Primate Skeleton Research Articles

PRIMATE ANATOMY, KINEMATICS, AND PRINCIPLES FOR HUMANOID DESIGN

The primate order of animals is investigated for clues in the design of humanoid robots. The pursuit is directed with a theory that kinematics, musculature, perception, and cognition can be optimized for specific tasks by varying the proportions of limbs, and in particular, the points of branching in kinematic trees such as the primate skeleton. Called the Bifurcated Chain Hypothesis, the theory is that the branching proportions found in humans may be superior to other animals and primates for the tasks of dexterous manipulation and other human specialties. The primate taxa are defined, contemporary primate evolution hypotheses are critiqued, and variations within the order are noted. The kinematic branching points of the torso, limbs and fingers are studied for differences in proportions across the order, and associated with family and genus capabilities and behaviors. The human configuration of a long waist, long neck, and short arms is graded using a kinematic workspace analysis and a set of design axioms for mobile manipulation robots. It scores well. The re-emergence of the human waist, seen in early prosimians and monkeys for arboreal balance, but lost in the terrestrial pongidae, is postulated as benefiting human dexterity. The human combination of an articulated waist and neck will be shown to enable the use of smaller arms, achieving greater regions of workspace dexterity than the larger limbs of gorillas and other hominoidea.

Baboon Bone Mineral Densities: Implications for the Taphonomy of Primate Skeletons in South African Cave Sites

C. K. Brain (e.g., 1981) documented an interesting difference in relative skeletal part representation between primates and bovids of similar live body size recovered from the fossil cave site of Swartkrans (South Africa). Hominids and baboons are represented primarily by skull parts and a paucity of postcranial bones, while small sized bovids (Size Classes 1 & 2) are represented by more equivalent abundances of all skeletal elements. Brain argued that the Swartkrans bones were primarily carnivore collected, and postulated that the difference in element frequencies between primates and bovids is the manifestation of less durable primate postcranial skeletons relative to those of bovids when either are subjected to a destructive process such as carnivore feeding. Experiments by Brain (1981) in which baboon and bovid carcasses were fed to large, African carnivores lend support to this hypothesis. Bovid postcranial elements survived carnivore feeding more frequently and more completely than those of primates. Assuming that bulk bone mineral density (bulk BMD) is a measure of durability, we supplement Brain's observational data by presenting the first systematic, element-by-element comparison of baboon and bovid postcranial bulk BMD measurements obtained by dual energy X-ray absorptiometry (DXA). While the bovid in our sample exhibits greater absolute bulk BMD values in 57·8% of all measured bone areas, when grouping areas by body region, a statistically significant difference in absolute bulk BMD values between the baboons and bovids is documented only in the hindlimb region (i.e., femur, tibia and patella). Density differences in other body regions are not statistically significant. Further, in only one case (i.e., small bovids in the Member 2 [1948–1953/1965–1975 excavation] assemblage) is there a significant and positive correlation between skeletal part frequencies of primates or bovids and bulk BMD. This suggests that, for the most part, primate and bovid skeletal part representation at Swartkrans is not the result of density-mediated processes. Differences in skeletal part representation between primates and bovids at Swartkrans may thus be attributable to factors other than bone density—such as bone size, length, shape, and/or the relative palatability of surrounding soft tissues on bones.

Scaling of postcranial joint size in hominoid primates

The scaling of sixteen articular dimensions in the locomotor skeleton of hominoid primates is examined with special reference to a recently proposed model of geometric similarity. Seven species are included in the analysis (gorillas, common chimpanzees, bonobos, orang-utans, siamang, lar gibbons, and modern humans of European descent); all specimens are adult individuals of known body mass (N=87). No significant sexual dimorphism in the scaling of joint size was observed. Overal results are compatible with the biomechanical model predictions of isometry, and lend additional support to the suggestion that joint stresses are of the same order of magnitude in animals differing vastly in body size and locomotor adaptations. The hindlimb and lumbosacral joints of humans, however, are consistently much larger than expected for their body mass. Full-time bipedality obviously precludes the sharing of weight support and propulsion with the forelimbs, and this fundamental difference is accurately reflected in the relative joint size of humans.

The primate postcranial skeleton. Studies in adaptation and evolution. Edited by Elizabeth Strasser and Marian Dagosto. New York: Academic press. 1988. iii + 265 pp., tables, figures, references. $8.95 (paper)

The primate postcranial skeleton. Studies in adaptation and evolution. Edited by Elizabeth Strasser and Marian Dagosto. New York: Academic press. 1988. iii + 265 pp., tables, figures, references. $8.95 (paper)

Major stages in the evolution of primate neurocrania

An important constraint on the evolution of primate skeletons is the isometric relationship which exists between skeletal weight and body weight. The evolution of primate skulls during the Tertiary and Quaternary periods indicates that redeployment of bone mass took place largely within the skull (i.e. between proximate ossifying centres) and that the major vector was from the splanchnocranium towards the neurocranium. This vector of bone mass redeployment accords well with the general treand within primates of increased encephalisation over time. There are however, several interesting examples of vectors which were oriented in the opposite sense, in particular in the robust australopithecine lineage, in which the emphasis on bone mass deployment was towards the splanchnocranium and away from the neurocranium. A fuller understanding of skeletal isometry, and a wider application in comparative anatomy may throw much light on the evolution of skeletal systems, and it may resolve somelong-standing debates. Among these may be identification of the selection pressures which have led to dental and alveolar reduction inHomo sapiens sapiens (bone mass redeployment into the neurocranium) and perhaps an explanatation for some types of osteoporosis in old people whose body weight decreases may result in isometric skeletal mass decreases (for every 100 gms muscle tissue loss, there will be about 7 gms of bone tissue loss).

The nature and basis of sexual dimorphism in the primate skeleton

This study sets out to document and analyse sexual dimorphism in the teeth and bones of five primate groups, including man. Specimens were only included in the analysis if their sexual attribution was reliable and was based on non‐osteological criteria. Ninety raw measurements, both cranial and post‐cranial, were used and 11 indices were computed from them.The parameters of each sample were computed in order to compare these results with previous estimates of dimorphism which have not always been based on reliably sexed samples. Correlation matrices were computed.The overall sex differences were subdivided into “shape” and “size” components using Penrose's size and shape distances and by computing the principal components of each data set. The visually apparent shape differences were confirmed metrically and then examined to see whether they could be explained by allometric effects or whether there was evidence for sexual differences in growth patterns.Using femur length as the independent variable, because of its correlation with overall size, allometric coefficients were computed for the logarithmically transformed data. The coefficients were in some cases very different between sexes but the majority did not achieve statistical significance. Of those that were significantly different only in Homo did such differences narrowly exceed the number that would be expected by chance alone.As the vast majority of allometric coefficients for the pooled male and female data differed from unity, the hypothesis that most of the considerable shape differences that exist between some male and female primates are due to underlying growth differences must be rejected. It is suggested that such differences are simply the result of disproportionate change in size.