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Postcranial Functional Morphology of Morotopithecus bishopi, with Implications for the Evolution of Modern Ape Locomotion
Abstract
The large-bodied hominoid from Moroto, Uganda has until recently been known only from proconsulid like craniodental remains and some vertebrae with modern ape like features. The discovery of two partial femora and the glenoid portion of a scapula demonstrates that the functional anatomy of Morotopithecus differed markedly from other early and middle Miocene hominoids. Previous studies have consistently associated the vertebral remains with a short, stiff back and with orthograde postures. Although the proximal femur more closely resembles the femora of monkeys than of apes and suggests a moderate degree of hip abduction, the distal femur resembles those of extant large bodied apes and suggests a varied loading regime and an arboreal repertoire that may have included substantial vertical climbing. The femoral shaft displays uniformly thick cortical bone, beyond the range of thickness seen in extant primates, and signifies higher axial loading than is typical of most extant primates. The glenoid fossa is broad and uniformly curved as in extant suspensory primates. Overall, Morotopithecus is reconstructed as an arboreal species that probably relied on forelimb-dominated, deliberate and vertical climbing, suspension and quadrupedalism. Morotopithecus thus marks the first appearance of certain aspects of the modern hominoid body plan by at least 20 Ma. If the suspensory and orthograde adaptations linking Morotopithecus to extant apes are synapomorphies, Morotopithecus may be the only well-documented African Miocene hominoid with a close relationship to living apes and humans.
... We accessed osteological collections housed in the Museum of Comparative Zoology, Harvard University and the Department of Anthropology, Ohio State University. We calculated sizestandardized measures of glenoid width and depth [53] and olecranon process length [19], following standard procedures with linear caliper measurements. ...
... Shoulder flexion was measured relative to the bole of the tree, which was parallel to the gravitational vector in most videos (figure 1; electronic supplementary material, figure S1). It is also the most functionally relevant reference point for exploring species-level contrasts in shoulder morphology and mobility [53]. Following similar reasoning [36], elbow extension was measured relative to the position of the upper arm. ...
... For instance, the early Miocene ape Morotopithecus (approx. 21 Ma) possessed an ape-like glenoid cavity, which is interpreted as evidence of 'forelimb suspensory and forelimb dominated climbing behaviours, including vertical ascension' (emphasis ours) [53]. The earliest evidence of olecranon reduction emerged later in Danuvius (12 Ma) and Hispanopithecus (10 Ma), and is fully modern with the appearance of Oreopithecus (7 Ma) [59,60]. ...
The forelimbs of hominoid primates (apes) are decidedly more flexible than those of monkeys, especially at the shoulder, elbow and wrist joints. It is tempting to link the greater mobility of these joints to the functional demands of vertical climbing and below-branch suspension, but field-based kinematic studies have found few differences between chimpanzees and monkeys when comparing forelimb excursion angles during vertical ascent (upclimbing). There is, however, a strong theoretical argument for focusing instead on vertical descent (downclimbing), which motivated us to quantify the effects of climbing directionality on the forelimb kinematics of wild chimpanzees (Pan troglodytes) and sooty mangabeys (Cercocebus atys). We found that the shoulders and elbows of chimpanzees and sooty mangabeys subtended larger joint angles during bouts of downclimbing, and that the magnitude of this difference was greatest among chimpanzees. Our results cast new light on the functional importance of downclimbing, while also burnishing functional hypotheses that emphasize the role of vertical climbing during the evolution of apes, including the human lineage.
... Two hominoid postcranial remains from Moroto II attributed to M. bishopi represent the oldest clear evidence of derived locomotor adaptations in hominoids: a lumbar vertebra [UMP 67-28; originally described by Walker and Rose (48)] indicative of a dorsoventrally stable lumbar spine consistent with orthogrady (37,49,50) and associated partial femora [UMP MORII 94′80; first described by Gebo et al. (32)] reflective of vertical climbing and slow forms of orthograde or pronograde clamber (15,50,51). These are core derived behaviors of the hominoid clade emphasized in the terminal branch forest frugivory hypotheses. ...
... Two hominoid postcranial remains from Moroto II attributed to M. bishopi represent the oldest clear evidence of derived locomotor adaptations in hominoids: a lumbar vertebra [UMP 67-28; originally described by Walker and Rose (48)] indicative of a dorsoventrally stable lumbar spine consistent with orthogrady (37,49,50) and associated partial femora [UMP MORII 94′80; first described by Gebo et al. (32)] reflective of vertical climbing and slow forms of orthograde or pronograde clamber (15,50,51). These are core derived behaviors of the hominoid clade emphasized in the terminal branch forest frugivory hypotheses. ...
... New catarrhine fossils from Moroto II include additional fragments of the right femur UMP MORII 94′80 attributed to Morotopithecus (32,50), which complete the previously partial shaft for a total length of 240.7 mm (data S1). Very few complete femora from large-bodied Miocene hominoids exist. ...
Living hominoids are distinguished by upright torsos and versatile locomotion. It is hypothesized that these features evolved for feeding on fruit from terminal branches in forests. To investigate the evolutionary context of hominoid adaptive origins, we analyzed multiple paleoenvironmental proxies in conjunction with hominoid fossils from the Moroto II site in Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C4 grasses in Africa based on a confirmed age of 21 million years ago (Ma). We demonstrate that the leaf-eating hominoid Morotopithecus consumed water-stressed vegetation, and postcrania from the site indicate ape-like locomotor adaptations. These findings suggest that the origin of hominoid locomotor versatility is associated with foraging on leaves in heterogeneous, open woodlands rather than forests.
... The morphology of the glenohumeral (shoulder) joint reflects the locomotor and postural behavior of different taxa (Jungers, 1991); in this regard, in primates, and in particular, in apes, the glenohumeral joint has been widely used to explore the differences in locomotor behaviors (e.g., Corruccini & Ciochon, 1978;Larson & Stern, 1986;Larson, 1988;Larson, 1995;MaClatchy et al., 2000;Roberts, 1974). ...
... The glenohumeral joint of apes-including gibbons and siamangs (hylobatids) and great apes (gorillas (Gorilla), chimpanzees (Pan), orangutans (Pongo), and humans (Homo))-has anatomical features that enable the forelimbs to be held in overhead positions that are required in locomotor activities such as suspension or vertical climbing (Ashton & Oxnard, 1964;Larson, 1988;Larson, 1995;MaClatchy et al., 2000;Roberts, 1974). These features include a craniallyoriented glenoid fossa (Ashton & Oxnard, 1964), a lateral projection of the glenohumeral joint (Ashton & Oxnard, 1964), and a small, oval, and flat articular surface of the glenoid cavity articulating with a large humeral head (Ashton & Oxnard, 1964;Fleagle, 2013;Godfrey et al., 1991;Larson, 1988;Larson, 1995). ...
... The size difference in hominoids between the small glenoid fossa and the large articular surface of the humeral head is indicative of increased mobility of the glenohumeral joint in hominoids (Larson & Stern, 1986;Larson, 1988;Larson, 1993;Larson, 1995;Roberts, 1974;Rose, 1989). Furthermore, an oval glenoid cavity, which is found in hominoids, some atelines, and cursorial mammals, presents a broader dorsoventral width relative to craniocaudal length, and a moderate craniocaudal and dorsoventral curvatures, allowing a wide range of axial movements (MaClatchy et al., 2000;Roberts, 1974). ...
Objectives: A morphocline of the glenoid cavity has been used to infer differences in
locomotor behaviors; however, the glenoid cavity is surrounded by the glenoid
labrum, a fibrocartilaginous structure that could influence the functionality of the glenoid.
The objectives of this study are to explore the effects of the glenoid labrum on
the area, depth, and morphology of the glenoid cavity in primates.
Materials and Methods: Photogrammetry was used to build 3D models of the
glenoid, with and without the labrum, and three- (3D) and two-dimensional
(2D) geometric morphometrics (GM) was applied. 2D areas were collected from
zenithal images for glenoids with and without labrum to evaluate the availability of
articular surface area.
Results: In the 2D GM the morphocline is present in the dry-bone sample but not
with the presence of the glenoid labrum. In the 3D GM there are differences between
species mainly concerning the depth of the glenoid cavity. 2D areas reveal that the
amount of articular area of the glenoid cavity increases with the presence of the
labrum, particularly in humans.
Discussion: The glenoid labrum changes the shape, increases the depth and the surface
area of the glenoid cavity, particularly in humans. Therefore, the glenoid labrum
might hold a functional role, increasing the stability of the glenohumeral joint of
primates in general, and especially in humans.
... When possible (exclusively in nondistorted, nondamaged specimens/regions), selected measurements were taken and then used to quantitatively compare Nacholapithecus with other African and Eurasian Miocene hominoids and a wide range of extant anthropoid primates, including platyrrhines, colobines, cercopithecines, and hominoids ( Fig. 2; Table 2). The Miocene hominoid sample ( Fig. 3; taxonomy after Alba, 2012) includes: the afropithecid Morotopithecus bishopi (UMP MORII 94 0 80; MacLatchy et al., 2000); the proconsulids Proconsul major (combination of NAP IX 46 0 99, NAP IX B 64, NAP IX 65 P. 67 fragments; Gommery et al., 1998Gommery et al., , 2002Senut et al., 2000), Turkanapithecus kalakolensis (KNM-WK 16950I; Leakey et al., 1988), Ekembo nyanzae (KNM-MW 13142A and KNM-RU 5527; Harrison, 1982;Ward et al., 1993), the kenyapithecine Equatorius africanus (BMNH M.16331; BMNH M.16332-3 is used for qualitative comparisons only; Le Gros Clark and Leakey, 1951;McCrossin, 1994), and the dryopithecines Dryopithecus fontani (IPS 41724; Moy a-Sol a et Pina et al., 2019) and Hispanopithecus laietanus (IPS 18800.29; Moy a-Sol a and K€ ohler, 1996;Pina et al., 2012). ...
... A round depression is observed on the lateral side of the medial condyle proximally, which is likely the attachment area of the posterior cruciate ligament. Otherwise, there are no remarkable features (e.g., buttresses: MacLatchy et al., 2000) observed. ...
... The patellar groove shape of Nacholapithecus is quadrangular and shallow ( Fig. 5; see also Fig. 7I; SOM Fig. S3; SOM 3D Model S1), as in Turkanapithecus (KNM-WK 16950I; Fig. 3C; Leakey et al., 1988), Morotopithecus (UMP MORII 94 0 80; Fig. 3A; MacLatchy et al., 2000) and probably Equatorius (KNM-MB 24727; see McCrossin, 1994: fig. 38 and p. 162). ...
The middle Miocene stem kenyapithecine Nacholapithecus kerioi (16–15 Ma; Nachola, Kenya) is represented by a large number of isolated fossil remains and one of the most complete skeletons in the hominoid fossil record (KNM-BG 35250). Multiple fieldwork seasons performed by Japanese–Kenyan teams during the last part of the 20th century resulted in the discovery of a large sample of Nacholapithecus fossils. Here, we describe the new femoral remains of Nacholapithecus. In well-preserved specimens, we evaluate sex differences and within-species variation using both qualitative and quantitative traits. We use these data to determine whether these specimens are morphologically similar to the species holotype KNM-BG 35250 (which shows some plastic deformation) and to compare Nacholapithecus with other Miocene hominoids and extant anthropoids to evaluate the distinctiveness of its femur. The new fossil evidence reaffirms previously reported descriptions of some distal femoral traits, namely the morphology of the patellar groove. However, results also show that relative femoral head size in Nacholapithecus is smaller, relative neck length is longer, and neck–shaft angle is lower than previously reported for KNM-BG 35250. These traits have a strong functional signal related to the hip joint kinematics, suggesting that the morphology of the proximal femur in Nacholapithecus might be functionally related to quadrupedal-like behaviors instead of more derived antipronograde locomotor modes. Results further demonstrate that other African Miocene apes (with the exception of Turkanapithecus kalakolensis) generally fall within the Nacholapithecus range of variation, whose overall femoral shape resembles that of Ekembo spp. and Equatorius africanus. Our results accord with the previously inferred locomotor repertoire of Nacholapithecus, indicating a combination of generalized arboreal quadrupedalism combined with other antipronograde behaviors (e.g., vertical climbing).
... Gebo et al. (1997) erected a new genus and species, Morotopithecus bishopi, to accommodate what was perceived to be distinct postcranial as well as craniofacial and dental anatomy, a view since promulgated by these and other authors (e.g. Cameron, 1998;MacLatchy and Pilbeam, 1999;Pickford et al., 1999;MacLatchy et al., 2000;Harrison, 2002;Finarelli and Clyde, 2004;Young and MacLatchy, 2004;Ward, 2015;Begun, 2015). ...
... The postcranial anatomy of hominoid remains known from Moroto differs from that of contemporaneous apes in several ways. As outlined by MacLatchy and colleagues (MacLatchy et al., 2000;, the well-preserved lumbar vertebra (UMP 67-28) resembles those of modern apes, and suggests a more dorsostable lower back unlike the flexible lumbar column of Ekembo; the scapular glenoid cavity is broad and evenly convex in both the coronal and transverse planes, a trait which is shared by modern apes with an enhanced capacity for circumduction of the shoulder; and the thick cortical bone, pronounced popliteus fossa, large medial condyle, and broad bicondylar dimensions of the femora suggest ape-like climbing behaviors. Together these features imply a different positional behavior from that inferred for other early Miocene taxa such as the Proconsul clade and Afropithecus, probably including a greater emphasis on orthogrady and differential use of the fore-and hindlimbs. ...
... In the case of Morotopithecus, subtle craniodental distinctions have been described, but dietary reconstructions have not yet been attempted. However, it has been shown to be distinct in terms of its locomotor anatomy from Ekembo, and is inferred to be distinct from Afropithecus, although overlapping elements remain elusive (Ward, 1998;MacLatchy et al., 2000). ...
... The ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, indicating that the transverse process must have projected from the dorsal pillar rather than the body. This matches the condition in genus Homo, extant great apes and extinct largebodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Filler, 2007;Susanna et al., 2014), and is unlike most extant primates including hylobatids where the transverse process emerges from the vertebral body (Slijper, 1942;Ward, 1993;Ankel-Simons, 2007;Williams and Russo, 2015). T9 vertebra The size of the ASI-VP-2/223 T9 dorsal pillar (DP Geo-Mean) is similar to that of H. sapiens, whereas the corresponding A.L. 288-1ad A. afarensis vertebra is significantly smaller (Table 12). ...
... The ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, indicating that the transverse process must have projected from the dorsal pillar rather than the body. This matches the condition in genus Homo, extant great apes and extinct largebodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Filler, 2007;Susanna et al., 2014), and is unlike most extant primates including hylobatids where the transverse process emerges from the vertebral body (Slijper, 1942;Ward, 1993;Ankel-Simons, 2007;Williams and Russo, 2015). T9 vertebra The size of the ASI-VP-2/223 T9 dorsal pillar (DP Geo-Mean) is similar to that of H. sapiens, whereas the corresponding A.L. 288-1ad A. afarensis vertebra is significantly smaller (Table 12). ...
... As in genus Homo, extant great apes and extinct large-bodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Susanna et al., 2014), the ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, which is an important indication that the transverse process must have projected from the dorsal pillar (unlike most primates including hylobatids). The dorsal position of the transverse processes corresponds with a reduced area for the erector spinae relative to the more ventral position in hylobatids, cercopithecoids and most mammals. ...
Seven A. anamensis vertebral fossils from the Assa Isse locality in Ethiopia's Middle Awash area dated to ~4.2 Ma constitute the oldest known australopith axial remains. Because the spine is the interface between major body segments, these fossils can be informative on the behavior and evolution of the first australopiths. Two C1 vertebrae are similar in size and morphology to H. sapiens, with synapomorphies signifying that like humans, A. anamensis lacked the atlantoclavicularis muscle, reducing their capacity for climbing relative to the great apes. The retroflexed C2 dens and very long C6 spinous process likely reciprocate the facial prognathism, long clivus and retroflexed foramen magnum of australopiths, rather than reflecting locomotor or postural behaviors. Two thoracic vertebrae are similar to Homo in shape and size with an enlarged endplate surface associated with mitigating high verti cal loads. The full costal facet of the T1 vertebra is unlike the extant great ape demifacet pattern and represents the oldest evidence for the derived univertebral pattern in hominins. Most other A. anamensis fossils demonstrate that cranially and postcranially the taxon was more primitive than its evolutionary successor A. afarensis. However, here we find many aspects of vertebral morphology independent of allometry are more derived in A. anamensis than its putative descendant A. afarensis. These fossils offer evidence indicating habitual bipedality in A. anamensis despite some plesiomorphic features related to craniofacial morphology and further our understanding of the adaptation and evolutionary significance of A. anamensis.
... The ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, indicating that the transverse process must have projected from the dorsal pillar rather than the body. This matches the condition in genus Homo, extant great apes and extinct largebodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Filler, 2007;Susanna et al., 2014), and is unlike most extant primates including hylobatids where the transverse process emerges from the vertebral body (Slijper, 1942;Ward, 1993;Ankel-Simons, 2007;Williams and Russo, 2015). T9 vertebra The size of the ASI-VP-2/223 T9 dorsal pillar (DP Geo-Mean) is similar to that of H. sapiens, whereas the corresponding A.L. 288-1ad A. afarensis vertebra is significantly smaller (Table 12). ...
... The ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, indicating that the transverse process must have projected from the dorsal pillar rather than the body. This matches the condition in genus Homo, extant great apes and extinct largebodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Filler, 2007;Susanna et al., 2014), and is unlike most extant primates including hylobatids where the transverse process emerges from the vertebral body (Slijper, 1942;Ward, 1993;Ankel-Simons, 2007;Williams and Russo, 2015). T9 vertebra The size of the ASI-VP-2/223 T9 dorsal pillar (DP Geo-Mean) is similar to that of H. sapiens, whereas the corresponding A.L. 288-1ad A. afarensis vertebra is significantly smaller (Table 12). ...
... As in genus Homo, extant great apes and extinct large-bodied hominoids such as Hispanopithecus and Morotopithecus (MacLatchy et al., 2000;MacLatchy, 2004;Susanna et al., 2014), the ASI-VP-2/470 T1 vertebral body lacks an emergent transverse process, which is an important indication that the transverse process must have projected from the dorsal pillar (unlike most primates including hylobatids). The dorsal position of the transverse processes corresponds with a reduced area for the erector spinae relative to the more ventral position in hylobatids, cercopithecoids and most mammals. ...
Australopitheus anamensis fossils demonstrate that craniodentally and postcranially the taxon was more primitive than its evolutionary successor Australopithecus afarensis. Postcranial evidence suggests habitual bipedality combined with primitive upper limbs and an inferred significant arboreal adaptation. Here we report on A. anamensis fossils from the Assa Issie locality in Ethiopia's Middle Awash area dated to ∼4.2 Ma, constituting the oldest known Australopithecus axial remains. Because the spine is the interface between major body segments, these fossils can be informative on the adaptation, behavior and our evolutionary understanding of A. anamensis. The atlas, or first cervical vertebra (C1), is similar in size to Homo sapiens, with synapomorphies in the articular facets and transverse processes. Absence of a retroglenoid tubercle suggests that, like humans, A. anamensis lacked the atlantoclavicularis muscle, resulting in reduced capacity for climbing relative to the great apes. The retroflexed C2 odontoid process and long C6 spinous process are reciprocates of facial prognathism, a long clivus and retroflexed foramen magnum, rather than indications of locomotor or postural behaviors. The T1 is derived in shape and size as in Homo with an enlarged vertebral body epiphyseal surfaces for mitigating the high-magnitude compressive loads of full-time bipedality. The full costal facet is unlike the extant great ape demifacet pattern and represents the oldest evidence for the derived univertebral pattern in hominins. These fossils augment other lines of evidence in A. anamensis indicating habitual bipedality despite some plesiomorphic vertebral traits related to craniofacial morphology independent of locomotor or postural behaviors (i.e., a long clivus and a retroflexed foramen magnum). Yet in contrast to craniodental lines of evidence, some aspects of vertebral morphology in A. anamensis appear more derived than its descendant A. afarensis.
... Afropithecinae Afropithecids are first recorded by afropithecines, which display a primitive nasoalveolar morphology (Begun and Gülec, 1998;Brown et al., 2005;Nakatsukasa and Kunimatsu, 2009;Begun, 2015) and differ from proconsulids in craniodental features probably related to sclerocarpic feeding (Leakey and Walker, 1997;Begun, 2015;Deane, 2017). The postcranial morphology of afropithecines is less thoroughly known than that of proconsulids, but similarly indicative of a pronograde body plan (Ward, 2015), except for some postcranial remains attributed to Morotopithecus bishopi Gebo et al., 1997, which are suggestive of orthograde behaviors (Sanders and Bodenbender, 1994;Gebo et al., 1997;MacLatchy et al., 2000MacLatchy et al., , 2019MacLatchy, 2004;Nakatsukasa, 2008). This species has sometimes been recovered as a stem hominid by cladistic analyses (Young and MacLatchy, 2004), but the most recent ones recovered it as a stem hominoid more basal than (Nengo et al., 2017;Gilbert et al., 2020a) or as basal as (Rossie and Hill, 2018) Afropithecus. ...
... bishopi) a junior synonym of Afropithecus turkanensis Leakey and Leakey, 1986a(Pickford, 2002, 2021Pickford et al., 2003Pickford et al., , 2017Patel and Grossman, 2006;Harrison, 2010a;Van Couvering and Delson, 2020). Under this view, the cranial differences between the two genera (Gebo et al., 1997;MacLatchy et al., 2000;Begun, 2015;Deane, 2017) might be attributable to pathological remodeling in the holotype of M. bishopi and diagenetic deformation in that of A. turkanensis (Pickford, 2002;Pickford et al., 2017), which other authors also consider to be badly distorted (Begun, 2015). Based on the dental differences between M. bishopi and A. turkanensis pointed out by MacLatchy et al. (2019), we tentatively favor the distinction of these taxa at least to the species rank but remain skeptical about the generic distinction for several reasons. ...
Hominoids diverged from cercopithecoids during the Oligocene in Afro-Arabia, initially radiating in that continent and subsequently dispersing into Eurasia. From the Late Miocene onward, the geographic range of hominoids progressively shrank, except for hominins, which dispersed out of Africa during the Pleistocene. Although the overall picture of hominoid evolution is clear based on available fossil evidence , many uncertainties persist regarding the phylogeny and paleobiogeography of Miocene apes (nonhominin hominoids), owing to their sparse record, pervasive homoplasy, and the decimated current diversity of this group. We review Miocene ape systematics and evolution by focusing on the most parsimonious cladograms published during the last decade. First, we provide a historical account of the progress made in Miocene ape phylogeny and paleobiogeography, report an updated classification of Miocene apes, and provide a list of Miocene ape species-locality occurrences together with an analysis of their paleobiodiversity dynamics. Second, we discuss various critical issues of Miocene ape phylogeny and paleobiogeography (hylobatid and crown hominid origins, plus the relationships of Oreopithecus) in the light of the highly divergent results obtained from cladistic analyses of craniodental and postcranial characters separately. We conclude that cladistic efforts to disentangle Miocene ape phylogeny are potentially biased by a long-branch attraction problem caused by the numerous postcranial similarities shared between hylobatids and hominidsddespite the increasingly held view that they are likely ho-moplastic to a large extent, as illustrated by Sivapithecus and Pierolapithecusdand further aggravated by abundant missing data owing to incomplete preservation. Finally, we argue thatdbesides the recovery of additional fossils, the retrieval of paleoproteomic data, and a better integration between cladistics and geometric morphometricsdMiocene ape phylogenetics should take advantage of total-evidence (tip-dating) Bayesian methods of phylogenetic inference combining morphologic, molecular, and chro-nostratigraphic data. This would hopefully help ascertain whether hylobatid divergence was more basal than currently supported.
... By inference, the high NSAs observed in early fossil hominoids (approx. 135°; Morotopithecus bishopii [97], Ekembo nyanzae [32]) suggests that these animals would have had expansive hip abduction capabilities, typically associated with arboreal versatility in modern primates. This would be significant in the context of hominoid evolution because many early hominoids are interpreted as having more 'monkey-like' postcranial morphology that is inconsistent with the orthograde, forelimb-dominated behaviours characterizing all living hominoids [1]. ...
Understanding how diverse locomotor repertoires evolved in anthropoid primates is key to reconstructing the clade's evolution. Locomotor behaviour is often inferred from proximal femur morphology, yet the relationship of femoral variation to locomotor diversity is poorly understood. Extant acrobatic primates have greater ranges of hip joint mobility—particularly abduction—than those using more stereotyped locomotion, but how bony morphologies of the femur and pelvis interact to produce different locomotor abilities is unknown. We conducted hypothesis-driven path analyses via regularized structural equation modelling (SEM) to determine which morphological traits are the strongest predictors of hip abduction in anthropoid primates. Seven femoral morphological traits and two hip abduction measures were obtained from 25 primate species, split into broad locomotor and taxonomic groups. Through variable selection and fit testing techniques, insignificant predictors were removed to create the most parsimonious final models. Some morphological predictors, such as femur shaft length and neck-shaft angle, were important across models. Different trait combinations best predicted hip abduction by locomotor or taxonomic group, demonstrating group-specific linkages among morphology, mobility and behaviour. Our study illustrates the strength of SEM for identifying biologically important relationships between morphology and performance, which will have future applications for palaeobiological and biomechanical studies.
... The phenotypic morphology of bones reflects habitual movement patterns practised during life (Bock, 1965), and this relationship between movement and bone shape, is a fundamental interpretive paradigm in bioarchaeology and palaeoanthropology (Jungers and Minns, 1979;Trinkaus and Ruff, 1999;MacLatchy et al., 2000;Madar et al., 2002;Ruff 2002;Ruff et al., 2006;Boyle et al 2020). Fossil hand and foot bones are rare, but they can be 3 useful for interpreting the evolution of locomotion as they are the primary biomechanical unit to interact with the environment (reviewed e.g., in Klenerman and Wood, ' o t and Aerts, 2008;Stolwijk et al., 2013;Vereecke et al., 2008). ...
The fossil record is scarce and incomplete by nature. Animals and ecological processes devour soft tissue and important bony details over time and, when the dust settles, we are faced with a patchy record full of variation. Fossil taxa are usually defined by craniodental characteristics, so unless postcranial bones are found associated with a skull, assignment to taxon is unstable. Naming a locomotor category based on fossil bone morphology by analogy to living hominoids is not uncommon, and when no single locomotor label fits, postcrania are often described as exhibiting a “mosaic” of traits. Here, we contend that the unavoidable variation that characterises the fossil record can be described far more rigorously based on extensive work in human neurobiology and neuroanatomy, movement sciences and motor control and biomechanics research. In neurobiology, degeneracy is a natural mechanism of adaptation allowing system elements that are structurally different to perform the same function. This concept differs from redundancy as understood in engineering, where the same function is performed by identical elements. Assuming degeneracy, structurally different elements are able to produce different outputs in a range of environmental contexts, favouring ecological robusticity by enabling adaptations. Furthermore, as degeneracy extends to genome level, genetic variation is sustained, so that genes which might benefit an organism in a different environment remain part of the genome, favouring species’ evolvability.
... If precision limb landing via swinging is perhaps only a minor factor amongst hominoids (only 26% ancestrally; see Fig. 4) in determining OC, then logically, it is also perhaps similarly so for other more challenging forms of locomotion in primates more 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 generally. This low (yet non-negligible) percentage may approximate the ancestral condition for Hominoidea-in concurrence with the evidence for suspensory locomotor behavior as ancient as 20mya in fossil genus Morotopithecus (MaClatchy et al., 2000). This is in spite the existence of several non-suspensory fossil apes that emerged after the 18mya split with hylobatids-17myo Proconsul, a putative ancestor to modern chimpanzees (Ward, 1993), and 12myo Sivapithecus, a putative ancestor to orangutans (Pilbeam et al., 1990). ...
Primate vision is thought to have evolved in connection with life in the trees. However, several inter-related origins theories—those addressing possible co-evolution with size, predation, diet, daylight, locomotion, and groups—also provide reasonable explanations of their distinct cranial-visual morphology. We hypothesized that demand for high-speed arboreal grasp-landing facilitated predation avoidance thereby reducing the need for lateral facing orbits. To test this proposed influence, in the context of a likely very multi-causal adaptive landscape, we consolidated published data on extant primate species including body mass, daily path length, arboreality, insectivory, frugivory, activity period, leaping, swinging, and group size. Phylogenetically controlled regressions, on three different taxonomic subsets of the primate order, highlight size and environmental influences as the most compelling factors explaining higher orbital convergence [OC]. Moreover, activity period and group size (in anthropoids) as well as arboreality and body mass (in non-anthropoids) associated convincingly with higher OC. After considering size and path length, suspensory (and to a lesser extent leaping-based) grasp-landed locomotion co-varied with OC, primarily in anthropoids. Nocturnality had negative, and leaping mixed, associations with OC—thus, with the exception of those relating to nocturnal-locomotion, all adaptive origins theories considered were at least partially corroborated. The conflicting associations of OC with leaping, is largely attributable to the exceptionally small (and more taxonomically contentious) members of the order. But prospects otherwise remain bright for our two freshly illuminating theories of grasp-swing, in anthropoids, and rear attack risk reduction [RARR], more generally, as they provide compelling alternatives to sized based models (e.g. predation deterrence and allometric scaling) in explaining deep divisions in the primate order.
... One example of this tendency is the study of primate shoulder evolution, where researchers often focus solely on traits of the scapula. The isolation of scapular measurements as a proxy for the overall functional and evolutionary morphology of the shoulder joint has been the precedent in primate studies for nearly a century (Schultz 1930(Schultz , 1950Ashton and Oxnard 1963, 1964a, 1964bOxnard 1963Oxnard , 1967Oxnard , 1969Ashton et al. 1965;Roberts 1974;MacLatchy et al. 2000;Larson et al. 2007;Feuerriegel et al. 2017;Selby and Lovejoy 2017). However, the scapula shares functional relationships with many elements across the skeleton. ...
The scapula shares developmental and functional relationships with traits of the basicranium, vertebral column, humerus, and clavicle. As a limb girdle, it also shares analogous characteristics with the pelvis. Despite these relationships, studies of primate shoulder evolution often focus on traits of the scapula in isolation. Such analyses may lead to spurious conclusions, as they implicitly model the scapula as evolving independent of other anatomical regions. Traits of the shoulder girdle share genetic covariances with each other, as well as potential covariances with dimensions of other skeletal elements. To create accurate models of shoulder evolution, it is imperative to account for the constraints imposed by these sources of covariance. Here, we use evolutionary quantitative methods to test a model in which shoulder morphological evolution is influenced by its developmental and functional covariances with the basicranium in the Colobus genus. This evolutionary relationship is also assessed with morphology of the pelvis to provide context to the evolutionary covariance among traits of the basicranium and shoulder girdle. Our results indicate potential evolutionary implications arising from covariances among the basicranium, shoulder, and pelvis. We further propose that the shoulder and basicranium may be examples of developmental, functional, and genetic covariances among traits that manifest an evolutionary suite of mutually constrained morphologies. We demonstrate novel evolutionary relationships among the shoulder girdle and basicranium that affect not only models of primate shoulder evolution but have broader implications for modeling trait evolution across the skeleton.
... The femur of Danuvius differs from Dryopithecus, and resembles Hispanopithecus, by its more gracile neck. It further differs from Dryopithecus in a steeper neck angle (134° versus 123°, 58 ), which is comparable to Hispanopithecus (132°), Oreopithecus (135°, 59 ) Ekembo nyanzae (134°, 43 ) and Morotopithecus (135°, 60 ). Danuvius further differs from both Spanish hominids by its lower great trochanter 58 . ...
... Because all living apes exhibit the aforementioned lumbar features to some extent, the specific positional behaviors to which such features might be linked is of interest to researchers, as is the issue of whether or not the ancestral crown hominoid possessed these derived vertebral features (Keith 1923;Harrison 1986;Sarmiento 1987;Benefit and McCrossin 1995;MacLatchy et al. 2000; but see Lovejoy et al. 2009;Reno 2014;Ward 2014). Researchers have spent a considerable amount of time attempting to link the lumbar vertebral features characteristic of living hominoids to specific types of postural and locomotor behaviors, including orthogrady/ brachiation (Keith 1923;Erikson 1963;Gebo 1996), arm hanging (Hunt 1991), quadrumanous climbing and bridging and/or vertical climbing (Cartmill and Milton 1977;Jungers 1984;Sarmiento 1998;Lovejoy et al. 2009), orthograde clambering and arboreal bipedalism (i.e., bipedal walking along branches; Crompton et al. 2008), and orthograde trunk sitting during foraging and feeding (Jolly 1970;Andrews and Groves 1976), while a number of researchers have attributed anatomical features to a more general "combination" of these positional behaviors (Tuttle 1975;Tuttle and Basmajian 1978;Ward 1993). ...
The evolution of hominoids was accompanied by a transformation of the primate body plan from a monkey-like ancestral condition to one characterized by a derived suite of postcranial features. While diagnostic hominoid features are found throughout the postcranial skeleton, the trunk, and especially the lumbar region, is one of the most functionally important and immediately noticeable aspects of hominoid anatomy. Hominoids have a reduced number of lumbar vertebrae that are generally distinguished from those of their cercopithecoid close relatives with respect to dimensions of lumbar vertebral bodies and pedicles, position and orientation of transverse processes, shape and orientation of spinous processes, and orientation of zygapophyses at the thoracolumbar transition. Traditional functional interpretations emphasize that these features stiffen the lower body and limit sagittal mobility during orthogrady and/or forelimb-dominated behaviors. More recent comparative research on nonhominoid primates and other mammals support that hominoid lumbar features confer axial stability in a variety of positional behaviors, while studies of experimental biomechanics have revealed more rotational capabilities in the hominoid trunk than previously thought, and analyses of back musculature offer new information about fiber-type differences between hominoids and other primates. Multiple models concerning reconstruction of the trunk morphology and behavior of the crown hominoid ancestor, and the sequence in which aspects of the hominoid trunk evolved, have surfaced over the last decade. Given the numerous chapters in this volume devoted to human spinal morphology and adaptations to bipedalism, our discussion is focused primarily on lumbar anatomy shared by all hominoids.
... Accurate reconstruction of locomotor behavior in the fossil record is dependent upon detailed assessments of behavioralmorphological relationships among extant taxa (Day, 1979). This is true even when fossil taxa exhibit morphologies not observed among living species, including mosaic combinations or intermediate expression of traits (MacLatchy et al., 2000;Ruff, 2002). ...
... Around the same age of between 16 to 18 Ma, Afropithecus appears to have had similar locomotion adaptations to Proconsul sensu lato (Leakey et al., 1988;Ward, 1998). On the other hand, Morotopithecus were arboreal African hominoids from about 20 Ma that are considered to have relied on some orthograde positional behaviors such as forelimb suspension and climbing; however, few parts of its postcranial skeleton have been found (MacLatchy et al., 2000). Following these species, between 14 and 17 Ma, Nacholapithecus, which were hominoids that lived in the trees, may have had more developed forelimbs and engaged relatively frequently in orthograde behavior such as vertical climbing; however, no evidence has been found to suggest a suspensory specialization (Nakatsukasa, 2004). ...
Recent fossil records have suggested that human erect bipedal locomotion started in Africa probably more than 6 million years ago. However, debate continues regarding how locomotion was acquired by our prehuman ancestors. Fossils and the genetic traits of recent humans and animals cannot answer this question directly. Therefore, the present paper reviews acquisition models of human bipedalism and explanations regarding how humans acquired bipedalism based on a comparative kinesiology of contemporary mammal species. Nonhuman primates are adequate models of human bipedal acquisition because of not only the phylogenetically close relationship with humans, but also the trend toward hindlimb dominance and orthograde positional behavior in daily life. Although dissimilar to the erect bipedalism seen in humans, nonhuman primates adopt bipedal positional behavior in the wild. All nonhuman primates use the arboreal environment, but some groups of species utilize the ground predominantly. Compared with relatively terrestrial nonhuman primates, relatively arboreal primates show more similarities with humans in their bipedal locomotion. Comparisons among primate species and between nonhuman primates and nonprimate mammals indicate that human-like bipedal characteristics are strongly related to arboreal life. Our prehuman ancestors likely started and adapted to bipedal locomotion while living in trees; this process is referred to as the generalized arboreal activity model. When humans began terrestrial locomotion, they likely performed proficient bipedalism from the first step. The generalized arboreal activity model presented here does not contradict the fossil records.
In 1938, the first distal femur of a fossil Australopithecus was discovered at Sterkfontein, South Africa. A decade later, another distal femur was discovered at the same locality. These two fossil femora were the subject of a foundational paper authored by Kingsbury Heiple and Owen Lovejoy in 1971. In this paper, the authors discussed functionally relevant anatomies of these two fossil femora and noted their strong affinity to the modern human condition. Here, we update this work by including eight more fossil Australopithecus distal femora, an expanded comparative dataset, as well as additional linear measurements. Just as Heiple and Lovejoy reported a half‐century ago, we find strong overlap between modern humans and cercopithecoids, except for inferiorly flattened condyles and a high bicondylar angle, both of which characterize modern humans and Australopithecus and are directly related to striding bipedalism. All other measured aspects of the femora are by‐products of these key morphological traits. Additional fossil material from the early Pliocene will help to inform the evolution of the hominin distal femur and its condition in the Pan‐Homo common ancestor that preceded bipedal locomotion.
Theropithecus brumpti is a primate known from numerous craniodental specimens in the Plio-Pleistocene Shungura Formation (Lower Omo Valley, Ethiopia), but the anatomy of its hindlimb is documented only by a few associated and mostly incomplete postcranial specimens. The adaptations of T. brumpti are still debated, with its substrate preferences and its use of squatting postures recently discussed based on anatomical differences when compared with its extant representative, Theropithecus gelada. Here, we describe an associated femur and tibia (L 869-1 and L 869-2) of a presumed T. brumpti male and a partial foot (L 865-1r and L 865-1t) of a male T. brumpti, dated to ca. 2.6 Ma and ca. 2.32 Ma respectively. Based on univariate and bivariate morphometric analyses, we provide new data on the morphological correlates of substrate preferences and postural behaviors of this fossil species. Our results are in agreement with previous analyses and present T. brumpti as a predominantly terrestrial primate. We demonstrate the presence of osteological correlates associated with the use of squatting behaviors in T. brumpti but also point to significant anatomical differences between this paleontological species and T. gelada. These differences blur the functional value of characters previously identified as diagnostic of T. gelada and its postural behavior. We further document the postcranial distinctiveness of the Theropithecus clade in relation to the Papio clade. This study thus provides new insights into the postcranial anatomy and paleoecology of an abundant fossil primate from the Plio-Pleistocene of eastern Africa.
Our knowledge of the functional and taxonomic diversity of the fossil colobine fauna (Colobinae Jerdon, 1867) from the Lower Omo Valley is based only on craniodental remains. Here we describe postcranial specimens of fossil colobines from the Usno Formation and Shungura Formation, and provide in-depth insights into their functional anatomy and taxonomy. Comparisons with previously described fossil colobine specimens from eastern Africa led us to identify specimens similar to Paracolobus mutiwa Leakey, 1982 and Rhinocolobus turkanaensis Leakey, 1982. Our results highlight the mixed locomotor substrate preferences of Paracolobus mutiwa and add new insights regarding its locomotor behaviors by identifying anatomical characteristics of the forelimb associated with climbing. Postcranial remains reminiscent of Rhinocolobus confirm the peculiar elbow morphology of this taxon and its apparent preference for arboreal substrates. We also document femoral, humeral, and tibial specimens with arboreal traits similar in size and morphology to extant Colobus Illiger, 1811 in Member L of the Shungura Formation. By providing these new data on the colobine paleocommunity from Shungura, our results contribute to the understanding of the biotic context surrounding Plio-Pleistocene faunas of the Turkana Depression and pave the way for future ecomorphological analyses.
This study reported the body mass (BM) estimates of the Middle Miocene fossil hominoid Nacholapithecus kerioi from Africa. The average BM estimates from all forelimb and hindlimb skeletal elements was 22.7 kg, which is slightly higher than the previously reported estimate of ~22 kg. This study revealed that Nacholapithecus has a unique body proportion with an enlarged forelimb relative to a smaller hindlimb, suggesting an antipronograde posture/locomotion, which may be related to the long clavicle, robust ribs, and some hominoid-like vertebral morphology. Because the BM of Nacholapithecus in this study was estimated to be below 30 kg, Nacholapithecus probably did not have relatively shorter and robust femora, which may result from other mechanical constraints, as seen in extant African hominoids. The BM estimate of Nacholapithecus suggests that full substantial modifications of the trunk and forelimb anatomy for risk avoidance and foraging efficiency, as seen in extant great apes, would not be expected in Nacholapithecus. Because larger monkeys are less arboreal (e.g., Mandrillus sphinx or Papio spp.), and the maximum BM among extant constant arboreal cercopithecoids is ~24 kg (male Nasalis larvatus), Nacholapithecus would be a constant arboreal primate. Although caution should be applied because of targeting only males in this study, arboreal quadrupedalism with upright posture and occasional antipronograde locomotion (e.g., climbing, chambering, descending, arm-swing, and sway) using the powerful grasping capacity of the hand and foot may be assumed for positional behavior of Nacholapithecus.
Since the first discovery of human fossils in the mid‐19th century, two subjects—our phylogenetic relationship to living and fossil apes and the ancestral locomotor behaviors preceding bipedalism—have driven the majority of discourse in the study of human origins. With few fossils and thus limited comparative evidence available to inform or constrain them, morphologists of the 19th and early mid‐20th centuries posited a range of scenarios for the evolution of bipedalism. In contrast, there exists a rich hominin fossil record and the acceptance of Pan (chimpanzees and bonobos) as our closest living relatives is nearly universal, yet consensus about the ancestral condition from which hominins evolved remains elusive. Notably, while the earliest known hominins are generally congruent with parsimonious inferences of an African ape‐like last common ancestor, our more distantly related Miocene ape cousins are frequently invoked as evidence in favor of more complex scenarios that require substantial homoplasy. Debate over these alternatives suggests that how we infer ancestral nodes and weigh evidence to test their relative likelihoods remains a stumbling block. Here we argue that a key contributor to this impasse includes the history of terminology associated with positional behavior, which has become confused over the last century. We aim to clarify positional behavior concepts and contextualize knuckle‐walking and other forms of posture and locomotion chimpanzees and gorillas engage in, while arguing that the presence of homoplasy in ape evolution does not alter the weight of evidence in favor of an African ape‐like evolutionary history of hominins.
The hominins diverged from other hominoids during the Miocene. This epoch holds clues to the time, place, and circumstances of our origin, but the search for that information offered surprises. Ape species proved to be far abundant than expected and discerning the first hominins amid the variety of forms is more challenging than expected. Traits thought to be uniquely human, including bipedalism, turned out to have evolved in parallel many times. The molecular clock allows us to use genetic comparisons to establish splitting times independently of the fossil record. Three genera, thought to be early hominins are described from the Late Miocene of Africa. This is still too meager a sample to answer our larger questions.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
Within the primate order, the morphology of the shoulder girdle is immensely variable and has been shown to reflect the functional demands of the upper limb. The observed morphological variation among extant primate taxa consequently has been hypothesized to be driven by selection for different functional demands. Evolutionary analyses of the shoulder girdle often assess this anatomical region, and its traits, individually, therefore implicitly assuming independent evolution of the shoulder girdle. However, the primate shoulder girdle has developmental and functional covariances with the basicranium and pelvic girdle that have been shown to potentially influence its evolution. It is unknown whether these relationships are similar or even present across primate taxa, and how they may affect morphological variation among primates. This study evaluates the strength of covariance and evolutionary potential across four anatomical regions: shoulder girdle, basicranium, pelvis, and distal humerus. Measures of morphological integration and evolutionary potential (conditioned covariance and evolutionary flexibility) are assessed across eight anthropoid primate taxa. Results demonstrate a consistent pattern of morphological constraint within paired anatomical regions across primates. Differences in evolutionary flexibility are observed among primate genera, with humans having the highest evolutionary potential overall. This pattern does not follow functional differences, but rather a separation between monkeys and apes. Therefore, evolutionary hypotheses of primate shoulder girdle morphological variation that evaluate functional demands alone may not account for the effect of these relationships. Collectively, our findings suggest differences in genetic covariance among anatomical regions may have contributed to the observable morphological variation among taxa.
Oreopithecus bambolii (8.3–6.7 million years old) is the latest known hominoid from Europe, dating to approximately the divergence time of the Pan -hominin lineages. Despite being the most complete nonhominin hominoid in the fossil record, the O. bambolii skeleton IGF 11778 has been, for decades, at the center of intense debate regarding the species’ locomotor behavior, phylogenetic position, insular paleoenvironment, and utility as a model for early hominin anatomy. Here we investigate features of the IGF 11778 pelvis and lumbar region based on torso preparations and supplemented by other O. bambolii material. We correct several crucial interpretations relating to the IGF 11778 anterior inferior iliac spine and lumbar vertebrae structure and identifications. We find that features of the early hominin Ardipithecus ramidus torso that are argued to have permitted both lordosis and pelvic stabilization during upright walking are not present in O. bambolii . However, O. bambolii also lacks the complete reorganization for torso stiffness seen in extant great apes (i.e., living members of the Hominidae), and is more similar to large hylobatids in certain aspects of torso form. We discuss the major implications of the O. bambolii lower torso anatomy and how O. bambolii informs scenarios of hominoid evolution.
Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old World monkeys, and their extinct relatives). However, locomotor diversity within this group has eluded characterization, bolstering a narrative that nearly all early catarrhines shared a primitive locomotor repertoire resembling that of the well-described arboreal quadruped Ekembo heseloni. Here we describe and analyse seven catarrhine capitates from the Tinderet Miocene sequence of Kenya, dated to ~20 Ma. 3D morphometrics derived from these specimens and a sample of extant and fossil capitates are subjected to a series of multivariate comparisons, with results suggesting a variety of locomotor repertoires were present in this early Miocene setting. One of the fossil specimens is uniquely derived among early and middle Miocene capitates, representing the earliest known instance of great ape-like wrist morphology and supporting the presence of a behaviourally advanced ape at Songhor. We suggest Rangwapithecus as this catarrhine’s identity, and posit expression of derived, ape-like features as a criterion for distinguishing this taxon from Proconsul africanus. We also introduce a procedure for quantitative estimation of locomotor diversity and find the Tinderet sample to equal or exceed large extant catarrhine groups in this metric, demonstrating greater functional diversity among early catarrhines than previously recognised.
Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old World monkeys, and their extinct relatives). However, locomotor diversity within this group has eluded characterization, bolstering a narrative that nearly all early catarrhines shared a primitive locomotor repertoire resembling that of the well-described arboreal quadruped Ekembo heseloni. Here we describe and analyse seven catarrhine capitates from the Tinderet Miocene sequence of Kenya, dated to ~20 Ma. 3D morphometrics derived from these specimens and a sample of extant and fossil capitates are subjected to a series of multivariate comparisons, with results suggesting a variety of locomotor repertoires were present in this early Miocene setting. One of the fossil specimens is uniquely derived among early and middle Miocene capitates, representing the earliest known instance of great ape-like wrist morphology and supporting the presence of a behaviourally advanced ape at Songhor. We suggest Rangwapithecus as this catarrhine’s identity, and posit expression of derived, ape-like features as a criterion for distinguishing this taxon from Proconsul africanus. We also introduce a procedure for quantitative estimation of locomotor diversity and find the Tinderet sample to equal or exceed large extant catarrhine groups in this metric, demonstrating greater functional diversity among early catarrhines than previously recognised.
Cambridge Core - Neurology and Clinical Neuroscience - Assembly of the Executive Mind - by Michael W. Hoffmann
The phylogenetic status of Oreopithecus bambolii from the late Miocene of Italy has been a source of much debate since the species was first described in 1872. This observation in itself is hardly surprising, since most fossil primates known since the end of the last century have acquired a complicated history of ideas on their taxonomic and phylogenetic placement. What is so unusual about Oreopithecus,however, is that this debate has continued to the present,
This chapter is dedicated to the memory of Johannes Hürzeler (1908–1995) whose profoundly important contribution to the study of Oreopithecus and the Baccinello faunas has influenced both of us to follow the same path. The “keeper of the abominable coalman” may no longer be with us, but his remarkable discoveries will undoubtedly continue to inspire and excite the imagination of future generations of vertebrate paleontologists.
and there are no indications from the current literature that its phylogenetic status is close to being resolved (e.g., Delson, 1988; Harrison, 1991; Andrews, 1992; Begun, 1994). The problem is especially perplexing because Oreopithecus is one of the best-known fossil primates. It is easy to comprehend how researchers might have difficulties establishing the relationships of fossil taxa based on one or two isolated teeth or just a few jaw fragments, but Oreopithecus is known from an almost complete subadult skeleton, several partial skeletons, and dozens of relatively complete mandibles and crania. We find ourselves, therefore, in the uncomfortable position of not being able to rely on the excuse favored by most paleontologists in this situation, that the solution to the problem lies in finding more and better material. In the case of Oreopithecus we have all the material we need; the shortcomings are not in the available evidence, but in the way that we view it. So why is it that several generations of primate paleontologists have failed to agree on the evolutionary status of Oreopithecus? A review of the literature clearly shows that part of the problem is as much sociological as it is scientific, involving a complex interplay of different philosophies, politics, and personalities that are difficult to tease apart from the purely empirical evidence. The consequence of these and other contributing factors is that Oreopithecus is perceived to be an “enigmatic anthropoid” (Delson, 1987), one that does not readily conform to our expectations of extinct hominioids based on other lines of evidence. However, is it really that Oreopithecus represents a piece of the puzzle that does not fit, or is it simply because the limitations that we impose on our expectations of hominoid evolution are too narrow, and that Oreopithecus is being made to fit the wrong puzzle altogether? We suspect that it is the latter that represents the crux of the Oreopithecus problem. Of the various factors that have served to confound recent attempts to resolve the phylogenetic relations of
Oreopithecus, three can be identified that we believe have had a particularly profound impact.
The preceding chapters of this volume have described a number of different approaches and solutions to the interpretation of hominoid evolutionary history. Given the breadth of approaches, it is difficult to compare results among researchers. Despite this diversity, however, there seems to be broad agreement on many issues in the complex evolutionary history of the Hominoidea.
Arboreal and semiterrestrial guenons show similar osteological features of the limbs across a wide range of species, environments, and geography, while the more terrestrially committed guenons exhibit greater morphological divergence. An ecomorphological comparison of two sympatric guenons living in Kibale Forest, Uganda, reveals an array of anatomical adaptations for terrestriality in the limbs of Cercopithecus lhoesti similar to those found in Erythrocebus patas. In contrast, Cercopithecus aethiops, although also frequent users of the terrestrial environment, generally exhibit fewer morphological adaptations characteristic of a terrestrial lifestyle. It appears that significant morphological modification for terrestriality has occurred twice within the diverse radiation of living guenons with C. aethiops perhaps representing a third group in the making. © 1994 Wiley-Liss, Inc.
Twenty nine post cranial specimens of a Kenyapithecus species, discovered at Nachola during the field seasons 1984 and 1986, are described in detail. The specimens come from baboon-sized animals, with a baboon-like degree of sexual dimorphism in size. This species of Kenyapithecus was a predominantly arboreal animal, utilizing a combination of pronograde quadrupedalism and orthograde climbing and clambering activities. Postcranially it most resembles Proconsul, but it is a slightly more drived hominoid.
Historical Remarks Bearing on the Discovery of Pan paniscus Whether by accident or by design, it was most fortunate that Robert M. Yerkes, the dean of American primatologists, should have been the first scientist to describe the characteristics of a pygmy chimpanzee, which he acquired in August 1923, when he purchased him and a young female companion from a dealer in New York. The chimpanzees came from somewhere in the eastern region of the Belgian Congo and Yerkes esti mated the male's age at about 4 years. He called this young male Prince Chim (and named his female, com mon chimpanzee counterpart Panzee) (Fig. I). In his popular book, Almost Human, Yerkes (1925) states that in all his experiences as a student of animal behavior, "I have never met an animal the equal of this young chimp . . . in approach to physical perfection, alertness, adaptability, and agreeableness of disposition" (Yerkes, 1925, p. 244). Moreover, It would not be easy to find two infants more markedly different in bodily traits, temperament, intelligence, vocalization and their varied expressions in action, than Chim and Panzee. Here are just a few points of contrast. His eyes were black and in his dark face lacked contrast and seemed beady, cold, expressionless. Hers were brown, soft, and full of emotional value, chiefly because of their color and the contrast with her light complexion.
Many distinctive synapomorphies of modern apes (and humans) are found in the postcranial skeleton. These characters reflect a basic adaptation, variably developed and practiced among modern species, to forelimb-dominated arboreal locomotion, including climbing, brachiation, and/or forelimb suspension (e.g., Cartmill and Milton, 1977; Fleagle et al., 1981; Hunt, 1992; Keith, 1923; Stern, 1971; Stern et al., 1977). The morphological pattern shared by modern hominoids has led to the general assumption that locomotor divergence was an initial hallmark of the hominoid lineage, setting them apart from their monkey-like forbears. As more is learned about the earliest hominoids, however, paleontologists realize that not all apes share a similar pattern of postcranial anatomy and locomotor behavior, and that the suite of features seen in extant apes evolved in a mosaic fashion over the course of hominoid evolutionary history (reviews and references in Begun et al., 1997a).
The African apes represent a group of closely related primate taxa that differ substantially in adult body size. The close phylogenetic affinity of pygmy chimpanzees (Pan paniscus), common chimpanzees (Pan troglodytes), and gorillas (Gorilla gorilla) is affirmed by both molecular and morphological data. Most biomolecular studies to date, however, have been unable to resolve the chimpanzee-gorilla-human trichotomy into a definitive chimpanzee-gorilla clade that would have humans as a sister group (e.g., Sarich, 1968, and this volume; Zihlman et al., 1978; Bruce and Ayala, 1979; Goodman, 1982). The evolutionary tree for humans and pongids based on cleavage maps of mitochondrial DNA (Ferris et al., 1981; Templeton, 1983) is a notable exception in this regard; these data first group pygmy and common chimpanzees into a phyletic unit that is linked next to gorillas. Humans are then joined to the African ape clade before the orangutan (Pongo pygmaeus). A variety of shared, unique features of the karyotypes of African apes lend strong credence to this phylogeny (Mai, 1983). Morphological analyses of the teeth and locomotor skeletons of pongids and humans [summarized in Ciochon (1983)] also corroborate the Ferris et al. branching sequence.
It is not the purpose of this chapter to provide definitive answers to any of the questions asked in its title, even though various aspects of these questions have formed a large part of the lively debate that has been conducted in recent years concerning Miocene hominoid postcrania. The material available for investigation has been increased significantly recently by new specimens from the early Miocene of East Africa [KNM-RU 2036C and KNM-RU 5872 specimens (Walker and Pickford, this volume, Chapter 12)], the later Miocene of Rudabánya, Hungary [Rud specimens (Morbeck, this volume, Chapter 14)], and the Potwar Plateau of Pakistan [most GSP specimens (Pilbeam et al., 1980)]. The main purpose of this chapter is to make some general comments on functional features of the morphology of some Miocene hominoid postcrania and on possible positional capabilities consistent with those features. Similarities to and differences from features of Miocene species evident in the postcrania of groups of living higher primates will be made purely in terms of function. Attention will be directed toward the larger bodied Miocene hominoids. Original specimens of all the East African and Asian material have been examined. The European material has been examined in cast form.
A renaissance of comparative primatological studies occurred during the past 15 years. It flourishes unabated. It is characterized by intensive focuses on function and inferential phylogenies and a dazzling battery of new and refurbished gadgetry and methods ranging from electromyography and cineradiography to computers and multivariate statistics for many seasons. This, coupled with an outpouring of information on the behavior of captive and free-ranging primates, their biomolecular particularities, and a remarkable number of new fossils, promises to elucidate aspects of some primate careers in a refreshingly solid note. Hopefully man will be among this newly illuminated lot.
Our understanding of early Miocene hominoid postcranial material has been built upon a fossil record that consists, for the most part, of unassociated fragments of different individuals from different sites. Although many skeletal parts have been known from small to large Proconsul species, major problems have arisen due to lack of knowledge of limb proportions and to difficulties in assigning postcrania to species based on teeth and jaws. Because of this our viewpoint has been heavily biased by interpretations based on the associated partial skeleton of P. africanus (Napier and Davis, 1959). Recently two things happened to change this situation. The first was the recognition that more parts of the associated skeleton, KNM-RU 2036, were still in blocks of matrix in the National Museums of Kenya and that more are likely still to be on the site, locality R114, Rusinga Island. This has led to the recognition of many more parts of this individual and their preparation from their matrix. Importantly, much of the hindlimb skeleton is now known. The second was the finding of the major part of an associated foot and leg skeleton that can be reasonably attributed to P. nyanzae at site R1–3, Rusinga Island. These new finds allow us to do several things:
1.
The limb proportions of P. africanus can be almost perfectly calculated for one individual.
2.
The estimate of body weight for this individual is now on a much sounder foundation than before.
3.
The hypotheses concerning locomotor adaptations that were based on the forelimb can now be checked against the hindlimb.
4.
The body weight of P. nyanzae can be estimated, based on the size of the leg and foot skeleton and other reasonably attributed parts.
5.
Comparisons can be made between the two species.
The genus Afropithecus Leakey & Leakey, 1986 contains fossil large hominoids probably of a single species, A. turkanensis, from four early Miocene sites east and west of Lake Turkana, Kenya. The type (KNM-WK 16999) is a palate, facial skeleton, and anterior part of the cranium of an adult, presumed male, individual. Apart from the type, there are many specimens of upper and lower teeth and several postcranial elements. Nearly all of these have now been described (Leakey and Leakey, 1986; Leakey et al., 1988; Leakey and Walker, 1985). There have been several discussions about the relationships of this genus and the tribe Afropithecini has been named for it together with Heliopithecus and Otavipithecus (Andrews, 1992). Not much has been written about the postcranial anatomy, but it has been favorably compared with Proconsul nyanzae (Leakey et al., 1988) and several functional analyses indicate that P. nyanzae was an arboreal, relatively slow-moving quadruped (Ward et al., 1993). It is likely that Afropithecus, like Proconsul, had a postcranial skeleton that is very close to the primitive hominoid condition.
The genus Proconsul was recognized over 60 years ago as the first Miocene anthropoid from sub-Saharan Africa (Hopwood, 1933). The collections of Proconsul fossils have grown steadily since then, so that it is now probably the best-known Miocene primate. We have hundreds of fossils of several species from many localities in Kenya and Uganda. Nearly every body part is now represented and much is known about sexual dimorphism, body proportions, growth and development, and paleoecology. Because of this, the functional anatomy of the genus is relatively well known.
A new genus and species, Nacholapithecus kerioi have been erected for the large-bodied Miocene hominoid specimens discovered from Nachola, Kenya.
This paper presents a review of the evolutionary relationships of the early catarrhine primates. The first stage of the analysis involves the reconstruction of the inferred ancestral morphotypes of the major groups of extant anthropoids. The introduction of the fossil taxa into the phylogenetic scheme represents the second and final stage of the analysis. The results of this cladistic analysis suggests that: (1) the parapithecids are a specialized group of basal anthropoids, (2) Oligopithecus savagei may represent the earliest recognizable catarrhine, (3) Propliopithecus (= Aegvptopithecus) and Pliopithecus apparently represent the successive sister taxa to the modern catarrhines, (4) Dendropithecus and Proconsul are best regarded as basal catarrhines of modern aspect, and (5) Victoriapithecus is a primitive cercopithecoid monkey which represents the siter taxon of the extant Old World monkeys.
Use of linear techniques to represent complex shapes has constrained morphological studies of the hip joint, with the result that functionally significant features have remained unquantified. This study uses a linear least squares sphere fit to the femoral head and acetabular subchondral bone as a framework for mapping the distribution of articular surface on the joint components of several extant anthropoids. The distribution of acetabular articular surface is believed to be related to mobility and the loading environment of the joint. Low dorsal and caudal lunate surfaces inPongopermit a wide range of abduction, while an extensive cranial lunate surface implies substantial cranial loading. The acetabula of pronograde monkeys has a uniform distribution of articular surface, presumably because the hip socket is loaded from cranial, dorsal and caudal directions.Panhas neither as much cranial lunate surface asPongo, nor as much dorsal lunate surface as the monkeys, suggesting a heterogeneous loading environment that may be a consequence of frequently using both orthograde and pronograde postures. The monkeys have a preponderance of articular surface on the anterior aspect of the femoral head, reflecting a greater emphasis on adducted, medially oriented postures and excursions than inPan.Evidence from the femur, and in the case ofProconsul, the acetabulum, was integrated with other data to reconstruct hip mobility and relate it to suspensory behavior in Miocene hominoids. Femoral articular configurations suggest that most Miocene hominoids had mobile hip joints, which would have facilitated climbing and hindlimb suspension, however, available humeral material does not support a similar mobility in the shoulder. The exception to this pattern are the fossil remains from Moroto, which combine a monkey-like hip, compatible with quadrupedal hip use, with a back that suggests orthograde adaptations.
The term quadrupedalism refers both to a locomotor mode involving the use of all four limbs to move on horizontal substrates and to a locomotor repertoire dominated by the locomotor mode of quadrupedalism. Among extant primates there are numerous types of quadrupedal repertoires and modes, only some of which have been well characterized in terms of their functional morphology. Most Miocene catarrhines are only known from fragmentary postcranial specimens, and do not closely resemble particular anthropoid taxa. Thus, their possible quadrupedalism can only be characterized in a fairly general way. Much of the postcranial skeleton is known for the hominoid Proconsul. Limb proportions and the detailed morphology of the trunk and limbs indicate a locomotor repertoire dominated by quadrupedalism. Proconsul's quadrupedal mode involved palmigrade hand placement, and fairly eclectic movement at the limb joints. Variations on this type of quadrupedal mode are likely for the hominoids Kenyapithecus, Dryopithecus, and Sivapithecus, although other components of the locomotor repertoire are likely to have been more strongly expressed in these genera. The primitive catarrhine Pliopithecus differs from Proconsul in having more gracile limbs and relatively longer forelimbs. These atelid-like features suggest a stronger representation of suspension and climbing in the locomotor repertoire. However, as in Proconsul, there are many features indicating the primacy of quadrupedalism. The primitive catarrhine Dendropithecus and its close relatives resemble Pliopithecus in many aspects of their locomotor morphology. The hominoid Oreopithecus differs from all the other Miocene taxa in having a Pongo -like locomotor repertoire dominated by climbing and suspension, but probably with a minor quadrupedal component. Oreopithecus apart, the known Miocene catarrhines are predominantly quadrupedal animals. This fact must be incorporated into any attempt to chart the emergence of the locomotor specializations of extant hominoids.
The criteria traditionally used to distinguish between species of Proconsul have been largely size-related and based primarily on the dentition. We present here new estimates of body mass for seven Proconsul from early Miocene (17·8 mybp) sites on Rusinga and Mfangano Islands, Kenya, derived from cross-sectional diaphyseal and articular dimensions of the femur, structural features that bear a close functional relationship to body mass in living species. The fossil specimens cluster into two major groups: one at just over 9 kg (including the well-known KNM-RU 2036), and the other between about 26 and 38 kg. Since a 3:1 to 4:1 body mass ratio between males and females of the same species is unknown among living primates or indeed land mammals, it seems most probable, contrary to some recent hypotheses, that at least two species of Proconsul are represented at these sites—the larger P. nyanzae and the smaller a new species formerly identified as P. africanus. The P. nyanzae specimens can be further divided into subgroups of about 35–38 kg and 26–28 kg, which may represent males and females of this species. In terms of size and general proportions, the P. nyanzae femora are most similar to those of pygmy chimpanzees, while the smaller Proconsul femora are similar to those of some living cercopithecines. The P. nyanzae femora also show evidence of a relatively mobile (ape-like) hip joint. However, in certain respects the general hindlimb bone proportions of the largest living cercopithecines and smallest great apes are similar, overlapping within the body size range of P. nyanzae, i.e., near 30 kg. The relatively shorter and thus more robust appearing femora of the larger living African apes may be a result of mechanical constraints associated with climbing in an anthropoid with a body mass significantly above this size range.
Tertiary climatic oscillations initiated the origin of anthropoid primates. A paleoecological model of anthropoid evolution is presented which assumes increasing global seasonality in the late Eocene. Size changes are effected to stabilize internal temperature fluctuations under cooler climatic conditions. Because larger body size is associated with diurnality and reduced litter size, these anthropoid behavoral and reproductive features also fit into the model. Dietary changes involving an emphasis on frugivory, which becomes a more predictable dietary mode under seasonal conditions, can be associated with the development of a post-orbital septum, a broad mesiodistal incisal span, the evolution of color vision, reduction of the olfactory bulbs, and the concomitant enlargement of areas of the brain relating to the processing of visual information. Finally, postural behavior or locomotion might be included in this model if frugivorous foraging and feeding behavior led to the development of a basic level of anthropoid locomotor morphology, involving adaptations for arboreal quadrupedalism.
Observational data were collected on the positional behavior of habituated adult female orangutans in the rain forest of the Kutai National Park, East Kalimantan, Indonesia. Results revealed the following about locomotion during travel: movement was concentrated in the understory and lower main canopy; and brachiation (without grasping by the feet) accounted for 11% of travel distance, quadrupedalism for 12%, vertical climbing for 18%, tree-swaying for 7%, and clambering for 51%. In climbing and clambering, the animal was orthograde and employed forelimb suspension with a mixture of hindlimb suspension and support. Thus suspension by the forelimbs occurred in at least 80% of travel. Locomotion in feeding trees resembled that during travel but with more climbing and less brachiation. Feeding was distributed more evenly among canopy levels than was travel, and use of postures (by time) included sitting 50%, suspension with the body vertical 11%, and suspension by hand and foot with the body horizontal 36%. The traditional explanation of the evolution of the distinctive hominoid postcranium stresses brachiation. More recently it has been proposed that climbing, broadly defined and partly equivalent to clambering in this study, is the most significant behavior selecting for morphology. The biomechanical similarity of brachiation and the orthograde clambering of orangutans precludes the present results from resolving the issue for the evolution of Pongo. The orangutan is by far the largest mammal that travels in forest canopy, and a consideration of the ways that its positional behavior solves problems posed by habitat structure, particularly the tapering of branches and gaps between trees, indicates that suspensory capacities have been essential in permitting the evolution and maintenance of its great body size.
Living Old World monkeys (OWM) and apes diverged from a common ancestral state during the Miocene in diametrically opposite ways: OWM evolved bilophodont molar dentition, and apes evolved specialized postcrania that enhanced capacities for suspension and propulsion by the forelimbs. During the evolution of OWM there was probably a selective premium on increasing energy gain from low quality food items. During the evolution of the apes there was a selective premium on reducing time expenditures in food harvest and travel such that animals were able to visit more food patches in a given interval of time. The immediate ancestors of the first OWM and apes of modern aspect were probably medium-sized arboreal frugivores with largely quadrupedal locomotor repertoires. The contrasting adaptive solutions exhibited by the 2 taxa would thus have been produced by different responses to analogous environmental circumstances, reduction in fruit abundance. Monkeys and apes currently overlap completely in dietary composition. Remaining contrasts in foraging strategies may lie in differences in the spatio-temporal distribution and patch sizes of food sources, with apes exploiting patchier resources.-from Authors
Recent Miocene fossil discoveries of large hominoids resemble orangutans. Since the evolution of large body size was functionally related to a powerful masticatory system in Miocene ape radiations, a better understanding of adaptations in extant orangutans will be informative of hominoid evolution. It is suggested here, based on the behavioral ecology of extant orangutans, that foraging energetics and large body size are tied to a dietary shift that provided access to and utilization of resources not generally available to other primates.
Field observations of two sympatric pitheciine species reveal that the positional repertoire of the white-faced saki, Pithecia pithecia, is dominated by leaping behaviors, whereas the bearded saki, Chiropotes satanas, is predominantly quadrupedal. Examination and comparison of the postcranial skeletal morphologies and limb proportions of these species display numerous features associated with their respective locomotor behaviors. These observations accord with associations found in other primate and mammalian groups and with predictions based on theoretical and experimental biomechanics. Preliminary observations of the skeletal morphology of Cacajao calvus demonstrate a marked similarity to that of Chiropotes. The fossil platyrrhine Cebupithecia sarmientoi displays greater similarity to Pithecia, suggesting that its positional repertoire also included significant leaping and clinging behaviors.
Postcranial specimens of Simiolus enjiessi and related taxa from the Lake Turkana region of Kenya are described. These specimens come from the early Miocene sites of Buluk, Kalodirr, and Moruorot. The specimens include 13 limb bones and one vertebra. Where comparisons are possible, the Simiolus material is quite similar to that of the other East African Miocene genera, Dendropithecus, Kalepithecus, Limnopithecus, and Micropithecus. These taxa share no derived features with extant hominoids and are best considered as primitive, non-cercopithecoid, non-hominoid catarrhines. The functional features of their postcrania are not closely similar to those of other Miocene catarrhines or of any extant anthropoids. The majority of postcranial features resemble those of generalized platyrrhines. These together with some specialized features, particularly of the humeroradial joint, point to the importance of arboreal quadrupedalism in the positional repertoire. The relative length of the long bones, together with specific features, especially of the humerus and femur, also indicate a suspensory capability, possibly expressed in postural activities and bridging behavior.
In lorisines (Loris, Nycticebus, Perodicticus, Arctocebus), the tip of the ulna is reduced to the dimensions of a styloid process, a new and more proximal ulnar head is developed, and the pisiform is displaced distally away from its primitive contact with the ulna. In someNycticebus, intra-articular tissues separate the ulna from the triquetrum. These traits are not seen in other quadrupedal primates, but they are characteristic of extant hominoids. Among hominoids, these features have been interpreted as adaptations to arm-swinging locomotion. Since hominoid-like features of the wrist joint are found in lorisines, but not in New World monkeys that practice arm-swinging locomotion, these features may have been evolved in both lorisines and large hominoids to enhance wrist mobility for cautious arboreal locomotion involving little or no leaping. Most of the other morphological traits characteristic of modern hominoids can be explained as adaptations to cautious quadrupedalism as well as to brachiation, and may have developed for different reasons in different lineages descended from an unspecialized cautious quadruped resembling Alouatta.
The scaling of hindlimb articular surface dimensions with body mass is investigated in Pan, Gorilla, Pongo, Macaca fascicularis, and, for the femoral head, two population samples of recent Homo sapiens sapiens. Articular dimensions scale very strongly with body mass within pongids at close to isometry. Body mass can be estimated relatively precisely given the appropriate reference group, with femoral head dimensions giving the best estimates. Several deviations from general scaling trends are also present and have functional implications. Positive allometry of the medial femoral condyle, and thus condyle asymmetry, is shown to be related to degree of varus (bowleggedness) of the knee, most marked in gorillas and declining in the smaller pongids and macaques. Macaques show somewhat smaller hindlimb articulations for their body mass, while modern humans have large femoral heads relative to body mass. Relative to diaphyseal cross-sectional dimensions (Ruff, 1987), orangutans and modern humans have large articulations and macaques small articulations. These proportional differences are explained in terms of differences between species in joint excursion, mode of locomotion, and activity level. Orangutans load their hind limbs less than other pongids due to more pronounced forelimb suspensory behavior and thus have less robust diaphyses, but maintain relatively large articulations to allow greater joint excursion, particularly hip abduction. Relatively smaller hindlimb articulations in macaques may be linked to reduced joint mobility relative to pongids. Modern humans, due to their bipedality, load the lower limb more than quadrupedal primates and thus have relatively large joints, but shaft dimensions remain smaller than expected, possibly at least partly because of lower activity levels. Within recent humans, femoral head dimensions are highly positively allometric. Because of this, femoral head size in two relatively complete early hominids (AL 288-1 and KNM-WT 15000) is approximately at or above what would be predicted for hominids of their respective body masses.
The available femora of lower and middle Pleistocene hominines were examined osteometrically and radiographically. This fossil sample was compared with samples of Romano-British and Bushmen femora. The results showed distinctive internal and external morphological patterns in the Homo erectus group. This pattern consisted, in part, of very thick cortical bone, narrow AP shaft diameters and a low point of minimum shaft breadth. Where preserved, the trabeculae of the medial femoral neck showed a distinctive diffuse pattern. The Trinil femora showed a basically sapient pattern although they demonstrated thickened cortical bone in the distal shaft. The restricted distribution of this thickened cortex suggests that it may not be homologous with the generally thickened cortex seen in Homo erectus. Several hypotheses are proposed to explain the thickened cortex in Homo erectus.
Dissertation (Ph. D.)--University College London, 1982. Includes bibliographical references. Photocopy.
Thesis (Ph. D.)--Johns Hopkins University, 1994. Includes vita. Bibliography: leaves 363-396. Microfilm.
Fossil hominoid remains from the Miocene site of Moroto II include a well preserved lumbar vertebra (UMP 67-28). This vertebra is associated with a palate that has been included in the hominoid tribe Afropithecini and referred by some to Afropithecus. UMP 67-28 originally was described as having close morphological affinities with lumbar vertebrae from African apes and humans (Walker & Rose, 1968). The present analysis, however, indicates that UMP 67-28 shares no exclusive proportional or structural similarities with lumbar vertebrae from any particular extant catarrhine. The Moroto vertebra is the size of lumbar elements from female chimpanzees and orang-utans or large male cercopithecoids. Regression analysis of vertebral body surface area suggests that the individual represented by UMP 67-28 had a body weight of approximately 38 kg. UMP 67-28 is similar to large-bodied hominoids in general, in position and orientation of its transverse process, absence of anapophyses, inclination of its neural spine, and pedicular shape, marking the earliest appearance in the catarrhine fossil record of lumbar morphology resembling that of modern hominoids. Conversely, vertebral body proportions in UMP 67-28 most closely resemble those in male baboons, and in other traits the specimen cannot be differentiated between hominoids and cercopithecoids. The overall morphology of UMP 67-28 indicates that lumbar vertebrae of the Moroto hominoid were mole derived toward the great ape condition than those of Proconsul heseloni and P. nyanzae. In contrast to Proconsul, UMP 67-28 shares features with other dorsostable-backed mammals, suggesting that the Moroto hominoid and Proconsul possessed very different locomotor capabilities. Dental traits linking the Moroto hominoid with other afropithecins are thought to correspond functionally to a fundamental shift in diet, relative to the primitive catarrhine condition. It is possible that evolution of the lumbar region of early hominoids toward the morphotype of extant large-bodied hominoids, evidenced in UMP 67-28, was adaptively driven by modifications in substrate use coincident with changes in resource acquisition. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/31743/1/0000682.pdf