Dental development in South African australopithecines. Part I: Problems of pattern and chronology

It is well known that humans take about twice as long as apes to mature. The traditional view that such delayed maturation was already present in australopithecines has been called into question during the past several years. We have approached this problem by looking at patterns of dental development in gracile and robust australopithecines from South Africa and comparing them to patterns found in extant humans and apes. We have employed both 2 and 3 dimensional computed tomography in our research. The dental growth patterns in these two australopithecine morphs differ, particularly in M1/I1 development. The robust australopithecines are more humanlike and the gracile australopithecines more apelike in this feature (“humanlike” and “apelike” are not used in any taxonomic sense). Pattern and chronology of dental development must be considered separately. Several major problem areas for future research are identified, most of which revolve around the issue of intra- versus interspecific variation.     

Alleged synapomorphy of the M1/I1 eruption pattern in robust australopithecines and Homo: evidence from high-resolution computed tomography

Ever since Broom and Robinson (1951) published their claim that the eruption pattern of permanent incisors in robust australopithecines was most similar to that of modern man and different from that of gracile australopithecines and apes, the accuracy of this observation has been the subject of periodic debate (e.g., Wallace: Ph.D. thesis, 1972; Dean: Am. J. Phys. Anthropol. 67:251-257, 1985; Grine: Am. J. Phys. Anthropol. 72:353-359, 1987). Part of the problem is that the developing incisors in one of the specimens most crucial to this argument (SK61) are difficult to visualize clearly by conventional radiographic techniques because of the heavy mineralization in the fossil. This study reanalyzes SK 61 by high-resolution computed tomography in order to contribute to the final resolution of its incisor development. Grine's (op. cit.) assessment of the incisors as the deciduous ones, not the permanent ones, is fully confirmed. This fact, in conjunction with the observation that permanent incisor root formation had only just commenced in this specimen, further weakens the argument of M1/I1 eruption pattern synapomorphy between Homo and robust australopithecines.     

Brief communication: Possible third molar impactions in the hominid fossil record

Impacted third molars affect 15%–20% of modern Americans and Western Europeans. In contrast, third molar impactions have not been reported in the early hominid fossil record. It is uncertain whether the lack of reports reflects an absence of impactions or a failure to recognize them. This communication is intended to raise awareness of the possibility of impactions by describing the appearance of impacted teeth and by noting two possible instances of impaction in early hominids. Specifically, the mandibular third molars of the Sterkfontein specimen, STS52b (Australopithecus africanus), and the left maxillary third molar of the Lake Turkana specimen, KNM-WT17400 (Australopithecus boisei), are positioned in a manner which suggests that they would not have erupted normally. Both specimens also exhibit strong crowding of the anterior dentition, providing further support for the view that these individuals lacked sufficient space for normal eruption of the third molars. Other published reports of dental crowding in the hominid fossil record are noted, and it is suggested that more attention be paid to dental impaction and dental crowding in hominid evolution. © 1993 Wiley-Liss, Inc.     

Further evidence on relative dental maturation and somatic developmental rate in hominoids.

New data on hominoid dental development are presented. Individual bivariate pairings of all mandibular teeth were made for African apes and humans. Data were analyzed with a full linear regression model. No statistically significant differences were found among apes, although a consistent pattern of earlier incisal development was observed in Pan relative to Gorilla. This is concordant with an earlier fusion of the premaxillary:maxillary suture in Pan. Only one tooth pair differed significantly by sex among apes. Two biologically distinct human samples (Libben and Hamann-Todd), although assessed differently (extraction and radiography) yielded virtually identical results. Humans differ from apes only by earlier relative calcification of their anterior teeth. This can be viewed as a consequence of reduced facial prognathism and a shift in hominid canine function.     

Plantigrady and foot adaptation in African apes: implications for hominid origins.

In living primates, except the great apes and humans, the foot is placed in a heel-elevated or semi-plantigrade position when these animals move upon arboreal or terrestrial substrates. Heel placement and bone positions in the non-great ape primate foot are designed to increase mobility and flexibility in the arboreal environment. Orangutans have further enhanced foot mobility by adapting their feet for suspension and thus similarly utilize foot positions where the heel does not touch the substrate. Chimpanzees and gorillas represent an alternative pattern (plantigrady), in which the heel contacts the surface of the support at the end of swing phase, especially during terrestrial locomotion. Thus, chimpanzees and gorillas possess feet adapted for both arboreal and terrestrial substrates. African apes also share several osteological features related to plantigrady and terrestrial locomotion with early hominids. From this analysis, it is apparent that hominid locomotor evolution passed through a quadrupedal terrestrial phase.     

Animal exploitation strategies during the South African Middle Stone Age: Howiesons Poort and post-Howiesons Poort fauna from Sibudu Cave

As one of the few sites that preserve fauna from the Howiesons Poort (HP) and the immediately post-HP Middle Stone Age (MSA), Sibudu Cave provides a unique opportunity to explore the range of variability in subsistence behaviors during this important phase in human behavioral evolution. In addition to providing information on subsistence, the faunal assemblage serves as a means of reconstructing the environmental conditions during these two periods. While the HP fauna is dominated by species that prefer closed (particularly forested) habitats, the fauna from the upper-most layers of the post-HP MSA are largely representative of open conditions. These results largely coincide with macrobotanical analyses and may simply indicate that the extent of the riverine forest near the site was greater during the HP. Alternatively, the pattern could be indicative of a marked intensification in the exploitation of the environment in the immediate vicinity of the shelter during the HP, perhaps resulting from a decline in the productivity of adjacent regions. We also document variation in the frequency of the different bovid size classes over time. The evidence shows a declining focus on the smallest bovids after the HP, with a parallel increase in the frequency of large and very large bovids. Beyond a heavy focus on small bovids, small mammals and suids also occur at higher frequencies during the HP. Although the HP faunal assemblage is largely unique as compared to the bulk of the MSA sequence at Sibudu, the evidence presented here suggests that the transition between the HP and the post-HP MSA may have been more gradual than abrupt. Our results indicate that the HP and post-HP MSA inhabitants of Sibudu Cave were capable hunters; however, hunting strategies appear to show marked variation over time. We propose that the variability in animal procurement strategies reflects a degree of behavioral plasticity beyond that generally attributed to MSA populations.     

Sex at Sterkfontein: 'Mrs. Ples' is still an adult female

The important question of whether the Australopithecus africanus hypodigm is taxonomically heterogeneous revolves largely around the interpretation of the morphological variation exhibited by the fossils from Sterkfontein. The sex assignment of these specimens is a critical component in the evaluation of their morphological variability. The Sts 5 cranium is pivotal in this regard because it is the most complete and undistorted specimen attributed to A. africanus. Although it has traditionally been regarded as an adult female, this view has been challenged. In particular, it has been argued recently that Sts 5 is a juvenile and that this, together with alveolar bone loss that has supposedly reduced the size of the canine socket, has led to its misinterpretation as a female. Virtual reconstruction of the M³ roots (and/or alveoli) contradicts arguments that these teeth were erupting at the time of death. Regardless, canine emergence and root completion are well ahead of M³ development in juvenile australopiths from Sterkfontein. Thus, even if the M³ root of Sts 5 was incomplete, its canine root would have been fully formed. Measurements of palate depth indicate that the alveolar margins of Sts 5 have not suffered from much (if any) bone loss in the region of the C/P³; any additional bone would result in a palate of truly exceptional depth. Therefore, the dimensions of the canine alveolus of Sts 5 can be regarded as proxies for those of the canine root. The canine root of Sts 5 is among the smallest recorded for any Sterkfontein australopith, which provides strong support for Robert Broom's initial attribution of sex to this specimen. There is no evidence to contradict the assertion that ‘Mrs. Ples’ is an adult female.     

The development of meiotic competence in the rat: Role of hormones and of the stage of follicular development

Hypophysectomy of 15-day-old rats (hypox) markedly reduced the normal development of meiotic competence and abolished the development of antral follicles between days 21 and 31 postpartum (pp). Here the correlation among age of the rats, stage of follicular development, and meiotic competence was examined. Administration of pregnant mare's serum gonadotropin (PMSG-3IU) or insertion of an estradiol-17β (E₂) capsule to hypox rats induced the development of meiotic competence provided the treatment started after day 20 pp. Hormonal treatments at an earlier age were not effective in inducing meiotic competence in hypox rats. The induction of meiotic competence by PMSG or E₂ was associated with an increase in the number of granulosa cells and formation of follicular antrum. The finding that PMSG and E₂ failed to induce meiotic competence when administered prior to day 21 pp suggests that the development of meiotic competence is an age-dependent process. When the hormonal treatments commenced after day 21, both follicular development and meiotic competence were induced.     

Physical growth in a transitional economy: the aftermath of South African apartheid

The economic transition in developing countries is not always the result of the change from a centrally-planned to a free-market economy, but may be found within an already existing free-market economy as a result of profound political change, as in South Africa. The release of Nelson Mandela in February 1990 heralded an end both to the political system of apartheid and to the concomitant social, political, and economic disenfranchisement of 30 million non-White people in South Africa. The first freely elected non-White government came to power in 1994 and initiated a number of social and economic reforms aimed at alleviating the worst consequences of apartheid. This paper examines the effect of post-apartheid economic and social transition on the growth and development of urban children. Over 4000 children born in Soweto and Johannesburg were enrolled in the Birth to Ten (BTT) birth-cohort study in 1990. Whilst these children were born with lower birth weights than in developed countries, they did grow strongly in infancy, particularly in weight, to reflect normal reference values for body mass index (BMI) by 1 year of age. While post-apartheid social and economic changes were expected to take some time to affect child growth and development, the rate of change has been slower than expected. Data from the BTT study demonstrate that the growth of White children continues to be superior to that of their non-White peers and differences that existed at birth and during infancy have not diminished during childhood and early adolescence. Whatever factors are changed at the national or community levels during economic (and social) transition in South Africa appear not yet to have resulted in improved child physical growth.     

Dental paleopathology and agricultural intensification in south Asia: new evidence from Bronze Age Harappa.

Patterns of dental disease among Bronze Age people of the Indus Valley Civilization are currently based on early and incomplete reports by non-specialists. This deficiency precludes accurate diachronic analysis of dental disease and its relationship with increasing agriculturalism in the Indian subcontinent. The objective of this paper is to document prevalence of dental disease at Harappa (2500-2000 B.C.), Punjab Province, Pakistan, comparatively evaluate the Harappan dental pathology profile, and use these data to assess theories regarding the dental health consequences of increasingly intensive agricultural dependence. Pathological conditions of the dentition included in the study are abscesses, ante-mortem tooth loss (AMTL), calculus, caries, hypoplasia, hypercementosis, pulp chamber exposure, and alveolar resorption. The Harappan dentition exhibits a dental pathology profile typical of a population whose subsistence base is agriculture. Dental caries at Harappa are present in 6.8% (n = 751) of the teeth and 43.6% (n = 39) of the more completely preserved dental specimens. The use of a caries correction factor is recommended to permit an estimate of caries induced AMTL in calculating the caries prevalence. All dental lesions are present at higher rates in this Harappan study sample than were reported in previous investigations, and important differences in prevalence of dental disease occur between the genders. Prevalence of dental disease increases in the greater Indus Valley as subsistence becomes more intensive and as food preparation and storage technology becomes more efficient.     

Glycogenosis type II: protein and DNA analysis in five South African families from various ethnic origins.

The molecular nature of lysosomal alpha-glucosidase deficiency was studied in five South African families with glycogenosis type II. Distinct ethnic origins were represented. Two new mutant acid alpha-glucosidase alleles were discovered. In two infantile patients from a consanguineous Indian family we found for the first time an acid alpha-glucosidase precursor of reduced size. The mutant precursor appeared normally glycosylated and phosphorylated but was not processed to mature enzyme. Abnormalities of the mRNA were not obvious, but digestion of genomic DNA with HindIII, BglII, and StuI revealed for each enzyme a fragment of increased length. Heterozygosity was demonstrated in the parents. Complete lack of acid alpha-glucosidase mRNA, as well as deficiency of precursor synthesis, was observed in two black baby girls from unrelated families. In these cases the length of all restriction-enzyme fragments was normal. Reduced enzyme synthesis but normal processing was registered in juvenile and young adult Cape colored patients. The extensive heterogeneity of glycogenosis type II is emphasized in these studies on various ethnic groups. The newly discovered mutants are valuable for the understanding of clinical diversity as a result of allelic variation.     

Measurements of tooth wear among Australian aborigines: II. Intrapopulational variation in patterns of dental attrition

The possible implications of variations in dental attrition patterns have necessitated a detailed assessment of the types, ranges, and causes of tooth wear. Hear we employ measurements of postcanine occlusal wear facets from a sample population of extant Australian aborigines. A principal components analysis was applied as a tool in determining common types of attritional patterns. It was concluded that the range of intrapopulational variation in dental wear patterns must be attributed to a multiplicity of sources in addition to such commonly cited causes as dietary variations, gender, age, and developmental eruption sequences.     

Dental development in Megaladapis edwardsi (Primates, Lemuriformes): implications for understanding life history variation in subfossil lemurs

Teeth grow incrementally and preserve within them a record of that incremental growth in the form of microscopic growth lines. Studying dental development in extinct and extant primates, and its relationship to adult brain and body size as well as other life history and ecological parameters (e.g., diet, somatic growth rates, gestation length, age at weaning), holds the potential to yield unparalleled insights into the life history profiles of fossil primates. Here, we address the absolute pace of dental development in Megaladapis edwardsi, a giant extinct lemur of Madagascar. By examining the microstructure of the first and developing second molars in a juvenile individual, we establish a chronology of molar crown development for this specimen (M1 CFT = 1.04 years; M2 CFT = 1.42 years) and determine its age at death (1.39 years). Microstructural data on prenatal M1 crown formation time allow us to calculate a minimum gestation length of 0.54 years for this species. Postnatal crown and root formation data allow us to estimate its age at M1 emergence (approximately 0.9 years) and to establish a minimum age for M2 emergence (>1.39 years). Finally, using reconstructions or estimates (drawn elsewhere) of adult body mass, brain size, and diet in Megaladapis, as well as the eruption sequence of its permanent teeth, we explore the efficacy of these variables in predicting the absolute pace of dental development in this fossil species. We test competing explanations of variation in crown formation timing across the order Primates. Brain size is the best single predictor of crown formation time in primates, but other variables help to explain the variation.     

Tectonics, orbital forcing, global climate change, and human evolution in Africa: introduction to the African paleoclimate special volume

The late Cenozoic climate of Africa is a critical component for understanding human evolution. African climate is controlled by major tectonic changes, global climate transitions, and local variations in orbital forcing. We introduce the special African Paleoclimate Issue of the Journal of Human Evolution by providing a background for and synthesis of the latest work relating to the environmental context for human evolution. Records presented in this special issue suggest that the regional tectonics, appearance of C(4) plants in East Africa, and late Cenozoic global cooling combined to produce a long-term drying trend in East Africa. Of particular importance is the uplift associated with the East African Rift Valley formation, which altered wind flow patterns from a more zonal to more meridinal direction. Results in this volume suggest a marked difference in the climate history of southern and eastern Africa, though both are clearly influenced by the major global climate thresholds crossed in the last 3 million years. Papers in this volume present lake, speleothem, and marine paleoclimate records showing that the East African long-term drying trend is punctuated by episodes of short, alternating periods of extreme wetness and aridity. These periods of extreme climate variability are characterized by the precession-forced appearance and disappearance of large, deep lakes in the East African Rift Valley and paralleled by low and high wind-driven dust loads reaching the adjacent ocean basins. Dating of these records show that over the last 3 million years such periods only occur at the times of major global climatic transitions, such as the intensification of Northern Hemisphere Glaciation (2.7-2.5 Ma), intensification of the Walker Circulation (1.9-1.7 Ma), and the Mid-Pleistocene Revolution (1-0.7 Ma). Authors in this volume suggest this onset occurs as high latitude forcing in both Hemispheres compresses the Intertropical Convergence Zone so that East Africa becomes locally sensitive to precessional forcing, resulting in rapid shifts from wet to dry conditions. These periods of extreme climate variability may have provided a catalyst for evolutionary change and driven key speciation and dispersal events amongst mammals and hominins in Africa. In particular, hominin species seem to differentially originate and go extinct during periods of extreme climate variability. Results presented in this volume may represent the basis of a new theory of early human evolution in Africa.     

Adult forms of glycogenosis type II. A defect in an early stage of acid alpha-glucosidase realization

The activity of acid alpha-glucosidase in cultured fibroblasts from adult patients with the lysosomal storage disease glycogenosis type II is only 10% of normal. A normal activity per molecule is found for the mature as well as for the precursor form of acid alpha-glucosidase in adult mutant fibroblasts. Excessive lysosomal breakdown of mature enzyme purified from mutant fibroblasts and taken up by acceptor cells does not occur. However, the NH4Cl-stimulated secretion of a precursor form of acid alpha-glucosidase by adult mutant fibroblasts is markedly reduced. The results are indicative of a defect during the production of acid alpha-glucosidase.     

Physical growth and development, neurological maturation, and behavioral functioning in two Ecuadorian Andean communities in which goiter is endemic. II. PTC taste sensitivity and neurological maturation

PTC (phenylthiocarbamide) taste sensitivity was correlated with a measure of visual-motor maturation in children six to 15 years of age in two Ecuadorian Andean communities in which goiter (enlargement of the thyroid gland) and cretinism are endemic. The children in one population received injections of iodine in oil IM in 1966 while the children in the other population did not. The correlations between PTC taste sensitivity and visual-motor maturation were significant in both sex groups in the non-iodized population, but not in the iodized population. There was also a significant increase in taste sensitivity with age in the non-iodized, but not the iodized, population. The data support the hypothesis that the sensitive “tasters” of PTC limit their ingestion of naturally occurring goitrogens and are at an adaptive advantage with respect to the less sensitive “tasters” and “non-tasters” in this area in which iodine intake is low and the consumption of food crops containing naturally occurring goitrogens is high.     

Part II: Dealing with parameter uncertainty and uncertainty due to choices in life cycle assessment

Results of product assessments are often criticised as to their handling of uncertainty. Therefore, it is necessary to develop a comprehensive methodology reflecting parameter uncertainty in combination with uncertainty due to choices in the outcome of LCAs. This paper operationalises the effect of combined parameter uncertainties in the inventory and in the characterisation factors for global warming and acidification for the comparison of two exemplary types of roof gutters. For this purpose, Latin Hypercube sampling is used in the matrix (inventory) method. To illustrate the influence of choices, the effect on LCA outcomes is shown of two different allocation procedures in open-loop recycling and three time horizons for global warming potentials. Furthermore, an uncertainty importance analysis is performed to show which parameter uncertainties mainly contribute to uncertainties in the comparison and the separate environmental profiles of the product systems. These results can be used to prioritise further data research.