Ashley S. Hammond

Determinants of Iliac Blade Orientation in Anthropoid Primates

Orientation of the iliac blades is a key feature that appears to distinguish extant apes from monkeys. Iliac morphology is hypothesized to reflect variation in thoracic shape that, in turn, reflects adaptations for shoulder and forearm function in anthropoids. Iliac orientation is traditionally measured relative to the acetabulum, whereas functional explanations pertain to its orientation relative to the cardinal anatomical planes. We investigated iliac orientation relative to a median plane using digital models of hipbones registered to landmark data from articulated pelves. We fit planes to the iliac surfaces, midline, and acetabulum, and investigated linear metrics that characterize geometric relationships of the iliac margins. Our results demonstrate that extant hominoid ilia are not rotated into a coronal plane from a more sagittal position in basal apes and monkeys but that the apparent rotation is the result of geometric changes within the ilia. The whole ilium and its gluteal surface are more coronally oriented in apes, but apes and monkeys do not differ in orientation of the iliac fossa. The angular differences in the whole blade and gluteal surface primarily reflect a narrower iliac tuberosity set closer to the midline in extant apes, reflecting a decrease in erector spinae muscle mass associated with stiffening of the lumbar spine. Mediolateral breadth across the ventral dorsal iliac spines is only slightly greater in extant apes than in monkeys. These results demonstrate that spinal musculature and mobility have a more significant effect on pelvic morphology than does shoulder orientation, as had been previously hypothesized. Anat Rec, 300:810–827, 2017.

Lower Ilium Evolution in Apes and Hominins: LOWER ILIUM EVOLUTION IN APES AND HOMININS

Elucidating the pelvic morphology of the Pan‐Homo last common ancestor (LCA) is crucial for understanding ape and human evolution. The pelvis of Ardipithecus ramidus has been the basis of controversial interpretations of the LCA pelvis. In particular, it was proposed that the lower ilium became elongate independently in the orangutan and chimpanzee clades, making these taxa poor analogues for the pelvis of the LCA. This study examines the variation in relative lower ilium height between and within living and fossil hominoid species (and other anthropoids), and models its evolution using available fossil hominoids as calibration points. We find nuanced differences in relative lower ilium height among living hominoids, particularly in regards to gorillas, which do not have elongate lower ilia (because they are likely to represent the plesiomorphic hominoid condition for this trait). We also show that differences in relative lower ilium height among hominoid taxa are not readily explained by differences in size between species. Our maximum likelihood ancestral state reconstructions support inferences that chimpanzees (Pan troglodytes in particular) and orangutans evolved their elongate lower ilia independently. We also find that the predicted lower ilium height of the Pan‐Homo LCA is shorter than all great apes except gorillas. This study adds to a growing body of evidence that finds different regions of the body show different evolutionary histories in different hominoids, and underscores that the unique combinations of morphologies of each modern and fossil hominoid species should be considered when reconstructing the mosaic nature of the Pan‐Homo LCA. Anat Rec, 300:828–844, 2017.

The Omo-Kibish I pelvis

Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (196xa0±xa05xa0ka). A partial hipbone (os coxae) of Omo I was recovered more than 30 years after the first portion of the skeleton was recovered, a find which is significant because human pelves can be informative about an individuals sex, age-at-death, body size, obstetrics and parturition, and trunk morphology. Recent human pelves are distinct from earlier Pleistocene Homo spp. pelves because they are mediolaterally narrower in bispinous breadth, have more vertically oriented ilia, lack a well-developed iliac pillar, and have distinct pubic morphology. The pelvis of Omo I provides an opportunity to test whether the earliest modern humans had the pelvic morphology characteristic of modern humans today and to shed light onto the paleobiology of the earliest humans. Here, we formally describe the preservation and morphology of the Omo I hipbone, and quantitatively and qualitatively compare the hipbone to recent humans and relevant fossil Homo. The Omo I hipbone is modern human in appearance, displaying a moderate iliac tubercle (suggesting a reduced iliac pillar) and an ilium that is not as laterally flaring as earlier Homo. Among those examined in this study, the Omo I ischium is most similar in shape to (but substantially larger than) that of recent Sudanese people. Omo I has features that suggest this skeleton belonged to a female. The stature estimates in this study were derived from multiple bones from the upper and lower part of the body, and suggest that there may be differences in the upper and lower limb proportions of the earliest modern humans compared to recent humans. The large size and robusticity of the Omo I pelvis is in agreement with other studies that have found that modern human reduction in postcranial robusticity occurred later in our evolutionary history.

Hip joint mobility in free-ranging rhesus macaques

OBJECTIVESnWe aimed to test for differences in hip joint range of motion (ROM) between captive and free-ranging rhesus macaques (Macaca mulatta), particularly for hip joint abduction, which previous studies of captive macaques have found to be lower than predicted.nnnMATERIALS AND METHODSnHip ROM was assessed following standard joint measurement methodology in anesthetized adult free-ranging rhesus macaques (nu2009=u200939) from Cayo Santiago, and compared with published ROM data from captive rhesus macaques (nu2009=u200916) (Hammond, , American Journal of Physical Anthropology). Significant differences between populations were detected using one-way analysis of variance (pu2009<u2009.05).nnnRESULTSnIn a sample of pooled sexes and ages, free-ranging macaques are capable of increased hip abduction, flexion, and internal rotation compared with captive individuals. These differences in joint excursion resulted in free-ranging individuals having significantly increased ROM for hip adduction-abduction, rotation, flexion-extension, and the distance spanned by the knee during hip abduction. When looking at data for a smaller sample of age-matched males, fewer ROM differences are significant, but free-ranging males have significantly increased hip abduction, internal rotation, range of flexion-extension, and distance spanned by the knee during hip abduction compared with captive males of similar age.nnnDISCUSSIONnOur results suggest that a spatially restrictive environment results in decreased hip mobility in cage-confined animals and ultimately limits the potential limb postures in captive macaques. These results have implications for selection of animal samples in model validation studies, as well as laboratory animal husbandry practices. KEYWORDS caging, Cayo Santiago, hip abduction, Macaca mulatta, nonhuman primate captive care.

The Anthropoid Crista Trochanterica and the Hip Joint Capsule.

The tubercle on the posterior aspect of the femoral neck (the crista trochanterica) has been repeatedly remarked upon because of its presence in early fossil apes, yet the function of this tubercle has eluded researchers. The prevailing explanation for the tubercle is that it relates to a strong ischiofemoral ligament, although none of the hypotheses for this bony projection have been systematically evaluated. This study surveyed 41 extant anthropoid species (nu2009=u2009267 individuals) for the presence of a crista trochanterica. The soft tissue structures of the hip joint were then dissected and described for a sample of anthropoid cadavers (nu2009=u200914) in order to evaluate different hypotheses related to function of this tubercle. This study confirmed that the crista trochanterica is found in most cercopithecoids and platyrrhines, and is not present in great apes. The tubercle is rarely present in hylobatids, contrary to prior reports. The ischiofemoral ligament is not usually well‐developed in anthropoids and does not fully explain the crista trochanterica morphology, although all cadavers displayed a well‐developed zona orbicularis running along the posterior aspect of the joint capsule. The hip joint capsule itself inserted along the crista trochanterica in some individuals, typically those with an elongate crista trochanterica, but was highly variable in regards to the position of the tubercle. The hypotheses for the crista trochanterica are considered within the context of these findings, although the exact function of the tubercle remains unresolved. Anat Rec, 299:60–69, 2016.

A partial Homo pelvis from the Early Pleistocene of Eritrea

Here we analyze 1.07-0.99 million-year-old pelvic remains UA 173/405 from Buia, Eritrea. Based on size metrics, UA 173/405 is likely associated with an already described pubic symphysis (UA 466) found nearby. The morphology of UA 173/405 was quantitatively characterized using three-dimensional landmark-based morphometrics and linear data. The Buia specimen falls within the range of variation of modern humans for all metrics investigated, making it unlikely that the shared last common ancestor of Late Pleistocene Homo species would have had an australopith-like pelvis. The discovery of UA 173/405 adds to the increasing number of fossils suggesting that the postcranial morphology of Homo erectus s.l. was variable and, in some cases, nearly indistinguishable from modern human morphology. This Eritrean fossil demonstrates that modern human-like pelvic morphology may have had origins in the Early Pleistocene, potentially within later African H.xa0erectus.

Introduction, Aims, Methodology and Materials

Strikingly, until the publication of this book comprehensive data about the soft tissues of our closest living relatives, the chimpanzees, was only available for common chimpanzees, as even Miller’s 1952 study of bonobo musculature was incomplete and restricted to a single individual. Few zoos keep bonobos and cadavers are difficult to come by, but thanks to the foresight of researchers at the Antwerp Zoo, which has one of the largest collections of bonobos in captivity, seven bonobo cadavers had been preserved. Thanks also to a collaboration between the Antwerp Zoo and the Applied Veterinary Morphology group of the Department of Veterinary Sciences at the University of Antwerp, arrangements were made for a team of researchers, including the authors of this book, to dissect all seven cadavers, which comprise males and females and fetal, infant, adolescent and adult stages.

Lower Limb Musculature and Lumbosacral Plexus

In this chapter, we describe the lower limb musculature musculature of the bonobos dissected by us and by other previous authors and compare it with that of common chimpanzees. The three major differences between the two chimpanzee species are that bonobos usually retain a scansorius and have popliteus-fibula and extensor hallucis longus-proximal big toe phalanx attachments: all these three features are usually missing in common chimpanzees and humans.

Upper Limb Musculature and Brachial Plexus

In this chapter we describe the upper limb musculature musculature of the bonobos dissected by us and by other previous authors, and compare it with that of common chimpanzees. The three major differences between the two chimpanzee species are: (1) the intermetacarpales and flexores breves profundi muscles in the hand of bonobos usually fuse to form dorsal interossei, a shared feature with modern humans; (2) bonobos usually have a stout tendon of the flexor digitorum profundus attaching to digit 1 (in modern humans the homologous tendon of the flexor pollicis longus to digit 1 is usually also stout; and (3) bonobos usually have an attachment between the pectoralis minor and the coracoid process of the scapula, as modern humans usually do.

Trunk, Diaphragmatic, Perineal and Coccygeal Musculature

In this chapter we describe the trunk, diaphragmatic, perineal and coccygeal musculature of the bonobos dissected by us and by other previous authors, and compare it with that of common chimpanzees. There are no major differences, for instance concerning the consistent presence of certain muscles in one species versus the consistent absence in the other, between the two chimpanzee species.