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Sex at Sterkfontein: 'Mrs. Ples' is still an adult female
... Both Australopithecus and early Homo shared a mixture of primitive and derived features which suggest a mixed adaptation to terrestrial bipedalism as well as arboreal life (Stringer and Andrews 2005). Many scholars also propose that the range of sexual dimorphism exhibited by these species was large, easily matching and possibly exceeding the maximum dimorphism observed in surviving primates such as gorillas and orangutans (Gordon, Green, and Richmond 2008;Grine et al. 2012;Hausler andSchmid 1995, 1997;Lockwood et al. 1996;Plavcan 2001Plavcan , 2012Tague and Lovejoy 1998;Wolpoff 1976). It follows from what is known about sexual dimorphism in extant primates that fierce male intrasexual competition typified these two genera and likely revolved around a form of polygynous group structure. ...
... Both Australopithecus and early Homo shared a mixture of primitive and derived features which suggest a mixed adaptation to terrestrial bipedalism as well as arboreal life (Stringer and Andrews 2005). Many scholars also propose that the range of sexual dimorphism exhibited by these species was large, easily matching and possibly exceeding the maximum dimorphism observed in surviving primates such as gorillas and orangutans (Gordon, Green, and Richmond 2008;Grine et al. 2012;Hausler andSchmid 1995, 1997;Lockwood et al. 1996;Plavcan 2001Plavcan , 2012Tague and Lovejoy 1998;Wolpoff 1976). It follows from what is known about sexual dimorphism in extant primates that fierce male intrasexual competition typified these two genera and likely revolved around a form of polygynous group structure. ...
... For Wolpoff (1976) and others (McHenry 1992(McHenry , 1994aToth and Schick 2009;contra: Lovejoy 2009;Plavcan 2001Plavcan , 2012, the apparently conflicting evidence can best be explained by the emergence of material culture during the Pliocene, leading to the diminished role of canine teeth as they were supplanted by extrasomatic means. Not only were cultural items argued to be more effective in cases of physical conflict, but that by brandishing them, early hominins could intimidate their rivals in a manner functionally equivalent to canine teeth (Gruter 1982;Wolpoff 1976). ...
Dental dimorphism is one of the primary means by which the mating systems of extinct hominins are studied. Its use has been particularly significant for describing the behaviors of Australopithecus and early Homo, and consequently the factors involved in the evolution of our own species. Analysis however, has tended to produce ambiguous and contrasting results, with no firm agreement as to what mating strategies these genera practiced. Interpretation is confounded by numerous problems such as a generally poor understanding of how dental dimorphism develops in primates, and what factors influence its expression. It is also not well known how these factors interact with different aspects of the dentition and to what relative extent these aspects are diagnostic of mating behavior. The failure in many cases to firmly establish the sex of fossil specimens has likewise hampered the interpretations of sexual dimorphism and by extension, mating behavior. Lastly, the ability to correlate dental dimorphism with mating systems, even in living primates, has met with only moderate success. For these reasons it is argued that dental dimorphism be used only to support the most general assertions about hominin social behavior.
... In 2012, the BL and MD diameters for the right canine alveolar socket were given by Grine et al. 11 as 7.2 mm and 6.9 mm, respectively. These values correspond closely to a BL value of 7.0 mm given by Thackeray 13 and a MD dimension of 6.9 mm obtained in this study. ...
... The measurement of 9 mm by Broom et al. 12 for the BL diameter of Sts 5 is larger than the BL diameter of 8 mm for a definite male specimen of A. africanus (Stw 505), and almost as large as the BL diameters for another male adult, TM 1511, estimated as 10.2 mm for the left canine 12 and 10.5 mm for the right canine 11 . Discovered in 1936, TM 1511 was not prepared in acetic acid. ...
... Relationships between BL and MD canine diameters for presumed male and female specimens of A. africanus are shown in Figure 1, based partly on data presented by Grine et al. 11 but (for the first time, in this study) including the position of Sts 5 based on BL and MD diameter measurements published by Broom et al. 12 in 1950 and recorded before the damage associated with acetic acid preparation. According to these data, the canine diameter measurements of Sts Figure 1 counter the statement by Grine et al. 11 that 'there is no evidence to contradict the assertion' that Sts 5 represents a female individual. ...
... Male Rak (1983Rak ( , 1985 Male Lockwood (1997Lockwood ( , 1999 Male Clarke (2008) Male Grine et al. (2012) TM 1512 Cranial Female Broom (1946) Specimen S2 ...
... Thackeray (2000) Female Clarke (2008) Female Grine et al. (2012) Sts 7 Mandibular Male Broom and Robinson (1950) Sts 17 Cranial Female Broom and Robinson (1950) Skull 6 Male Rak (1983Rak ( , 1985 Female Lockwood (1997Lockwood ( , 1999 Female Grine et al. (2012) Sts 19 Cranial Female Broom and Robinson (1950) Skull 8 ...
... Thackeray (2000) Female Clarke (2008) Female Grine et al. (2012) Sts 7 Mandibular Male Broom and Robinson (1950) Sts 17 Cranial Female Broom and Robinson (1950) Skull 6 Male Rak (1983Rak ( , 1985 Female Lockwood (1997Lockwood ( , 1999 Female Grine et al. (2012) Sts 19 Cranial Female Broom and Robinson (1950) Skull 8 ...
The identification of species in the fossil record has long vexed paleontologists because of its inherent difficulty, and it has long preoccupied them because of its fundamental significance. Australopithecus africanus exemplifies this difficulty and importance. This species, as commonly defined, is viewed by some as having played a role in the evolution of the genus Homo, while others consider it to have been uniquely related to Paranthropus. A third opinion places it near the base of the evolutionary divergence of the “robust” australopith and human lineages. Various analyses find A. africanus to be phylogenetically unstable, and this is almost certainly owing to its craniodental variability. This has led to questions concerning the taxonomic homogeneity of the assemblages from Taung, Sterkfontein, and Makapansgat that comprise its hypodigm. Initial discoveries at these sites were attributed to different species and possibly genera, but subsequent studies suggested that these fossils represent a single, albeit variable taxon. This paradigm has become current conventional paleoanthropological wisdom, but observations about the degree and pattern of variability evinced by these fossils have raised anew the possibility that the A. africanus hypodigm is taxonomically heterogeneous. Various workers have proposed that at least some of these fossils belong to a different taxon, but there is notable lack of agreement over the manner in which they should be sorted. Morphometric studies tend to find little, if any, support for taxonomic heterogeneity, but they may not have directly addressed those features that have been suggested to differ. Novel innovative technological and quantitative approaches are required to adequately address the possible taxonomic heterogeneity of the A. africanus hypodigm.
... Ples') has served an important role in the popular press and has also been frequently used as a reference point for discussion of the cranial anatomy of A. africanus (e.g., Tobias, 1967; Rak, 1983 Rak, , 1985 Lockwood and Tobias, 2002; Kimbel et al., 2004). This specimen has received special attention in the last ten years as a focus of controversy over its sex and ontogenetic age at death (Grine et al., 2012). There is considerable debate over the attribution of age and gender for this specimen, and resolving these issues will play an important role in taxonomic debates over the A. africanus holotype (Grine et al., 2012). ...
... This specimen has received special attention in the last ten years as a focus of controversy over its sex and ontogenetic age at death (Grine et al., 2012). There is considerable debate over the attribution of age and gender for this specimen, and resolving these issues will play an important role in taxonomic debates over the A. africanus holotype (Grine et al., 2012). Sts 5 was initially identified as female (Broom, 1947; Broom and Robinson, 1950), primarily due to the size of the canine root socket (the specimen is edentulous). ...
... Computed tomography (CT) scans of Sts 5 indicated to some researchers (Thackeray et al., 2002) that the C and M 3 root apices are open and, thus, the morphological pattern could indicate an interpretation of the specimen as a young subadult male. This explanation, however, has been challenged by those who interpret the right M 3 roots as showing closed apices (Grine et al., 2012), which would only be present in a fully adult specimen. The valence of the pattern of sutural closure is also disputed. ...
... Wolpoff (1974) opined that most of the outer bone table is missing and this was confirmed later by Thackeray (1997). Sts 5 is variably described as an adult female (Broom, 1947;Clarke, 2008;Grine et al., 2012) or an adolescent male (Thackeray et al., 2002;see review in;Grine, 2013). ...
... The ectocranial surface is complete (Wolpoff, 1974). The specimen is commonly assigned to A. africanus (e.g., Tobias, 1999, 2002), as either a female or male (see reviews in Grine et al., 2012;Grine, 2013). Clarke (2008Clarke ( , 2013 considered it as a female of A. prometheus. ...
The Sterkfontein Caves site is one of the richest early hominin fossil localities in Africa. More specifically, the fossiliferous deposits within the lower-lying Jacovec Cavern have yielded valuable hominin remains; prominent among them is the Australopithecus partial cranium StW 578. Due to the fragmentary nature of the braincase, the specimen has not yet been formally assigned to a species. In this context, we employ microtomography to quantify cranial thickness and composition of StW 578 in order to assess its taxonomic affinity. As comparative material, we investigate 10 South African hominin cranial specimens from Sterkfontein (StW 505, Sts 5, Sts 25, Sts 71), Swartkrans (SK 46, SK 48, SK 49) and Makapansgat (MLD 1, MLD 10, MLD 37/38), attributed to either Australopithecus or Paranthropus, as well as 10 extant human and 10 extant chimpanzee crania. Thickness variation in and structural arrangement of the inner and outer cortical tables and the diploë are automatically assessed at regular intervals along one parasagittal and one coronal section. Additionally, topographic cranial vault thickness distribution is visualized using color maps. Comparisons highlight an absolutely and relatively thickened condition of the StW 578 cranial vault versus those of other South African Plio-Pleistocene hominins. Moreover, in StW 578, as well as in the Australopithecus specimens Sts 5 and Sts 71 from Sterkfontein, the diploic layer contributes substantially to cumulative vault thickness (i.e., >60%). Within the comparative sample investigated here, StW 505 and Sts 71 from Sterkfontein Member 4, both attributed to Australopithecus, most closely resemble StW 578 in terms of cranial vault thickness values, tissue proportions, and two- and three-dimensional distributions. Including additional Plio-Pleistocene Australopithecus and Paranthropus crania from South and East Africa in future studies would further help establish morphological variability in these hominin taxa.
... Un des exemples les plus marquants pour ce taxon en Afrique du Sud est celui de "Mrs Ples". Alors qu'il s'agit du crâne le plus complet d'Australopithecus africanus disponible à ce jour, il subsiste toujours des interrogations sur son attribution sexuelle (Broom et Robinson, 1950 ;Grine et al., 2012). ...
... At the same time, Thackeray (1997;Potze and Thackeray, 2010;Thackeray et al., 2002a, b) have argued that Sts 5 is a juvenile -a juvenile male to be precise -and could reasonably be interpreted as belonging to the same individual as Sts 14 (Thackeray et al., 2002b). However, several lines of evidence point to the fact that Sts 5 is a fully adult individual, and a reasonably old one at that (Bonmatí et al., 2008;Grine et al., 2012;Villmoare et al., 2013). ...
The possibility that the fossils attributed to Australopithecus africanus represent more than a single species is of significance because of the pivotal role that A. africanus has played in discussions about hominin evolution. The A. africanus hypodigm that is currently widely recognized evinces considerable variation in a number of craniodental characters, and this has led to speculation that more than one australopith taxon may be represented among the specimens from Sterkfontein. Although crania, mandibles and teeth have dominated these taxonomic discussions, the Sterkfontein postcranial remains also have been invoked. While several workers have proposed that some of the craniodental remains from Sterkfontein can be partitioned into two groups, there is a notable lack of agreement among them as to their actual sorting. Most of the craniodental observations that have been put forward in support of arguments for taxonomic heterogeneity of the Sterkfontein australopith assemblage have been subjective and anecdotal in nature. So too, the postcranial evidence that has been cited in support of more than one australopith species at Sterkfontein has been largely subjective, and limited to a small number of elements. The results of quantitative statistical analyses of the craniodental and postcranial fossils that have been undertaken to date are not necessarily consistent with the hypothesis of taxonomic heterogeneity.
... Because the inner ear is not influenced by postnatal growth and development (Jeffery and Spoor, 2004;Richard et al., 2010), in this study we combine adult and juvenile specimens (see below (Broom, 1947;Thackeray and Gommery, 2002), is the most complete and well-preserved cranium attributed to A. africanus (Broom, 1947;. Sts 5 is variably described as an adult female (Broom, 1947;Clarke, 2008;Grine et al., 2012;Villmoare et al., 2013) or an adolescent male (Thackeray et al., 2002a;Tawane and Thackeray, 2018; see review in Grine, 2013). In this study, we focus on its right inner ear. ...
... Sts 5 ('Mrs Ples') is the most complete and well-preserved cranium attributed to A. africanus (Broom, 1947;. Sts 5 has been variably described as an adult female (Broom, 1947;Clarke, 2008;Grine et al., 2012) or an adolescent male (Thackeray et al., 2002; see review in Grine, 2013). Sts 5 was found in Member 4 of the Sterkfontein Formation (Broom, 1947). ...
One of the most crucial debates in human paleoneurology concerns the timing and mode of the emergence of the derived cerebral features in the hominin fossil record. Given its exceptional degree of preservation and geological age (i.e., 3.67 Ma), StW 573 (‘Little Foot’) has the potential to shed new light on hominin brain evolution. Here we present the first detailed comparative description of the external neuroanatomy of StW 573. The endocast was virtually reconstructed and compared to ten southern African hominin specimens from Makapansgat, Malapa, Sterkfontein and Swartkrans attributed to Australopithecus and Paranthropus. We apply an automatic method for the detection of sulcal and vascular imprints. The endocranial surface of StW 573 is crushed and plastically deformed in a number of locations. The uncorrected and therefore minimum cranial capacity estimate is 408 cm3 and plots at the lower end of Australopithecus variation. The endocast of StW 573 approximates the rostrocaudally elongated and dorsoventrally flattened endocranial shape seen in Australopithecus and displays a distinct left occipital petalia. StW 573 and the comparative early hominin specimens share a similar sulcal pattern in the inferior region of the frontal lobes that also resembles the pattern observed in extant chimpanzees. The presumed lunate sulcus in StW 573 is located above the sigmoid sinus, as in extant chimpanzees, while it is more caudally positioned in SK 1585 and StW 505. The middle branch of the middle meningeal vessels derives from the anterior branch, as in MH 1, MLD 37/38, StW 578. Overall, the cortical anatomy of StW 573 displays a less derived condition compared to the late Pliocene/early Pleistocene southern African hominins (e.g., StW 505, SK 1585).
... Three-dimensional visualization software can be used to piece together fossil fragments, separate the fossil from the surrounding matrix, replace missing parts, and correct distortions (Gunz et al., 2009;Strait et al., 2009;Benazzi et al., 2011;Grine et al., 2012;Benazzi et al., 2014). The first step in virtual fossil reconstruction is to segment the bone from the surrounding air, spaces, and matrix. ...
In recent years, finite element analysis (FEA) has emerged as a useful tool for the analysis of skeletal form-function relationships. While this approach has obvious appeal for the study of fossil specimens, such material is often fragmentary with disrupted internal architecture and can contain matrix that leads to errors in accurate segmentation. Here we examine the effects of varying the detail of segmentation and material properties of teeth on the performance of a finite element model of a Macaca fascicularis cranium within a comparative functional framework. Cranial deformations were compared using strain maps to assess differences in strain contours and Procrustes size and shape analyses, from geometric morphometrics, were employed to compare large scale deformations. We show that a macaque model subjected to biting can be made solid, and teeth altered in material properties, with minimal impact on large scale modes of deformation. Macaca models clustered tightly by bite point rather than by modelling simplification approach, and fell out as being distinct from another species. However localised fluctuations in predicted strain magnitudes were recorded with different modelling approaches, particularly over the alveolar region. This study indicates that, while any model simplification should be undertaken with care and attention to its effects, future applications of FEA to fossils with unknown internal architecture may produce reliable results with regard to general patterns of deformation, even when detail of internal bone architecture cannot be reliably modelled. Anat Rec, 2014. © 2014 Wiley Periodicals, Inc.
... The restored dental arches also supply new morphometric data for Sts 52. As this specimen, because of its relative good preservation, has been regularly included in A. africanus comparative samples (i.e., Grine et al., 2012), these new data are particularly important for future morphometric comparisons (Table 1, but see also Supporting Information Tables 3, 4). For example, the new palatal breadth places Sts 52 close to Sts 71 and Stw 13 (see Supporting InformationTable 4). ...
The functional restoration of the occlusal relationship between maxillary and mandibular tooth rows is a major challenge in modern dentistry and maxillofacial surgery. Similar technical challenges are present in paleoanthropology when considering fragmented and deformed mandibular and maxillary fossils. Sts 52, an Australopithecus africanus specimen from Sterkfontein Member 4, represents a typical case where the original shape of the dental arches is no longer preserved. It includes a partial lower face (Sts 52a) and a fragmented mandible (Sts 52b), both incomplete and damaged to such an extent to thwart attempts at matching upper and lower dentitions. We show how the preserved macrowear pattern of the tooth crowns can be used to functionally reconstruct Sts 52's dental arches. High-resolutiondental stone casts of Sts 52 maxillary and mandibular dentition were mounted and repositioned in a dental articulator. The occlusal relationship between antagonists was restored based on the analysis of the occlusal wear pattern of each preserved tooth, considering all dental contact movements represented in the occlusal compass. The reconstructed dental arches were three-dimensional surface scanned and their occlusal kinematics tested in a simulation. The outcome of this contribution is the first functional restoration of A. africanus dental arches providing new morphometric data for specimen Sts 52. It is noteworthy that the method described in this case study might be applied to several other fossilspecimens. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
Interpreting morphological variation within the early hominin fossil record is particularly challenging. Apart from the fact that there is no absolute threshold for defining species boundaries in palaeontology, the degree of variation related to sexual dimorphism, temporal depth, geographic variation or ontogeny is difficult to appreciate in a fossil taxon mainly represented by fragmentary specimens, and such variation could easily be conflated with taxonomic diversity. One of the most emblematic examples in paleoanthropology is the Australopithecus assemblage from the Sterkfontein Caves in South Africa. Whereas some studies support the presence of multiple Australopithecus species at Sterkfontein, others explore alternative hypotheses to explain the morphological variation within the hominin assemblage. In this review, I briefly summarize the ongoing debates surrounding the interpretation of morphological variation at Sterkfontein Member 4 before exploring two promising avenues that would deserve specific attention in the future, that is, temporal depth and nonhuman primate diversity.
The size and morphology of male maxillary canines were compared among living/fossil apes, fossil hominins, and modern humans in the course of evolution. Results were summarized as follows: (1): The crown size of the upper canine had already reduced in the late Miocene hominins, such as Sahelanthropus tchadensis and Orrorin tugenensis. Then, size reduction continued successively until the emergence of H. sapiens. (2): In occlusal view, a crown outline was mainly oval with the major axis lying in mesiodistal direction among extant and fossil apes. In Australopithecus afarensis and later hominins, labiolingually elongated oval crown shape became common. (3): In lingual view, the crown outline in extant and fossil apes was a tall and distorted triangle with a wide base. Exceptionally, the outline showed a distorted tetragon in Ouranopithecus. In hominins, the outline showed pentagonal or diamond shape in common. (4): The mesial and distal crown shoulders were located close to the cervical ridge in extant and fossil apes. In hominins, the shoulders moved to a higher position towards the apex. (5): A mesial incisal groove was well-defined and long yet deep groove, running from the cusp apex towards the crown base in extant and fossil apes. On the other hand, the incisal groove became short, and was continuous with the marginal groove in Ardipithecus and Australopithecus. In H. erectus and later hominins, there was no incisal groove, and only the mesial marginal groove was observed. (6): The marginal ridge was short in extant and fossil apes, being located at the basal crown. This ridge extended from the cervical region to the apex in Ouranopithecus. In Ar. ramidus and later hominins, the marginal ridge extended even longer towards the apex. (7): A mesiolingual ridge was thick and rounded, running from the apex to the cervical region along mesial incisal groove in extant and fossil apes. In hominins, this ridge ran vertically through the center of the crown. (8): The width of the cervical ridge was narrow in extant and fossil apes. In hominins, the width becomes wider relative to the crown height, and the basal tubercle also developed.
AFTER A DECADE OF CAREFUL EXCAVATION, it is now possible to explain how the skeleton came to be in that isolated position in the cavern. Furthermore, it is apparent that the fossil does not belong to either Australopithecus africanus or to A. afarensis, but to an individual belonging to, or closely affiliated to, the second Australopithecus species that is represented in Sterkfontein Member 4 and Makapansgat.
The late Miocene-Pliocene emergence of the Hominini coincides with considerable mammalian faunal turnover in Africa, including the endemic radiation of groups such as ruminants, suids, and cercopithecids; the first appearance through immigration of taxa such as Equus and Giraffa; the demise of previously successful groups such as anthracotheres; and, overall, an increased representation of taxa adapted to more open savanna-mosaic environments. Most, if not all, of the major taxonomic events for the tribe occur in Africa, including the emergence of our own species. Only two hominin species (from one eurytopic genus) are found entirely outside Africa (Homo neanderthalensis and Homo floresiensis), and all hominins are restricted to the continent until just under two million years ago. The principal adaptive changes of the tribe also occur in Africa. Early hominins are distinguished by a suite of postcranial features showing reliance on terrestrial bipedalism. By the late Pliocene (and possibly sooner), these adaptations gave hominins one of the most efficient forms of locomotion of all mammals. This chapter describes the systematic paleontology of Hominini.
During the past few years, the proposal of a new species, A. afarensis that is more primitive than A. africanus in many respects has forced many researchers to reformulate their ideas on the subject of hominid evolution, and resulted in a multiplicity of hypotheses about evolutionary relationships within the Hominidae. Most of the current hypotheses agree that the course of evolution from the earliest species of the genus Homo, H. habilis, through H. erectus to H. sapiens was essentially linear. The major point of contention is which species was the last ancestor of H. habilis. Species that have recently been considered for this role include A. afarensis. A. africanus and various as yet undiscovered species of Australopithecus, Homo, or some other genus. We shall use phylogenetic analysis to develop a new perspective of this subject. -from Authors
Whilst reduced size, altered shape and diminished sexual dimorphism of the canine-premolar complex are diagnostic features of the hominin clade, little is known about the rate and timing of changes in canine size and shape in early hominins. The earliest Australopithecus, Australopithecus anamensis, had canine crowns similar in size to those of its descendant Australopithecus afarensis, but a single large root alveolus has suggested that this species may have had larger and more dimorphic canines than previously recognised. Here we present three new associated dentitions attributed to A. anamensis, recently recovered from the type site of Kanapoi, Kenya, that provide evidence of canine evolution in early Australopithecus. These fossils include the largest mandibular canine root in the hominin fossil record. We demonstrate that, although canine crown height did not differ between these species, A. anamensis had larger and more dimorphic roots, more like those of extant great apes and Ardipithecus ramidus, than those of A. afarensis. The canine and premolar occlusal shapes of A. anamensis also resemble those of Ar. ramidus, and are intermediary between extant great apes and A. afarensis. A. afarensis achieved Homo-like maxillary crown basal proportions without a reduction in crown height. Thus, canine crown size and dimorphism remained stable during the early evolution of Australopithecus, but mandibular root dimensions changed only later within the A. anamensis-afarensis lineage, coincident with morphological changes in the canine-premolar complex. These observations suggest that selection on canine tooth crown height, shape and root dimensions was not coupled in early hominin evolution, and was not part of an integrated adaptive package.
The cranium and associated matrix of Sts 5, a cranium of
Australopithecus africanus is re-examined in the context of an unfused
sagittal suture and the position of the temporal lines. These lines are
not developed as a sagittal crest although they are close to the
mid-sagittal line. A comparative study of the presence of sagittal
crests in male, female, juvenile and adult specimens of extant great
apes ( Gorilla, Pan, Pongo) suggests that the existence of a sagittal
crest is influenced to a greater extent by anatomical age rather than by
the sex of the individuals.
The aim of this study was to develop a comprehensive evidence-based atlas to estimate age using both tooth development and alveolar eruption for human individuals between 28 weeks in utero and 23 years. This was a cross-sectional, retrospective study of archived material with the sample aged 2 years and older having a uniform age and sex distribution. Developing teeth from 72 prenatal and 104 postnatal skeletal remains of known age-at-death were examined from collections held at the Royal College of Surgeons of England and the Natural History Museum, London, UK (M 91, F 72, unknown sex 13). Data were also collected from dental radiographs of living individuals (M 264, F 264). Median stage for tooth development and eruption for all age categories was used to construct the atlas. Tooth development was determined according to Moorrees et al. (J Dent Res 42 (1963a) 490–502; Am J Phys Anthropol 21 (1963b) 205–213) and eruption was assessed relative to the alveolar bone level. Intraexaminer reproducibility calculated using Kappa on 150 teeth was 0.90 for 15 skeletal remains of age <2 years, and 0.81 from 605 teeth (50 radiographs). Age categories were monthly in the last trimester, 2 weeks perinatally, 3-month intervals during the first year, and at every year thereafter. Results show that tooth formation is least variable in infancy and most variable after the age of 16 years for the development of the third molar. Am J Phys Anthropol, 2010. © 2010 Wiley-Liss, Inc.
Smith ([1986] Nature 323:327–330) distinguished patterns of development of teeth of juvenile fossil hominids as being “more like humans” or “more like apes” based on statistical similarity to group standards. Here, this central tendency discrimination (CTD) is tested for its ability to recognize ape and human patterns of dental development in 789 subadult hominoids. Tooth development of a modern human sample (665 black southern Africans) was scored entirely by an outside investigator; pongid and fossil hominid samples (59 Pan, 50 Gorilla, and 14 fossil hominids) were scored by the author. The claim of Lampl et al. ([1993] Am. J. Phys. Anthropol. 90:113–127) that Smith's 1986 method succeeds in only 8% of human cases was not sustained. Figures for overall success of classification (87% humans, 68% apes) mask important effects of teeth sampled and age class. For humans, the power of CTD varied between 53% and 92% depending on the number and kind of teeth available—-nearly that of a coin toss when data described only two nearby teeth, but quite successful with more teeth or distant teeth. For apes, only age class affected accuracy: “Infant” apes (M1 development ⩽ root cleft complete, unemerged) were usually classed as humans, probably because the present developmental standard for great apes is in substantial error under 3 years of age. “Juvenile” apes (M1 ⩾ root 1/4), however, were correctly discriminated in 87% of cases. Overall, CTD can be considered reliable (accuracy of 92% for humans and 88% for apes) when data contrast development of distant dental fields and subjects are juveniles (not infants). Restricting analysis of fossils to specimens satisfying these criteria, patterns of dental development of gracile australopithecines and Homo habilis remain classified with African apes. Those of Homo erectus and Neanderthals are classified with humans, suggesting that patterns of growth evolved substantially in the Hominidae. To standardize future research, the computer program that operationalizes CTD is now available. © 1994 Wiley-Liss, Inc.
Several different models of sexual dimorphism in the South African australopithecines are compared with sexual dimorphism in the living primates. Australopithecine dimorphism is placed in an evolutionary context, and contrasting trends in the hominid and pongid lineages are shown. Evidence suggesting that the australopithecines were an extremely polytypic taxon is presented, and a high level of both inter and intra population variation is indicated.
Debate about species recognition in the primate fossil record is pervasive. Numerous studies have come to different conclusions regarding the sexual and taxonomic composition of, for example, Proconsul samples from East Africa (Kelley, 1987; Pickford, 1986), Sivapithecus from Asia (Kay, 1982a,b; Wu and Oxnard, 1983), hominoids from Rain Ravine (Kay, 1982a, Martin and Andrews, 1984), Australopithecus afarensis (Cole and Smith, 1987; Johanson et al, 1982; Kimbel et ai, 1985; Kimbel and White, 1988; Olson, 1981, 1985; Senut and Tardieu, 1985), A. africanus (Zwell and Pilbeam, 1972), and Homo habilis (Wood, 1985, this volume), to name a few. Since the majority of fossil specimens consist of teeth, a good deal of this debate centers on the interpretation of dental variation.
The most complete cranium of Australopithecus africanus yet discovered is Sts 5, found by Robert Broom and John Robinson on 18 April 1947, at Sterkfontein, 75 km southwest of Pretoria.1-4 Sts 5 was discovered as a result of a dynamite blast which split the cranium into two pieces. Broom subsequently prepared the specimen at the Transvaal Museum, using chisels and other mechanical techniques. Calcified matrix encasing the fossil was broken into many pieces, some of which have been in store since the time of discovery. Six of these matrix fragments retaining thin cranial bone have recently been labelled i-vi as part of Sts 5 (Table 1). Four are shown in Fig. 1. Details of unfused sagittal sutures in fragment iii are visible in Fig. 2. It would be technically difficult but not impossible to remove the thin bone fragments adhering to the calcified sedimentary matrix, and to re-attach them to the cranial vault of Sts 5. However, this has not been attempted because the matrix fragments carry potentially interesting taphonomic information.
Bringing together a variety of accomplished dental researchers, this book covers a range of topics germane to the study of human and other primate teeth. The chapters encompass work on individuals to samples, ranging from prehistoric to modern times. The focus throughout the book is the methodology required for the study of modern dental anthropology, comprising the scientific methods in use today - ranging from simple observation to advanced computer-based analyses - which can be utilized by the reader in their own dental research. Originating from the 20th anniversary meeting of the Dental Anthropology Association, this is a valuable reference source for graduate students, academic researchers and professionals in the social and life sciences, as well as clinicians.
Critical review of methods of production and use of chronologies of formation of human teeth.
'Mrs Ples' (Sts 5) is the most complete cranium of Australopithecus africanus from Plio-Pleistocene deposits dated c. 2.6 million years BP from Sterkfontein in Gauteng Province, South Africa. On the basis of the apparent small size of canine sockets, Robert Broom considered the specimen to be a female. Morphological characteristics, combined with results of statistical analyses, are consistent with the suggestion that Sts 5 may represent a small adult male rather than an adult female specimen of A. africanus.
This paper describes a quantitative cladistic study of hominid phylogeny. Measurements between homologous landmarks were taken from a variety of fossil hominids and from 140 modern primate specimens. The measurements were confined to the cranium, mandible and dentition. The effect of size was removed from the data using an adaptation of Kazmierczack's transformation, and the transformed data were coded directly into discrete, ordered character states. Cladograms were constructed for different OTU combinations, using the PAUP phylogeny program to find minimum length (maximum parsimony) trees. The trees were rooted by including a single hypothetical outgroup which was calculated from a previous, separate, analysis of six extant primate taxa.The most parsimonious cladogram for conventionally-defined hominid taxa is consistent with the phylogenetic hypothesis advanced by Kimbel et al. (1984). Subdivision of early Homo, according to criteria that emphasize the size variation in this group, has little impact on the phylogenetic relationships of the group. An alternative division of early Homo, based on a phenetic analysis of shape, suggests that one subgroup is primitive while the other has affinities with the “robust” australopithecines.
The spheno-occipital synchondrosis and clivus in 32 males and 21 females, aged 2 days to 24 years 11 months, were studied post mortem to ascertain the time of closure of the synchondrosis. The material studied consisted of the major part of the clivus and dorsum sellae, which were decalcified and serially sectioned in the sagittal plane. The first sign of closure of the synchondrosis was the appearance of a bony bridge in the superior part. Closure was found to occur about 2 years earlier in girls than in boys. The synchondrosis was never completely open in any of the females above 13 years 9 months, the corresponding age for the boys was 16 years. The major part of the dorsum sellae of preparations from young subjects consisted of cartilage and minor cartilaginous areas were seen in almost all preparations from subjects below 17 years and occasionally also from subjects above this age.
Heterochrony is commonly proposed as a mechanism producing evolutionary changes, and some researchers identify two ways that heterochrony may be conceptualized. ‘Growth heterochrony’ examines ancestor-to-descendant differences in the ontogeny of size relative to shape, while ‘sequence heterochrony’ focuses on differences in the order of occurrence of events during ontogeny. Methods introduced here are allied with sequence heterochrony in that ontogeny is modelled as if it were a sequence of events; however, events are differently defined in this study. Using data from 16 primate species, I demonstrate that discriminant function analysis of data on developmental timing provides an additional tool for exploring the relationship between ontogeny and phylogeny. Patterns in the timing of tooth eruption, craniofacial sutural closure, and postcranial epiphyseal fusion can be used to classify individuals of all ages to their correct taxon. Taxon differences in these patterns can be characterized and described by interpreting correlations between discriminant functions and developmental events. Discriminant analysis has the advantages of: (1) being applicable to taxa for which there are too few individuals to be able to reconstruct ontogenetic sequences, including fossil species; (2) preserving intraspecific developmental variation during analysis; (3) being sensitive to very subtle differences in ontogenetic timing.
Three age estimation techniques using ectocranial and/or endocranial suture closure are tested on a sample of known age from Spitalfields, London in order to determine the value of cranial suture closure as an indicator of age at death. The three techniques are those proposed by Acsádi and Nemeskéri, Meindl and Lovejoy and Perizonius. Results indicate that the Acsádi and Nemeskéri technique, which is based on endocranial sutures, can be used to distinguish young and middle-aged individuals in the Spitalfields sample but gives no information for crania over the age of 50 years. Age estimation using the Meindl and Lovejoy and Perizonius (Old system) techniques, which use ectocranial sutures, was found to be subject to a number of complicating factors, of which sexual dimorphism in the rate and pattern of closure is the most significant. A method of estimating age at death based on both endocranial and ectocranial suture closure is developed on the basis of the Spitalfields sample. The technique attempts to overcome some of the problems associated with both intra- and interpopulation variation in cranial suture closure. For a truly accurate age-estimation technique based on cranial suture closure we would need to know more about the causes and functions of suture closure in human populations.
Skeletons of Gombe chimpanzees representing both sexes and ages from infancy to old age are examined in detail by a variety of techniques. The combination of biological and lifetime behavioural data presents an integrated view of individuals which make up a local population. These skeletons reflect species-patterned growth, development and ageing. Furthermore, individual variation is related to lifetime experiences: for example, the impact of nutrition, injury and disease on survival and reproduction in the physical and psychosocial environments. Size, shape and internal structure of bones and teeth record life-history features associated with both primary and secondary life-history characters. These case studies emphasize the role of the individual in the evolutionary process.
Interpretation of dental development of fossil hominids requires understanding of and comparison with the pattern and timing of dental development among living humans and pongids. We report the first study of crown and root calcification in the lower permanent molar teeth among chimpanzees (Pan troglodytes) of known chronological age. A series of 99 lateral head radiographs of 16 captive-born chimpanzees were analyzed. Radiographs were taken at irregular intervals throughout the entire postnatal period of dental development from birth to 13 years of age. Permanent mandibular molars were rated on an eight-point maturation scale from initial radiographic appearance through crown and root calcification and apical closure of the root canals. In addition, we were able to document initial crown calcification and completion, as well as root completion and apical closure in incisors, canines, and premolars. Our results show several differences from the widely cited developmental schedule for pongid dentitions of Dean and Wood (Folia Primatol. 36:111–127, 1981). We found a much greater degree of temporal overlap in calcification of the crowns of adjacent molars, a pattern very unlike that usually seen in human dental development, which is characterized by delays between the onset of crown calcification in the molar series. Also, the ages and durations of crown and root formation in our chimp sample differ from the estimates proposed by Dean and Wood. By more clearly establishing the nature of developmental schedules and the timing of major events in the pongid dentition, these results should aid in the ongoing controversies concerning the human or pongid nature of dental development among Plio-Pleistocene hominids.
The evidence for sagittal cresting, and more generally the position of the temporal lines is reviewed in the South African australopithecine sample. The position of the lines is dependent on both the allometric relation of the masticatory apparatus to cranial size and on individual variation. In the Swartkrans specimens, with generally bigger body size, the influence of allometry predominates, actually overshadowing the influence of individual variation. At Sterkfontein and Makapansgat with generally smaller body size and a resulting smaller allometric ratio, individual variation has a greater influence. Of the eleven adult South African specimens, the four largest are crested. The one smaller crested specimen comes from Sterkfontein. The crested Makapan specimen is intermediate in size. The pattern of australopithecine cresting is somewhat different from other hominoids, and is part of a total morphological pattern suggesting adaptation to a diet requiring powerful crushing during mastication.
This review begins by setting out the context and the scope of human evolution. Several classes of evidence, morphological, molecular, and genetic, support a particularly close relationship between modern humans and the species within the genus Pan, the chimpanzee. Thus human evolution is the study of the lineage, or clade, comprising species more closely related to modern humans than to chimpanzees. Its stem species is the so-called ‘common hominin ancestor’, and its only extant member is Homo sapiens. This clade contains all the species more closely-related to modern humans than to any other living primate. Until recently, these species were all subsumed into a family, Hominidae, but this group is now more usually recognised as a tribe, the Hominini. The rest of the review sets out the formal nomenclature, history of discovery, and information about the characteristic morphology, and its behavioural implications, of the species presently included in the human clade. The taxa are considered within their assigned genera, beginning with the most primitive and finishing with Homo. Within genera, species are presented in order of geological age. The entries conclude with a list of the more important items of fossil evidence, and a summary of relevant taxonomic issues.
Among extant hominoids degrees of sexual dimorphism and combined-sex coefficients of variation of canine teeth dimensions are highly correlated. Based on this relationship and coefficients of variation of four species of the genus Australopithecus, we predict degrees of canine dimorphism for these extinct hominids. The estimates show that A. afarensis is as dimorphic as the pygmy chimpanzee, A. boisei slightly less dimorphic than the pygmy chimpanzee, A. robustus slightly more dimorphic than the lar gibbon, while A. africanus overiaps with the lar gibbon as well as a modern human sample. These estimates represent degrees of canine dimorphism substantially lower than results based upon prior sexing of individual specimens. The relationship between canine dimorphism and body weight dimorphism is also analyzed. All four species of Australopithecus are considerably less dimorphic in canine size for their body weight dimorphism than expected. This dissociation of canine size dimorphism and body weight dimorphism is shared with modern humans, and thus represents a unique hominid trait. We interpret the moderate to strong body weight dimorphism in australopithecines as the result of intra- and intersexual selection typical of a polygynous mating structure, while the rather mild canine dimorphism is interpreted in terms of the “developmental crowding” model for reduction in canine size.
Although cladistic analysis provides one of the most useful approaches to discovering the phyletic relatiosships among the species of Australopithecus and early Homo, methodological problems continue to beset any attempt to apply it in this context. Two of the most pressing problems are redundancy of traits due to similarity of underlying function and overrepresentation of some anatomical or functional systems in trait lists. In an attempt to mitigate these problems, we collapse our list of 77 traits into sets of traits using two methods. The first method segregates traits into seven groups by anatomical region. The second method segregates traits by function into five complexes which correspond fairly well with recognized trends in the evolution of early hominids (adaptation for heavy chewing, reduction of the anterior dentition, basicranial flexion, increased orthognathism and encephalization).
This study reassesses body weight sexual dimorphism inA. afarensis by applying equations that predict body weight from hindlimb joint size in a comparative sample of modern apes and humans. The resulting estimates show a level of body size dimorphism in this fossil hominid to be below that seen in modern gorillas or orang-utans, greater than modern species ofPan, and well above modernH. sapiens. This degree of dimorphism fits with the behavioral model proposed byFoley & Lee, 1989 in whichA. afarensis lived in large kin-related multimale groups with females that are not kin-related. The moderate level of body size sexual dimorphism found in this study removes one objection to the lumping of all Hadar hominids into a single species.
New fossils recovered from the Pliocene of Ethiopia and attributed to Australopithecus afarensis (White et al., 1993; Kimbel et al., 1994) provide an opportunity to reassess size variation and sexual dimorphism in jaws and limb bones of these early hominids. In this study two related questions are addressed using exact randomization methods. First, is it possible to observe the fossil size range within samples of modern hominoids? Second, and moving beyond minimum/maximum possibilities to probabilities , what is the likelihood of sampling such differences in extant hominoids? Fossil minimum/maximum ranges in size and shape are defined by linear measurements from mandibular specimens A.L. 444-2b vs. A.L. 207-13, humeri MAK-VP-1/3 vs. A.L. 288-lm, and the proximal femora A.L. 333-3 vs. A.L. 288-lap. Modern reference samples include gorillas, orang-utans, common chimpanzees and several human groups (all of known sex). All possible pairwise contrasts (in size ratios and average Euclidean distances) are computed within each sample [e.g. within a sample of 50 gorillas (25 males, 25 females) 1225 total contrasts are possible of which 625 are opposite sex contrasts], and the probability of finding a difference as great as that seen in the fossil pair is noted.The maximum observed size (sex) difference in the fossil mandibles, humeri and proximal femora is either rare or not observed in human and chimpanzee samples, is rare to uncommon in orang-utans, and is unusual even in gorillas. Specimens recovered in the future will undoubtedly increase the fossil ranges, and thereby further reduce the probabilities of matching such differences in modern taxa. These results could imply that multiple taxa exist within the fossil assemblage. If the fossils from Hadar and Maka (and Laetoli) are assumed instead to be from one sexually dimorphic species, then the degree of sexual dimorphism of A. afarensis would have been at least as extreme as that of the most dimorphic living apes, the gorilla and orang-utan. It follows that a strictly monogamous social structure would have been highly unlikely.