William L. Jungers

Body Size and Scaling of Limb Proportions in Primates

Extant terrestrial mammals span an enormous size range, from tiny pygmy shrews weighing in at less than 5 g to massive African elephants tipping the scales at over 2500 kg (Eisenberg, 1981). Despite such marked differences in adult body mass, Alexander et al. (1979) report that the lengths and diameters of limb bones in a shrew-to-elephant size series scale surprisingly close to geometric similarity; i.e., linear dimensions are almost proportional to (mass)173. Although adult members of the order Primates cannot match the overall range of body sizes in mammals, the size distribution of living primate species is still quite impressive, ranging from dwarf galagos and mouse lemurs (—60–70 g) at one end of the spectrum to male gorillas (>200 kg in some individuals) at the other. Given the unexpected results of the Alexander et al. (1979) study, it is reasonable to wonder if the linear dimensions of the long bones of adult primates also conform to the expectations of geometric similarity. A few minutes of casual observation at the zoo or natural history museum would probably suffice to allow one to reject this null hypothesis for primate limb proportions. Galagos and tarsiers simply do not resemble gibbons or gorillas very much with regard to their respective bodily proportions. Locomotor differences between these extremes seem equally obvious and appear to be correlated with differences in limb proportions.

Morphometrics of the callitrichid forelimb: A case study in size and shape

Mosimann and colleagues formulated a technique that distinguishes between size and shape, based on the concept of geometric similarity and the distinction between “log size-and-shape” and “log shape” variables. We extend these formulations in an examination of the forelimb of three callitrichid species (adultSaguinus oedipus, Saguinus fuscicollis, andCallithrix jacchus). We employ principal components analysis to explore the relationship between variance explained by size-and-shape versus shape alone. Independence of shape vectors is examined via correlation analysis. Then we use log shape data to construct intersample (species means) and total sample (between all paris of individuals) matrices of average taxonomic distances. These distance matrices are subjected to cluster analysis and principal coordinate ordinations. Results of principal components analysis suggest that after isometric size is removed, there remains sufficient shape information to discriminate among the three taxa. Careful examination and quantification of the relationships between shape and size suggest that size information (e.g., geometric mean) is fundamental for understanding shape differences within and among callitrichid species; in other words, most aspects of forelimb shape are significantly correlated with size. Contrary to conventional wisdom, we also demonstrate that such correlations are not “spurious”. Ordinations and clustering of log shape distance matrices (based on means and individuals) support the notion that, despite differences in size, the two tamarins are more similar in shape than either is toC. jacchus (despite size similarity betweenS. fuscicollis andC. jacchus). Although shape variation in the forelimb of calliirichids may have a functional component, the phylogenetic signal remains strong and serves to group individuals accordingly.

Structural and mechanical indicators of limb specialization in primates

The structural mechanics of femora and humeri from primates representing a wide spectrum of habitual locomotor activities were examined to determine how cross-sectional properties vary with functional specializations of the extremities. Average bending rigidities of the midshaft of humerus and femur were measured in 60 individuals of four nonhuman primate species (Macaca nemestrina, Macaca fascicularis, Presbytis cristata, Hylobates lar) using single-beam photon absorptiometry. Linear regression analyses of the loge transformed data were used to assess the relative usage of the forelimb and hindlimb in propulsion and weight bearing, and to evaluate deviations from generalized mammalian quadrupedalism. The results suggest that average bending rigidities of the humerus and femur in primates reflect the extent to which the forelimb and hindlimb are used differently in locomotion; deviations of average bending rigidity from geometric similarity indicate functional variations from generalized mammalian quadrupedalism and the ratio of humeral to femoral bending rigidity can be used to identify trends towards hindlimb or forelimb dominance in locomotion and can be employed in general to determine how the limb was used.

Body size and morphometric affinities of the appendicular skeleton in Oreopithecus bambolii (IGF 11778)

Abstract A new estimate of body mass is provided for the partial skeleton of Oreopithecus bambolii (IGF 11778) based on multiple regression analysis of body mass on joint size in living hominoids. Based on a variety of statistical criteria, an estimate of 32 kg seems most plausible. This value is much greater than predicted by tooth size, but is lower than most prior estimates from the postcranium. Appendicular dimensions (humerus, radius, femur, tibia, and ilium lengths) are placed into a comparative size-related context in a variety of ways: percentage departures from expected values for other catarrhines, “narrow allometry”, and multivariate analysis of mass-adjusted—variables. Oreopithecus emerges as most similar overall to female orang-utans, and substantial similarity between these two taxa is inferred for positional repertoire and substrate use.

A hominoid proximal humerus from the Early Miocene of Rusinga Island, Kenya

Abstract Recently, an isolated proximal humerus of an early Miocene hominoid was discovered at Rusinga Island, Kenya. The precise taxonomic allocation of this specimen is currently problematic, but the fossil almost certainly belongs to either Dendropithecus macinnesi or Proconsul africanus . The humeral head is expanded above the greater tuberosity in the new fossil suggesting that this early Miocene hominoid possessed a relatively mobile shoulder joint for climbing as well as for postural and feeding activities, and that rapid protraction at the shoulder joint was not important. This proximal humeral morphology contrasts with that of Aegyptopithecus , but is quite similar to that of Pliopithecus . Among extant primates, a similar proximal humeral morphology occurs in several platyrrhines such as Alouatta , but living apes share several apparently derived features of the proximal humerus which are lacking in the Rusinga Island specimen.

Analysis of individual, intraspecific and interspecific variability in quantitative parameters of caprine tooth enamel structure

Qualitative and quantitative features of mammalian tooth enamel structure are increasingly being used in taxonomic and phylogenetic analyses, although the variability shown by these traits has not received adequate consideration. This study evaluates the variability displayed by nine quantitative parameters in deep, intermediate, and superficial molar enamel in the closely related bovids Ovis aries and Capra hircus. These parameters are assessed in terms of the absolute and/or relative variability evinced at a given depth within a single individual, among conspecific individuals, and between species samples. The degrees of relative variability expressed at a given depth are comparable among conspecific individuals and between taxonomic samples. Nevertheless, in many instances, there are significant differences in absolute variability amongst individuals. Also, in four parameters for which individual specimen averages could be calculated, the equality of these means among conspecifics can be rejected. Variability is not equivalent at different enamel depths. The null hypothesis of equality of individual, conspecific variances can be rejected most commonly for parameters measured in deep and superficial enamel, and coefficients of variation also tend to be higher for deep and superficial enamel than for enamel of intermediate depth. The greater variability displayed by deep and especially superficial enamel may be related to the initial onset and the terminal phase of ameloblastic secretory activity. Taxonomic and phylogenetic analyses that utilize quantitative data on enamel structure are valid only if comparisons have been made at equivalent enamel depths.

Estimation and Evidence in Forensic Anthropology

Identifications in forensic anthropology occur in two rather different contexts. One context is that of “estimation,” when a biological profile from unidentified remains is built in the hope of eventually identifying said remains. Another context is in evidentiary proceedings, where biological information from the remains is used to contribute to a probability statement about the likelihood of a correct identification. Both of these contexts can occur when stature is the biological parameter of interest, and so the authors take data related to stature as the example in this chapter. The unifying method in both contexts is the application of Bayes’ theorem. Therefore, this chapter opens with a review of some of the characteristics of a Bayesian analysis.

Selection, Morphological Integration, and Strepsirrhine Locomotor Adaptations

Clades with taxa that have multiple locomotor adaptations represent a direct way to test the relationship between adaptation and integration. If integration is influenced by functional requirements, integration should be most apparent where selection is strongest and less evident where selection has been relaxed. If integration is primarily regulated by genetic constraints, integration should be present irrespective of selection pressures. Here we use patterns of integration in the strepsirrhine fore- and hind limbs as a test case. Strepsirrhine locomotion is relatively well-studied, and there are multiple clades that share different locomotor modes. We found that quadrupeds have greater limb integration than vertical leapers. These results suggest that variation can be expressed if selection for integration is relaxed. However, an unexpected pattern was revealed, in which there appears to be some broader regulatory mechanism controlling overall limb integration. Our tests identified a strong correlation between integration of the forelimb and integration of the hind limb. This broader mechanism may be evidence of the primitive genetic control of limb integration.

Analysis of enamel ultrastructure in archaeology: The identification of Ovis aries and Capra hircus dental remains

Abstract Ultrastructural features of deep, intermediate and superficial enamel were quantitatively assessed for the mandibular first permanent molars of 10 specimens each of the domestic sheep ( Ovis aries ) and goat ( Capra hircus ). The means of a number of variables differed interspecifically at high levels of statistical significance, especially with regard to the enamel of intermediate depth. A canonical discriminant function analysis employing nine variables at all three enamel depths resulted in the correct taxonomic assignment of 95% of the specimens comprising the present sample. These results, coupled with the simple preparative and analytical methods presented here, may enable archaeozoologists to utilize enamel ultrastructure in order to discriminate between fragmentary dental remains of these caprine species.

Variability of biological similarity criteria

The allometric cancellation technique for determining similarity criteria (dimensionless numbers) insures that these ratios are essentially free from size-dependent variation. However, with the traditional methods of calculating such values, other important sources of variation are not examined. A correlation analysis of residuals demonstrates that many similarity criteria are actually highly variable relationships among organisms and frequently have questionable empirical validity.