton, including cranial and postcranial elements. It is tentatively regarded as an additional specimen of B. schultzi according to a unique combination of traits (including autapomorphies). Conversely, the new specimen is stouter than the other specimens of B. schultzi, as shown by femoral Robustness Index. Based on femoral circumference, the estimated body mass of the new specimen is approximately 15 kg, which is far higher than the previous estimations for other specimens of B. schultzi (i.e., approximately 7 kg). In fact, the new specimen and some specimens of Eoraptor lunensis and Saturnalia tupiniquim were found to be significantly stouter than coeval sauropodomorphs. Therefore, instead of all being constructed as gracile, the earliest sauropodomorphs experienced an unappreciated intraspecific variation in robustness. This is interesting because more precise data on species body mass are crucial in order to better understand the complex terrestrial ecosystems in which dinosaurs originated.

Predicting body mass in Ruminantia using postcranial measurements.

Size plays an important role in mammalian ecology. Accurate prediction of body mass is therefore critical for inferring aspects of ecology in extinct mammals. The unique digestive physiology of extant ruminant artiodactyls, in particular, is suggested to place constraints on their body mass depending on the type of food resources available. Therefore, reliable body mass estimates could provide insight into the habitat preferences of extinct ruminants. While most regression equations proposed thus far have used craniodental predictors, which for ungulates may produce misleading estimates based on indirect relationships between tooth dimensions and size, postcranial bones support the body and may be more accurate predictors of body mass. Here, I use phylogenetically informed bivariate and multiple regression techniques to establish predictive equations for body mass in 101 species of extant ruminant artiodactyls based on 56 postcranial measurements. Within limb elements, stepwise multiple regression models were typically preferred, though bivariate models often received comparable support based on Akaike's information criterion scores. The globally preferred model for predicting mass is a model including both proximal and distal width of the humerus, though several models from the radioulna received comparable support. In general, widths of long bones were good predictors, while lengths and midshaft circumferences were not. Finally, I show that where the best elements for prediction are unavailable for fossil taxa, selection of the model with lowest percent prediction error for the lowest level clade to which the fossil can be assigned could be a productive and novel way forward for predicting mass and subsequently aspects of ecology in fossil mammals.

A probable koala from the Oligocene of central Australia provides insights into early diprotodontian evolution

Diprotodontians are the morphologically and ecologically most diverse order of marsupials. However, an approximately 30-million-year gap in the Australian terrestrial vertebrate fossil record means that the first half of diprotodontian evolution is unknown. Fossil taxa from immediately either side of this gap are therefore critical for reconstructing the early evolution of the order. Here we report the likely oldest-known koala relatives (Phascolarctidae), from the late Oligocene Pwerte Marnte Marnte Local Fauna (central Australia). These include coeval species of Madakoala and Nimiokoala, as well as a new probable koala (?Phascolarctidae). The new taxon, Lumakoala blackae gen. et sp. nov., was comparable in size to the smallest-known phascolarctids, with body-mass estimates of 2.2–2.6 kg. Its bunoselenodont upper molars retain the primitive metatherian condition of a continuous centrocrista, and distinct stylar cusps B and D which lacked occlusion with the hypoconid. This structural arrangement: (1) suggests a morphocline within Phascolarctidae from bunoselenodonty to selenodonty; and (2) better clarifies the evolutionary transitions between molar morphologies within Vombatomorphia. We hypothesize that the molar form of Lumakoala blackae approximates the ancestral condition of the suborder Vombatiformes. Furthermore, it provides a plausible link between diprotodontians and the putative polydolopimorphians Chulpasia jimthorselli and Thylacotinga bartholomaii from the early Eocene Tingamarra Local Fauna (eastern Australia), which we infer as having molar morphologies consistent with stem diprotodontians.

Quantifying the gastral mass in Early Cretaceous ornithuromorphs (Aves, Ornithothoraces) from the Jehol avifauna

AbstractSome birds intentionally ingest stones to facilitate digestion of hard foodstuffs, a behaviour inherited from non‐avian dinosaurs and present in some of the earliest birds, as evidenced by clusters of gastroliths preserved within the abdominal cavity of a wide range of dinosaurs and Cretaceous birds. For the first time, high‐resolution computed laminographic and computed tomographic scans were used to reconstruct the gastral mass in two species of non‐neornithine ornithuromorph birds from the Lower Cretaceous Jehol Group. Four specimens of each taxon were analysed. Preservation of the gastral mass in most of these specimens is in situ and regarded as complete or nearly so. The number of gastroliths, their total volume, and their total mass relative to the estimated body mass were calculated for each specimen. The resultant gastral mass to body mass ratios fall within the range observed in extant birds, supporting previous inferences that the digestive system in non‐neornithine ornithuromorphs was comparable to that of extant taxa. Compared to available data for non‐volant non‐avian theropods, the gastral mass is proportionately smaller in birds suggesting that the evolution of flight constrained gastral mass size in the theropod lineage. Currently available data on gastral mass characteristics suggests that Iteravis ate larger food particles compared to Archaeorhynchus but cannot be used to determine diet more precisely. Better understanding of the relationship between gastral mass characteristics and food items across a broader range of extant taxa may provide an indirect but important method through which to infer diet and digestive function in archosaurs.

Reviewing the body size of some extinct Brazilian Quaternary Xenarthrans

ABSTRACTHere we estimate the body mass of 10 iconic species of extinct xenarthrans (cingulates and sloths) from the Quaternary of Brazil using two sets of predictive equations based on postcranial variables. Our results revealed that one of these methods is more reliable in estimating the body mass of the evaluated taxa, even though both methods provide accurate results. The body mass estimates for cingulates indicate that they would have been heavier than previously proposed. Among extinct sloths, the results appear to be within the range of previous estimates. Compared to previously proposed body mass estimates for the same species, we suggest that the results presented in this study are more robust due to using predictive equations with high predictive power and developed using a broader phylogenetic dataset, including extant relatives.

Validating a linear regression equation using mid-upper arm circumference to predict body mass index

Estimating body mass index (BMI) in hospitalised patients for nutritional assessment is challenging when measurement of weight and height is not feasible. The study aimed to validate a previously published regression equation to predict BMI using mid-upper arm circumference (MUAC). We also evaluated the proposed global MUAC cut-off of ≤24cm to detect undernutrition. We measured standing height, weight, and MUAC prospectively in a sample of stable patients. Agreement between calculated and predicted BMI was evaluated using Bland-Altman analysis. We studied 201 patients; 102 (51%) were male. Median (IQR age was 42 (29-50) years. 95% limits of agreement between predicted and calculated BMI were+0.6767 to+1.712 and the bias was+1.076. MUAC ≤24cm was 97% sensitive and 83% specific to detect undernutrition. BMI derived from MUAC had poor calibration for estimating actual BMI. However, low MUAC has good discriminative accuracy to detect undernutrition.

Anterior diaphyseal curvature of the femur and tibia has biomechanical consequences during unloaded uphill locomotion

The biomechanics of limb bone curvature are complex, and though anterior curvature clearly exhibits some relationship with behavior, the mechanisms shaping it and its biomechanical purpose remain unclear. Among both Neanderthals and humans, anterior limb bone curvature correlates strongly with other limb bone adaptations known to reflect high mobility, particularly in steep variable terrain. We developed a computational musculoskeletal model to test the impact of opposing patterns of human femoral and tibial anterior curvature on muscle kinetics during a proxy for uphill walking: stair-climbing. Femoral and tibial laser scans were used from two archaeological individuals matched for estimated body mass, bi-iliac breadth, and crural index but with reverse patterns of anterior diaphyseal curvature. A default OpenSim musculoskeletal model was modified twice – once to each individual’s anatomy – and the resulting models performed stair-climbing gait simulations with experimentally-collected motion capture data. Both custom MSk models followed the general gait kinematics expected based on stair-climbing gait studies, but differed in muscle kinetics in key areas. When a curved femur was paired with a straight tibia, the opposite pattern of recruitment of bi-articular superficial hamstring muscles was observed compared to the pairing of a straight femur with a curved tibia. Pairing a curved femur with a straight tibia was also associated with reduced soleal recruitment and an increased reliance on secondary ankle plantarflexors. These effects are attributed to variation in muscle moment arms about the knee and the relationships that curvature likely has with other three-dimensional morphological variation within the bone/limb. While the tissue-level mechanisms shaping anterior limb bone curvature remain poorly understood, results of the current study suggest that opposing patterns of variation in long bone curvature within the leg do elicit different kinetic solutions to the problem of achieving the same gait kinematics during uphill locomotion. This is an important first step not just in better understanding the biomechanical impact of anatomical variation in bone curvature on locomotion, but also contributes more broadly to the recognition in biological anthropology of variability in the relationship between locomotor function and underlying skeletal structure.

Equus suessenbornensis from Akhalkalaki (Georgia, Caucasus): a review with new insights on the paleoecology, paleobiogeography and evolution of the palearctic large-sized equids during the Early – Middle Pleistocene Transition

Equus suessebornensis is one of the most intriguing species of the Early and Middle Pleistocene Eurasian Equus. Although it was described from the Middle Pleistocene site of Süssenborn, in recent years its biochronological correlation has been extended to the Early Pleistocene, raising a debate in the scientific community. In this contribution, we provide a complete ontogenically-based description of the Akhalkalaki E. suessenbornensis samples, and we compare it by multivariate and statistical analyses with the Early and Middle Pleistocene European fossil record. Moreover, we provide new paleoecological insights utilizing body mass, mesowear and net primary productivity estimates. Our outcomes provide a new perspective on the E. suessenbornensis morphology and variability, but also new interpretations for its paleoecology, biochronology, paleobiogeography and evolution. Eventually, these results provide a reassessment of equid evolution during the Early – Middle Pleistocene Transition in Western Eurasia, a critical period for the dynamics of the Quaternary faunas and paleoenvironments.

How to weigh a fossil mammal? South American notoungulates as a case study for estimating body mass in extinct clades

How to weigh a fossil mammal? South American notoungulates as a case study for estimating body mass in extinct clades

Ursidae (Mammalia, Carnivora) from the Quaternary of western Rio Grande do Sul, Brazil: Taxonomical, stratigraphic, and chronological aspects

All known Pleistocene South American fossil ursids belong to Arctotherium, an extinct genus of tremarctine bears. Its occurrence encompasses many countries in Central and South America, with findings mainly from Argentina. In Brazil, the genus is recorded in eight states, highlighting Rio Grande do Sul due to its provenance from fluvial deposits. In contrast, all other Brazilian records come from caves or fossil tanks. The Arctotherium material from Rio Grande do Sul comes from the Passo do Juquiry site, located on the banks of the Quaraí River, which marks the frontier between Brazil and Uruguay. The fossils are MCN-PV 1940/A-K, a set of postcranial bones: first to sixth lumbar vertebrae, sacrum, left scapula, left humerus, right portion of the pelvic girdle, and left femur. The anatomic description of these bones confirmed their belonging to Arctotherium sp. due to their size, the form of the vertebral processes, the presence of the entepicondylar foramen of the humerus, and the morphology of the trochlea and capitulum. Body mass estimates resulted in values mostly above 400 kg. The first absolute age from Passo do Juquiry indicated 40,000 years BP. The stratigraphic framework of the outcrop conformed to a floodplain fines facies association, a succession of mudstones with carbonate nodules on top. This facies association has lithological correlations to the Brazilian Touro Passo Formation, the Uruguayan Sopas Formation, and the Argentinean Toropí/Yupoí Formation. While having similar features, the ages of the lithologically correlated facies associations do not always line up, indicating that the evolution of the Uruguay River basin throughout the Late Pleistocene followed a pattern, but not synchronously. The presence of carbonate levels suggests that the climate during the time of deposition was drier than the present one, with the carbonate-less middle layer representing a more humid period.

The postcranial anatomy of Gorgonops torvus (Synapsida, Gorgonopsia) from the late Permian of South Africa

Gorgonopsians are among the most recognizable groups of synapsids from the Permian period and have an extensive but mostly cranial fossil record. By contrast, relatively little is known about their postcranial anatomy. Here, we describe a nearly complete, semi-articulated skeleton of a gorgonopsian (identified as Gorgonops torvus) from the late Permian Endothiodon Assemblage Zone of the South African Karoo Basin and discuss its paleobiological implications. Known gorgonopsian postcrania indicate morphological conservatism in the group, but the skeletal anatomy of Gorgonops does differ from that of other gorgonopsians in some respects, such as in the triangular radiale and short terminal phalanges in the manus, and a weakly developed distinction between pubis and ischium in ventral aspect of the pelvic girdle. Similarities between the specimen described herein and a historically problematic specimen originally referred to “Scymnognathus cf. whaitsi” confirm referral of the latter specimen to Gorgonops. Since descriptions of gorgonopsian postcrania are rare, new interpretations of the lifestyle and ecology of Gorgonopsia can be drawn from our contribution. We conclude that gorgonopsians were likely ambush predators, able to chase their prey over short distances and pin them down with strong forelimbs before using their canines for the kill. This is evidenced by their different fore- and hindlimb morphology; the former stouter and more robust in comparison to the longer, more gracile, back legs. Furthermore, the completeness of the study specimen facilitates calculation of an estimated body mass of approximately 98 kg, similar to that of a modern lioness.

Application of creatinine height index in patients with trauma for the evaluation of psoas muscle mass: A clinical validation study.

The creatinine height index (CHI) is an estimate of lean body mass. We hypothesize that a modified CHI estimate using serum creatinine (sCr) levels in patients with normal renal function when performed soon after injury would reflect preinjury protein nutrition status. The urine CHI (uCHI) was calculated using the 24-h urine sample. The serum-derived estimated CHI (sCHI) was calculated using the sCr on admission. Correlation between abdominal computed tomographyimages at specific lumbar vertebral levels and total body fat and muscle content was used for comparison as an independent measurement of nutrition status unlikely to be substantially altered by trauma. A total of 45 patients were enrolled, all with a significant injury burden (median injury severity score [ISS] = 25; interquartile range, 17-35). The calculated sCHI on admission was 71.0% (SD = 26.9%) and likely underestimates the CHI when compared with uCHI (mean = 112.5%, SD = 32.6%). Stratifying by degree of stress demonstrated that in a group of 23 moderately and severely stressed patients, uCHI (mean = 112.7%, SD = 5.7%) and sCHI (mean = 60.8%, SD = 1.9%) were significantly different and without correlation (r = -0.26, P = 0.91). In patients without stress, there was a significant negative correlation between sCHI and psoas muscle area (r = -0.869, P = 0.03), and in patients with severe stress there was a significant positive correlation between uCHI and psoas muscle area (r = 0.733, P = 0.016). The CHI calculated from the initial sCr is not an appropriate estimate of uCHI in critically ill trauma patients and is not a valid measure of psoas muscle mass in this setting.

The estimation and evolution of hominin body mass.

Body mass is a critical variable in many hominin evolutionary studies, with implications for reconstructing relative brain size, diet, locomotion, subsistence strategy, and social organization. We review methods that have been proposed for estimating body mass from true and trace fossils, consider their applicability in different contexts, and the appropriateness of different modern reference samples. Recently developed techniques based on a wider range of modern populations hold promise for providing more accurate estimates in earlier hominins, although uncertainties remain, particularly in non-Homo taxa. When these methods are applied to almost 300 Late Miocene through Late Pleistocene specimens, the resulting body mass estimates fall within a 25-60 kg range for early non-Homo taxa, increase in early Homo to about 50-90 kg, then remain constant until the Terminal Pleistocene, when they decline.