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O M Pearson

Publications and source records attributed to O M Pearson.

9 recordsLinked to original sources
PubMed2001

Eight hundred-year-old human remains from the Ituri tropical forest, Democratic Republic of Congo: the rock shelter site of Matangai Turu Northwest.

Little is known about human prehistory in the central African lowland tropical forest due to a paucity of archaeological evidence. Here we report results from our archaeological investigations of a late Holocene site in the northeast Congo Basin, with emphasis on a single skeleton from the rock shelter site of Matangai Turu Northwest, in the Ituri Forest, Democratic Republic of Congo. The skeleton dates from approximately 810 BP (1235 calibrated AD) and is associated with Later Stone Age lithics, animal bone and shell remains from wild taxa, fruit endocarps from forest trees, phytoliths from tropical forest plants, Late Iron Age ceramics, and a single iron artifact. Phytolith analysis indicates that the habitat was dense tropical forest, without evidence of domesticated food.

Adult↗
PubMed2001

Articular area responses to mechanical loading: effects of exercise, age, and skeletal location.

How reliable are reconstructions of body mass and joint function based on articular surface areas? While the dynamic relationship between mechanical loading and cross-sectional geometry in long bones is well-established, the effect of loading on the subchondral articular surface area of epiphyses (hereafter, articular surface area, or ASA) has not been experimentally tested. The degree to which ASA can change in size and shape is important, because articular dimensions are frequently used to estimate body mass and positional behavior in fossil species. This study tests the hypothesis that mechanical loading influences ASA by comparing epiphyses of exercised and sedentary sheep from three age categories: juvenile, subadult, and adult (n = 44). ASA was measured on latex molds of subchondral articular surfaces of 10 epiphyses from each sheep. Areas were standardized by body mass, and compared to diaphyseal cross-sectional geometrical data. Nonparametric statistical comparisons of exercised and control individuals found no increases in ASA in response to mechanical loading in any age group. In contrast, significant differences in diaphyseal cross-sectional geometry were detected between exercised and control groups, but mostly in juveniles. The conservatism of ASA supports the hypothesis that ASA is ontogenetically constrained, and related to locomotor behavior at the species level and to body mass at the individual level, while variations in diaphyseal cross-sectional geometry are more appropriate proxies for individual variations in activity level.

Age Factors↗
PubMed2000

Basicranial influence on overall cranial shape.

This study examines the extent to which the major dimensions of the cranial base (maximum length, maximum breadth, and flexion) interact with brain volume to influence major proportions of the neurocranium and face. A model is presented for developmental interactions that occur during ontogeny between the brain and the cranial base and neurocranium, and between the neurobasicranial complex (NBC) and the face. The model is tested using exocranial and radiographic measurements of adult crania sampled from five geographically and craniometrically diverse populations. The results indicate that while variations in the breadth, length and flexion of the cranial base are mutually independent, only the maximum breadth of the cranial base (POB) has significant effects on overall cranial proportions, largely through its interactions with brain volume which influence NBC breadth. These interactions also have a slight influence on facial shape because NBC width constrains facial width, and because narrow-faced individuals tend to have antero-posteriorly longer faces relative to facial breadth than wide-faced individuals. Finally, the model highlights how integration between the cranial base and the brain may help to account for the developmental basis of some morphological variations such as occipital bunning. Among modern humans, the degree of posterior projection of the occipital bone appears to be a consequence of having a large brain on a relatively narrow cranial base. Occipital buns in Neanderthals, who have wide cranial bases relative to endocranial volume, may not be entirely homologous with the morphology occasionally evident in Homo sapiens.

Adult↗
PubMed1998

Additional human fossils from Klasies River Mouth South Africa.

A fragmentary temporal bone and partial atlas from the Middle Stone Age (MSA) at Klasies River Mouth (KRM) are described and analyzed. The atlas (SAM-AP 6268) is comparable to Levantine "Early Modern", Neandertal and recent human vertebrae. The temporal (SAM-AP 6269) is similar to recent African homologues except that the posteromedial wall of the glenoid fossa is composed entirely of the squamous temporal, a situation that appears to be infrequent among other Pleistocene fossils. The KRM glenoid fossa is also mediolateraly broad and anteroposteriorly short in comparison with many, but not, all recent specimens. Nevertheless, the KRM temporal is decidedly modern, both morphologically and metrically, by comparison with other Pleistocene specimens. The limited evidence provided by this bone is consistent with that of other MSA cranial remains from this site in suggesting an overall, if somewhat ambiguous pattern of morphological modernity.

Animals↗
PubMed1997

Re-analysis of the hominid radii from Cave of Hearths and Klasies River Mouth, South Africa.

Two of the few postcranial fragments from the late Early Stone Age and/or the Middle Stone Age of southern Africa are the proximal radii from the Cave of Hearths and Klasies River Mouth. The Cave of Hearths fossil is metrically indistinguishable from both archaic (e.g., Neandertals) and recent humans, and presents a mosaic of primitive and modern features. The primitive include a relatively slender neck and thick cortical bone (the latter of which distinguishes recent humans from archaic, Early Modern, and Upper Paleolithic hominids); the modern includes an anteromedially (rather than medially) facing radial tuberosity. Its extreme collo-diaphyseal angle is unusual, although it can be matched by modern homologues. The neck-shaft angle of some Neandetral and Early Modern radii also appears to match that of the Cave of Hearths specimen. The Klasies River Mouth radius also has thick cortical bone of the neck. It is morphologically indistinguishable from Early Modern and Neandertal homologues. These, and other fossils, suggest a mosaic pattern of evolution in the postcranial skeleton of the late Early Stone Age and/or Middle Stone Age inhabitants of sub-Saharan Africa.

Animals↗
PubMed1996

Chin morphology and sexual dimorphism in the fossil hominid mandible sample from Klasies River Mouth.

The site of Klasies River Mouth (KRM) in South Africa has produced a small sample of early Upper Pleistocene hominid remains that have been a focus for discussions of the origins of modern humans. Despite certain primitive characteristics exhibited by these fossils, proponents of a single recent origin have attributed them to early modern humans. Critics of this hypothesis have emphasized the significance of the archaic features evident in this sample, including the absence of pronounced chins among the mandibular specimens. This study compares the size range and chin morphology exhibited by the KRM mandibles with that of Neandertals, Upper Pleistocene humans, and recent humans. The extreme sexual dimorphism documented among the KRM fossils reflects the presence of a very small individual, and previous efforts to classify the KRM sample as archaic on the basis of their robusticity have failed to address the significance of this diminutive hominid. While each KRM fossil falls within the 95% envelope of variability established for chin development in a comparative modern sample, a similarly low frequency of pronounced chins is very unlikely to be found in any recent human population. The morphological pattern of the KRM mandibles is clearly distinct from that of Neandertals and of recent humans.

Animals↗
PubMed1995

Fossil Homo femur from Berg Aukas, northern Namibia.

The proximal half of a hominid femur was recovered from deep within a paleokarst feature at the Berg Aukas mine, northern Namibia. The femur is fully mineralized, but it is not possible to place it in geochronological context. It has a very large head, an exceptionally thick diaphyseal cortex, and a very low collodiaphyseal angle, which serve to differentiate it from Holocene homologues. The femur is not attributable to Australopithecus, Paranthropus, or early Homo (i.e., H. habilis sensu lato). Homo erectus femora have a relatively longer and AP flatter neck, and a shaft that exhibits less pilaster than the Berg Aukas specimen. Berg Aukas also differs from early modern femora in several features, including diaphyseal cortical thickness and the degree of subtrochanteric AP flattening. The massive diaphyseal cortex of Berg Aukas finds its closest similarity within archaic H. sapiens (e.g., Castel di Guido) and H. erectus (e.g., KNM-ER 736) samples. It has more cortical bone at midshaft than any other specimen, although relative cortical thickness and the asymmetry of its cross-sectional disposition at this level are comparable with those of other Pleistocene femora. The closest morphological comparisons with Berg Aukas are in archaic (i.e., Middle Pleistocene) H. sapiens and Neandertal samples.

Adult↗
PubMedDate not supplied

Activity, climate, and postcranial robusticity: implications for modern human origins and scenarios of adaptive change.

Postcranial robusticity--the massiveness of the skeleton--figures prominently in the debate over the origin of modern humans. Anthropologists use postcranial robusticity to infer the activity levels of prehistoric populations, and changes in robusticity are often used to support scenarios of adaptive change. These scenarios explain differences in morphology as the result of a change in lifestyle (habitual activity). One common scenario posits that early modern humans were more gracile than Neandertals because the modern humans' complex culture required less physical exertion. However, lifestyle is only one of many influences on morphology. Climate has clear correlations with physique and skeletal proportions. Analysis of recent humans that differ in terms of lifestyle and climatic adaptations reveals that limb bone robusticity varies with climate as much as or more than with lifestyle. Many of the differences in robusticity between Neandertals and early modern humans appear to be related to climatic adaptations. The results support the single-recent origin model of modern human origins. The differences in robusticity between Neandertals and early modern humans suggest that population replacement rather than local evolution best explains the emergence of modern humans in Europe. Both climatic adaptations (primarily body proportions) and lifestyle should be considered in analyses of robusticity.

Activities of Daily Living↗