Brief Communication: Shape analysis of the MT 1 proximal articular surface in fossil hominins and shod and unshod Homo

As a follow-up study to Proctor et al. (Am J Phys Anthropol 135 (2008) 216-224), this study quantifies the first metatarsal proximal articular surface using three-dimensional morphometrics to test for differences in articular surface shape between habitually shod and habitually unshod humans. In addition, differences in shape between Homo, Pan, Gorilla, and Hylobates are compared to the fossil hominin specimens A. L. 333-54, Stw 562, Stw 573 ("Little Foot"), OH 8, SKX 5017, and SK 1813. No difference in surface shape was found between habitually shod and habitually unshod humans. There is a clear quantitative division in articular surface shape between humans and apes that is more pronounced than a previous study by Proctor et al. (Am J Phys Anthropol 135 (2008) 216-224), due to additional landmarks present in this study. The specimen OH 8 is indistinguishable from modern Homo. The fossils A. L. 333-54, Stw 562, and Stw 573 are intermediate in shape between humans and apes. The specimens SKX 5017 and SK 1813 have a more apelike articular surface. When combined with other characteristics, this trait suggests that Paranthropus used a degree of abduction during locomotion that was much less than that in extant apes, but greater than that in Australopithecus, allowing for some small degree of grasping ability.     

New first metatarsal (SKX 5017) from Swartkrans and the gait of Paranthropus robustus

A new complete hallucal metatarsal (SKX 5017) was recovered from the "lower bank" of Member 1 at Swartkrans (ca. 1.8 m.y. BP). The new metatarsal is attributed to Paranthropus robustus, the predominant hominid found in Member 1 (greater than 95% of hominid individuals). SKX 5017 is similar to Olduvai Hominid 8-H from bed I, Olduvai (ca. 1.76 m.y. BP), and both resemble humans most closely among extant hominoids. The base, shaft, and head of SKX 5017 suggest human-like foot posture and a human-like range of extension (= dorsiflexion) at the hallucal metatarsophalangeal joint, while at the same time the distal articular surface indicates that a human-like toe-off mechanism was absent in Paranthropus. The fossil evidence suggests that Homo habilis and Paranthropus may have attained a similar grade of bipedality at roughly 1.8 m.y. BP.     

Hominin first metatarsals (SKX 5017 and SK 1813) from Swartkrans: a morphometric analysis.

Two hominin metatarsals from Swartkrans, SKX 5017 and SK 1813, have been reported by Susman and Brain [1988. New first metatarsal (SKX 5017) from Swartkrans and the gait of Paranthropus robustus. Am. J. Phys. Anthropol. 79, 451-454] and Susman and de Ruiter [2004. New hominin first metatarsal (SK 1813) from Swartkrans. J. Hum. Evol. 47, 171-181]. They found these bones to have both primitive and derived traits indicating that, while being bipedal, these hominines had a unique toe-off mechanism. We have undertaken additional multivariate morphometric analyses, comparing the fossils to the first metatarsals of modern humans and extant apes. The largest proportion of discrimination lies in the different locomotor functions: apes on the one hand and the humans and fossils on the other. While the fossils have the closest affinity to humans, they have a unique biomechanical pattern suggesting a more facultative form of bipedalism. The implications of this are, while morphometric analyses do not necessarily directly capture the described primitive and derived traits, the associated functional pattern is held within the broader morphology of the bone.     

The articular surface of the temporal bone in certain fossil hominoids

Although quantitative variations exist between living Man ( Homo sapiens sapiens ) and the extant great apes ( Pongo, Pan, Gorilla ) in such features of the articular surface of the temporal bone (a part of the temporomandibular joint) as the proportionate development of the postglenoid tubercle, the relative prominence of the articular tubercle and the slope of its posterior face, these do not individually effect a clear differentiation between the four extant genera. But in multivariate combination of these features, although Pan and Pongo are relatively closely associated, Gorilla and Homo sapiens sapiens are distinct, and also clearly differentiated from each other. The differences between genera of extant apes are, on average, as great as those between extant Man and individual apes.
As portrayed by such multivariate compound, this anatomical region in four fossil groups displays a unique configuration differentiating Homo sapiens neanderthalensis, Homo erectus pekinensis, Australopithecus africanus and Australopithecus robustus both from one another and from extant types. The differences are such that the fossil species lie uniquely and not intermediate between extant groups.
Definable age changes in this multivariate compound occur in both Man and apes but neither these, nor overall differences between adults, appear to be associated with marked contrasts in the pattern of jaw movement. It would thus seem improbable that inferences can be made from these features about the type of jaw movement that characterized the several fossil groups.     

Functional capabilities of modern and fossil hominid hands: three-dimensional analysis of trapezia

Three-dimensional (3D) trapezium models from Homo sapiens, Gorilla gorilla, Pan troglodytes, Australopithecus afarensis (A.L.333-80), and Homo habilis (O.H.7-NNQ) were acquired through laser digitizing. Least-square planes were generated for each articular surface, and the angles between the planes were compared. Each extant species displays an overall pattern that distinguishes it from the others. The observed angles in G. gorilla and P. troglodytes are more similar to one other than either is to H. sapiens. Our results, obtained from using new 3D modeling and analytical tools, raise interesting questions about the functional capabilities of the fossil trapezia. Multivariate statistical analyses indicate that A.L.333-80 is morphologically more similar to that of modern humans, whereas the O.H.7 trapezium is more similar to that of the gorilla. Significant differences between A.L.333-80 and the extant species occur, but some similarities to humans suggest the ability to form the distinctively human forceful pad-to-side and three-jaw chuck grips. Some key morphological differences from humans highlighted and quantified by our research suggest limitations in the functional capabilities of the O.H.7 trapezium, particularly in those that facilitate pronation at the base of the second metacarpal. If the O.H.7 trapezium represents part of the hand responsible for manufacturing and using the stone tools found at Olduvai, our results suggest that the hand manipulated the stones in a way for which we have no modern analog. Alternative considerations are that the O.H.7 trapezium is not representative of other trapezia from its species (i.e., N=1), or that it represents another primate or hominid species.     

The eruption pattern of the permanent incisors and first permanent molars in Australopithecus (Paranthropus) robustus

This study aims to reassess the claim that the eruption sequence of the permanent incisor and first permanent molar teeth of Australopithecus (Paranthropus) robustus is identical with that in modern Homo sapiens. Eight fossil hominid mandibles of equivalent dental developmental age were chosen for comparative study. Emphasis has been placed upon the comparative timing of events within the growth period rather than eruption sequence alone. The results of this study indicate that Homo sapiens and Australopithecus (Paranthropus) robustus share the same pattern of permanent molar and incisor eruption and that this is significantly different from the pattern of eruption shared by the great apes, Australopithecus africanus and Australopithecus afarensis.     

Effects of size and locomotor adaptations on the hominid pelvis: evaluation of australopithecine bipedality with a new multivariate method

Three pelves and eight innominate bones belonging to the fossil species, Australopithecus africanus, Australopithecus robustus, Homo erectus, and Homo sapiens, have been studied biometrically and compared with those of recent humans and apes. A new method of logarithmic factorial analysis suppresses both the size effects and the size reference on pelvic proportions. In combination with principal component analysis it allows specializations to be dissociated from allometrical variations. Some morphological differences on the hominid pelvis prove to be mainly allometric. However, the pelvic morphology of australopithecines is clearly differentiated from that of the genus Homo (including H. erectus, OH 28, KNMER 3227). A. africanus (Sts 14, MLD 7, AL 288) is nearer the humans than is A. robustus (SK 50, SK 3155), which appears to be more specialized in the australopithecine lineage. The pelvic morphology of A. africanus, as integrated with the articular pelvic-femoral link, appears to be biometrically equivalent to that of humans.     

Proximal metatarsal articular surface shape and the evolution of a rigid lateral foot in hominins

This study quantifies the proximal articular surface shape of metatarsal (MT) 4 and MT 5 using three-dimensional morphometrics. Humans and apes are compared to test whether they have significantly different shapes that are skeletal correlates to comparative lateral foot function. In addition, shod and unshod humans are compared to test for significant differences in surface shape. The MT 4 fossils OH 8, Stw 628, and AL 333-160, and the MT 5 fossils AL 333-13, AL 333-78, OH 8, and Stw 114/115 are compared with humans and apes to assess whether they bear greater similarities to humans, which would imply a relatively stable lateral foot, or to apes, which would imply a flexible foot with a midfoot break. Apes have a convex curved MT 4 surface, and humans have a flat surface. The MT 4 fossils show greater similarity to unshod humans, suggesting a stable lateral foot. Unshod humans have a relatively flatter MT 4 surface compared with shod humans. There is much overlap in MT 5 shape between humans and apes, with more similarity between humans and Gorilla. The fossil MT 5 surfaces are generally flat, most similar to humans and Gorilla. Because of the high degree of shape overlap between humans and apes, one must use caution in interpreting lateral foot function from the proximal MT 5 surface alone.     

Early hominin limb proportions

Recent analyses and new fossil discoveries suggest that the evolution of hominin limb length proportions is complex, with evolutionary reversals and a decoupling of proportions within and between limbs. This study takes into account intraspecific variation to test whether or not the limb proportions of four early hominin associated skeletons (AL 288-1, OH 62, BOU-VP-12/1, and KNM-WT 15000) can be considered to be significantly different from one another. Exact randomization methods were used to compare the differences between pairs of fossil skeletons to the differences observed between all possible pairs of individuals within large samples of Gorilla gorilla, Pan troglodytes, Pongo pygmaeus, and Homo sapiens. Although the difference in humerofemoral proportions between OH 62 and AL 288-1 does not exceed variation in the extant samples, it is rare. When humerofemoral midshaft circumferences are compared, the difference between OH 62 and AL 288-1 is fairly common in extant species. This, in combination with error associated with the limb lengths estimates, suggests that it may be premature to consider H. (or Australopithecus) habilis as having more apelike limb proportions than those in A. afarensis. The humerofemoral index of BOU-VP-12/1 differs significantly from both OH 62 and AL 288-1, but not from KNM-WT 15000. Published length estimates, if correct, suggest that the relative forearm length of BOU-VP-12/1 is unique among hominins, exceeding those of the African apes and resembling the proportions in Pongo.Evidence that A. afarensis exhibited a less apelike upper:lower limb design than A. africanus (and possibly H. habilis) suggests that, if A. afarensis is broadly ancestral to A. africanus, the latter did not simply inherit primitive morphology associated with arboreality, but is derived in this regard. The fact that the limb proportions of OH 62 (and possibly KNM-ER 3735) are no more human like than those of AL 288-1 underscores the primitive body design of H. habilis.     

Radius of Paranthropus robustus from member 1, Swartkrans formation, South Africa

Recently recovered hominid postcrania from Member 1, Swartkrans Formation include the proximal and distal ends of a right radius attributed to a single individual of Paranthropus robustus. These fossils are essentially similar to Australopithecus afarensis, A. africanus, and P. boisei homologues. The head manifests an ape-like circumferentia articularis, and the distal end has prominent medial, dorsal, and lateral tubercles and a well developed brachioradialis crest, features also commonly exhibited by extant great apes. The volar set of the P. robustus radiocarpal joint, like that of Australopithecus homologues, more closely resembles the neutral condition exhibited by Homo than the greater flexion evinced by living apes. Compared with fossil and recent specimens of Homo, the configuration of the P. robustus radial head suggests enhanced stability against medial displacement during pronation and supination; the strong crest for the attachment of brachioradialis may attest to enhanced forearm flexor capability. In addition, this crest and the prominent dorsal tubercles may indicate enhanced hand extensor and, therefore, hand flexor capabilities. The differences in radial morphology between Paranthropus and Homo may relate to significant behavioral differences between these two synchronic taxa.     

New hominin first metatarsal (SK 1813) from Swartkrans

A recently recognized hominin hallucal metatarsal, SK 1813, from Swartkrans bears a suite of primitive and derived traits. Comparisons with extant apes, modern humans, SKX 5017, and Stw 562 reveals similar morphology in all three fossils and that these early hominins, while bipedal, possessed a unique toe-off mechanism. The implications of this are that both primitive and derived traits must be used to establish the total biomechanical pattern.     

Earliest complete hominin fifth metatarsal—Implications for the evolution of the lateral column of the foot

StW 114/115, from Sterkfontein, South Africa, is the earliest complete hominin fifth metatarsal. Comparisons of StW 114/115 to modern humans, extant apes, and partial hominin metatarsals AL 333‐13, AL 333‐78, SKX 33380, OH 8, and KNM‐ER 803f reveal a similar morphology in all six fossils consistent with habitual bipedality. Although StW 114/115 possesses some primitive characters, the proximal articular morphology and internal torsion of the head are very human‐like, suggesting a stable lateral column and the likely presence of lateral longitudinal and transverse tarsal arches. We conclude that, at least in the lateral component of the foot of the StW 114/115 individual, the biomechanical pattern is very similar to that of modern humans. This, however, may not have been the case in the medial column of the foot, as a mosaic pattern of hominin foot evolution and function has been suggested. The results of this study may support the hypothesis of an increased calcaneo‐cuboid stability having been an early evolutionary event in the history of terrestrial bipedalism. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Associated cranial and forelimb remains attributed to Australopithecus afarensis from Hadar, Ethiopia

A partial skeleton from Hadar, Ethiopia (A.L. 438-1) attributed to Australopithecus afarensis is comprised of part of the mandible, a frontal bone fragment, a complete left ulna, two second metacarpals, one third metacarpal, plus parts of the clavicle, humerus, radius, and right ulna. It is one of only a few early hominin specimens to preserve both cranial and postcranial elements. It also includes the first complete ulna from a large A. afarensis individual, and the first associated metacarpal and forelimb remains. This specimen, dated to approximately 3Ma, is among the geologically youngest A. afarensis fossils and is also one of the largest individuals known. Its ulnar to mandibular proportions are similar to those of the geologically older and much smaller A.L. 288-1, suggesting that body size increased without disproportional enlargement of the mandible. Overall, however, analysis of this large specimen and of the diminutive A.L. 288-1 demonstrates that the functional morphology of the A. afarensis upper limb was similar at all body sizes; there is no evidence to support the hypothesis that more than one hominin species is present at Hadar. Morphologically, all apparent apomorphic traits of the elbow, forearm, wrist, and hand of A.L. 438-1 are shared uniquely with humans. Compared to humans, A.L. 438-1 does have a more curved ulna, although A.L. 288-1 does not, and it appears to have had slightly less well-developed manipulatory capabilities of its hands, although still more derived than in apes. We conclude that selection for effective arboreality in the upper limb of Australopithecus afarensis was weaker than in non-hominins, and that manipulative ability was of greater selective advantage than in extant great apes.     

The first rib of hominoids

Homo sapiens is unique among extant hominoids in displaying a univertebral articular pattern for the first rib; that is, the head of the first rib articulates only with the body of the first thoracic vertebra. All other hominoids, indeed virtually all other mammals, display a bivertebral pattern; that is, the head of the first rib articulates with the bodies of both the seventh cervical and the first thoracic vertebrae, as well as the intervening disk. Two fossil hominid partial first ribs, A.L. 288-lax and A.L. 333-118, show that the univertebral pattern was fully established in the hominid lineage by the appearance of Australopithecus afarensis. Four hypotheses, based in functional anatomy, can be postulated for the evolution of the univertebral pattern: (1), it increases the volume (via increased length) of the neck, which could, in turn, compensate for the functional loss of the laryngeal sac systems in hominid vocalization; (2), it is a consequence of the more barrel-shaped thorax in hominids; (3), it is a consequence of functional modifications in the hominid shoulder girdle; and/or (4), it is a consequence of modifications in hominid first rib motion while breathing in an upright stance. Fossil evidence supports all but the first hypothesis, and most strongly supports the third. However, evidence for the first hypothesis does suggest that the evolution of descent of the upper respiratory system in the hominid lineage may have been permitted by the presence of the univertebral pattern, while the reverse is probably not true. Furthermore, fossil evidence for the third hypothesis shows that, by the appearance of A. afarensis, the hominid upper limb had been freed from locomotor constraints, which concomitantly confirms full adaptation to upright posture. Thus, because of their potential relationship with upright posture, the two remaining hypotheses (i.e., "thoracic shape" and "first rib movement during breathing") also have support from the fossil evidence.     

Principal components analysis of distal humeral shape in Pliocene to recent African hominids: the contribution of geometric morphometrics

The shape of the distal humerus in Homo, Pan (P. paniscus and P. troglodytes), Gorilla, and six australopithecines is compared using a geometric approach (Procrustes superimposition of landmarks). Fourteen landmarks are defined on the humerus in a two-dimensional space. Principal components analysis (PCA) is performed on all superimposed coordinates. I have chosen to discuss the precise place of KNM-KP 271 variously assigned to Australopithecus anamensis, Homo sp., or Praeanthropus africanus, in comparison with a sample of australopithecines. AL 288-1, AL 137-48 (Hadar), STW 431 (Sterkfontein), and TM 1517 (Kromdraai) are commonly attributed to Australopithecus afarensis (the two former), Australopithecus africanus, and Paranthropus robustus, respectively, while the taxonomic place of KNM-ER 739 (Homo or Paranthropus?) is not yet clearly defined. The analysis does not emphasize a particular affinity between KNM-KP 271 and modern Homo, nor with A. afarensis, as previously demonstrated (Lague and Jungers [1996]     

Evidence for a dual pattern of cranial venous sinuses on the endocranial cast of Taung (Australopithecus africanus)

According to published accounts, an enlarged occipital-marginal sinus system is absent in Australopithecus africanus, although it occurs in high frequencies in A. robustus, A. Boisei, and Hadar hominids commonly designated A. afarensis. In this report, we describe, for the first time, an enlarged occipital-marginal sinus system on the endocranial cast of the Taung specimen, which is part of the holotype of A. africanus. In addition, well-developed right transverse and sigmoid sinuses are represented on the Taung endocast. The various components of the dual venous sinus system on the Taung endocast are measured, and the system is compared to those of other fossil hominids. The compresence of a lateral sinus system and enlarged occipital and marginal sinuses occurs in two Hadar specimens, 2 specimens of A. robustus crassidens, 1 A. boisei specimen, and several early H. sapiens crania. Hence, the presence of strong transverse sinus impressions in a fragmentary specimen may not be interpreted as an indication that an enlarged occipital-marginal sinus system was not present in the original specimen. Conversely, lack of transverse sinus grooves in a fragmentary specimen does provide indirect evidence than an enlarged occipital-marginal system would probably have been present in the whole specimen, as in 2 specimens of A. boisei. Including Taung, enlarged occipital and marginal sinuses occur in 1 out of 5, or 20%, of A. africanus specimens. This figure compares well with the range of mean frequencies in modern human cranial series (1.5 to 28%), but is much lower than are the frequencies for A. boisei, A. robustus, and the Hadar hominids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contours of the hominoid lateral tibial condyle with implications for Australopithecus

Tibial condyle shape is alleged to vary among fossil tibiae attributed to Australopithecus, and has been argued to reflect functional differences of the knee. Convex anteroposterior curvature of the lateral tibial condyle in A. africanus has been interpreted to indicate a more chimpanzee-like locomotor repertoire than the flatter lateral tibial condyles of A. afarensis (Berger and Tobias, 1996, J. Hum. Evol. 30, 343). Alternatively, Latimer, Ohman, and Lovejoy (1987, Am. J. Phys. Anthropol. 74, 155) have suggested that in response to increased transarticular loads accompanied by larger body mass, joints should become flatter as size increases, both within and among species, so that the variation observed among hominin fossils reflects size alone rather than functional differences. In this study, three-dimensional surface areas of the lateral tibial condyle of humans, chimpanzees, and gorillas were computed using a Digibot II (Digibotics) laser scanner and the DataSculpt v.4.6 engineering software package to evaluate joint surface contours, and compared to two-dimensional surface area and arc and chord length measurements of the anteroposterior and mediolateral axes. Extant species measurements were then compared to those of A. afarensis (A.L. 129-1b, A.L. 288-1aq, A.L. 333x-26, A.L. 333-42) and A. africanus (Stw 514a). Results do not support the hypothesis that A. afarensis and A. africanus differ in condylar topology. They also do not support the hypothesis that joint surfaces become flatter with increased transarticular load accompanying increased body size, as curvature of the lateral tibial condyle in anteroposterior and mediolateral planes is not negatively allometric. However, femoral condylar shape is not included in this study, which may better reflect joint surface responses to increased body size. Finally, there is no basis from this study to reconstruct differences in locomotor behavior among fossil hominin taxa based on lateral tibial condyle morphology.     

禄丰古猿(Lufengpithecus lufengensis)牙齿釉质生长线与个体发育问题研究

运用扫描电子显微镜,对4枚禄丰古猿牙齿（恒齿）的釉质结构进行了观察研究。发现：禄丰古猿牙齿釉质表面有明显的釉面横纹结构;釉面横纹的密度向牙颈方向逐渐增大;观察记数了4枚牙齿的釉面横纹数,进而推算出牙冠的形成时间和年龄。与化石人科成员、现代人及现生大猿比较,禄丰古猿牙冠发育模式及时间,与南方古猿纤细种比较接近或相似,明显长于南方古猿粗壮种,有别于现生大猿。     

Species attribution of the Swartkrans member 1 first metacarpals: SK84 and SKX 5020

Susman (Am. J. Phys. Anthropol. 75:277-278, 79:451-474; Science 240:781-784; In FE Grine (ed): Evolutionary History of the "Robust" Australopithecines. New York: Aldine de Gruyter, pp. 149-172) has attributed the morphologically similar SK 84 and SKX 5020 hominid first metacarpals to Homo erectus and Australopithecus robustus, respectively, and has inferred that both species exhibited derived pollical morphologies, indicating refined precision grips. Consideration of the structure of his taphonomic arguments indicates that there are no adequate nonmorphological reasons to attribute these specimens securely to one or the other of the craniodentally represented species at Swartkrans. His morphological arguments fail to note any significant differences between the two specimens. Only the contrast in size between the small SK 84 and large SKX 5020 bones might warrant a species distinction; yet comparison of their length ratio to distributions of modern human first metacarpal length ratios indicates that it is not possible to reject conclusively the null hypothesis that they are conspecific. Therefore, early hominid adaptive scenarios based on a derived Homo-like manual functional morphology in A. robustus remain without a secure paleontological basis.     

Dental topography and diets of Australopithecus afarensis and early Homo

Diet is key to understanding the paleoecology of early hominins. We know little about the diets of these fossil taxa, however, in part because of a limited fossil record, and in part because of limitations in methods available to infer their feeding adaptations. This paper applies a new method, dental topographic analysis, to the inference of diet from fossil hominin teeth. This approach uses laser scanning to generate digital 3D models of teeth and geographic information systems software to measure surface attributes, such as slope and occlusal relief. Because it does not rely on specific landmarks that change with wear, dental topographic analysis allows measurement and comparison of variably worn teeth, greatly increasing sample sizes compared with techniques that require unworn teeth. This study involved comparison of occlusal slope and relief of the lower second molars of Australopithecus afarensis (n=15) and early Homo (n=8) with those of Gorilla gorilla gorilla (n=47) and Pan troglodytes troglodytes (n=54). Results indicate that while all groups show reduced slope and relief in progressively more worn specimens, there are consistent differences at given wear stages among the taxa. Early Homo shows steeper slopes and more relief than chimpanzees, whereas A. afarensis shows less slope and relief than any of the other groups. The differences between the two hominin taxa are on the same order as those between the extant apes, suggesting similar degrees of difference in diet. Because these chimpanzees and gorillas differ mostly in fallback foods where they are sympatric, results suggest that the early hominins may likewise have differed mostly in fallback foods, with A. afarensis emphasizing harder, more brittle foods, and early Homo relying on tougher, more elastic foods.