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Broken Fingers: Retesting Locomotor Hypotheses for Fossil Hominoids Using Fragmentary Proximal Phalanges and High-Resolution Polynomial Curve Fitting (HR-PCF)
Abstract
Phalangeal curvature has frequently been used as a proxy indicator of fossil hominoid and hominin positional behavior and locomotor adaptations, both independently and within the context of broader discussions of the postcranium as a whole. This study used high-resolution polynomial curve fitting (HR-PCF) to measure the shaft curvature of fragmentary proximal phalanges that have previously been excluded from analyses of phalangeal curvature owing to design limitations of existing methods. In doing so, the available sample of fossil specimens was increased substantially, making it possible to test prevailing locomotor hypotheses for many taxa with new specimens. The results generated from the HR-PCF analysis of extant primate manual and pedal phalangeal samples suggest that, although capable of identifying suspensory hominoids with some degree of accuracy, phalangeal curvature values reported for extant terrestrial and arboreal quadrupeds overlap considerably. Consequently, it is difficult to reliably predict the locomotor adaptations for fossil taxa with phalangeal curvatures similar to these groups, although the curvature values reported for most taxa were broadly consistent with existing locomotor hypotheses. Only the curvature values reported for Pierolapithecus, which are most similar to those of suspensory hominoids, are inconsistent with previously published locomotor hypotheses. Likewise, although not inconsistent with bipedality, curvature values reported for Australopithecus confirm earlier conclusions that, despite a general reduction in phalangeal length relative to Pan, these taxa have similar and overlapping ranges of phalangeal curvature.
... For example, proximal phalanges vary greatly within and among extant primate taxa in terms of how curved the shafts are (hereafter referred to as phalangeal curvature; Figure 1). Highly suspensory primates (e.g., Pongo, Hylobates, Symphalangus, and Ateles) have very curved proximal phalanx shafts (i.e., high phalangeal curvatures), whereas habitually terrestrial pronograde species (e.g., Gorilla and Papio) along with bipeds (i.e., humans) have straighter shafts (i.e., low phalangeal curvatures) (e.g., Deane & Begun, 2008;Rein, 2011;Stern et al., 1995). Primates that are more generalist in their substrate preference (e.g., Pan and Macaca) tend to have phalangeal curvature that is intermediate or more variable in grade compared with these two extremes (e.g., Jungers et al., 1997). ...
... The resulting a coefficient (or quadratic coefficient) is then used as a proxy metric for curvature where a larger a value is equivalent to a narrower parabola and signifies a more curved bone. In general, this method can distinguish extant species based on habitual locomotor behavior, with suspensory orangutans having larger a values and bipedal humans having smaller values for a (Deane et al., 2005;Deane & Begun, 2008). A second argument subsequently made by Deane and Begun (2008) against using IA was that it has limited paleoanthropological utility because a large number of fossil phalanges are broken and only complete bones can be used to calculate IA correctly. ...
... In general, this method can distinguish extant species based on habitual locomotor behavior, with suspensory orangutans having larger a values and bipedal humans having smaller values for a (Deane et al., 2005;Deane & Begun, 2008). A second argument subsequently made by Deane and Begun (2008) against using IA was that it has limited paleoanthropological utility because a large number of fossil phalanges are broken and only complete bones can be used to calculate IA correctly. These authors suggested that a benefit of using PCF is that it allows for the inclusion of more fossils in comparative analyses than would be possible if using IA alone. ...
Current approaches to quantify phalangeal curvature assume that the long axis of the bone's diaphysis approximates the shape of a portion of a circle (included angle method) or a parabola (second-degree polynomial method). Here we developed, tested, and employed an alternative geometric morphometrics-based (GM) approach to quantify diaphysis shape of proximal phalanges in humans, apes and monkeys with diverse locomotor behaviors. One hundred landmarks of the central longitudinal axis were extracted from 3D surface models and analyzed using 2DGM methods, including generalized Procrustes analyses. Principal components analyses were performed and PC1 scores (>80% of variation) represented the dorsopalmar shape of the bone's central longitudinal axis and separated taxa consistently and in accord with known locomotor behavioral profiles. The most suspensory taxa, including orangutans, hylobatids and spider monkeys, had significantly lower PC1 scores reflecting the greatest amounts of phalangeal curvature. In contrast, bipedal humans and the quadrupedal cercopithecoid monkeys sampled (baboons, proboscis monkeys) exhibited significantly higher PC1 scores reflecting flatter phalanges. African ape (gorillas, chimpanzees and bonobos) phalanges fell between these two extremes and were not significantly different from each other. PC1 scores were significantly correlated with both included angle and the a coefficient of a second-degree polynomial calculated from the same landmark dataset, but had a significantly higher correlation with included angles. Our alternative approach for quantifying diaphysis shape of proximal phalanges to investigate dorsopalmar curvature is replicable and does not assume a priori either a circle or parabola model of shape, making it an attractive alternative compared with existing methodologies.
... Phalangeal curvature is a predominant topic in the comparative primate literature, and discussions surrounding its functional meaning have played a major role in the interpretation of hand function during locomotion in extant and fossil primates (Susman 1979 ;Stern and Susman 1983 ;Susman et al. 1984 ;Stern et al. 1995 ;Jungers et al. 1997 ;Richmond 1998 ;Deane et al. 2005 ;Deane and Begun 2008 ;Matarazzo 2008 ;Rein 2011 ). When compared to most mammals, including euarchontans like tree shrews, nonhuman primates have relatively curved phalanges. ...
... The most common approach considers the bone's included angle (IA), which assumes that the bone's curvature represents an arc length on the perimeter of a circle (Susman et al. 1984 ;Stern et al. 1995 ). An alternative method uses high-resolution polynomial curve fi tting (HR-PCF), which assumes that a second-order polynomial or a parabolic shape provides a better representation of an anatomical curve (Deane et al. 2005 ;Deane and Begun 2008 ). Despite theoretical differences and assumptions, both methods show that increased curvature of phalanges is a functional adaptation for arboreality and is most accentuated in suspensory species (Figs. ...
... 4.4b and 4.5 ;Table 4.5 ). However, it is important to note that there can be substantial variation and overlap in phalangeal curvature across species (see, e.g., Fig. 3 in Deane and Begun 2008 ). Still, the most terrestrial quadrupedal species have both fl at proximal and middle phalanges. ...
The primate hand consists of five rays: a pollex containing a metacarpal and two phalanges and four ulnar rays each containing a metacarpal and three phalanges. Morphology of these elements is related to a number of factors including behavior (such as locomotor mode and manipulatory capabilities) and phylogenetic relatedness. This chapter briefly reviews the evolutionary history of the primate hand, discusses the intrinsic proportions of bones within the rays, and emphasizes the general osteology and morphological diversity among primates and their close relatives. The functional and evolutionary consequences of anatomical specializations are reviewed. Where clear gaps in the literature exist, new preliminary descriptions and data are presented.
... The shaft curvature is comparable to that of Nasalis ( Fig. 17.4 ). However, median values for Gorilla , Alouatta , Trachypithecus , and a number of fossil taxa all fall within the 50 % interquartile range of Proconsul , indicating a relatively generalized degree of curvature (Deane and Begun 2008 ). The trochlea is moderately canted palmarly and is moderately tall with a ventral fl are and a shallow trochlear groove. ...
... 17.4 ). Phalangeal curvature is essentially the same as Proconsul (Deane and Begun 2008 .) However, the median PP is short relative to the median Mc (80 %; see Patel et al. 2009 ). ...
... SSFs are better developed than in Proconsul . The longitudinal curvature is greater than in Proconsul and marginally overlaps with the range of Pan (Fig. 17.4 ), although Deane and Begun ( 2008 ), using polynomial curve fi tting (PCF), report a curvature close to the median for hylobatids. The overall shape of MP is similar to that in P. nyanzae and G. alpani (Fig. 17.5 ). ...
Hands of extant hominoids are highly derived compared with those of non-hominoid catarrhines. The evolution of the ape hand started from an appendage very well suited for powerful pollical-assisted grasping that supplied a balancing function in response to the loss of tail as seen in the early Miocene Proconsul (or Ekembo). Nacholapithecus from the early Middle Miocene of Africa had hands that were adapted for a primitive pollical-assisted grasping function, but absolutely large and more powerful. This might be an initial change toward forelimb-dominated positional behaviors while retaining the generally plesiomorphic postcrania. Pierolapithecus from the late Middle Miocene of Europe is clearly derived and may represent an ‘intermediate’ form evolving toward the extant great ape-like suspension/orthogrady in a mosaic way: enhanced ulnar deviation and midcarpal supination, yet lacking complete radial-side loading of the wrist and specializations for a hook-like grip. Late Miocene Eurasian great apes exhibit varying degrees (or modes) of suspension and orthograde adaptations. However, the hand anatomy that invokes such behaviors is not always morphologically identical across these apes, suggesting independent specialization for those behaviors. A reduction of the pollex in relation to the fingers, a trait common in extant apes, is not observed in any of these species. This may suggest that above-branch quadrupedalism/climbing with power grasping was an indispensable locomotor behavior, even in these apes. It is unclear in the fossil record when and where extant ape-like hands evolved.
... This is thanks in large part to the partial skeleton of Pierolapithecus . In details of its lumbar vertebrae (lower backbone) and hand, Pierolapithecus shows unambiguous indications of suspensory, orthograde (vertical trunk) adaptations, though it is probably not as suspensory as later Miocene and living great apes (Almécija et al. 2007 ;Deane and Begun 2008 ). ...
... My examination of these specimens indicates to me that Lufengpithecus is highly suspensory, probably to a degree similar to that of modern orang utans. An analysis of the curvature of the phalanges reached the same conclusion (Deane and Begun 2008 ). ...
... However, these features, in particular the broad pelvis and certain characteristics of the foot, have led some to conclude that Oreopithecus was primarily bipedal in the trees (Rook et al. 1999 ). Given the large number of suspensory features of the postcranial anatomy of Oreopithecus , most researchers think it is unlikely that Oreopithecus was a biped (Deane and Begun 2008 ;Susman 2004 ). ...
This chapter reviews the main patterns in the fossil ape record and how they inform about the evolutionary history of the living apes. It covers the origin of the hominoids at the end of the Oligocene (about 25 Ma, or millions of years ago), their successive hominoid radiations in Africa, Europe and Asia, and the disappearance of nearly all fossil apes at end of the Miocene. It also briefly discusses the pongine radiation in the Miocene. The fossil apes from western Eurasia also experience an impressive radiation during the Late Miocene. There are three samples of Late Miocene apes from East Africa that have been interpreted as more directly related to living African apes and humans than any Eurasian taxon. The evolutionary relations among fossil and recent hominoids will probably take many more years to resolve, if they are ever resolved.
... doi:10.1371/journal.pone.0039617.g004 curved phalanges [7,8,25,74], femoral morphology [7,23] and femoral neck cortical thickness distribution [25]. Hispanopithecus is therefore a key taxon for understanding the emergence of modern locomotor behaviors amongst hominoids. ...
... This is most clearly shown by the orientation and development of the coronoid process (indicative of a spool-shaped humeral trochlea) and the relatively reduced olecranon process of the CF ulna, which provide stability during rotatory movements and further allow for full extension of the elbow during suspensory behaviors [45,51,54,55]. Hence, the CF specimen agrees with previous assessments based on the spoolshaped trochlea of H. hungaricus [10,42,44], and further reinforces previous inferences of suspensory behaviors in H. laietanus [7,8,24,25,74]. ...
... From a locomotor viewpoint, Hispanopithecus is the oldest ape documenting unquestioned suspensory adaptations, shared by all extant crown hominoids (hylobatids and hominids), thus being of utmost significance for understanding the emergence of modern hominoid positional behaviors. The proximal ulna from CF, being the most complete available for the genus Hispanopithecus, reflects an elbow complex suitable for preserving stability along the full range of flexion/extension and enabling a broad range of pronation/ supination, thus confirming previous inferences of specialized suspensory behaviors [7,8,[23][24][25]74]. However, the rib, clavicular and scapular remains display a mixture of primitive and derived features, suggesting that Hispanopithecus, in spite of orthograde features, possessed a locomotor repertoire currently unknown among extant hominoids. ...
... Modern human and Neandertal proximal and intermediate phalanges (IPs) are shorter, less curved and less robust, with poorly developed flexor tendon attachments compared with those of extant great apes (Fig. 7). Australopiths and OH7 generally demonstrate an intermediate condition, being slightly longer, more curved and/or more robust than the typical modern human/Neandertal morphology, but less so than observed in the extant apes 11,12,27,30,36 . ...
... Although there is variation across fossil hominins, a combination of both highly curved PPs and IPs is unusual; extant apes and most fossil hominins, such as A. afarensis and OH7, generally have more strongly curved PPs and comparatively straight IPs. Experimental, behavioural and morphological evidence has demonstrated that phalangeal curvature is an adaptive response to the habitual stresses of locomotion, with more arboreal primates, especially those that often engage in suspension or climbing, having stronger longitudinal curvature compared with more terrestrial primates [36][37][38][39][40][41][42] . Biomechanically, curvature reduces the overall strain experienced by the phalanx during flexed-finger grasping postures, because a curved bone is more closely aligned with the joint reaction forces 40,42 . ...
... In the scaphoid-trapezium-trapezoid analysis (Fig. 5a), sample sizes were as follows: 106 modern humans, 65 Pan, 57 Gorilla, 8 Pongo, 1 Neandertal and 1 H. naledi; in the capitate-hamate analysis (Fig. 5b) High-resolution polynomial curve fitting methodology. All phalangeal curvatures were quantified using high-resolution polynomial curve fitting (HR-PCF) methods 36,41,58 . Although HR-PCF analysis is not software dependent, all curvatures were quantified using proprietary HR-PCF curve fitting software 41 . ...
A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during loco-motor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.
... A recent work by Deane and Begun (2008), based on a discriminant analysis of phalangeal curvature, classifies both Hispanopithecus and Pierolapithecus as suspensory taxa. Leaving aside the considerable differences in phalangeal curvature between these taxa, Deane and Begun's (2008) approach also overlooks many of the morphological and proportional differences between the phalanges of the two abovementioned taxa. ...
... A recent work by Deane and Begun (2008), based on a discriminant analysis of phalangeal curvature, classifies both Hispanopithecus and Pierolapithecus as suspensory taxa. Leaving aside the considerable differences in phalangeal curvature between these taxa, Deane and Begun's (2008) approach also overlooks many of the morphological and proportional differences between the phalanges of the two abovementioned taxa. As such, merely classifying both taxa as 'suspensory' is an oversimplification, because it does not take into account that the locomotor repertoire of each particular taxon is a combination of several locomotor modes, which are practiced in different frequencies and which have a different significant from an adaptive viewpoint in each particular taxon (see for example Thorpe and Crompton 2006, regarding orangutans). ...
... Accordingly, despite their similar classification in Deane and Begun's (2008) analysis, the differences in phalangeal curvature between Pierolapithecus and Hispanopithecus (around 20º) are highly suggestive that the locomotor repertoires of these taxa emphasized different kinds of arboreal behaviors. Table 2.5. ...
... They also observed that the distal articular facets of the metatarsals do not extend dorsally, and thus Proconsul/Ekembo did not habitually dorsiflex its digits . Diaphyseal curvature is similar to that of arboreal quadrupeds (Deane & Begun, 2008). The distal hallucial phalanx has a broad and flat proximal extremity with a well-marked insertion for the tendon of flexor hallucis longus muscle and a welldeveloped apical tuft, indicating strong hallucial flexors and large loads on the tip of the hallux . ...
... If this inferred morphology (from Figure 1 of Moyà-Solà et al., 2004) is indeed accurate, it suggests only partial adaptations in the foot Marked distal projection of the medial malleolus a Strongly keeled trochlear surface on the tibia a Articular facet on the talus is not expanded distally a Metaphyseal shape of the distal tibia that is not mediolaterally expanded a Lateral rays Broad metatarsal bases b Robust metatarsals with thick plantar tubercles b Proximal articular facet angled medially relative to the diaphyseal long axis b a Tallman et al. (2013), b Begun (1994) of this taxon for vertical climbing and scrambling. This interpretation is consistent with analyses from the rest of the skeleton, which suggest only modest adaptations for orthogrady (Moyà-Solà et al., 2004;Hammond et al., 2013), and the retention of quadrupedal locomotion (Almécija et al., 2009; but see Deane & Begun, 2008 for an alternative locomotor interpretation based on the hand phalanges). ...
Feet are relatively well represented in the Miocene hominoid fossil record, and taxa present a variety of adaptations. The oldest, African taxa generally present feet with evidence of strong hallucial grasps and some modest eversion-inversion capabilities, but that were narrow like cercopithecoids and probably still fairly rigid, functioning as a lever for propulsion during quadrupedal locomotion. For many taxa, there is evidence that the forelimb is adapted to orthograde locomotion while the foot presents traits that imply rather standardized quadrupedal movements, suggesting that they had a type of locomotion that has no modern equivalent. Evidence of an anterior foot that is more mobile and splayed occurs with the later Asian and European taxa. It is only with the 6–7 million year-old European Oreopithecus that pedal morphology indicates a locomotor mode closely resembling that of extant large apes with mobile, strongly grasping feet, a specialization for arboreal scrambling and careful climbing and a more generalized orthograde posture. More research is needed, however, to establish the extent of independent acquisition of these traits in extant great apes.
... The inference that Pierolapithecus lacked specific suspensory adaptations in spite of possessing an orthograde body plan (Moy a-Sol a et al., 2004) was mostly based on differences in phalangeal morphology and relative proportions to body mass, as compared to Hispanopithecus and extant apes. Such a contention was subsequently challenged by some authors (Begun and Ward, 2005;Deane and Begun, 2008) but supported by additional evidence by Moy a-Sol a and coworkers (Moy a-Sol a et al., 2005;Alm ecija et al., 2009;Alba et al., 2010a). Regarding suspensory adaptations, both Dryopithecus and Pierolapithecus (besides Nacholapithecus and most other middle Miocene apes) would differ from the late Miocene Hispanopithecus laietanus from Can Llobateres 2 (9.6 Ma; Casanovas-Vilar et al., 2016), which already shows clear adaptations to below-branch suspension (Moy a-Sol a and K€ ohler, 1996;Alm ecija et al., 2007;Alba et al., 2010aAlba, 2012;Pina et al., 2012) in spite of still retaining some primitive features consistent with some degree of above-branch quadrupedalism (Alm ecija et al., 2007Tallman et al., 2013). ...
... The habitual engagement in antipronograde behaviors such as vertical climbing or below-branch suspension could have similarly ameliorated the problem (Cartmill, 1985). Vertical climbing in this taxon would be supported by the presence of some external traits associated with a wider range of excursion at the hip (e.g., rounded femoral head; Moy a-Sol a et al. Deane and Begun, 2008) as well as for the D. fontani humerus from Saint-Gaudens (e.g., Richmond and Whalen, 2001;contra Begun, 1992). Nevertheless, given the mosaic nature of locomotor evolution in hominoids, additional remains, representing other anatomical regions, would be necessary to test further such locomotor inferences, particularly for D. fontani. ...
Only a few postcranial remains have been assigned to the Miocene great ape Dryopithecus fontani, leading to uncertainties in the reconstruction of its overall body plan and positional behavior. Here we shed light on the locomotor repertoire of this species through the study of the femoral neck cortical bone (FNCB) distribution of IPS41724, a partial proximal femur from the Abocador de Can Mata locality ACM/C3-Az (11.9 Ma, middle Miocene; Valle�s-Penede�s Basin, Spain) attributed to this taxon. This specimen was scanned through computed tomography to measure the superior (SUP) and inferior (INF) cortical thicknesses at the middle and the base of the femoral neck. Measurements were compared with a sample of extant primates and the femur IPS18800.29 from the younger great ape Hispanopithecus laietanus from Can Llobateres 2 (9.6 Ma, late Miocene; Valle�s-Penede�s Basin), previously shown to display a homoge- neous FNCB distribution at the midneck section coupled with postcranial adaptations to below-branch suspensory behaviors. Our analyses indicate an asymmetric FNCB distribution for IPS41724 (SUP/INF index 1⁄4 ~0.4 at the midneck and base of the neck sections), comparable with that of quadrupedal pri- mates and bipedal hominins (including early australopiths), but contrasting with the homogeneous FNCB distribution of Hispanopithecus and extant great apes. An asymmetrical FNCB distribution has been associated with stereotyped loads at the hip joint (as in both quadrupedal and bipedal taxa). Our results therefore support a significant quadrupedal component of the positional behavior of Dryopithecus, thus strengthening the argument that plesiomorphic generalized quadrupedalism was still a major locomotor behavior for Miocene great apes. If that were the case, it could have deep implications for the origins of hominin bipedalism.
... The proximal phalanges are relatively long compared to a modern human, but short compared with modern apes (Latimer & Lovejoy, 1990b;Susman et al., 1984). Additionally, the curvature of the pedal phalanges is found to be African ape-like when measuring either the included angle or a polynomial curve fitting technique (Deane & Begun, 2008 Fortunately, the physical remains of A. afarensis can be measured against 3.66 Ma fossilized footprints preserved at Laetoli, Tanzania (Leakey & Harris, 1987). The first footprints discovered and suggested to be from a bipedal hominin were Laetoli "A", a set of 5 consecutive bipedal prints that were never fully excavated (Leakey, 1978;Leakey & Hay, 1979;White & Suwa, 1987). ...
... The phalanx is long, though it is relatively shorter than the PP4 of modern apes (Haile-Selassie et al., 2009). The longitudinal curvature falls within the range of modern chimpanzees(Deane & Begun, 2008). ...
Bipedalism is a hallmark of being human and the human foot is modified to reflect this unique form of locomotion. Leonardo da Vinci is credited with calling the human foot “a masterpiece of engineering and a work of art.” However, a scientific approach to human origins has revealed that our feet are products of a long, evolutionary history in which a mobile, grasping organ has been converted into a propulsive structure adapted for the rigors of bipedal locomotion. Reconstructing the evolutionary history of foot anatomy benefits from a fossil record; yet, prior to 1960, the only hominin foot bones recovered were from Neandertals. Even into the 1990s, the human foot fossil record consisted mostly of fragmentary remains. However, in the last two decades, the human foot fossil record has quadrupled, and these new discoveries have fostered fresh new perspectives on how our feet evolved. In this review, we document anatomical differences between extant ape and human foot bones, and comprehensively examine the hominin foot fossil record. Additionally, we take a novel approach and conduct a cladistics analysis on foot fossils (n = 19 taxa; n = 80 characters), and find strong evidence for mosaic evolution of the foot, and a variety of anatomically and functionally distinct foot forms as bipedal locomotion evolved.
... For example, dorsopalmarly curved phalanges have been shown to experience less strain during grasping a branch with flexed PIP and MCP joints than straight phalanges (Preuschoft, 1973;Richmond, 1998Richmond, , 2007Jungers et al., 2002;Nguyen et al., 2014). The current musculoskeletal model assumes the phalanges are straight and thus the greater phalangeal curvature of orangutans (60 of curvature for orangutans compared to 42 for chimpanzees; Susman et al., 1984; see also Stern et al., 1995;Deane and Begun, 2008;Matarazzo, 2008;Rein, 2011;Patel and Maiolino, 2016) could alter joint angles and decrease the muscular loading during this grip. ...
... The simulations are based by necessity on a human hand model for which only the segment lengths have been changed for great apes and fossil hominins. Interspecific variation in bony morphology (e.g., phalangeal curvature; Susman et al., 1984;Stern et al., 1995;Deane and Begun, 2008;Patel and Maiolino, 2016) and range of motion according to specific joint morphology (Napier, 1962;Tuttle, 1969;Lewis, 1989;Marzke, 1992Marzke, , 1997Tocheri et al., 2008;Marzke et al., 2010;Orr et al., 2010) will certainly affect the results of the model. Furthermore, no adaptations of muscle trajectories and moment arms were implemented in the models, which can lead to errors in estimating the force of each muscle. ...
... For example, the specialized wrist, palm and finger bones of African apes permit terrestrial knuckle-walking (e.g., Schultz, 1930;Tuttle, 1967Tuttle, , 1969Corruccini, 1978;Inouye, 1994;Matarazzo, 2008). In addition, various characteristics of ape phalanges are correlated strongly and positively with their arboreal vocation as climbers and suspensory locomotorists (e.g., Susman, 1979;Stern et al., 1995;Richmond, 2007;Deane and Begun, 2008;Rein, 2011). ...
... A reliable indicator of primate postural and locomotor behavior is the relative longitudinal curvature of the phalanges, especially the MPPs. Among extant taxa, it is habitual climbers and suspensory locomotorists that show the most marked MPP curvatures (e.g., Marzke, 1983;Susman, 1983, 1995;Susman et al., 1984;Begun, 1993;Hamrick et al., 1995;Jungers et al., 1997;Moy a-Sol a et al., 2004Alm ecija et al., 2007Alm ecija et al., , 2009Richmond, 2007;Deane and Begun, 2008;Tocheri et al., 2008;Rein, 2011;Kivell, 2015;Patel and Maiolino, 2016). This correlation might be predicated on the fact that longitudinal curvature ultimately lessens the strain transmitted to MPPs via suspensory behaviors by reducing bending of their diaphyses (Richmond, 2007;Nguyen et al., 2014). ...
We describe eleven hominin metacarpals and phalanges recovered from Jacovec Cavern and Member 4 of the Sterkfontein Formation between 1998 and 2003. Collectively, the fossils date in excess of 2.0 Ma, and are probably attributable to Australopithecus africanus and/or Australopithecus prometheus. When combined with results of previous studies on Australopithecus postcranial functional morphology, the new data presented here suggest that at least some late Pliocene and/or early Pleistocene hominins from Sterkfontein were arboreally adept. This finding accords with the reconstruction of the site's >2.0 Ma catchment area as well-vegetated and containing significant woody components. In addition, most of the new specimens described here evince morphologies that indicate the hands from which they derived lacked complete modern humanlike manual dexterity, which is integral to the manufacture and use of intentionally shaped stone tools. The absence of lithic artifacts from both stratigraphic units from which the fossils were excavated is consistent with this conclusion.
... The faunal assemblage at R. II preserves an abundance of forestdwelling taxa, including the hominoid Rudapithecus hungaricus. Rudapithecus is an extinct member of the great ape and human clade, on the basis of numerous cranial and postcranial features (Begun, 1992(Begun, , 2009Kordos and Begun, 2002;Deane and Begun, 2008;Kivell and Begun, 2009). Both the morphology and life history pattern of this fossil ape suggest that it was a large-bodied, suspensory frugivore, which would have been highly dependent on forested conditions and year-round access to fruit resources (Begun, 1992, Ungar andKay, 1995;Ungar, 1996Ungar, , 2005Kordos and Begun, 2002;Kivell and Begun, 2009;Smith et al., 2010;Deane et al., 2013;DeMiguel et al., 2014). ...
... Within the gradient of open to closed canopy forest at R. II Rudapithecus would have likely occupied more humid, and densely closed canopy habitats. The postcranial morphology of Rudapithecus is consistent with adaptations related to derived suspensory arboreality suggestive of the presence of densely closed canopy forest at or near R. II, including strongly curved phalanges (Begun, 1988;Deane and Begun, 2008), and features of the elbow, wrist and femur (Begun, 1992(Begun, , 2007Kordos and Begun, 2002;Kivell and Begun, 2009). ...
Examining how species use and partition resources within an environment can lead to a better understanding of community assembly and diversity. The rich early Late Miocene (early Vallesian) deposits at Rudabánya II (R. II) in northern central Hungary preserve an abundance of forest dwelling taxa, including the hominoid Rudapithecus hungaricus. Here we use the carbon and oxygen stable isotope compositions of tooth enamel carbonate from 10 genera of medium to large-bodied mammals to evaluate resource use and partitioning among the herbivore community, and to reconstruct the paleoenvironment of Rudapithecus. The range of stable carbon and oxygen isotope values (δ 13 C E and δ 18 O E) displayed by the R. II fauna indicates a variable forest environment, which included both open and closed canopy habitats. The relatively low δ 13 C E and δ 18 O E values found in all sampled taxa are consistent with high levels of precipitation and humidity. Significant differences in stable isotope values were observed among the sampled fauna, supporting the interpretation of resource specialization and partitioning. Higher δ 13 C E values found in Aceratherium incisivum (Rhinocerotidae), Lucentia aff. pierensis (Cervidae), Hippotherium intrans (Equidae), Tetralophodon longirostris (Gomphotheriidae), Propotamochoerus palaeochoerus and Parachleuastochoerus kretzoii (Suidae) suggest foraging in more open canopy habitats, while lower δ 13 C E values found in Miotragocerus sp. (Bovidae), Dorcatherium naui (Tragulidae), and Micromeryx flourensianus (Moschidae) imply a preference for more densely canopied habitats. Several of the sampled taxa yielded relatively higher δ 18 O E and δ 13 C E values indicative of fruit consumption, including the small ruminants, cervid, and bovid. The analyzed isotope values reflect a moderate degree of dietary niche overlap between taxa. An abundance of plant resources likely allowed for the coexistence of this diverse community of predominantly browsing herbivores. Within the gradient of more open to closed canopy forest, it is likely that Rudapithecus occupied dense closed canopy habitats where access to fruit was relatively continuous. The progressive fragmentation and replacement of humid forests by more open and seasonal woodlands during the late Vallesian would have had a significant influence on the extinction of this fossil ape.
... The faunal assemblage at R. II preserves an abundance of forestdwelling taxa, including the hominoid Rudapithecus hungaricus. Rudapithecus is an extinct member of the great ape and human clade, on the basis of numerous cranial and postcranial features (Begun, 1992(Begun, , 2009Kordos and Begun, 2002;Deane and Begun, 2008;Kivell and Begun, 2009). Both the morphology and life history pattern of this fossil ape suggest that it was a large-bodied, suspensory frugivore, which would have been highly dependent on forested conditions and year-round access to fruit resources (Begun, 1992, Ungar andKay, 1995;Ungar, 1996Ungar, , 2005Kordos and Begun, 2002;Kivell and Begun, 2009;Smith et al., 2010;Deane et al., 2013;DeMiguel et al., 2014). ...
... Within the gradient of open to closed canopy forest at R. II Rudapithecus would have likely occupied more humid, and densely closed canopy habitats. The postcranial morphology of Rudapithecus is consistent with adaptations related to derived suspensory arboreality suggestive of the presence of densely closed canopy forest at or near R. II, including strongly curved phalanges (Begun, 1988;Deane and Begun, 2008), and features of the elbow, wrist and femur (Begun, 1992(Begun, , 2007Kordos and Begun, 2002;Kivell and Begun, 2009). ...
Examining how species use and partition resources within an environment can lead to a better understanding of community assembly and diversity. The rich early Late Miocene (early Vallesian) deposits at Rudabánya II (R. II) in northern central Hungary preserve an abundance of forest dwelling taxa, including the hominoid Rudapithecus hungaricus. Here we use the carbon and oxygen stable isotope compositions of tooth enamel carbonate from 10 genera of medium to large-bodied mammals to evaluate resource use and partitioning among the herbivore community, and to reconstruct the paleoenvironment of Rudapithecus. The range of stable carbon and oxygen isotope values (δ13CE and δ18OE) displayed by the R. II fauna indicates a variable forest environment, which included both open and closed canopy habitats. The relatively low δ13CE and δ18OE values found in all sampled taxa are consistent with high levels of precipitation and humidity. Significant differences in stable isotope values were observed among the sampled fauna, supporting the interpretation of resource specialization and partitioning. Higher δ13CE values found in Aceratherium incisivum (Rhinocerotidae), Lucentia aff. pierensis (Cervidae), Hippotherium intrans (Equidae), Tetralophodon longirostris (Gomphotheriidae), Propotamochoerus palaeochoerus and Parachleuastochoerus kretzoii (Suidae) suggest foraging in more open canopy habitats, while lower δ13CE values found in Miotragocerus sp. (Bovidae), Dorcatherium naui (Tragulidae), and Micromeryx flourensianus (Moschidae) imply a preference for more densely canopied habitats. Several of the sampled taxa yielded relatively higher δ18OE and δ13CE values indicative of fruit consumption, including the small ruminants, cervid, and bovid. The analyzed isotope values reflect a moderate degree of dietary niche overlap between taxa. An abundance of plant resources likely allowed for the coexistence of this diverse community of predominantly browsing herbivores. Within the gradient of more open to closed canopy forest, it is likely that Rudapithecus occupied dense closed canopy habitats where access to fruit was relatively continuous. The progressive fragmentation and replacement of humid forests by more open and seasonal woodlands during the late Vallesian would have had a significant influence on the extinction of this fossil ape.
... The flexor sheath ridges are longer than in Ouranopithecus (Table 5). The curvature seems to be more pronounced, although less than in more arboreal primates (Deane and Begun, 2008). The distal articular surface extends less dorsally. ...
... The last behaviour is not consistent with the data from Ouranopithecus. The suspensory capabilities of Pierolapithecus are also supported (Deane and Begun, 2008) from the curvature estimated from high-resolution polynomial curve fitting, but see also Alba et al. (2010) who argue that in Pierolapithecus " suspension … .would not have been practised to the same degree as in hylobatids, orangutans, Hispanopithecus.. " (259) and Deane and Begun (2010). ...
Two well preserved phalanges, one proximal and one intermediate, are identified and described. They constitute the first postcrania ever described of Ouranopithecus macedoniensis (Primates, Hominoidea) from the late Miocene locality of Ravin de la Pluie (RPl), Macedonia (Greece). They are isolated specimens, and the only ones known for their genus. The hypotheses that these specimens derive either from the hand or from the foot were tested. Comparisons with living apes of known positional behaviour were made to assess the functional signal in these specimens. The proximal phalanx, either manual or pedal, closely matches the proximal phalanges of terrestrial quadrupedal primates or the bipedal primate Homo. With respect to the intermediate phalanx we show that it closely matches phalanges of quadrupedal terrestrial primates. The terrestriality of Ouranopithecus, here reconstructed from phalangeal remains, is in agreement with our previous results of dental studies (thick check teeth enamel and microwear pattern of incisors and molars), which indicate that it was a hard object feeder living near the ground.
... At the same time, however, Pierolapithecus retains adaptations for powerful grasping, above-branch palmigrady in the phalanges and metacarpals (Moy a-Sol a et al., 2004, 2005; Alm ecija et al., 2009; Alba et al., 2010; Alba, 2012). Such a mosaic of features has led to conflicting views as to whether this taxon possessed (Begun and Ward, 2005; Deane and Begun, 2008, 2010) or lacked (Moy a-Sol a et al., 2005; Alm ecija et al., 2009; Alba et al., 2010; Alba, 2012) suspensory adaptations. Irrespective of the latter, the phalangeal morphology of Pierolapithecus shows that this taxon displayed a locomotor repertoire unlike modern hominoids, combining orthograde behaviors with above-branch quadrupedalism (palmigrady ). ...
... However, an adaptation to suspensory behaviors in Oreopithecus is at odds with the relatively short metacarpals and phalanges (Moy a-Sol a et al., 1999; see discussion in Alm ecija et al., 2012, 2014). Both in its moderate phalangeal relative length (Moy a-Sol a et al., 1999) and curvature (Susman, 2004; Deane and Begun, 2008; Alm ecija et al., 2014), Oreopithecus seems more comparable with Pierolapithecus than to either Hispanopithecus or extant highly suspensory apes (i.e., hylobatids and orangutans; Alm ecija et al., 2007, 2009; Alba et al., 2010), which might be explained as a symplesiomorphy (Alm ecija et al., 2014). In any case, the possession of a less shortened lumbar region in both Oreopithecus and Hispanopithecus strongly suggests that the morphology shared by extant great apes (i.e., African apes and pongines) might have been to some extent independently derived from a more generalized condition, as similarly suggested recently for the proximal morphology of the femur (Alm ecija et al., 2013). ...
... The polynomial curve fitting is to fit data to the graph of a polynomial function and reduce noise effect (Guruswami and Zuckerman 2016). It has been widely utilized in modelling the trend of data in research and application (Deane and Begun 2008;Wang et al. 2019). In this study, a high order polynomial function was applied to fit the R 2 values over the 267 (270-3) narrow spectral bands, for each date separately. ...
The growth stage best suitable for wheat yield phenotyping has been a hot topic. This study provides a fresh insight into it, from the perspective of spectral correlation between wheat genotype replications. A number of 340 wheat genotypes and their replication were distributed in separate parts (west and east) of an experiment field (2019–2020) in Ashland, Kansas, USA. Unmanned aerial vehicle based hyperspectral images (400–100 nm) of the experiment field were taken over the late growing season, on 29 May 2020, 5 June 2020, and 12 June 2020, respectively. For each narrow spectral band, we calculated a coefficient of determination (R²) between the reflectance of genotype replications. Results suggest that R² is relatively stable within visible spectrum (450–700 nm) and within near-infrared (NIR) spectrum (770–1000 nm), though it tends to be higher for the visible bands. Moreover, while the R² of the visible bands decreases across the three dates, it increases for the near-infrared bands. These findings suggest that genetic information is better reflected in visible reflectance than in near-infrared reflectance. Among the three dates, the one when highest intra-genotype spectral correlation over visible spectrum was observed might be the best timing to discriminate yield levels of different genotypes.
... Several morphological features of manual and pedal phalanges, such as phalangeal curvature and dorsal canting, as well as of other forelimb van HETEREN ET AL. bones, have been shown to be related to locomotory behavior in primates (Deane & Begun, 2008;Jungers et al., 1997;Matarazzo, 2008;Rein et al., 2011;Rein et al., 2015;Richmond, 2007;Rose, 1986;Rose et al., 1996;Susman, 1979). In primates, increased dorsal canting is associated with increased quadrupedal behavior, whereas more palmarly oriented proximal articular surfaces are associated with suspensory behavior (Rein & McCarty, 2012). ...
Objectives
As hands and feet are serially repeated corresponding structures in tetrapods, the morphology of fingers and toes is expected to covary due to a shared developmental origin. The present study focuses on the covariation of the shape of proximal finger and toe phalanges of adult Homo sapiens to determine whether covariation is different in the first ray relative to the others, as its morphology is also different.
Material and methods
Proximal phalanges of 76 individuals of unknown sex (Muséum national d'Histoire naturelle, Paris, and the Natural History Museum, London) were digitized using a surface scanner. Landmarks were positioned on 3D surface models of the phalanges. Generalized Procrustes analysis and two-block partial least squares (PLS) analyses were conducted. A novel landmark-based geometric morphometric approach focusing on covariation is based on a PCoA of the angles between PLS axes in morphospace. The results can be statistically evaluated.
Results
The difference in PCo scores between the first and the other rays indicates that the integration between the thumb and the big toe is different from that between the lateral rays of the hand and foot.
Discussion
We speculate that the results are possibly the evolutionary consequence of differential selection pressure on the big toe relative to the other toes related to the rise of bipedalism, which is proposed to have emerged very early in the hominin clade. In contrast, thumb morphology and its precision grip never ceased undergoing changes, suggesting less acute selection pressures related to the evolution of the precision grip.
... These morphological traits are most strongly expressed in recent modern humans, which are nearly exclusively terrestrial in their locomotor adaptation. In contrast, the body plan of extant, nonhuman apes (hereafter, simply 'apes') reflects an adaptation to orthogrady and suspension (Keith, 1923;Gebo, 1996;Williams and Russo, 2015) with relatively long arms and large upper limb joints (Ruff, 1988), elongated, curved phalanges (Deane and Begun, 2008), and other morphological features suitable for arboreal behaviors (Gebo, 1996). Although chimpanzees, bonobos, and gorillas possess adaptations to terrestrial quadrupedalism (Gebo, 1996), including their knuckle-walking hand posture and heel-strike plantigrade foot posture (Gebo, 1992;Prang, 2019), they retain traits linked to an ancestry characterized by vertical climbing and suspension in some form (Gebo, 1996). ...
The evolution of bipedalism and reduced reliance on arboreality in hominins resulted in larger lower limb joints relative to the joints of the upper limb. The pattern and timing of this transition, however, remains unresolved. Here, we find the limb joint proportions of Australopithecus afarensis , Homo erectus , and Homo naledi to resemble those of modern humans, whereas those of A. africanus , Australopithecus sediba , Paranthropus robustus , Paranthropus boisei , Homo habilis , and Homo floresiensis are more ape-like. The homology of limb joint proportions in A. afarensis and modern humans can only be explained by a series of evolutionary reversals irrespective of differing phylogenetic hypotheses. Thus, the independent evolution of modern human-like limb joint proportions in A. afarensis is a more parsimonious explanation. Overall, these results support an emerging perspective in hominin paleobiology that A. afarensis was the most terrestrially adapted australopith despite the importance of arboreality throughout much of early hominin evolution.
... Each known, measureable hominin proximal phalanx from Sterkfontein Member 4 shows high longitudinal curvature and/or robust flexor sheath ridges (e.g., Pickering et al., 2018;Ricklan, 1987Ricklan, , 1988Ricklan, , 1990, features linked to the ability to flex the fingers powerfully and to a significant degree of arboreal behavior in primates (e.g., Deane & Begun, 2008;Rein, 2011;Richmond, 2007;Stern, Jungers, & Susman, 1995;Susman, 1979). The morphology of the distal epiphyseal rim of the StW 354 radius agrees with the interpretation that Member 4 hominins had strong fingers, well-suited for climbing . ...
Objectives
We provide descriptions and functional interpretations of 11 >2.0 Ma hominin vertebral and upper limb fossils from Sterkfontein.
Materials and methods
We employed taphonomic methods to describe postmortem damage observed on the fossils. We used osteometric tools and measurements to generate quantitative descriptions, which were added to qualitative descriptions of the fossils. These observations were then interpreted using published data on the same skeletal elements from extant and extinct hominoid taxa.
Results
Six of the fossils carry carnivore tooth marks. Two vertebrae show morphologies that are consistent with fully developed lordosis of the lumbar spine, but which are not completely consistent with bipedal loading of the same intensity and/or frequency as reflected in the lumbars of modern humans. A clavicle shows a combination of humanlike and apelike features, the latter of which would have endowed its hominin with good climbing abilities. When combined, analyses of fragmentary radius and ulna fossils yield more ambiguous results.
Discussion
The new fossil collection presents a mix of bipedal and climbing features. It is unclear whether this mix indicates that all Sterkfontein hominins of >2.0 Ma were terrestrial bipeds who retained adaptations for climbing or whether the collection samples two differently adapted, coeval hominins, Australopithecus africanus and Australopithecus prometheus, both of which are represented at Sterkfontein by skull remains. Regardless, the significant frequency of tooth‐marked fossils in the sample might indicate that predation was a selection pressure that maintained climbing adaptations in at least some Sterkfontein hominins of this period.
... B) Comparison (in degrees) of included angles of the arc formed by manual phalanges in extant hominoids and extinct hominins. All phalanges from rays II to V were included due to relatively low intraspecific and intra-individual variation of their longitudinal curvature (Stern et al., 1995;Deane and Begun, 2008;Almecija et al., 2009). A 2D approach was preferred because it makes simple comparisons possible. ...
... The morphology of the pisiform, the hamate, the metacarpals and the proximal phalanges probably enhanced the suspensory and climbing capacities in this taxon (Stern & Susman, 1983, Tuttle, 1981. The highly curved digits are also indicative of suspensory and arboreal locomotion (Dean & Begun, 2008;Susman et al., 1984). The cranially oriented glenoid fossa in Au. afarensis suggests that they used their upper limbs in elevated positions (Green & Alemseged, 2012;McHenry, 1986;Stern & Susman, 1983 and by the metacarpal diaphyses, which are stronger than in H. sapiens (Coffing, 1998). ...
Objectives:
The locomotor and manipulative abilities of australopithecines are highly debated in the paleoanthropological context. Australopithecus afarensis and Australopithecus sediba likely engaged in arboreal locomotion and, especially the latter, in certain activities implying manipulation. Nevertheless, their degree of arboreality and the relevance of their manipulative skills remain unclear. Here we calculate the pronation efficiency of the forearm (Erot ) in these taxa to explore their arboreal and manipulative capabilities using a biomechanical approach.
Materials and methods:
Three-dimensional humeral images and upper limb measurements of A.L. 288-1 (Au. afarensis) and MH2 (Au. sediba) were used to calculate Erot using a previously described biomechanical model.
Results:
Maximal Erot in elbow flexion occurs in a rather supinated position of the forearm in Au. afarensis, similarly to Pan troglodytes. In elbow extension, maximal Erot in this fossil taxon occurs in the same forearm position as in Pongo spp. In Au. sediba the forearm positions where Erot is maximal are largely coincident with those for Hylobatidae.
Conclusions:
The pattern in Au. afarensis suggests relevant arboreal capabilities, which would include vertical climbing, although it is suggestive of poorer manipulative skills than in modern humans. The similarity between Au. sediba and Hylobatidae is difficult to interpret, but the differences between Au. sediba and Au. afarensis suggest that the capacity to rotate the forearm followed different evolutionary processes in these australopithecine species. Although functional inferences from the upper limb are complex, the observed differences between both taxa point to the existence of two distinct anatomical models.
... In contrast to the derived morphology of the wrist and palm, however, the fingers of H. naledi are strongly curved; more curved than australopiths, including Au. afarensis [11]. Phalangeal curvature is one of the best indicators of function in the hand89909192. The degree of longitudinal curvature is strongly correlated with the degree of arboreal locomotion across primates, with climbing and, especially, suspensory taxa showing much stronger curvature than terrestrial quadrupedal or bipedal taxa [89 –91]. ...
For several decades, it was largely assumed that stone tool use and production were abilities limited to the genus Homo. However, growing palaeontological and archaeological evidence, comparative extant primate studies, as well as results frommethodological advancements in biomechanics andmorphological analyses, have been gradually accumulating and now provide strong support for more advanced manual manipulative abilities and tool-related behaviours in pre-Homo hominins than has been traditionally recognized. Here, I review the fossil evidence related to early hominin dexterity, including the recent discoveries of relatively complete early hominin hand skeletons, and newmethodologies that are providing a more holistic interpretation of hand function, and insight into how our early ancestors may have balanced the functional requirements of both arboreal locomotion and tool-related behaviours. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
... Lufengpithecus (Andrews & Harrison 2005;Begun 2007Begun et al. 2006b;Begun & Ward 2005;Deane & Begun 2008, Harrison & Rook 1997Harrison & Rook 1997;Moya-Sola & Kohler 1996;Sarmiento 1987;Schwartz 1997;Susman 1985). ...
... Recent interpretations of metacarpals and phalanges attributed to Pierolapithecus (Moyà- Solà et al., 2004, 2005; Almécija et al., 2009) and Hispanopithecus (Moyà-Solà et al., 1996; Almécija et al., 2007) suggest that adaptations to arboreal palmigrady may have persisted through much of hominoid evolution and that at least some suspensory features evolved independently in modern lineages (Moyà-Solà et al., 2004, 2005; Almécija et al., 2007, 2009; Alba et al., 2010; but see Begun and Ward, 2005; Deane and Begun, 2008, 2010; Begun, 2009). ...
... Interestingly, the opposite condition to that displayed by Epipliopithecus is found among several stem hominoids and putative stem great apes, in which orthograde features are found without being associated with forelimb suspensory adaptations. Thus, the Middle Miocene stem great ape Pierolapithecus (12.9 Ma), as evidenced by various anatomical regions, displays an orthograde body plan with no ulnocarpal articulation but without suspensory adaptations in the hand, thereby suggesting that suspensory adaptations are at least homoplastic between hylobatids and hominids (Moy a-Sol a et al., 2004,2005; Alm ecija et al., 2009; Alba et al., 2010;Alba, 2012; but see Deane and Begun, 2008, for a different interpretation). This might also be argued for pongines and hominines (Alba, 2012), especially given the apparently pronograde body plan without suspensory adaptations in the Middle Miocene (12 Ma) pongine Sivapithecus (Pilbeam et al., 1990;Madar et al., 2002). ...
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.
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 forefoot plays a key role in both the grasping and leverage roles of the foot and has therefore been critical to the interpretation of pedal function at various stages of primate evolution. This chapter reviews laboratory-based observational and experimental studies of the morphology, intrinsic proportions, and loading patterns of the metatarsals and phalanges to explore their roles in orientation of the forefoot, grasping, and toe-off. The metatarsal heads exhibit morphological diversity that reflects habitual position and the loading environment of the phalanges at the end of stance phase. Phalangeal curvature and prehensility are good indicators of arboreality in fossil primates, as these features of the distal forefoot have been tightly associated with arboreality in extant forms. Two aspects of the forefoot define our Order: the nail-bearing distal phalanges and the grasping hallux, though the latter has been repurposed for powerful leverage in humans. The most distal elements of the forefoot exhibit an apical tuft and a nail rather than a claw (excepting the grooming claw of strepsirrhines and the tegulae of Daubentonia and the callitrichines). The hallux, more than any element of the foot, illustrates the tradeoffs between grasping and leverage in the primate foot, being a central element in a power grasp and a key point for loading in toe-off. Modern techniques of 3-dimensional visualization as well as new fossils have propelled our understanding of morphological variation in the primate forefoot, but considerable opportunity exists for incorporating functional studies into our interpretation of the evolutionary trajectory of forefoot morphology. The primate forefoot reflects the complex adaptations to arboreal life in primates, and our locomotor evolution is written in changes to forefoot anatomy seen in the fossil record.
The hydrolysis time is directly related to the flavor of the Maillard reaction, but existing proxy models cannot simulate and model the variation curves of vital volatile components. This study developed a predictive model for modelling and simulating key volatile compounds of Maillard reaction products (MRPs) derived from beef tallow residue hydrolysate. Results showed the degree of hydrolysis increased with hydrolysis time, and the most significant improvement in the roast flavor and overall acceptance was when hydrolyzing 4 h. Based on flavor dilution value and the relative odor activity value, nine key volatile components were identified, and 2-ethyl-3,5-dimethylpyrazine with roast flavor was the highest. Compared with Polynomial Curve Fitting (PCF) and Cubic Spline Interpolation (CSI), key volatile compounds of MRPs could be better modeled and simulated by the Curve Prediction Model (CPM). All results suggested that CPM could predict the changes in key volatile components produced by MRPs.
Molar enamel thickness and distribution pattern inform on the functional and dietary adaptation of extant and fossil primates. However, no systematic analysis of enamel thickness has been conducted on Lufengpithecus, a large-bodied fossil hominoid that lived in Southwest China during the late Miocene. In this study, we quantify two-dimensional (2D) enamel thickness and distribution of 68 lightly worn molars of Lufengpithecus (L.) lufengensis using micro-CT scanning data and compare it with modern humans, extant great apes, and fossil hominoids. The results indicate L. lufengensis has relatively thick enamel. It is slightly thicker than extant Pongo and comparable to some thick-enamel fossil pongines, but thinner than modern humans and most fossil hominins. The enamel distribution of L. lufengensis is distinctively unbalanced with relatively more enamel deposited on the cuspal region than the basal region in the molar crown, different from that found in modern humans and extant great apes. Concerning its palaeoecological and functional adaptations, we suggest that the features of thick-enamel and unbalanced distribution pattern in L. lufengensis is related to its adaptation to tough food and broader diets in a seasonal subtropical habitat.
Although extensive research has been carried out in recent years on the origin and evolution of human bipedalism, a full understanding of this question is far from settled. Miocene hominoids are key to a better understanding of the locomotor types observed in living apes and humans. Pierolapithecus catalaunicus, an extinct stem great ape from the middle Miocene (c. 12.0 Ma) of the Vallès‐Penedès Basin (north‐eastern Iberian Peninsula), is the first undoubted hominoid with an orthograde (erect) body plan. Its locomotor repertoire included above‐branch quadrupedalism and other antipronograde behaviours. Elucidating the adaptive features present in the Pierolapithecus skeleton and its associated biomechanics helps us to better understand the origin of hominoid orthogrady. This work represents a new biomechanical perspective on Pierolapithecus locomotion, by studying its patella and comparing it with those drawn from a large sample of extant anthropoids. This is the first time that the biomechanical patellar performance in living non‐human anthropoids and a stem hominid has been studied using finite element analysis (FEA). Differences in stress distribution are found depending on body plan and the presence/absence of a distal apex, probably due to dissimilar biomechanical performances. Pierolapithecus’ biomechanical response mainly resembles that of great apes, suggesting a similar knee joint use in mechanical terms. These results underpin previous studies on Pierolapithecus, favouring the idea that a relevant degree of some antipronograde behaviour may have made up part of its locomotor repertoire. Moreover, our results corroborate the presence of modern great ape‐like knee biomechanical performances back in the Miocene.
The Evolutionary Biology of the Human Pelvis - by Cara M. Wall-Scheffler January 2020
Cambridge Core - Biological Anthropology and Primatology - The Evolutionary Biology of the Human Pelvis - by Cara M. Wall-Scheffler
Forensic anthropologists are frequently faced with the challenge of individualizing and sorting commingled remains in a variety of scenarios. A number of protocols have been proposed to standardize the methodological approach to individuating commingled remains, some of which are focused on pair-matching. A recent study by Karell et al. (2016) proposed a virtual method for pair-matching humeri using a semi-automatic procedure that gave encouraging results. With regards to the phalanges, there are only a handful of studies focusing on identifying and siding phalanges, as well as exploring their directional and functional asymmetry. Yet, they are still as important as every other bone when sorting commingled human remains in various situations, such as archaeological common burials and mass graves, commingled decomposed remains resulting from atrocities, accidents or natural disasters. This study investigates a new method for pair-matching, a common individualization technique, using digital three-dimensional models of bone: mesh-to-mesh value comparison (MVC) as proposed by Karell et al. (2016). The MVC method digitally compares the entire three-dimensional geometry of two bones using an iterative closest point (ICP) algorithm to produce a single value as a proxy for their similarity. The method is automated with the use of Viewbox software 4.1 beta for a simultaneous comparison of all possible pairs. For this study, 515 phalanges from 24 individuals of mixed ancestry were digitized using CT scans and the 3D modeling program AMIRA 5.3.3. The models were also hollowed (internal information of compact and trabecular bone removed) to test the method with simulated surface scan models. The subsequent data—over 73,000 comparisons—were assessed using sensitivity and specificity rates via ROC analysis to indicate how well the automated version of MVC pair-matched phalanges. The best bone in terms of pair-matching was the proximal phalanx of Digit 3 with 87.5% sensitivity and 92.4% specificity rates at a threshold value of 0.488 for the unhollowed bones. The specificity drops slightly (91.1%) when the hollowed models are compared. To compare the performance of the method in all phalanges, the specificity was set to 95%—allowing for a 5% acceptable error—and the adjusted sensitivity was compared. The highest sensitivity, namely 68.8%, was noted for Digit 2 proximal phalanx for both unhollowed and hollowed models. Thus far, our preliminary results indicate that the MVC method performs well when pair-matching phalanges, though it is less accurate than pair-matching other types of bones. The introduction of 95% specificity threshold allows for rejecting pairs in great confidence, which could, for instance, significantly reduce the number of DNA comparisons required for the remaining possible matches. In addition, the similar results obtained from hollowed and unhollowed models indicate that the internal information included in the unhollowed models adds little to the identification of true pairs. This means that if a CT scan is not available, the method could be applied to surface models produced by light and laser scanners as well. While additional work needs to be done to verify these preliminary results, this research has the potential to expand the repertoire of individualization methods.
Substantial differences among the pelves of anthropoids have been central to interpretations of the selection pressures that shaped extant hominoids, yet the evolution of the hominoid pelvis has been poorly understood due to the scarcity of fossil material. A recently discovered partial hipbone attributed to the 10 million-year-old fossil ape Rudapithecus hungaricus from Rudabánya, Hungary, differs from the hipbones of cercopithecids and earlier apes in functionally significant ways. Comparisons were made to extant and other fossil anthropoids using combination of non-landmark-based and linear metrics. Measurements were taken on 3D polygonal models of hipbones collected using laser scans. These metrics capture functionally relevant morphology given the incomplete preservation of the Rudapithecus specimen. This fossil displays features that reflect changes in spinal musculature and torso structure found only in extant great and lesser apes among hominoids. Rudapithecus has an expanded cranial acetabular lunate surface related to orthograde positional behaviors, a shallow acetabulum and relatively short ischium like orangutans and hylobatids. It displays evidence of moderately coronally-oriented iliac blades as in all extant apes and Ateles, and flaring iliac blade shape of siamangs and great apes, associated with some level of spinal stiffness. However, this fossil lacks the long lower ilium that characterizes chimpanzees, gorillas and orangutans, associated with their reduction of the number of lumbar vertebrae. The R. hungaricus pelvis demonstrates that the extreme elongation of the lower ilium seen in extant great apes does not necessarily accompany adaptation to orthograde posture and forelimb-dominated arboreal locomotion in hominoid evolution. Lower iliac elongation appears to have occurred independently in each lineage of extant great apes, supporting the hypothesis that the last common ancestor of Pan and Homo may have been unlike extant great apes in pelvic length and lower back morphology.
The postcranial skeleton of living apes is characterized by a number of derived features that are attributable to the frequent forelimb-dominated orthograde positional behavior such as suspension or vertical climbing. Their axial skeletons exhibit a common specialization, e.g., a decreased number of lumbar vertebrae concomitant with an increase in sacral vertebrae, loss of an external tail, spinal invagination into the thoracic and abdominal cavities, and craniocaudally short and dorsoventrally deep lumbar vertebral centrum. So far, over 30 genera of apes have been discovered from Miocene fossil localities in Africa and Eurasia. However, axial skeletal specimens are available in only a handful of apes. Fossil apes (~19–15 Ma, Kenya) from the beginning and mid-part of the Miocene in Africa (Ekembo and Nacholapithecus) were essentially deliberate arboreal pronograde quadrupeds and retained primitive catarrhine axial skeletal morphology: long and dorsomobile lumbar spine, short sacrum, and absence of spinal invagination (as inferred from ventral position of the lumbar transverse process), though Nacholapithecus shows a hint of an early transition to orthograde positional behavior. However, they did not have an external tail, and their tail loss is almost certainly a shared derived feature with living apes. The penultimate lumbar vertebra of Morotopithecus (20.6 Ma, Uganda) exhibits craniocaudally short and dorsoventrally deep centrum and dorsal position of the transverse process. While these features resemble those in living apes, the evolutionary pattern of the dentognathic morphology and paleobiogeography of Miocene apes suggest that derived lumbar anatomy of Morotopithecus is a product of parallel evolution. European ape fossil record illustrates a progressive evolution toward orthogrady. The stem great ape which spread into Eurasia from Africa between 17 and 16 Ma was pronograde-like contemporary African fossil apes. Pierolapithecus (~12 Ma, Spain) is the earliest known orthograde (but perhaps non-suspensory) ape in Europe although its spine might be less dorsostable compared to extant great apes. Hispanopithecus (9.6 Ma, Spain) had acquired a full suite of orthograde and suspensory characters comparable to extant great apes. Oreopithecus (~8–7 Ma, Italy) also has a fully orthograde spine although its lumbar spine has some distinct features from Hispanopithecus. Some authors have proposed that orthogrady evolved in European and African ape lineages (and Asian as well) independently. However, some others propose that a European orthograde ape dispersed into Africa during the Late Miocene gave rise to the extant African apes and humans. Besides this issue, opinions are divided whether the dorsostable spine in the extant African apes is homologous or homoplastic. Postcranial anatomy of Ardipithecus ramidus suggests to some that the last common ancestor of the extant African apes and humans had an intermediate body plan between pronogrady and orthogrady (“multigrady”) with spinal invagination but without enhanced dorsostability as that in extant great apes. However, an argument continues with regard to this interpretation. Postcranial fossils of African Miocene apes are totally absent after ~12 Ma until the appearance of the earliest putative humans. For further clarification of the evolution of the hominoid spine, new discoveries of postcranial elements of Late Miocene African apes are needed.
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.
Phalangeal curvature is a term describing the presence of convex curvature along the dorsal surface of manual and pedal phalanges. In extant primates, phalangeal curvature is most pronounced in species that engage in high frequencies of arboreal locomotion. For this reason, it has long been used to infer climbing behaviors in fossil primates. This association is supported by research that suggests phalangeal curvature lowers the forces experienced by digits during grasping. The interpretation of phalangeal curvature as a trait indicative of climbing has contributed to long-standing debates regarding the locomotion of well-known fossil hominids. However, proper application of this feature towards interpreting fossil behavior relies on determining if it is a plastic or inherited trait, which is still being explored.
Skeletal functional morphology in primates underlies many fossil interpretations. Understanding the functional correlates of arboreal grasping is central to identifying locomotor signatures in extinct primates. We tested 3 predictions linking substrate orientation and digital grasping pressures: (1) below-branch pressures are greater than above-branch and vertical-branch pressures; (2) there is no difference in pressure exerted across digits within autopods at any substrate orientation, and (3) there is no difference in pressure exerted between homologous digits across autopods at any substrate orientation. Adult males and females from 3 strepsirrhine species crossed an artificial arboreal substrate oriented for above-, below- and vertical-branch locomotion. We compared digital pressures within and across behaviors via ANOVA and Tukey's Honest Significant Difference test. Results show limited support for all predictions: below-branch pressures exceeded vertical-branch pressures and above-branch pressures for some digits and species (prediction 1), lateral digits often exerted greater pressures than medial digits (prediction 2), and pedal digits occasionally exerted greater pressures than manual digits during above-branch and vertical orientations but less often for below-branch locomotion (prediction 3). We observed functional variability across autopods, substrate and species that could underlie morphological variation within and across primates. Future work should consider the complexity of arboreality when inferring locomotor modes in fossils.
Torso-orthograde (TO)-positional behavior
and an associated suite of postcranial morphological specializations
, both of which are often linked to the evolution of large body size
, are considered hallmarks of hominoid evolution
. These features are thought to have played an important role in the Old World monkey-ape divergence and the development of upright bipedal locomotion
in our own lineage. Compared to early theorists, who considered hylobatids an appropriate model for investigating the initial stages of hominoid evolution, more recent reconstructions of the last common ancestor of hominoids
have advocated a larger-bodied, more generalized ape very different from hylobatids as the most likely morphotype. While field observations from the large-bodied non-human hominids (i.e., Asian and African apes) confirm that they do in fact utilize an expansive TO-positional repertoire, no detailed data from hylobatids has been available until now to fully evaluate this hypothesis in light of all hominoid taxa. Using recently published positional behavior data from a population of adult white-handed
gibbons
(
Hylobates lar
) from Khao Yai National Park
, Thailand
, and integrating these data with a diverse anthropoid primate comparative sample, we reevaluate differences in positional behavior of extant cercopithecoids
and hominoids. The comparative dataset agrees with recent suggestions that all living apes share a diverse TO-positional repertoire, relative to that of cercopithecoid monkeys. The question, whether or not TO-anatomical specializations and behavior among the Hominoidea represent homologous or homoplastic traits or both, could not yet be answered conclusively, despite the fact that homologous evolution is the more parsimonious explanation, due to a lack of support from the fossil record. Nevertheless, an upright (TO) and enhanced exploitation of the arboreal tree canopy
by our ape ancestors were likely key evolutionary novelties that helped to shape the origin of hominins. Only an expansive understanding of the diversity of both extant and extinct apes
will help to comprehensively unravel our enigmatic origins.
To understand the hand of living primates from an adaptive perspective, data on the morphological pattern of the earliest primates is required. This chapter discusses what is known about the early evolution of primate hands based on fossils of Paleogene plesiadapiforms (potential stemprimates), adapiforms, omomyiforms, and anthropoids. Implications of these data for understanding locomotor transitions during the origin and early evolutionary history of primates is considered.
Though the number of plesiadapiform species known from well preserved postcranial skeletons remains small, known species are similar to extant primates in both their intrinsic hand proportions and hand-to-body size proportions. Nonetheless, the presence of claws and a different metacarpophalangeal form in plesiadapiforms suggests grasping mechanics unlike those of either extant primates or Eocene adapiforms and omomyiforms. We find that non-adapine adapiforms and the basal omomyiform Teilhardina resemble tarsiers and some galagos in having extremely elongated proximal phalanges and digit rays relative to metacarpals. Looking at hand-to-body size proportions, all sampled adapiforms appear to be average compared to extant primate diversity, whereas Teilhardina seems to have had extremely large hands for its size like tarsiers and Daubentonia. Non-adapine adapiforms and omomyiforms exhibit carpal features suggesting more limited dorsiflexion, greater ulnar deviation, and a more habitually divergent (or abducted) pollex than observed plesiadapiforms. Together, features differentiating adapiforms and omomyiforms from plesiadapiforms indicate increased reliance on vertical clinging and grasp-leaping, possibly in combination with predatory behaviors in ancestral euprimates.
Understanding how primate hands have become adapted to meet a variety of locomotor and manipulative demands requires detailed knowledge of the functional consequences associated with evolutionary changes in the anatomy. Given the complex configuration of the bones and articulations that compose the hand and wrist, this is a challenging task. Such an endeavor must take into account data on hand use in living primates and how the mechanics of the bones and joints facilitate these activities. The application of biomedical imaging, computer modeling, and engineering techniques to study structure and function provides an important mechanical link between fine-scale morphological studies and necessarily courser in vivo observations on hand use. This chapter reviews recent attempts to incorporate such methods to better quantify aspects of bone shape, joint kinematics, and load transmission in the hand. Examples are provided of how such studies might illuminate key shifts in the function of the hominin hand as it evolved from its primitive condition as a primarily locomotor structure to a derived organ principally involved in manipulative tasks such as tool making and use.
For many years John Fleagle's text on the adaptation and evolution of primates and early hominoid fossils was the the text of choice for teachers and research workers alike. Now, as the only such work in print, this new edition brings this coverage up to date with the latest fossil finds and most current research.The book retains its grounding in the extant primate groups as the best way to understand the fossil trail and the evolution of these modern forms. But this coverage is now streamlined, making reference to the many new and excellent books on living primate ecology and adaptation - a field that has burgeoned since the first edition of Primate Adaptation and Evolution. By drawing out the key features of the extant families and referring to more detailed texts, Fleagle sets the scene and also creates space for a thorough updating of the exciting developments in primate palaeontology - and the reconstruction through early hominid species - of our own human origins.Illustrated with many of the classic pictures from earlier editions - and whole new suite of illustrations, revised evolutionary trees and tables - this book remains the indispensible text on this fascinating subject.
The methods and techniques of light microscopy and scanning electron microscopy are briefly described, and the advantages of polarization microscopy are discussed. Particularly, light microscopy is a useful tool to diagnose fossil bone at the micro-level. Selected samples of fossilized human bones (e.g., Australopithecus, Homo erectus, Homo neanderthalensis, and Paleolithic Homo sapiens) were examined using plain and polarized light. The histomorphological findings show that microscopic research adds much to what can be found by macroscopic examination or by X-ray techniques. In particular, emphasis is placed on morphological structures that give clues to the taxonomy and the functional anatomy of early hominids. Furthermore, morphological structures which originated during the lifetime of the individual (e.g., individual age at death, physical strain, diseases) are explicable. Future perspectives of microscopic analyses are discussed.
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 fossil remains of nine individuals attributable to the Miocene hominoid genus Proconsul were recovered during 1984 and 1985 from the Kaswanga Primate Site on Rusinga Island, Kenya. Among the thousands of bone fragments recovered were hundreds of phalangeal fragments, which have been collected and assembled into 247 separate identifiable phalanges or phalangeal fragments, representing nine of ten identified Kaswanga individuals. This sample is many times larger than any other Miocene hominoid phalangeal sample, and preserves several examples of every hand and foot phalanx from both sexes (deduced from associated cranial remains) in several age categories. This allows for a much greater understanding of normal ranges of variation and for a more detailed reconstruction of positional behavior in Proconsul.
Thesis (Ph. D.)--State University of New York at Stony Brook, 1998. Includes bibliographical references (leaves 217-237).
Measurements of the chord length (alpha M0.31) and diameter (alpha M0.35) of the femora, tibiae, humeri and radii from 32 species of mammals, ranging in approximate body mass from 0.020-3500 kg, support previous data which show that mammalian long bones scale close to geometric similarity. Scaling of peak stresses based on these measurements of limb bone geometry predicts that peak stress increases alpha M0.28, assuming that the forces acting on a bone are directly proportional to an animal's weight. Peak locomotory stresses measured in small and large quadrupeds contradict this scaling prediction, however, showing that the magnitude of peak bone stress is similar over a range of size. Consequently, a uniform safety factor is maintained. Bone curvature (alpha M-0.09) and limb bone angle relative to the direction of ground force (alpha M-0.07) exhibit a slight, but significant, decrease with increasing body mass. Duty factor measured at the animal's trot--gallop transition speed does not change significantly with body size. The moment arm ratio of ground force to muscular force exerted about a joint was found to decrease dramatically for horses as compared to ground squirrels and chipmunks. This six-fold decrease (alpha M-0.23) provides preliminary data which appear to explain, along with the decrease in bone curvature and angle, the similar magnitudes of peak bone stress developed during locomotion in different sized animals. The crouched posture adopted by small quadrupeds while running may allow greater changes in momentum (when accelerating or decelerating) or a decrease in the forces exerted on their limbs.
Comparative morphological and functional analyses of the skeletal remains of Oreopithecus bambolii, a hominoid from the Miocene Mediterranean island of Tuscany-Sardinia (Italy), provides evidence that bipedal activities made up a significant part of the positional behavior of this primate. The mosaic pattern of its postcranial morphology is to some degree convergent with that of Australopithecus and functionally intermediate between apes and early hominids. Some unique traits could have been selected only under insular conditions where the absence of predators and the limitation of trophic resources play a crucial role in mammalian evolution.
Textural properties and functional morphology of the hip bone cancellous network of Oreopithecus bambolii, a 9- to 7-million-year-old Late Miocene hominoid from Italy, provide insights into the postural and locomotor behavior of this fossil ape. Digital image processing of calibrated hip bone radiographs reveals the occurrence of trabecular features, which, in humans and fossil hominids, are related to vertical support of the body weight, i.e., to bipedality.
A partial hominoid skeleton just older than 15 million years from sediments in the Tugen Hills of north central Kenya mandates
a revision of the hominoid genus Kenyapithecus, a possible early member of the great ape–human clade. The Tugen Hills specimen represents a new genus, which also incorporates
all material previously referable to Kenyapithecus africanus. The new taxon is derived with respect to earlier Miocene hominoids but is primitive with respect to the younger species
Kenyapithecus wickeri and therefore is a late member of the stem hominoid radiation in the East African Miocene.
Recent paleontological discoveries in Madagascar document the existence of a diverse clade of palaeopropithecids or "sloth lemurs": Mesopropithecus (three species), Babakotia (one species), Palaeopropithecus (three species), and Archaeoindris (one species). This mini-radiation of now extinct ("subfossil") lemurs is most closely related to the living indrids (Indri, Propithecus, and Avahi). Whereas the extant indrids are known for their leaping acrobatics, the palaeopropithecids (except perhaps for the poorly known giant Archaeoindris) exhibit numerous skeletal design features for antipronograde or suspensory positional behaviors (e.g., high intermembral indices and mobile joints). Here we analyze the curvature of the proximal phalanges of the hands and feet. Computed as the included angle (theta), phalangeal curvature develops in response to mechanical use and is known to be correlated in primates with hand and foot function in different habitats; terrestrial species have straighter phalanges than their arboreal counterparts, and highly suspensory forms such as the orangutan possess the most curved phalanges. Sloth lemurs as a group are characterized by very curved proximal phalanges, exceeding those seen in spider monkeys and siamangs, and approaching that of orangutans. Indrids have curvatures roughly half that of sloth lemurs, and the more terrestrial, subfossil Archaeolemur possesses the least curved phalanges of all the indroids. Taken together with many other derived aspects of their postcranial anatomy, phalangeal curvature indicates that the sloth lemurs are one of the most suspensory clades of mammals ever to evolve.
Molecular studies suggest that the lineages leading to humans and chimpanzees diverged approximately 6.5-5.5 million years (Myr) ago, in the Late Miocene. Hominid fossils from this interval, however, are fragmentary and of uncertain phylogenetic status, age, or both. Here I report new hominid specimens from the Middle Awash area of Ethiopia that date to 5.2-5.8 Myr and are associated with a wooded palaeoenvironment. These Late Miocene fossils are assigned to the hominid genus Ardipithecus and represent the earliest definitive evidence of the hominid clade. Derived dental characters are shared exclusively with all younger hominids. This indicates that the fossils probably represent a hominid taxon that postdated the divergence of lineages leading to modern chimpanzees and humans. However, the persistence of primitive dental and postcranial characters in these new fossils indicates that Ardipithecus was phylogenetically close to the common ancestor of chimpanzees and humans. These new findings raise additional questions about the claimed hominid status of Orrorin tugenensis, recently described from Kenya and dated to approximately 6 Myr.
Sivapithecus was resident in South Asia for over 5 million years. Its first appearance (ca. 12.7 Ma) and its last occurrence (ca. 6.8 Ma) in Siwalik sediments are likely to have coincided with global climatic and tectonic/eustatic events. Based on all available material, mostly limited to teeth, it appears that Sivapithecus experienced little significant anatomical change throughout this long period of time, nor is there evidence that the genus was extensively speciose. We do know that it was not a very common taxon in the Siwaliks. Assuming limited taphonomic bias in collecting, the genus probably never represented more than 1% of the overall mammalian community. For these reasons, the taxonomic status of Sivapithecus is still very much an open question, and we still have a rather limited understanding of the functional biology of its masticatory and locomotor systems. However, important new specimens attributable to Sivapithecus have been recovered over the last several years from Pakistan, and these new fossils, in conjunction with intensive pro-grams of magnetostratigraphic and sedimentological correlation have done much to narrow the focus on discussion. Nevertheless, neither the fossils nor the contextual data have brought consensus to the question of the relation ships of Sivapithecus to other Miocene large hominoid taxa outside of South Asia, or to the living great apes and humans. It is my intention here to evaluate the placement of Sivapithecus within the Hominoidea using all available fossil material, including some new specimens not yet formally described.
Seventeen hominoid fossils recovered from Pliocene strata at Aramis, Middle Awash, Ethiopia make up a series comprising dental, cranial and postcranial specimens dated to around 4.4 million years ago. When compared with Australopithecus afarensis and with modern and fossil apes the Aramis fossil hominids are recognized as a new species of Australopithecus-A. ramidus sp. nov. The antiquity and primitive morphology of A. ramidus suggests that it represents a long-sought potential root species for the Hominidae.
In this paper, I present an updated version of the hylobatian model for
the proximate ancestors of the Hominidae. The hylobatians are
hypothesized to have been relatively small creatures that were
especially adapted for vertical climbing on tree trunks and vines and
for bipedalism on horizontal boughs. They were no more disposed toward
suspensory behaviours than are modern chimpanzees and bonobos. According
to this evolutionary scenario, bipedalism preceded the emergence of the
Hominidae. The earliest hominids would be recognized as diurnally
terrestrial bipeds that stood with full extension of the knee joints and
walked with greater extension of the lower limbs than is common in
non-human primates that are induced to walk bipedally on the ground. The
wealth of hominid fossils from the Hadar Formation, Ethiopia, and the
Laetolil Formation, Tanzania, are generally compatible with the
hylobatian model. They show that by ca. 4 Ma B.P. habitually
terrestrial, bipedal hominids had evolved from arboreal ancestors. The
Hadar hominids had curved fingers and toes, strong great toes and
thumbs, and other features that suggest that they were rather recently
derived from arboreal hominids and that they probably continued to enter
trees, perhaps for night rest and some foraging. The hominid hand bones
from Hadar evince no features that are distinctly related to
knuckle-walking. They relate neatly to counterparts in the hand of O.H.
7, a specimen that was found with stone tools. However, there is no
evidence that the Hadar hominids of 3 Ma ago engaged in tool behaviour.
Last autumn marked the 25th anni- versary of the discovery of "Lucy." While that certainly was a momentous event in paleoanthropology, it had no less profound an effect on my aca- demic life, for it presaged my eventual seduction into the arena of hominid fossil interpretation. My friend John Fleagle, editor of Evolutionary An- thropology, says I may introduce this paper with a history of that experi- ence. He assures me this is appropri- ate because I have now reached the age when young people in the field have no idea who I am.
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.
It has previously been reported that brachiating primates, particularly gibbons, are characterized by distinctively straight forelimb long bones, yet no hypotheses have been proposed to explain why straight limb bones may be adaptive to suspensory locomotion. This study explores quantitatively the curvature of the long bones in 13 species of anthropoid primates and analyzes the functional consequences of curvature in biomechanical terms. These analyses demonstrate that, whereas the humeri of gibbons and spider monkeys are functionally less curved than those of other taxa, the ulnae of brachiators are neither more nor less curved than those of other anthropoids, and the gibbon radius is far more curved than would be predicted from body size alone. The humerus is likely significantly less curved in brachiators because of its torsion-dominated loading regime and the greatly increased stress magnitude developed in torsionally loaded curved beams. The large curvature of the radius is localized in the region of attachment of the supinator muscle. Analysis presented here of muscle mass allometry in catarrhines demonstrates that gibbons are characterized by an extremely massive supinator, and the large radial curvature is therefore most likely due to forearm muscle mechanics. This study also demonstrates that the overall pattern of limb bone curvature for anthropoids is distinct from the pattern reported for mammals as a whole. This distinctive scaling relationship may be related to the increased length of the limb bones of primates in comparison to other mammals.
Numerous studies of the locomotor skeleton of the Hadar hominids have revealed traits indicative of both arboreal climbing/suspension and terrestrial bipedalism. These earliest known hominids must have devoted part of their activities to feeding, sleeping and/or predator avoidance in trees, while also spending time on the ground where they moved bipedally. In this paper we offer new data on phalangeal length and curvature, moφhology of the tarsus and metatarsophalangeal joints, and body proportions that further strengthen the argument for arboreality in the Hadar hominids. We also provide additional evidence on limb and pedal proportions and on the functional anatomy of the hip, knee and foot, indicating that the bipedality practiced at Hadar differed from that of modern humans. Consideration of the ecology at Hadar, in conjunction with modern primate models, supports the notion of arboreality in these earliest australopithecines. We speculate that selection for terrestrial bipedality may have intensified through the Plio-Pleistocene as forests and woodland patches shrunk and the need arose to move increasingly longer distances on the ground. Only with Homo erectus might body size, culture and other factors have combined to ‘release’ hominids from their dependence on trees.
Dryopithecus has been known longer than most fossil primate taxa, but until recently was only represented by fragmentary jaws and isolated teeth. New specimens, including postcrania and relatively complete cranial remains, provide much new evidence on the biology of Dryopithecus and its relations t o other primates. The phylogenetic evidence indicates that Dryopithecus is probably more closely related to the African apes and humans than is Sivapithecus. When compared closely to living forms, Dryopithecus shares more with gorillas. This does not imply a close relationship between Dryopithecus and gorillas, since the similarities between the two are all primitive characters. Instead, it suggests that chimps and humans, which lack these characters, share a series of alternative character states that are derived, and indicative of a close evolutionary relationship between them. Humans probably diverged from a very chimp-like ancestor characterized by much of the ecology and behavior of living chimps, including knuckle-walking. But the earliest humans must have been ecologically quite distinctive, and not very much like any living primate, to account for the dramatic morphological changes that mark human origins. © 1994 Wiley-Liss, Inc.
Anatomical descriptions are presented for the foot bones recovered from the Hadar Formation during the 1974–1977 field seasons inclusive.
Comparisons of hominoid metacarpals and phalanges reveal differences, many of which are closely linked to locomotor hand postures. The African apes display features of the metacarpals and phalanges which distinguish them from the other Hominoidea. These features are most evident in digits III and IV. The orangutan hand is demonstrably less well adapted to knuckle-walking and is distinctive in its adaptation to power and hook grasping of vertical and horizontal supports, respectively. Orangutan fingers possess a “double-locking” mechanism (Napier, '60), and a slight ulnad shift in the axis of the hand which results in lengthened phalanges of ray IV. Hylobatid apes are more like orangutans in their finger morphology than any of the other Hominoidea, but exhibit unique features of their own. These include elongate phalanges of fingers II-V. Human metacarpals II-V form two sets composed of II-III, and IV-V. The heads of both metacarpals II and III are characterized by axial torsion. This reflects the enhanced manipulatory role of the third finger in humans. Human distal phalanges are unique in the development of pronounced apical tufts.
Multivariate analysis of metacarpal III and proximal III yields variables that array the extant apes along an arboreal-terrestrial axis, from hylobatid apes to male gorillas. The positions of taxa on this discriminant concur with observations on the locomotion of free-ranging apes.
Observations on the behavior of living hominoids show generic differences in the use and posture of the wrist joint. Both
orang-utans and hylobatids usually use the wrist in suspensory behaviors. However, orang-utans emphasize markedly adducted
and flexed wrist postures, while hylobatids emphasize violent forearm and wrist rotation. African apes, especially the gorilla,
use the wrist more frequently than other hominoids for terrestrial quadrupedal weight-bearing. Humans use the wrist less frequently
for supportive purposes than do other hominoids. These behavioral differences correspond to structural specializations in
the proximal carpal joint of each of the hominoid genera. Although each of the hominoid genera has apparently modified its
proximal carpal joint best to serve its characteristic behaviors, all hominoids share a unique proximal carpal joint that
permits approximately 160ℴ of forearm rotation. The hylobatid proximal carpal joint is specialized in exhibiting a marked
development of those structures limiting forearm rotation, but it is in most respects the least derived— that is, closest
to the nonhominoid anthropoids. Chimpanzees show a proximal carpal joint that is more generalized than those of the other
great apes but more derived than that of hylobatids. The human and gorilla proximal wrist joints, on the other hand, show
marked modifications for weight-bearing in terrestrial behaviors. Orang-utans have the most derived proximal carpal joint,
which in many respects parallels that of the slow-climbing nonhominoid primates. The comparative anatomy and structural specializations
of the wrist joint support (a) an early divergence of hylobatids from the common hominoid stock, (b) a common ancestry for
gorillas and humans separate from the other hominoids, and (c) a long independent evolutionary period for orang-utans since
their divergence from the common hominoid stock, or one that was marked by strong selection pressures for wrist specializations.
Unfortunately, the generalized condition of the chimpanzee’s wrist joint and the very derived condition of the orang-utan
wrist provide uncertain evidence as to which of the two was first to diverge from the common hominoid stock. Identification
of hominoid wrist specializations as reflecting real phylogenetic relationships or parallelisms depends on how well the phytogeny
inferred from wrist morphology accords with those arrived at from the study of other systems.
The paleontological evidence pertaining to the evolution of the modern diversity in structure and function of primate hands is reviewed. A reconstructed digit ofPlesiadapis shows characters and functional capacities typical of an arboreal way of life. In euprimates, we describe the strepsirhine morphotype hand, characterized by a relatively high degree of pollical divergence, features of the ulnocarpal articulation that imply an enhanced capacity for ulnar deviation, and relatively long digits; this hand is specialized for grasping. Hand remains ofSmilodectes, Adapis and a Messel adapiform reveal a remarkable diversity in carpal structure achieved in these Eocene adapiforms, due to differing locomotor evolutionary pathways. The subfossil lemuriformsMegaladapis andPalaeopropithecus both show stereotyped (but different) grasping capabilities.
The simiiform morphotype hand combines a relatively low degree of pollical divergence, features of the ulnocarpal articulation that imply a limited capacity for ulnar deviation, and relatively long metacarpals and short digits. This type of hand anatomy is mechanically well-suited to arboreal palmigrade quadrupedalism. The hands ofPliopithecus andMesopithecus are generally monkey-like.Oreopithecus' hand fits with its presumed suspensory habits. The hand ofProconsul suggests palmigrade quadrupedalism and climbing.Australopithecus afarensis' hand remains primarily a branch-grasping organ, with indications of enhanced manipulatory abilities.Homo habilis andParanthropus robustus illustrate two lines of increased tool-use abilities.
The euprimate morphotype hand was elongated, had a short carpus and limited mobility, but the corresponding locomotor mode remains speculative. Considerations on hand evolution in some living primate groups are included in the final summary of hand evolution in primates.
Two calcanei, a cuboid, and three manual phalanges of Late Miocene Sivapithecus from Pakistan are described. The morphology of the foot bones suggests that considerable rotation around the long axis of the foot resulted from movements at the subtalar and transverse tarsal joints. This was accompanied by other movements at the subtalar joint. Articular features of the phalanges are similar to those of palmigrade quadrupeds. However, features of shaft curvature and robusticity imply that the fingers were also subjected to tensile stresses. The combined evidence of these and previously described specimens suggests that arboreal quadrupedalism and climbing were distinctive features of Sivapithecus positional behavior.
Functional features of the articular surfaces of the joints of the elbow region are described for a number of extant and fossil anthropoids. At the humeroradial and proximal radioulnar joints of extant hominoids a complex of features occurs that guarantees stability throughout extensive pronation-supination movements. By contrast, in extant non-hominoids the morphology of these joints is such as to permit more limited movement and to provide a close-packed position in full pronation. Ramapithecines and Oreopithecus resemble extant hominoids in these features, while Proconsul exhibits some features of both groups of extant anthropoids. The other Oligocene and Miocene anthropoids investigated all resemble extant non-hominoids. Major differences in the humeroulnar joint relate mostly to different means of stabilizing the joint. In extant hominoids, Oreopithecus, and ramapithecines the joint is truly trochleiform and is stabilized against forces acting in any direction. In other Oligo-Miocene anthropoids except Proconsul, and in extant non-hominoids, the main joint surface is more cylindrical, and is stabilized by an anterodistally projecting flange medially and a posteriorly projecting flange laterally. These features are best developed in cercopithecoids. It is suggested that in cebids the humeroulnar joint is translatory, but that it is non-translatory in all the extant and fossil catarrhines considered.
Proximal phalanges recovered from Oligocene sediments of the Jebel Qatrani Formation, Fayum Province, Egypt, are attributed to the anthropoids Aegyptopithecus and Apidium. A multivariate discriminant function analysis using phalangeal shape indices proved reliable for distinguishing between manual and pedal proximal phalanges of extant primates, and these data can be applied to classify phalanges of fossil primates. Manual and pedal phalanges of Aegyptopithecus show features clearly related to a quadrupedal arboreal lifestyle involving frequent and powerful digital flexion: plantar tubercles are prominent, the flexor sheath ridges are well developed, shaft height increases proximally, shaft cortices are thickest in their distal halves, and the phalanges display strong dorsoventral curvature. Proximal phalanges of Aegyptopithecus resemble those of extant Alouatta, and to a lesser extent those of colobine primates, in these respects. These fossil phalangeal specimens resemble quadrupedal cercopithecids in having large palmar and plantar tubercles, flaring basal apophyses, robust shafts, and dorsally extended and proximodorsally tilted metacarpal and metatarsal facets. Manual and pedal phalanges of Apidium have straight, robust shafts with cortices of equal thickness throughout, relatively dorsoventrally compressed condyles, weak flexor ridges, and a flared base for insertion of the collateral ligaments and interosseous musculature. These features suggest a locomotor repertoire for Apidium that is well suited for stable digital extension during quadrupedal running on horizontal substrates with little emphasis on grasping capabilities. These features compare most favourably with those of the phalanges of extant Saimiri.
In recent years there have been renewed attempts to elucidate the phylogenetic affinities and taxonomic status of Oreopithecus bambolii from the late Miocene of Europe. The majority of previous workers who have studied the material have concluded that it represents a hominoid primate, albeit a rather specialized one. Several recent workers have revived the earlier suggestion that Oreopithecus may be a cercopithecoid primate, based mainly on presumed synapomorphies of the dentition. Although there are some general structural similarities between the cheek teeth of Oreopithecus and those of Old World monkeys, comparisons indicate that this resemblance is likely to be due to functional convergence, related to dietary similarities, rather than due to a close phyletic relationship. The cranio-dental features of Oreopithecus appear to be a combination of primitive catarrhine characters and autapomorphies.Much more informative evidence for determining the phyletic affinities of Oreopithecus is provided by the postcranial skeleton. Oreopithecus shares with the living hominoids a unique range of derived catarrhine features of the postcranium that are so detailed that there seems little possibility that they could have been developed independently in the two taxa. The present evidence best supports the conclusion that Oreopithecus has its closest affinities with the living hominoids. However, the relationships of Oreopithecus to taxa within the Hominoidea have proved difficult to ascertain, owing to a lack of synapomorphies with living representatives of the superfamily. In view of the uniquely derived facial characteristics of Oreopithecus bambolii, the species clearly warrants inclusion in a distinct hominoid family, the Oreopithecidae.
A major contribution of previous analyses of Miocene hominoid postcrania is the recognition of a great ape grade of locomotor morphology in the late Miocene. However, in the absence of a consideration of the taxonomic and phylogenetic implications of the specimens concerned, the importance of this conclusion remains unappreciated. This paper presents a revised view of the positional implications of late Miocene hominid fossils and considers some of the taxonomic and phyletic implications of these specimens. The taxonomic status of a number of large catarrhine specimens from Europe (attributed to Dryopithecus, Sivapithecus, Austriacopithecus, Paidopithex, Rudapithecus) is discussed. The functional and phyletic significance of this material reveals a complex pattern of behavioral and phyletic diversity among large-bodied catarrhines in Europe and suggests that this diversity evolved in situ from circum-Mediterranean middle Miocene ancestors.
Mechanical hypotheses concerning the function of chimpanzee anatomical specializations are examined in light of recent positional behavior data. Arm-hanging was the only common chimpanzee positional behavior that required full abduction of the humerus, and vertical climbing was the only distinctive chimpanzee positional behavior that required forceful retraction of the humerus and flexion of the elbow. Some elements of the chimpanzee anatomy, including an abductible humerus, a broad thorax, a cone-shaped torso, and a long, narrow scapula, are hypothesized to be a coadapted functional complex that reduces muscle action and structural fatigue during arm-hanging. Large muscles that retract the humerus (latissimus dorsi and probably sternocostal pectoralis major and posterior deltoid) and flex the elbow (biceps brachii, probably brachialis and brachioradialis) are argued to be adaptations to vertical climbing alone. A large ulnar excursion of the manus and long, curved metacarpals and phalanges are interpreted as adaptations to gripping vertical weight-bearing structures during vertical climbing and arm-hanging. A short torso, an iliac origin of the latissimus dorsi, and large muscles for arm-raising (caudal serratus, teres minor, cranial trapezius, and probably anterior deltoid and clavicular pectoralis major) are interpreted as adaptations to both climbing and unimanual suspension.
New humeri of two species of the Miocene hominoid Sivapithecus are described from near Chinji in Pakistan from between approximately 9 and 11 Myr ago. Sivapithecus, a middle and late Miocene hominoid from Turkey and Indo-Pakistan, is overall unlike any living hominoid, although facial-palatal similarities to the extant orangoutan, Pongo, have been used to support a hypothesis of close relationship. Living hominoids have postcranial similarities assumed to be shared derived, among them features of the proximal humerus. However, the new Sivapithecus proximal humeri differ from those of living hominoids, supporting an alternative hypothesis in which Sivapithecus and Pongo are not closely related. It is not clear how to choose between these incompatible hypotheses.
The history of discovery and interpretation of primate footprints at the site of Laetoli in northern Tanzania is reviewed. An analysis of the geological context of these tracks is provided. The hominid tracks in Tuff 7 at Site G in the Garusi River Valley demonstrate bipedality at a mid-Pliocene datum. Comparison of these tracks and the Hadar hominid foot fossils by Tuttle has led him to conclude that Australopithecus afarensis did not make the Tanzanian prints and that a more derived form of hominid is therefore indicated at Laetoli. An alternative interpretation has been offered by Stern and Susman who posit a conforming "transitional morphology" in both the Tanzanian prints and the Ethiopian bones. The present examines both hypotheses and shows that neither is likely to be entirely correct. To illustrate this point, a reconstruction of the foot skeleton of a female A. afarensis is undertaken, and the results are compared to the Laetoli tracks. We conclude that A. afarensis represents the best candidate for the maker of the Laetoli hominid trails.
New hand fossils from Swartkrans (dated at about 1.8 million years ago) indicate that the hand of Paranthropus robustus was
adapted for precision grasping. Functional morphology suggests that Paranthropus could have used tools, possibly for plant
procurement and processing. The new fossils further suggest that absence of tool behavior was not responsible for the demise
of the "robust" lineage. Conversely, these new fossils indicate that the acquisition of tool behavior does not account for
the emergence and success of early Homo.
Forty-six specimens of a large Miocene hominoid, Afropithecus turkanensis, recently recovered from northern Kenya preserve many morphological details that are described. The specimens include cranial, mandibular, and postcranial parts. They are compared briefly with other Miocene hominoids. It is suggested that Afropithecus may have affinities with Heliopithecus, Kenyapithecus, and the large hominoid from Moroto and Napak, although it is noted that the comparative material is limited in the number of common anatomical parts preserved.
The postcranial skeleton of Australopithecus afarensis from the Hadar Formation, Ethiopia, and the footprints from the Laetoli Beds of northern Tanzania, are analyzed with the goal of determining (1) the extent to which this ancient hominid practiced forms of locomotion other than terrestrial bipedality, and (2) whether or not the terrestrial bipedalism of A. afarensis was notably different from that of modern humans. It is demonstrated that A. afarensis possessed anatomic characteristics that indicate a significant adaptation for movement in the trees. Other structural features point to a mode of terrestrial bipedality that involved less extension at the hip and knee than occurs in modern humans, and only limited transfer of weight onto the medial part of the ball of the foot, but such conclusions remain more tentative than that asserting substantive arboreality. A comparison of the specimens representing smaller individuals, presumably female, to those of larger individuals, presumably male, suggests sexual differences in locomotor behavior linked to marked size dimorphism. The males were probably less arboreal and engaged more frequently in terrestrial bipedalism. In our opinion, A. afarensis from Hadar is very close to what can be called a "missing link." We speculate that earlier representatives of the A. afarensis lineage will present not a combination of arboreal and bipedal traits, but rather the anatomy of a generalized ape.
It has been generally assumed and theoretically argued that the curvature of finger and toe bones seen in some nonhuman primates is associated with cheiridial use in an arboreal setting. Assessment of such curvature in fossil primates has been used to infer the positional behavior of these animals. Several methods of quantifying curvature of bones have been proposed. The measure most commonly applied to phalanges is that of included angle, but this has come under some criticism. We consider various other approaches for quantifying phalangeal curvature, demonstrating that some are equivalent to use of included angle, but that one--normalized curvature moment arm (NCMA)--represents a true alternative. A comparison of NCMA to included angle, both calculated on manual and pedal proximal phalanges of humans, apes, some monkeys, and the Hadar fossils, revealed that these two different measures of curvature are highly correlated and result in very similar distributional patterns.
Seventeen hominoid fossils recovered from Pliocene strata at Aramis, Middle Awash, Ethiopia make up a series comprising dental, cranial and postcranial specimens dated to around 4.4 million years ago. When compared with Australopithecus afarensis and with modern and fossil apes the Aramis fossil hominids are recognized as a new species of Australopithecus--A. ramidus sp. nov. The antiquity and primitive morphology of A. ramidus suggests that it represents a long-sought potential root species for the Hominidae.
Recent discussions of the pedal morphology of Australopithecus afarensis have led to conflicting interpretations of australopithecine locomotor behavior. We report the results of a study using computer aided design (CAD) software that provides a quantitative assessment of the functional morphology of australopithecine metatarsophalangeal joints. The sample includes A. afarensis, Homo sapiens, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus. Angular measurements of the articular surfaces relative to the long axes of the metatarsals and phalanges were taken to determine whether the articular surfaces are plantarly or dorsally oriented. Humans have the most dorsally oriented articular surfaces of the proximal pedal phalanges. This trait appears to be functionally associated with dorsiflexion during bipedal stride. Pongo has the most plantarly oriented articular surfaces of the proximal pedal phalanges, probably reflecting an emphasis on plantarflexion in arboreal positional behaviors, while the African hominoids are intermediate between Pongo and Homo for this characteristic. A. afarensis falls midway between the African apes and humans. Results from an analysis of metatarsal heads are inconclusive with regard to the functional morphology of A. afarensis. Overall, the results are consistent with other evidence indicating that A. afarensis was a capable climber.
A partial skeleton attributed to Proconsul nyanzae (KNM-MW 13142) is described. The fossils were found at a site on Mfangano Island, Kenya, which dates to 17.9 +/- .1 million years ago. KNM-MW 13142 consists of six partial vertebrae (T12-S1), a nearly complete hipbone, most of the right femur and left femoral shaft, a fragmentary tibia and fibula, and a nearly complete talus and calcaneus. This skeleton provides the first pelvic fossil known for any East African Miocene hominoid. The new Proconsul specimen is compared to a large sample of extant anthropoids to determine its functional and phylogenetic affinities. In most aspects of its anatomy, KNM-MW 13142 closely resembles nonhominoid anthropoids. This individual had a long, flexible spine, narrow torso, and habitually pronograde posture, features characteristic of most extant monkeys. Evidence of spinal musculature suggests a generalized condition intermediate between that of cercopithecoids and hylobatids. The hindlimb of KNM-MW 13142 exhibits relatively mobile hip and ankle joints, with structural properties of the femur like those of hominoids. This mix of features implies a pattern of posture and locomotion that is unlike that of any extant primate. Many aspects of the Proconsul nyanzae locomotor skeleton may represent the primitive catarrhine condition.
The evolution of skeletal adaptations to orthograde postures, characteristic of extant hominoids, is of great interest as it provides the key to understanding the origins of apes and humans. We report here the recent discovery of an extraordinary partial skeleton of Dryopithecus laietanus from Can Llobateres (Spain). It provides evidence that orthograde postures and locomotion appeared at least 9.5 million years ago. Our results indicate that the body structure of this Miocene ape closely resembles that of extant hominoids and differs from the pronograde pattern of Miocene proconsulids in a set of important morphological characters. Dryopithecus also shows more traits reflecting structural adaptations for suspension than occurs in African apes. A similar positional behaviour is inferred for Sivapithecus indicus, thus strengthening previous hypotheses linking both Miocene forms with Pongo.
The vertical-climbing account of the evolution of locomotor behavior and morphology in hominid ancestry is reexamined in light of recent behavioral, anatomical, and paleontological findings and a more firmly established phylogeny for the living apes. The behavioral record shows that African apes, when arboreal, are good vertical climbers, and that locomotion during traveling best separates the living apes into brachiators (gibbons), scrambling/ climbing/brachiators (orangutans), and terrestrial quadrupeds (gorillas and chimpanzees). The paleontological record documents frequent climbing as an ancestral catarrhine ability, while a reassessment of the morphology of the torso and forelimb in living apes and Atelini suggests that their shared unique morphological pattern is best explained by brachiation and forelimb suspensory positional behavior. Further, evidence from the hand and foot points to a terrestrial quadrupedal phase in hominoid evolution prior to the adoption of bipedalism. The evolution of positional behavior from early hominoids to hominids appears to have begun with an arboreal quadrupedal-climbing phase and proceeded though an orthograde, brachiating, forelimb-suspensory phase, which was in turn followed by arboreal and terrestrial quadrupedal phases prior to the advent of hominid bipedality. The thesis that protohominids climbed down from the trees to become terrestrial bipeds needs to be reexamined in light of a potentially long history of terrestriality in the ancestral protohominid.