Epiphyseal fusion and dental development in Pan paniscus with comparisons with Pan troglodytes.

OBJECTIVES: Compared with frequent studies of skeletal development in chimpanzees, relatively little is known about bonobo skeletal development. This study seeks to explore the relationship between skeletal and dental development in both species of Pan. New data are presented for fusion sites not previously observed in bonobos. MATERIALS AND METHODS: In a sample of 34 Pan paniscus and 168 Pan troglodytes subadults, state of fusion was recorded for 30 epiphyseal fusion sites using a three-stage system of unfused, midfusion, and complete fusion based on Wintheiser, Clauser, and Tappen. Stage of dental development for permanent mandibular dentition was assessed using the Demrijian, Goldstein, and Tanner method. These data allowed for comparisons of both species of Pan and the two subspecies of P. troglodytes. RESULTS: The sequence of fusion events was generally consistent between the two species, but some exceptions may exist for the knee and ankle. The number of fusion events that occurred after complete dental mineralization was similar in both species. No statistically significant differences were found in the fusion timing for the subspecies of P. troglodytes. DISCUSSION: Bolter and Zihlman suggested that fusion at the acetabulum occurs earlier in Pan paniscus, while fusion of epiphyses at the knee are delayed, compared with P. troglodytes. Our data do not indicate earlier fusion of the acetabulum, but fusion events at the knee may complete later relative to dental mineralization in Pan pansicus. Compared with Homo sapiens, both P. troglodytes and Pan paniscus demonstrate later completion of epiphyseal fusion relative to dental mineralization.

A multivariate approach to assess variation in tooth mineralization using free-lived and captive-raised chimpanzees (P. troglodytes).

OBJECTIVES: Understanding variation in dental development among primates is important to accurately characterize species-specific sequences and times of tooth formation. Conventional approaches that summarize dental development data (i.e., dental maturity score, DMS) inherently omit information about the full range of variation in raw scores; thus, classic bivariate analyses are limited for exploring patterns of variation in detail. Here we report a new multivariate approach to simultaneously assess all raw dental scores, for all teeth, among all individuals for all groups, thus retaining much greater detail about population-specific patterns of variation. METHODS: We scored (0-12) permanent tooth mineralization using radiographs of mandibles of captive-raised known-age chimpanzees (Pan troglodytes; n = 114) and free-lived age-unknown conspecifics (n = 54). As a test of our method we also scored free-lived baboons (Papio anubis, n = 50) because of well-described contrasting patterns of permanent molar initiation between Papio and Pan. Using principal component analysis (PCA), we investigated how crypt, crown and root formation scores covaried with each other in all three genera, and with chronological age in captive chimpanzees. RESULTS: PCA successfully captured additional detail about variation among raw scores. Also, compared to DMS, PC1 scores correlated equivalently well with known ages but had lower prediction error. CONCLUSIONS: We found different patterns of variation in scores between younger juvenile free and captive chimpanzees but saw no wholesale differences between groups. Pan and Papio showed different patterns of variation, further validating this multivariate approach to visualize, quantify and compare raw dental score datasets among primate species.

Epiphyseal fusion in Pan troglodytes relative to dental age.

Previous studies on different aspects of chimpanzee growth and development have documented dental eruption and development, long bone and somatic growth, and to a lesser extent, skeletal fusion. Such data are useful in comparative and evolutionary studies of growth and some aspects of life history evolution in apes and early hominids. However, few studies have integrated dental development and other aspects of skeletal development, and none of these have been able to incorporate a large study sample. This study documents dental mineralization and skeletal epiphyseal fusion in a mixed-sex sample of 155 Pan troglodytes skeletons, and aims to: a) document the pattern of dental and skeletal developmental in chimpanzees; b) compare male and female developmental patterns in chimpanzees; and c) compare these chimpanzee developmental patterns to general patterns of dental and skeletal development in published human studies. The analysis of both dental and skeletal development in this sample demonstrates clearly that dental development is complete before the fusion of the many skeletal epiphyses, in contrast to the pattern observed in humans. Age estimates for individuals were calculated using previously published regression equations for dental development and used to estimate fusion ages. These appear to be accurate in that our estimates are similar to published ranges. These data improve our understanding about chimpanzee dental and skeletal development and provide a basis for further comparison between extant apes and humans, as well as those extinct species represented by fossil partial skeletons.

New species of Cercopithecoides from Haasgat, North West Province, South Africa.

Analyses of new cercopithecid fossil specimens from the South African site of Haasgat point to craniofacial affinities with the genus Cercopithecoides. Detailed metric and non-metric comparisons with South African Cercopithecoides williamsi, and other East African Cercopithecoides species, Cercopithecoides kimeui, Cercopithecoides meaveae, Cercopithecoides kerioensis, and Cercopithecoides alemyehui demonstrate that the Haasgat fossils have distinct craniofacial morphology and dental metrics. Specifically, material from Haasgat probably represents one of the smaller Cercopithecoides, differing from the others in its particular suite of features that vary within the genus. It is unique in its more vertical ramus, associated with a relatively lengthened mandibular body. Haasgat Cercopithecoides has a particularly narrow interorbital region between relatively larger ovoid orbits, with articulation of the maxillary bones at a suture above the triangular nasal bones. Furthermore, the maxillary arcade is more rounded than other Cercopithecoides, converging at the M(2) and M(3). The conclusion drawn from this analysis is that the Pleistocene Haasgat fossils are colobines representing a distinct taxon of Cercopithecoides, Cercopithecoides haasgati, thus adding a second species of the genus to southern Africa.

The history and composition of the Raymond A. Dart Collection of Human Skeletons at the University of the Witwatersrand, Johannesburg, South Africa.

The Raymond A. Dart Collection of Human Skeletons (Dart Collection) is housed in the School of Anatomical Sciences at the University of the Witwatersrand, Johannesburg, South Africa, and comprises one of the largest documented cadaver-derived human skeletal assemblages in the world. This collection originated in the early 1920s as a result of the efforts of Raymond Dart and continues to grow. The skeletons included represent varied indigenous and immigrant populations from southern Africa, Europe and Asia. This contribution documents the history of the collection and provides an updated inventory and demographic assessment of this valuable research collection. According to a recent inventory the Dart Collection currently comprises 2,605 skeletons representing individuals from regional SA African (76%), White (15%), Coloured (4%) and Indian (0.3%) populations. A large proportion of the skeletons (71%) represent males. The recorded ages at death range from the first year to over 100 years of age, but the majority of individuals died between the ages of 20 and 70. The Dart Collection has been affected by collection procedures based on availability. All of the cadavers collected before 1958, and large proportions subsequently, were derived from unclaimed bodies in regional South African hospitals. Some details of documentation (age at death, population group) are estimates and some aspects of the collection demographics (sex ratios) do not closely reflect any living South African population. Our inventory and analysis of the Dart Collection is aimed to assist researchers planning research on the materials from this collection.

Presence of the maxillary sinus in fossil Colobinae (Cercopithecoides williamsi) from South Africa.

Extant cercopithecoid monkeys, except macaques, are distinguished among primates by their lack of paranasal pneumatization, including the maxillary sinus (MS). Analysis of this structure, widespread among Eutheria, suggests that its loss occurred in the cercopithecoid common ancestor; thus, the presence of the MS in macaques is not strictly homologous to that in other primates. CT analysis of the fossil species Victoriapithecus macinnesi supports this view, demonstrating the lack of the MS in this stem cercopithecoid. Recent evidence, however, has documented the presence of the MS in extinct cercopithecoids from the late Miocene and Pliocene. This study reports on CT examination of two fossil crania attributed to Cercopithecoides williamsi from South Africa, dated in the range, 3.0-1.5 Ma. BF 42a is a complete cranium from Bolts Farm; MP113 is an intact facial skeleton, including the anterior cranial vault, from the Makapansgat Limeworks. Both demonstrate MS presence, unknown in extant colobines and unexpected in most cercopithecoid monkeys. The relative size of the MS of BF 42a is similar to that of extant tropical and subtropical macaques. The presence of sinuses in several extinct colobines suggests that our understanding of the evolutionary history of these primates, and of the MS, is incomplete, and that other fossil cercopithecoids should be examined for this feature. The developmental plasticity exhibited in this feature, indicated by multiple loss and reemergence, provides further evidence that paranasal pneumatization has undergone a complex history of suppression and expression.

Orbital forcing and the spread of C4 grasses in the late Neogene: stable isotope evidence from South African speleothems.

Reconstructing Plio-Pleistocene African paleoenvironments is important for models of early hominin evolution, but is often hampered by low-resolution or discontinuous climatic data. Here, we present high-resolution stable oxygen and carbon isotope time series data from two flowstones (secondary cave deposits) from the South African hominin-bearing Makapansgat Valley. The age of the older of the two flowstones (Collapsed Cone) is constrained by magnetostratigraphy to approximately 4-5 Ma; the younger flowstone (Buffalo Cave) grew between 2.0-1.5 Ma, as determined by magnetostratigraphy and orbital tuning of the isotopic data. The carbon isotope data is used as a proxy for the proportion of C(4) grasses in the local environment and the oxygen isotope data reflects monsoon rainfall intensity. The carbon isotope evidence indicates that in the late Miocene/early Pliocene, the local environment was dominated by C(3) vegetation, whereas, in the Plio-Pleistocene, it was composed of a mixture of C(3) and C(4) vegetation. This suggests that C(4) grasses became a significant part of the Makapansgat Valley ecosystem at approximately 4-5 Ma, towards the end of the late Neogene global expansion of C(4) grasses. After this initial expansion, South Africa experienced further fluctuations in the proportion of C(3) and C(4) vegetation during the Plio-Pleistocene, in response to regional and global climatic changes. Most notably, the Buffalo Cave flowstone provides evidence for C(4) grass expansion at ca. 1.7 Ma that we suggest was a response to African aridity caused by the onset of the Walker Circulation in the Pacific Ocean at this time.

Speleology and magnetobiostratigraphic chronology of the GD 2 locality of the Gondolin hominin-bearing paleocave deposits, North West Province, South Africa.

Speleological, paleomagnetic, mineral magnetic, and biochronological analyses have been undertaken at the Gondolin hominin-bearing paleocave, North West Province, South Africa. Two fossiliferous but stratigraphically separate sequences, GD2 and GD1/3, which were once part of a large cavern system, have been identified. Although some comparative paleomagnetic samples were taken from the GD 1, 3, and 4 localities that are currently under investigation, the research presented here focuses on the fossil-rich, in situ deposits at locality GD 2, excavated by E.S. Vrba in 1979. The GD 2 deposits are dominated by normal-polarity calcified clastic deposits that are sandwiched between clastic-free flowstone speleothems. The lower flowstone has a sharp contact with the red siltstone deposits and is of reversed polarity. The capping flowstone shows a change from normal to reversed polarity, thereby preserving a polarity reversal. While the paleomagnetic work indicates that the GD 2 fossil material was deposited during a normal-polarity period, the shortness of the sequence made matching of the magnetostratigraphy to the geomagnetic polarity time scale (GPTS) impossible without the aid of biochronology. While lacking multiple time-sensitive taxa, the recovery of specimens attributable to Stage III Metridiochoerus andrewsi is consistent with a deposition date between 1.9 and 1.5 Ma. A comparison of the magnetostratigraphy with the GPTS therefore suggests that the fauna-bearing siltstone of GD 2 date to the Olduvai normal-polarity event, which occurred between 1.95 and 1.78 Ma, and that the reversal from normal to reversed polarity identified in the capping flowstone dates to 1.78 Ma. The main faunal layers therefore date to slightly older than 1.78 Ma. Deposits from the GD 1 locality are dominated by reversed directions of magnetization, which show that this deposit is not of the same age as the faunal layers from the GD 2 locality.

Recent paleoanthropological excavations of in situ deposits at Makapansgat, South Africa--a first report.

The Makapansgat Limeworks is a significant Pliocene site both for its sample of 35 hominin fossils as well as its wealth of fossil fauna. The lithological and paleontological successions reveal local environmental changes that are important for understanding the context of hominin evolution in southern Africa. Yet most of the site's fossils were found in dumps left behind by quarry operations, and the paleoecological interpretations rest upon debatable assumptions about the original fossil provenience. We have recently initiated systematic paleoanthropological excavations at Makapansgat to recover well provenanced fossils in order to: 1) assess whether faunal successions are discernable in the Makapansgat sequence; 2) assist environmental interpretations of the site; 3) and potentially recover the oldest hominins in South Africa, roughly coincident with Australopithecus afarensis in East Africa. This paper presents a summary of our current paleoenvironmental research at the Limeworks and preliminary results of ongoing in situ excavations.