How large were the australopithecines?

Stature of the African early hominids is estimated from most of the available fragments of fossil long bones by means of regression analysis. The average height of the South African gracile australopithecines is predicted to be 145.1 cm (4′9″) where n = 4 and of the South African robust forms, 152.7 cm (5′) where n = 3. The East African early hominids are somewhat taller (x = 163.0 cm or 5′4″, where n = 7). Variability in stature is high even within the same site which is probably a reflection of fairly strong sexual dimorphism in body size. Evidence is presented which suggests that at least in one form of early hominid the size proportions of fore- and hindlimbs are different than in modern man. There is also evidence that average stature may have increased through time. The most significant of these findings is that the two forms of early hominids in South Africa are possibly more similar in stature than is usually cited. This does not imply necessarily that the two forms did not differ significantly in robustness or weight.     

Femoral lengths and stature in Plio-Pleistocene hominids

This study reports the femoral lengths of 31 Plio-Pleistocene hominids dated between 3.1 and 0.7 million years ago, and uses those lengths to estimate stature by way of the femur-stature ratio reported by Feldesman et al. (Am. J. Phys. Anthropol. 78:219-220, 1989). By this method the average female Australopithecus afarensis is 105 cm and the average male is 151 cm. The respective values are 115 and 138 cm for A. africanus. As defined by Howell (In VJ Maglio and HBS Cooke (eds): The Evolution of African Mammals. Cambridge: Harvard University Press, 1978) and Johanson et al. (Kirtlandia 28:1-14, 1978), Homo habilis is a sexually dimorphic species, with females standing 118 cm and males 157 cm. Such apparently strong dimorphism may be due to the possibility that there are actually two species of nonrobust hominids between 2 and 1.7 m.y.a. The estimate for the female Australopithecus boisei is 124 cm and for the male, 137 cm, but these estimates are especially difficult to be certain of because there are no femora that can be positively identified as male A. boisei. Australopithecus robustus is estimated to be 110 cm (female) and 132 cm (male). African Homo erectus stood 160 cm (female) and 180 cm (male). From these estimates several generalizations are apparent. First, there is apparently strong sexual dimorphism in stature in A. afarensis and H. habilis, but less in the other species. Second, the "robust" australopithecines were relatively small statured. Third, it is apparently not true that humans have been getting progressively taller throughout their evolutionary history. Some individuals were as tall as modern humans 3 m.y.a., by 2 m.y.a. one individual stood about 173 cm, and by 1.7 m.y.a. a stature of 180+ cm was not uncommon.     

Basicranial anatomy of Plio-Pleistocene hominids from East and South Africa

The results of a metrical analysis of the basicranium of 19 Plio-Pleistocene fossil hominid crania are presented. The sample includes crania attributed to Australopithecus africanus, Australopithecus boisei, and robustus, and Homo erectus as well as crania whose attribution is still under discussion. These results confirm significant differences between the cranial base patterns of the "gracile" and "robust" australopithecines and the three crania attributed to Homo erectus have a pattern which resembles that of modern humans. None of the crania examined from East Africa sites have base patterns which resemble that of the "gracile" australopithecines. The crania KNM-ER 407 and 732 have patterns which are compatible with them being smaller-bodied females of Australopithecus boisei; KNM-ER 1470 and 1813 have base patterns which most closely resemble that of Homo erectus. The cranial base pattern of KNM-ER 1805 is compatible with its inclusion in either Australopithecus boisei or Homo. When account is taken of the immaturity of Taung, the evidence of its cranial base pattern suggests that if it had reached adulthood it would have resembled the "gracile" australopithecine crania from Sterkfontein and Makapansgat.     

Limb-size proportions in Australopithecus afarensis and Australopithecus africanus

Previous analyses have suggested that Australopithecus africanus possessed more apelike limb proportions than Australopithecus afarensis. However, due to the errors involved in estimating limb length and body size, support for this conclusion has been limited. In this study, we use a new Monte Carlo method to (1) test the hypothesis that A. africanus had greater upper:lower limb-size proportions than A. afarensis and (2) assess the statistical significance of interspecific differences among these taxa, extant apes, and humans. Our Monte Carlo method imposes sampling constraints that reduce extant ape and human postcranial measurements to sample sizes comparable to the fossil samples. Next, composite ratios of fore- and hindlimb geometric means are calculated for resampled measurements from the fossils and comparative taxa. Mean composite ratios are statistically indistinguishable (alpha=0.05) from the actual ratios of extant individuals, indicating that this method conserves each sample's central tendency. When applied to the fossil samples, upper:lower limb-size proportions in A. afarensis are similar to those of humans (p=0.878) and are significantly different from all great ape proportions (p< or =0.034), while Australopithecus africanus is more similar to the apes (p> or =0.180) and significantly different from humans and A. afarensis (p< or =0.031). These results strongly support the hypothesis that A. africanus possessed more apelike limb-size proportions than A. afarensis, suggesting that A. africanus either evolved from a more postcranially primitive ancestor than A. afarensis or that the more apelike limb-size proportions of A. africanus were secondarily derived from an A. afarensis-like ancestor. Among the extant taxa, limb-size proportions correspond with observed levels of forelimb- and hindlimb-dominated positional behaviors. In conjunction with detailed anatomical features linked to arboreality, these results suggest that arboreal posture and locomotion may have been more important components of the A. africanus behavioral repertoire relative to that of A. afarensis.     

Humeral outlines in some hominoid primates and in Plio-Pleistocene hominids

A method of drawing outlines of the distal end of the humerus is presented and carried out on some pongids (Pan troglodytes, Pan paniscus, Pongo pygmaeus), on modern man, and on some casts of Plio-Pleistocene hominids. It appears that these outlines are good indicators of the overall morphology and permit the distinguishing of the different hominoids. For example, the morphology of the pillars surrounding the fossa olecrani is useful for this purpose. In modern man, the lateral pillar is quadrangular, contrasting with the triangular medial one. In pongids, both of them are triangular; however, it is possible to note differences between Pongo and Pan. In the South Asian ape, there is a stronger anteroposterior flattening of the pillars as well as the diaphysis. The similarity of the shape of the pillars might be considered as a result of an adaptation to suspension. The differences might be due to different weights of the animals. Plio-Pleistocene hominids are variable with regard to the morphology of this region. For example, Gombore IB 7594 is similar to Homo. KNM ER 739 exhibits features intermediate between hominids and pongids. Finally, AL 288.1M is closer to pongids. These results confirm a previous anatomical work.     

precision holding in humans,non-human primates,and Plio-Pleistocene hominids

Human Evolution - Four Types of precision holding in the human hand have been identified and described in accordance with the contrasting regional properties of a differentiated ungual pulp of the...     

Further hominids from the Plio-Pleistocene of Koobi Fora, Kenya

Fifty-eight new fossil hominids from Plio-Pleistocene sediments east of Lake Turkana, Kenya, are described. They include cranial, mandibular, dental, and postcranial parts. Some are illustrated.     

Reassessing manual proportions in Australopithecus afarensis

Previous analyses of hand morphology in Australopithecus afarensis have concluded that this taxon had modern human‐like manual proportions, with relatively long thumbs and short fingers. These conclusions are based on the A.L.333 composite fossil assemblage from Hadar, Ethiopia, and are premised on the ability to assign phalanges to a single individual, and to the correct side and digit. Neither assignment is secure, however, given the taphonomy and sample composition at A.L.333. We use a resampling approach that includes the entire assemblage of complete hand elements at Hadar, and takes into account uncertainties in identifying phalanges by individual, side and digit number. This approach provides the most conservative estimates of manual proportions in Au. afarensis. We resampled hand long bone lengths in Au. afarensis and extant hominoids, and obtained confidence limits for distributions of manual proportions in the latter. Results confirm that intrinsic manual proportions in Au. afarensis are dissimilar to Pan and Pongo. However, manual proportions in Au. afarensis often fall at the upper end of the distribution in Gorilla, and very lower end in Homo, corresponding to disproportionately short thumbs and long medial digits in Homo. This suggests that manual proportions in Au. afarensis, particularly metacarpal proportions, were not as derived towards Homo as previously described, but rather are intermediate between gorillas and humans. Functionally, these results suggest Au. afarensis could not produce precision grips with the same efficiency as modern humans, which may in part account for the absence of lithic technology in this fossil taxon. Am J Phys Anthropol 152:393–406, 2013. © 2013 Wiley Periodicals, Inc.     

Bears,pigs, and Plio-Pleistocene hominids: A case for the exploitation of belowground food resources

Belowground plant parts were important potential food resources in the habitats associated with Pliocene and early Pleistocene hominids. The food gathering and dental adaptations of three groups of modem mammals — bears, pigs, and humans — testify to the earlier convergence of these animals on this resource. Since belowground food reserves are relatively unaffected by the factors controlling aboveground food supply (fire, drought, and grazing stress), exploitation of this stable nutritional bank had distinct energetic and behavioral advantages for hominids.     

Chimpanzee variation facilitates the interpretation of the incisive suture closure in South African Plio-Pleistocene hominids

For a better understanding of early hominid growth patterns, we need to compare skeletal maturation among humans and chimpanzees. This study provides new data on variation of the incisive suture closure in extant species to facilitate the understanding of growth patterns among South African Plio-Pleistocene hominids. The complete anterior closure of the incisive suture occurs early during human life, mostly before birth. In contrast, in chimpanzees a complete anterior closure occurs mostly after the eruption of either the first permanent molars (pygmy chimpanzees) or the third molars (common chimpanzees). The first aim of this study is to test whether the patterns of closure of both the anterior and palatal components of the incisive suture in chimpanzees accurately mirror their polytypism by investigating 720 museum specimens of known geographical origin. Then we use the data gleaned from the incisive suture closure in chimpanzees to determine whether there are different growth patterns among South African Plio-Pleistocene hominids and to interpret them. Results about the pattern of incisive suture closure are consistent with the differences among chimpanzees as revealed by molecular data. Thus, the variation in chimpanzee patterns of incisive suture closure facilitates the interpretation of morphology in South African fossil hominids. In Australopithecus (Paranthropus) robustus as compared to Australopithecus africanus, the complete anterior closure and, probably, the complete palatal closure of the incisive suture occurs during early life in the same way as they occur in humans. Moreover, the closure pattern observed on Stw 53, a supposed early Homo from Sterkfontein Member 5, is similar to that seen in A. africanus and in chimpanzees. Thus, with respect to the anterior component of the incisive suture, A. africanus and Stw 53 retain the primitive feature for which A. (P.) robustus and Homo share the derived character state. Finally, it is worth noting that the Taung child does not show the robust condition. Am J Phys Anthropol 105:121–135, 1998. © 1998 Wiley-Liss, Inc.     

A morphometric study of limb proportions in leaping prosimians

Study of individual limb proportions—most notably, for instance, of the intermembral index—distinguishes from most other primates those various prosimians capable of leaping. The present investigation analyzes 24 measures of limb proportions (taken by F.-K. Jouffroy and J. Lessertisseur) from 161 specimens representing 12 species of prosimians, using the multivariate statistical method of multiple discriminant analysis (carried out by R. German and C.E. Oxnard). The results indicate that there are three major gradients: (1) indriids, (2) cheirogaleines, and (3) galagines plus Tarsius, radiating from a fourth centrally located group of species, Lemur, Lepilemur, and Hapalemur. It is likely that the morphometric relationships displayed here can be associated with behavioral (locomotor) parallels among these various forms. Though leaping is a most important adaptation among prosimians, it seems clear that it has evolved separately a number of times, and it seems at least likely that the biomechanical nature of the adaptation differs in different groups. The results, therefore, present certain new hypotheses about prosimian locomotion that can only be tested with further field and laboratory studies. This study also emphasizes the fact that anatomical adaptation is complex. Though the analysis of each anatomical region separately provides a similar qualitative picture of the variation among genera, it is only in the analysis of all measures taken together that the complete pattern described above appears. Though no new variables have been added in that analysis, new information is obviously contained within the results. Since this information stems from the interactions of the variables, it must be due to associations between these anatomical areas.     

Depositional environments, archeological occurrences and hominids from Members E and F of the Shungura Formation (Omo basin, Ethiopia)

The several known archeological occurrences from the Shungura Formation (Members E and F) are discussed within the context of their particular depositional and paleoenvironmental settings, and the broader context of the Pliocene of the Turkana Basin. These assemblages date from 2·3–2·4 Ma, and are among the oldest yet known in Africa. In situ archeological assemblages are restricted to the distal edge of fluviatile levees, behind gallery forests and at the edge of open savanna. Extensive and rather dense scatters of slightly disturbed quartz artifacts are linked to large expanses of braided stream situations. Lag components are derived from stream beds. There is no available evidence of occupation either under riverine or deltaic forest settings or on dryland. Hominid skeletal remains from this interval, none of which occur at or are directly associated with such archeological occurrences, are attributed to two hominid taxa. Most specimens represent a “robust” australopithecine and are attributed here to A. aethiopicus. A few hominid teeth are attributed to aff. Homo sp.     

Proximal femur articulation in Pliocene hominids

The supposed "nonhuman anthropoid"-type femur head articular surface described for the Pliocene hominid specimen A.L.288-1 ("Lucy") by Stern and Susman in 1983 is present in significant numbers of modern human femora. This nonmetric skeletal trait was also found to be sex-related in modern human samples examined.     

Body size and proportions in early hominids.

The discovery of several associated body parts of early hominids whose taxonomic identity is known inspires this study of body size and proportions in early hominids. The approach consists of finding the relationship between various measures of skeletal size and body mass in modern ape and human specimens of known body weight. This effort leads to 78 equations which predict body weight from 95 fossil specimens ranging in geological age between 4 and 1.4 mya. Predicted weights range from 10 kg to over 160 kg, but the partial associated skeletons provide the essential clues as to which predictions are most reliable. Measures of hindlimb joint size are the best and probably those equations based on the human samples are better than those based on all Hominoidea. Using hindlimb joint size of specimens of relatively certain taxonomy and assuming these measures were more like those of modern humans than of apes, the male and female averages are as follows: Australopithecus afarensis, 45 and 29 kg; A. africanus, 41 and 30 kg; A. robustus, 40 and 32 kg; A. boisei, 49 and 34 kg; H. habilis, 52 and 32 kg. These values appear to be consistent with the range of size variation seen in the entire postcranial samples that can be assigned to species. If hominoid (i.e., ape and human combined) proportions are assumed, the males would be 10 to 23 kg larger and the females 4 to 10 kg larger.     

Variations in enamel thickness and structure in East African hominids

Tooth fragments are an appreciable but neglected proportion of fossil hominid specimens. The present study on 47 naturally fractured enamel surfaces of premolar and molar teeth of Plio-Pleistocene East African hominids measured enamel thickness, slope of incremental lines (striae of Retzius), and the morphology of Hunter Schreger bands (HSBs). Specimens allocated to three categories--"robust" australopithecines (EAFROB), "early Homo" (EAFHOM), and "unknown"--were photographed in ethanol with polarised light. Enamel thickness was measured on the occlusal (OT), cuspal (CT), and lateral (LT) aspects. The angle of intersection of striae of Retzius (D) with the enamel-dentine junction (EDJ) was recorded, together with the degree of curvature and width of Hunter-Schreger bands (HSB). Absolute measurements of enamel thickness were scaled by using two allometry correction factors. Absolute thicknesses of all enamel measurements were significantly greater in the EAFROB (OT 3.1 mm; CT 3.3 mm; LT 2.4 mm) compared with EAFHOM (OT 1.4 mm; CT 1.6 mm; LT 1.6 mm) categories. Correction for size reduces the mean difference between the two taxa, but CT and OT thickness remain significantly different (P less than 0.05). HSBs in EAFROB were relatively straight and narrower (means = 52.8 micron) than in EAFHOM, which are more curved and wider (means = 62.0 micron), suggesting greater enamel prism decussation in early Homo. The slope of striae was less in EAFROB permanent molars (means = 23 degrees) compared with EAFHOM (means = 31 degrees), indicating faster rates of coverage during crown formation in "robust" australopithecines. We conclude that the study of fractured enamel surfaces can contribute to our understanding of the systematic relationships and patterns of enamel growth of early hominids.     

Body proportions of Homo habilis reviewed

The ratio of fore- to hindlimb size plays an important role in our understanding of human evolution. Although Homo habilis was relatively modern craniodentally, its body proportions are commonly believed to have been more apelike than in the earlier Australopithecus afarensis. The evidence for this, however, rests, on two fragmentary skeletons, OH 62 and KNM-ER 3735. The upper limb of the better-preserved OH 62 from Olduvai Gorge is long and slender, but its hindlimb is represented mainly by the proximal portion of a thin femur of uncertain length. The present analysis shows that upper-to-lower limb shaft proportions of both OH 62 and AL 288-1 (A. afarensis) fall in the modern human range of variation, although OH 62 also falls inside that of chimpanzees due to their overlap in small individuals. Despite being more fragmentary, the larger-bodied KNM-ER 3735 lies outside the chimpanzee range and close to the human mean. Because the differences between any of the three individuals are compatible with the range of variation seen in extant hominoid groups, it is not legitimate to infer more primitive upper-to-lower limb shaft proportions for either H. habilis or A. afarensis. Femur length of OH 62 can only be estimated by comparison. Its closest match in size and morphology is with the gracile OH 34 specimen, which therefore provides a better analogue for the reconstruction of OH 62 than the stocky AL 288-1 femur that is traditionally used. OH 34's slender proportions are hardly due to abrasion, but match those of a modern human of that body-size, suggesting that the relative length of OH 62's leg may have been human-like. Brachial proportions, however, remained primitive. Long legs may imply long distance terrestrial travel. Perhaps this adaptation evolved early in the genus Homo, with H. habilis providing an early representative of this important change.     

Computed tomography and enamel thickness of maxillary molars of Plio-Pleistocene hominids from Sterkfontein, Swartkrans, and Kromdraai (South Africa): An exploratory study.

This paper is one in a series which explores the possibility of using the non-destructive CT technique to identify patterns in tooth enamel distribution and structure of hominid molars from Plio-Pleistocene sites in South Africa, notably Swartkrans, Sterkfontein, and Kromdraai. Whereas previous investigators have emphasised gross differences in absolute and relative or average enamel thickness between hominid taxa, the present study highlights differences in enamel thickness over functionally significant regions of the crown. Differences in the distribution of enamel in A. robustus, A. africanus, and Homo sp. are identified through the use of bivariate and multivariate analyses, and are interpreted in terms of dietary regimes.     

Longitudinal study of dental development in chimpanzees of known chronological age: Implications for understanding the age at death of Plio-Pleistocene hominids

Reconstruction of life history variables of fossil hominids on the basis of dental development requires understanding of and comparison with the pattern and timing of dental development among both living humans and pongids. Whether dental development among living apes or humans provides a better model for comparison with that of Plio-Pleistocene hominids of the genus Australopithecus remains a contentious point. This paper presents new data on chimpanzees documenting developmental differences in the dentitions of modern humans and apes and discusses their significance in light of recent controversies over the human or pongid nature of australopithecine dental development. Longitudinal analysis of 299 lateral head radiographs from 33 lab-reared chimpanzees (Pan troglodytes) of known chronological age allows estimation of means and standard deviations for the age at first appearance of 8 developmental stages in the mandibular molar dentition. Results are compared with published studies of dental development among apes and with published standards for humans. Chimpanzees are distinctly different from humans in two important aspects of dental development. Relative to humans, chimpanzees show advanced molar development vis a vis anterior tooth development, and chimpanzees are characterized by temporal overlap in the calcification of adjacent molar crowns, while humans show moderate to long temporal gaps between the calcification of adjacent molar crowns. In combination with recent work on enamel incremental markers and CAT scans of developing dentitions of Plio-Pleistocene hominids, this evidence supports an interpretation of a rapid, essentially “apelike” ontogeny among australopithecines. © 1996 Wiley-Liss, Inc.