The use of cranial variables for the estimation of body mass in fossil hominins

Estimating body mass/size/weight remains a crucial precursor to the evaluation of relative brain size and to achieving an understanding of brain evolution in fossil species. Despite the obvious close association between the metrics of postcranial elements and body mass a number of factors combine to reduce their utility. This study examines the feasibility of cranial variables for predicting body mass. The use of traditional regression procedures, independent contrasts analysis, and variance partitioning all support the hypothesis that cranial variables are correlated with body mass even when taking phylogeny into account, with r values typically ranging between 0.52 and 0.98. Body mass estimates derived for fossil hominins using cranial variables are similar to those obtained from previous studies using either cranial or postcranial elements. In particular, upper facial breadth and orbital height display strong predictive capability. Average body masses derived from Least Squares Regression (LSR) equations were used to calculate estimates of body mass for three hominin species. This resulted in estimates of between 30 kg and 47 kg for Australopithecus africanus, 48 kg and 52 kg for Paranthropus robustus, and 75 kg for Homo neanderthalensis. It is proposed that regression equations derived for the order primates are used to estimate body mass for archaic hominins, while hominoid based equations are most suited for Homo.     

Estimating fossil hominin body mass from cranial variables: An assessment using CT data from modern humans of known body mass

Body mass estimates are integral to a wide range of inferences in paleoanthropology. Most techniques employ postcranial elements, but predictive equations based on cranial variables have also been developed. Three studies currently provide regression equations for estimating mass from cranial variables, but none of the equations has been tested on samples of known mass. Nor have the equations been compared to each other in terms of performance. Consequently, this study assessed the performance of existing cranial equations using computed tomography scans from a large, documented sample of modern humans of known body mass. Virtual models of the skull were reconstructed and measured using computer software, and the resulting variables were entered into three sets of published regression equations. Estimated and known body masses were then compared. For most equations, prediction errors were high and few individuals were estimated within ±20% of their known mass. Only one equation satisfied the accuracy criteria. In addition, variables that had been previously argued to be good predictors of mass in hominins, including humans, did not estimate mass reliably. These results have important implications for paleoanthropology. In particular, they emphasize the need to develop new equations for estimating fossil hominin body mass from cranial variables. Am J Phys Anthropol 154:201–214, 2014. © 2014 Wiley Periodicals, Inc.     

Taxonomic and functional implications of mandibular scaling in early hominins

Body mass estimates for fossil hominin taxa can be obtained from suitable postcranial and cranial variables. However, the nature of the taphonomic processes that winnow the mammalian fossil record are such that these data are usually only available for the minority of the specimens that comprise the hypodigm of a species. This study has investigated the link between species mean body mass and the height and width of the mandibular corpus in a core sample of 23 species of extant simians. The slopes of the least-squares regressions for the whole sample and for the hominoid subset are similar. However, the intercepts differ so that for a given body mass, a hominoid will generally have a smaller mandible than a generalized simian. The same mandibular measurements were taken on 75 early hominin mandibles assigned to eight species groups. When mandibular corpus height- and width-derived estimates of body mass for the fossil taxa were compared with available postcranial and cranial-derived body mass estimates, the eight early hominin species sort into four groups. The first, which includes A. afarensis and A. africanus, has mandibles which follow a “generalized simian” scaling relationship. The second group, which comprises the two “robust” australopithecine species, P. boisei and P. robustus, has mandibles which scale with body mass as if they are “super-simians,” for they have substantially larger mandibles than a simian with the same body mass. The two “early Homo” species, H. habilis sensu stricto and H. rudolfensis, make up the third group. It has mandibular scaling relationships that are intermediate between that of the comparative simian sample and that of the hominoid subsample. The last of the four groups comprises H. ergaster and H. erectus; their mandibles scale with body mass as if they were hominoids, so that of the four groups they have the smallest mandibles per unit body mass. These results are related to comparable information about relative tooth size. Their relevance for attempts to interpret the dietary adaptations of early hominins are explored. Am J Phys Anthropol 105:523–538, 1998. © 1998 Wiley-Liss, Inc.     

Long bone articular and diaphyseal structure in Old World monkeys and apes. II: Estimation of body mass

Body mass estimation equations are generated from long bone cross-sectional diaphyseal and articular surface dimensions in 176 individuals and 12 species of hominoids and cercopithecoids. A series of comparisons is carried out to determine the best body mass predictors for each of several taxonomic/locomotor groupings. Articular breadths are better predictors than articular surface areas, while cross-sectional shaft strengths are better predictors than shaft external breadths. Percent standard errors of estimate (%SEEs) and percent prediction errors for most of the better predictors range between 10-20%. Confidence intervals of equations using sex/species means are fairly representative of those calculated using individual data, except for sex/species means equations with very low %SEEs (under about 10%), where confidence intervals (CIs) based on individuals are likely to be larger. Given individual variability, or biological "error," this may represent a lower limit of precision in estimating individual body masses. In general, it is much more preferable to determine at least broad locomotor affinities, and thus appropriate modern reference groups, before applying body mass estimation equations. However, some structural dimensions are less sensitive to locomotor distinctions than others; for example, proximal tibial articular M-L breadth is apparently "locomotor blind" regarding body mass estimation within the present study sample. In other cases where locomotor affiliation is uncertain, mean estimates from different reference groups can be used, while for some dimensions no estimation should be attempted. The techniques are illustrated by estimating the body masses of four fossil anthropoid specimens of Proconsul nyanzae, Proconsul heseloni, Morotopithecus bishopi, and Theropithecus oswaldi.     

Rudabánya: A late miocene subtropical swamp deposit with evidence of the origin of the African apes and humans

Rudabánya, a rich late Miocene fossil site in northern central Hungary, has yielded an abundant record of fossil primates, including the primitive catarrhine Anapithecus and the early great ape Dryopithecus. While the affinities of Anapithecus are not clear, Dryopithecus is clearly a great ape sharing numerous characteristics of its dental, cranial and postcranial anatomy with living great apes. Like all Miocene hominids (great apes and humans), Dryopithecus is more primitive in a number of ways than any living hominid, which is probably related to the passage of time since the divergence of the various lineages of living hominids, allowing for similar refinements in morphology and adaptation to take place independently. On the other hand, Dryopithecus (and Ouranopithecus) share derived characters with hominines (African apes and humans), and Sivapithecus (and Ankarapithecus) share derived characters with orangutans, thus dating the split between pongines and hominines to a time before the evolution of these fossil great apes. Pongines and hominines follow similar fates in the late Miocene, the pongines moving south into Southeast Asia from southern or eastern Asia and the hominines moving south into East Africa from the Mediterranean region, between 6 to 9 Ma.     

Body mass reconstruction on the basis of selected skeletal traits

The objective of this paper is: to estimate the body mass of the skeletons with the mechanical method (femoral head body mass estimation method--FH) and non-mechanical method (stature/living bi-iliac breadth body mass estimation method--ST/LBIB); to compare the reliability and potential use of results obtained with both methods. The material (46 skeletons, 26 males, 20 females) used in the study came from the medieval burial ground in Cedynia, Poland. Body mass reconstruction according to non-mechanical method was made using equations proposed by Ruff et al. (2005). Body mass estimation based on the mechanical method was calculated using formulas proposed by Ruff et al. (1995). In the mechanical body mass reconstruction method, femoral superoinferior breadth was used. Reconstruction of body weight using the non-mechanical method was based on maximum pelvic breadth and reconstructed body height. The correlation between bi-iliac breadth and femoral head measurements and the correlation between femoral head and reconstructed body height were also calculated. The significance of differences between the body mass of male and female individuals was tested with the Mann-Whitney U-test. The significance of differences between body mass values obtained with the mechanical (FH) and the non-mechanical method (ST/ LBIB) was tested using Pearson's correlation. The same test was used for the calculation of the relationship between bi-iliac breadth and femoral head measurements and between femoral head and reconstructed body height. In contrast to females, in males there is no statistically significant correlation between body mass estimated with the mechanical method (FH) and the non-mechanical method (ST/LBIB). In both sexes there was not statistically significant correlation between bi-iliac breadth and femoral head measurements. Only in the females group the correlation between femoral head and reconstructed body height was statistically significant. It is worth to continue the research. The obtained results would be a valuable contribution to the knowledge on body mass reconstruction methods.     

Correlation of tooth size and body size in living hominoid primates, with a note on relative brain size in Aegyptopithecus and Proconsul.

Second molar length and body weight are used to test the correlation between tooth size and body size in living Hominoidea. These variates are highly correlated (r= 0.942, p less than 0.001), indicating that tooth size can be used in dentally unspecialized fossil hominoids as one method of predicting the average body weight of species. Based on tooth size, the average body weight of Aegyptopithecus zeuxis is estimated to have been beteen 4.5 and 7.5 kg, which is corroborated by known cranial and postcranial elements. Using Radinsky's estimates of brain size, the encephalization quotient (EQ) for Aegyptopithecus was between 0.65 and 1.04. A similar analysis for Proconsul africanus yields a body weight between 16 and 34 kg, and an EQ between 1.19 and 1.96.     

New estimates of early hominid body size

Body weights for 12 early hominid specimens are estimated based on an analysis of four variables shown to have high correlation with body size in living Old World primates. Average size estimates of around 36 kg are suggested for gracile early hominids and around 59 kg for robust early hominids. Size variation is considerably more pronounced in the robust group than in the gracile group, suggesting substantially greater sexual dimorphism in the former.     

Regression equations for the estimation of stature and body mass using a Greek documented skeletal collection

Body size is an important variable in bioarchaeological and forensic studies, making the accurate calculation of stature and body mass imperative. Given that anatomical and morphometric approaches offer accurate results but require a particularly good preservation of the skeletal material, whereas mathematical and mechanical methods are more easily applicable but they are largely population-specific, the present paper uses a ‘hybrid’ approach in order to generate regression equations for the prediction of stature and body mass in a modern Greek sample. Specifically, anatomical and morphometric methods were used to calculate the stature and body mass of the individuals and regression equations using the Ordinary Least Squares and Reduced Major Axis methods were generated with long bone lengths and femoral head breadth as predictors. The obtained equations exhibit low random and directional error and perform better than existing equations designed using different samples from the United States, Europe, and the Balkans. Therefore, these equations are more appropriate for modern Greek material.     

Allometric patterns of cranial bone thickness in fossil hominids

The interspecific allometry of five measures of total cranial bone thickness is examined in 10 extant catarrhine genera and two fossil hominid samples representing A. africanus and Asian H. erectus. Analysis of the modern sample shows that most interspecific variation in vault thickness can be accounted for by variation in body size. Correlation values are moderate to high (r = 0.75–0.98), and all variables exhibit positive allometry. The bone thickness:body mass relationship of modern humans broadly conforms with that of other primates. However, in the distribution of relative thickness throughout the skull, H. sapiens is distinguished by relative thickening of the parietal and extreme relative thinning of the temporal squama. The bone thickness:body mass relationship in the two early hominid species is examined using published mean body weight estimates generated from post-cranial predictor variables. A. africanus exhibits great similarity to modern humans in its relation to the catarrhine regression data and in the distribution of relative thickness throughout the skull. H. erectus also shows a modern human-like pattern in the distribution of its relative thickness; however, its bone thickness:body mass relationship is dissimilar to that displayed by all other taxa, including the other hominid species. On the basis of these results, it is suggested that the published body weight estimate assigned to H. erectus greatly underestimates actual mean body size for Asian members of this species. © 1996 Wiley-Liss, Inc.     

Size and shape variation in the proximal femur of Australopithecus africanus

Aside from use as estimates of body mass dimorphism and fore to hind limb joint size comparisons, postcranial elements have not often contributed to assessments of variation in Australopithecus africanus. Meanwhile, cranial, facial, and dental size variation is interpreted to be high or moderately high. Further, the cranial base and face express patterns of structural (shape) variation, which are interpreted by some as evidence for the presence of multiple species. Here, the proximal femur is used to consider postcranial size and shape variation in A. africanus. Original fossils from Makapansgat and Sterkfontein, and samples from Homo, Pan, Gorilla, and Pongo were measured. Size variation was assessed by comparing the A. africanus coefficient of variation to bootstrapped distributions of coefficient of variation samples for each taxon. Shape variation was assessed from isometrically adjusted shape variables. First, the A. africanus standard deviation of log transformed shape variables was compared to bootstrapped distributions of logged standard deviations in each taxon. Second, shape variable based Euclidean distances between fossil pairs were compared to pairwise Euclidean distance distributions in each reference taxon. The degree of size variation in the A. africanus proximal femur is consistent with that of a single species, and is most comparable to Homo and Pan, lower than A. afarensis, and lower than some estimates of cranial and dental variation. Some, but not all, shape variables show more variation in A. africanus than in extant taxa. The degree of shape difference between some fossils exceeds the majority of pairwise differences in the reference taxa. Proximal femoral shape, but not size, variation is consistent with high estimates of A. africanus cranial variation.     

中国人和日本人在人种上的关系——颅骨测量性状的统计分析研究

本研究以北亚、东亚、东南亚和大洋洲一大片区域为背景探索日本人的起源和亲缘关系。结果显示日本旧石器时代港川人、绳文时代和现代人与大约同时期的华南居民有最接近的亲缘关系;从绳文时代到现代日本人的时代变化具有与后者(以及华北居民)相同的趋势。     

Biomechanical allometry in hominoid thoracic vertebrae

Considerable differences in spinal morphology have been noted between humans and other hominoids. Although comparative analyses of the external morphology of vertebrae have been performed, much less is known regarding variations in internal morphology (density) and biomechanical performance among humans and closely related non-human primates. In the current study we utilize density calibrated computed tomography images of thoracic vertebral bodies from hominoids (n = 8-15 per species, human specimens 20-40 years of age) to obtain estimates of vertebral bone strength in axial compression and anteroposterior bending and to determine how estimates of strength scale with animal body mass. Our biomechanical analysis suggests that the strength of thoracic vertebral bodies is related to body mass (M) through power law relationships (y ∝ M^b) in which the exponent b is 0.89 (reduced major axis) for prediction of axial compressive strength and is equal to 1.89 (reduced major axis) for prediction of bending strength. No differences in the relationship between body mass and strength were observed among hominoids. However, thoracic vertebrae from humans were found to be disproportionately larger in terms of vertebral length (distance between cranial and caudal endplates) and overall vertebral body volume (p < 0.05). Additionally, vertebral bodies from humans were significantly less dense than in other hominoids (p < 0.05). We suggest that reduced density in human vertebral bodies is a result of a systemic increase in porosity of cancellous bone in humans, while increased vertebral body volume and length are a result of functional adaptation during growth resulting in a vertebral bone structure that is just as strong, relative to body mass, as in other hominoids.     

Morphology of Afropithecus turkanensis from Kenya

Forty-six specimens of a large Miocene hominoid, Afropithecus turkanensis, recently recovered from northern Kenya preserve many morphological details that are described. The specimens include cranial, mandibular, and postcranial parts. They are compared briefly with other Miocene hominoids. It is suggested that Afropithecus may have affinities with Heliopithecus, Kenyapithecus, and the large hominoid from Moroto and Napak, although it is noted that the comparative material is limited in the number of common anatomical parts preserved.     

New body mass estimates for Omomys carteri,a middle Eocene primate from North America

We report new body mass estimates for the North American Eocene primate Omomys carteri. These estimates are based on postcranial measurements and a variety of analytical methods, including bivariate regression, multiple regression, and principal components analysis (PCA). All body mass estimation equations show high coefficients of determination (R²), and some equations exhibit low prediction errors in accuracy tests involving extant species of body size similar to O. carteri. Equations derived from PCA-summarized data and multiple regression generally perform better than those based on single variables. The consensus of estimates and their statistics suggests a body mass range of 170–290 g. This range is similar to previous estimates for this species based on first molar area (Gingerich, J Hum Evol 10:345–374, 1981; Conroy, Int J Primatol 8:115–137, 1987). Am J Phys Anthropol 109:41–52, 1999. © 1999 Wiley-Liss, Inc.     

A family study of anthropometric traits in a Punjabi community: II. An investigation of familial transmission

Path analysis is used to characterize family resemblance for anthropometrics in twins and nuclear families from the Punjabi population of India. Significant positive assortative mating exists with respect to many body measurements, but not for cranial or facial variables. Evidence of a maternal effect for five measurements of bone diameter is reported. Twin resemblance is increased by a component not found in other pairs of relatives for all variables except nasal height, facial length, ear length, and head breadth. Although all variables have significant transmissible components, many have parameter estimates which are not consistent with strictly polygenic inheritance. Some form of cultural transmission is implicated for such variables, especially for those related to fatness levels.     

Body size prediction from juvenile skeletal remains

There are currently no methods for predicting body mass from juvenile skeletal remains and only a very limited number for predicting stature. In this study, stature and body mass prediction equations are generated for each year from 1 to 17 years of age using a subset of the Denver Growth Study sample, followed longitudinally (n = 20 individuals, 340 observations). Radiographic measurements of femoral distal metaphyseal and head breadth are used to predict body mass and long bone lengths are used to predict stature. In addition, pelvic bi-iliac breadth and long bone lengths are used to predict body mass in older adolescents. Relative prediction errors are equal to or smaller than those associated with similar adult estimation formulae. Body proportions change continuously throughout growth, necessitating age-specific formulae. Adult formulae overestimate stature and body mass in younger juveniles, but work well in 17-year-olds from the sample, indicating that in terms of body proportions they are representative of the general population. To illustrate use of the techniques, they are applied to the juvenile Homo erectus (ergaster) KNM-WT 15000 skeleton. New body mass and stature estimates for this specimen are similar to previous estimates derived using other methods. Body mass estimates range from 50 to 53 kg, and stature was probably slightly under 157 cm, although a precise stature estimate is difficult to determine due to differences in linear body proportions between KNM-WT 15000 and the Denver reference sample.     

Locomotor Behavior and Body Mass of Paramys delicatus (Ischyromyidae,Rodentia) and Commentary on Other Early North American Paramyines

Paramyine ischyromyids are one of the first ancestral rodent groups to appear in North America. Studying ecological indicators of these extinct animals enables us to better understand how they integrated into North American mammalian communities. In this study we reassess the locomotor behavior of a nearly complete skeleton of a paramyine, Paramys delicatus (AMNH FM 12506), using functional limb indices and living squirrels as extant analogues. We then used the results of the functional limb index study to select an appropriate locomotor group for body mass estimations of Paramys delicatus and other early North American (Wasatchian-Bridgerian) paramyines. This was done because body mass is strongly tied to locomotor patterns and more reliable body mass estimates can be generated from an extant sample that functionally resembles the fossils being studied. Functional limb indices were calculated for three locomotor groups (arboreal, semifossorial, and gliding) of living sciurids. Comparisons among arboreal, semifossorial, and gliding sciurids show that the functional indices related to mechanical advantage of muscles and limb robusticity enable distinction among locomotor groups; however, there is considerable overlap between arboreal and semifossorial taxa. Paramys delicatus was found to have generally greater mechanical advantages and limb robusticity than most living squirrels, including semifossorial taxa. As these traits are associated with semifossorial squirrels that frequently use scratch-digging, this suggests that Paramys delicatus and perhaps other early paramyines were likely proficient scratch-diggers. However, indices reflecting limb proportions of paramyines suggest that these early rodents may have used more hind limb dominated locomotion than do living squirrels. Body mass estimations for early paramyines were therefore derived from a semifossorial squirrel sample. Statistical comparisons suggest that many of the most reliable estimators for body mass in Paramys delicatus and other paramyines are those derived from humeral dimensions, with the most reliable estimate being humeral head superoinferior breadth. Using these estimators, individual body mass estimates of early paramyines range from 3391 to 4005 g for Paramys delicatus, 1137–1329 g for Paramys copei, 1291 g for Paramys taurus, and 3357 g for Notoparamys costilloi. All body mass estimations derived from postcranial elements are substantially larger than previously published estimates derived from the dentition, which may be because postcranial elements play a larger role in supporting body weight.

     

Hominid cranial capacity versus time: A regression approach

The application of a linear regression approach to hominid data shows that there is more regularity in hominid cranial capacity over time than has been supposed. Two outcomes of this analysis are: (1) the possibility that the South African Australopithecus africanus sites are older than the presently accepted estimates of perhaps around 2·5 million years and (2) the suggestion that the Ngandong (Solo) cranial material is also considerably older than generally assumed; probably, in excess of approximately 250,000 years B.P.