Sam D. Stout

Morphology of the Drifting Osteon

Drifting osteons were followed longitudinally through the cortex of human and baboon long bones using serial sections. Direction of transverse drift was recorded at different cross-sectional levels of the same systems, and maximum angular change in drift direction was measured for each system. Most drifting osteons exhibit: (1) substantial (∼90°) variation in the direction of transverse drift along their longitudinal axes, (2) intermittent regions of concentric (type I) morphology, and (3) change in drift direction over time, evident at single cross-sectional levels. Additionally, 3-dimensional reconstruction reveals that the basic multicellular units (BMUs) responsible for creating drifting osteons are morphologically distinct from the cutting-cone–closing-cone model BMUs that produce other types of osteons. The stimulus involved in the activation and guidance of drifting BMUs is unclear, but it is likely that the complex strain environment experienced by long bone cortices exerts a significant influence on their morphology.

Population-specific histological age-estimating method: a model for known African-American and European-American skeletal remains.

Previously developed histological age-estimating methods have been based on samples lacking interpopulation variability. A comparison of age-associated rib histomorphometrics between an European-American sample and an African-American sample indicates that ethnicity can have a significant effect on osteon population density (OPD), osteon cross-sectional area (On.Ar), and relative cortical area (Ct.Ar/Tt.Ar). Based upon these findings, new histological age-predicting formulae are presented that are recommended when estimating age for African-American or European-American skeletal remains. A general formula that is applicable to remains of unknown ethnicity is also provided.

Computer-Assisted 3D Reconstruction of Serial Sections of Cortical Bone to Determine the 3D Structure of Osteons

Abstract. The objective of this study was to create three-dimensional (3D) images for the histomorphological study of osteons. Medical imaging technology was used to register digitized 2D images of serial decalcified histological sections of bone, to segment the tissues of interest from the surrounding tissues, and to create 3D reconstructions from the segmented structures. Examination of the 3D reconstructions did not support suggestions in the literature that osteons have a spiraling organization. In contrast, the 3D reconstructions indicated that osteons have a complex pattern of organization that is dominated by branching. Examination of the reconstructions also suggested that osteons described in the literature as being dumbbell shaped are actually artifacts of the plane of sectioning. This study demonstrated the applicability of imaging and visualization technology developed for the 3D reconstruction of medical images to the reconstruction of digitized 2D images of serial sections of bone and additionally demonstrated the feasibility of using 3D reconstructions for the histomorphological study of osteons.

Histological Structure and Its Preservation in Ancient Bone

Histology has recently become a popular research method for the study of ancient skeletal remains. Nonmodern bone, however, has been exposed to a variety of diagenic conditions, many of which can significantly alter the structure and composition of bone. The paleohistologist must, therefore, distinguish postmortem changes from those occurring in living osseous tissue. The purpose of this paper is to review our present state of knowledge concerning histological structure and its preservation in ancient bone. Although the term paleohistology was suggested as recently as 1949 (Graf 1949), the fact that histological structure is often preserved in ancient skeletal remains has been known for some time. Queckett identified many gross histological features in animal fossils as early as 1849 (cited by Graf 1949). Some 30 years later, Aeby (1878) undertook an extensive histological analysis of bones and teeth from a variety of fossil genera. He was able to demonstrate that the canals and lacunae are still observable even after fossilization. Aeby (1878) and Schaffer (1889), utilizing polarized light microscopy, were able to demonstrate that the characteristic birefringence seen in fresh bone is also observable in bone of considerable antiquity. Since these pioneering works in paleohistology, advances in technology have led to greater understanding of the extent to which histology is preserved in ancient bone and what variation can be expected due to the variety of conditions to which bones have been exposed. Shackleford (1966), using electron microscopy and electron diffraction, found that soil conditions and age generally do not greatly affect the preservation of histological structure. Solomon and Hasse (1967) examined the histomorphology and histochemistry of bone from sites in Israel that differed in age, soil composition, and moisture content. Their findings suggest that exposure to water is the least favorable condition for preservation. The length of time bone has been dead seems to have little effect on preservation.

The relative accuracy and reliability of histological aging methods

Histological aging methods of Kerley and of Ahlqvist and Damsten were applied to bone samples from thirteen individuals of known age at death. Relative accuracy and reliability were determined for six of Kerleys predicting formulas for the femur, fibula and tibia, and his profile method, Ahlqvist and Damstens femoral predicting formulas, and age determined by averaging ages predicted by Kerleys six formulas. Averaging age estimates by Kerleys six formulas (mean regression) was found to produce the overall greatest accuracy and reliability. Dividing the sample into two age groups (13 - 51 and 60 - 102 years) altered the results only slightly. Kerleys femoral intact osteon formula produced the greatest accuracy for individuals in the younger age category, while his fibular osteon fragment formula was most accurate for older ages. Mean regression produced the greatest reliability for all age classes. Based upon both accuracy and reliability, averaging age predictions by Kerleys regression formulas appears to be the method of choice for broad application of histological aging.

The use of bone histomorphometry in skeletal identification: the case of Francisco Pizarro.

Two lines of approach are utilized in a histomorphometric analysis of a rib sample from the postcranial remains believed to be those of Francisco Pizarro. Using a newly developed age predicting formula, age at death is estimated to be 62 years. This age agrees with several ages reported in historical documents. The histomorphometry of cortical area/total area (C/T) ratio, mean osteonal cross-sectional area, and mean annual Haversian bone formation rate conform to those of a healthy individual in his early sixties.

Skeletal biology over the life span: a view from the surfaces.

The biocultural interpretation of skeletal remains is based upon the foundation of skeletal biology. In this review we examine the current state of skeletal biology research outside of the mainstream anthropology literature. The focus is on the structural changes of bone development and growth, and modeling and repair in the four bone surfaces: periosteal, Haversian, endosteal, and trabecular. The pattern of skeletal changes is placed within the framework of the human life span. New perspectives and direction of research on the environmental, biological, and genetic influences on modeling and remodeling processes are discussed chronologically at each bone surface. Implications for biological anthropologists are considered. This approach emphasizes variation in skeletal biology as a dynamic record of development, maturity, and aging.

The effects of long-term immobilization on the histomorphology of human cortical bone.

SummaryThe cortical bone histomorphometrics, total visible osteon density, and mean osteonal cross-sectional area were determined for the major long bones and sixth ribs of two individuals with neurological deficit. One was a multiple sclerosis patient who had been in a wheelchair for 15 years. The other was a quadriplegic as a result of poliomyelitis. Statistically significant differences in osteon densities occurred only in the case of the quadriplegic. Nevertheless, in that subject, the total visible osteon densities for bones of the right arm were not statistically different from those of their age-matched (control) radii. Medical history records revealed that there had been partial use of this limb. These results support the belief that mechanical stress is an important factor in the maintenance of normal cortical bone remodeling. In addition, since there were subnormal osteon densities and normal mean osteonal cross-sectional areas, immobilization appears to be characterized by reduced activation frequency with a normal amount of bone turnover per BMU.

Intrapopulation variation in stature and body proportions: Social status and sex differences in an Italian medieval population (Trino Vercellese, VC)

The phenotypic expression of adult body size and shape results from synergistic interactions between hereditary factors and environmental conditions experienced during growth. Variation in body size and shape occurs even in genetically relatively homogeneous groups, due to different occurrence, duration, and timing of growth insults. Understanding the causes and patterns of intrapopulation variation can foster meaningful information on early life conditions in living and past populations. This study assesses the pattern of biological variation in body size and shape attributable to sex and social status in a medieval Italian population. The sample includes 52 (20 female, 32 male) adult individuals from the medieval population of Trino Vercellese, Italy. Differences in element size and overall body size (skeletal height and body mass) were assessed through Monte Carlo methods, while univariate non-parametric tests and Principal Component Analysis (PCA) were employed to examine segmental and overall body proportions. Discriminant Analysis was employed to determine the predictive value of individual skeletal elements for social status in the population. Our results highlight a distinct pattern in body size and shape variation in relation to status and sex. Male subsamples exhibit significant postcranial variation in body size, while female subsamples express smaller, nonsignificant differences. The analysis of segmental proportions highlighted differences in trunk/lower limb proportions between different status samples, and PCA indicated that in terms of purely morphological variation high status males were distinct from all other groups. The pattern observed likely resulted from a combination of biological factors and cultural practices.

Exploring the multidimensionality of stature variation in the past through comparisons of archaeological and living populations

Adult stature variation is commonly attributed to differential stress-levels during development. However, due to selective mortality and heterogeneous frailty, a populations tall stature may be more indicative of high selective pressures than of positive life conditions. This article examines stature in a biocultural context and draws parallels between bioarchaeological and living populations to explore the multidimensionality of stature variation in the past. This study investigates: 1) stature differences between archaeological populations exposed to low or high stress (inferred from skeletal indicators); 2) similarities in growth retardation patterns between archaeological and living groups; and 3) the apportionment of variance in growth outcomes at the regional level in archaeological and living populations. Anatomical stature estimates were examined in relation to skeletal stress indicators (cribra orbitalia, porotic hyperostosis, linear enamel hypoplasia) in two medieval bioarchaeological populations. Stature and biocultural information were gathered for comparative living samples from South America. Results indicate 1) significant (P < 0.01) differences in stature between groups exposed to different levels of skeletal stress; 2) greater prevalence of stunting among living groups, with similar patterns in socially stratified archaeological and modern groups; and 3) a degree of regional variance in growth outcomes consistent with that observed for highly selected traits. The relationship between early stress and growth is confounded by several factors-including catch-up growth, cultural buffering, and social inequality. The interpretations of early life conditions based on the relationship between stress and stature should be advanced with caution.