Cortical bone distribution in the femoral neck of hominoids: implications for the locomotion of Australopithecus afarensis.

Contiguous high resolution computed tomography images were obtained at a 1.5 mm slice thickness perpendicular to the neck axis from the base of the femoral head to the trochanteric line in a sample of 10 specimens each of Homo sapiens, Pan troglodytes, and Gorilla gorilla, plus five specimens of Pan paniscus. Superior, inferior, anterior, and posterior cortical thicknesses were automatically measured directly from these digital images. Throughout the femoral neck H. sapiens displays thin superior cortical bone and inferior cortical bone that thickens distally. In marked contrast, cortical bone in the femoral neck of African apes is more uniformly thick in all directions, with even greater thickening of the superior cortical bone distally. Because the femoral neck acts as a cantilevered beam, its anchorage at the neck-shaft junction is subjected to the highest bending stresses and is the most biomechanically relevant region to inspect for response to strain. As evinced by A.L. 128-1, A.L. 211-1 and MAK-VP-1/1, Australopithecus afarensis is indistinguishable from H. sapiens, but markedly different from African apes in cortical bone distribution at the femoral neck-shaft junction. Cortical distribution in the African ape indicates much greater variation in loading conditions consistent with their more varied locomotor repertoire. Cortical distribution in hominids is a response to the more stereotypic loading pattern imposed by habitual bipedality, and thin superior cortex in A. afarensis confirms the absence of a significant arboreal component in its locomotor repertoire.

Paleodemography of the Carlston Annis (Bt-5) Late Archaic skeletal population.

The study presents a demographic assessment of the Carlston Annis (Bt-5) Late Archaic hunting and gathering population recovered from the banks of the Green River in west-central Kentucky. The shell midden habitation and cemetery site originally yielded the remains of 390 individuals. Radiocarbon dates place site occupation between 3,000 and 4,500 y.b.p. The skeletal sample consisted of 354 individuals ranging in age from 7 months in utero to 70 + years. Subadults were aged by seriation of dental and skeletal developmental criteria. Adult ages were determined by the multifactorial summary age method that employed 1) five indicators of adult skeletal age at death, 2) the procedure of age indicator seriation, and 3) differential weighting of age assessments as determined by principal components analysis. Adult sex diagnoses were based on qualitative assessment of pelvic and cranial morphological criteria. The Bt-5 life table analysis yields an E0 of 22.4 years, crude birth of 45, mean family size of 3.3, gross reproductive rate of 2.7, generation length of 26.6 years, and B of .076, indicating a healthy population with a substantial capability to replace succeeding generations. Survivorship profiles and demographic parameters that compare the Carlston Annis (Bt-5) and Indian Knoll (Oh-2) skeletal series are presented. Both populations display type II survivorship curves, with high infant mortality and early onset of elevated mortality rates in adults. Major differences between Bt-5 and Oh-2 demographic parameters concern adult sex ratio and adult age distribution over 30 years. These differences are interpreted to reflect census errors in the Oh-2 demographic reconstruction that were possibly introduced by selective methodological biases and/or taphonomic factors.

Hamann-Todd Collection aging studies: osteoporosis fracture syndrome.

The study presents a retrospective analysis of distal radius, proximal femur, vertebral, and sacral fractures that occurred in 938 Hamann-Todd Collection skeletons. Individuals included in the investigation were retrieved from dissecting room cadavers in Cleveland, Ohio, between the years 1910 and 1940. Demographic analysis showed that the mean ages at death for blacks and whites included in the study were 41.9 and 53.8 years, respectively. Evaluations of fracture repair status were made for all fractures that were identified. Observations that document side of involvement and unilateral/bilateral distribution were made for distal radius and hip fractures. It was found that the age-, sex-, and race-related fracture patterns which characterize the early 20th century Hamann-Todd sample strongly correspond in distribution and magnitude to those seen in modern American and European urban industrial communities. The distal radius, hip, vertebral, and sacral fractures which were identified in individuals over 60 years of age appear to be a primary result of skeletal fragility due to age progressive bone loss. However, it is suggested that the early onset and high frequency of distal radius fractures seen in climacteric Caucasian women may be more directly due to accidental falls initiated by a greater frequency, intensity, and duration of vasomotor disturbances which are known to accompanay estrogen withdrawal in perimenopausal white females.

Relative tibia long bone growth in the Libben and Bt-5 prehistoric skeletal populations.

Patterns of tibia long bone growth were examined for the Libben Late Woodland and Bt-5 Late Archaic hunter-gatherer skeletal groups. Subadults included in the analyses ranged in age from birth to 10 years. The primary goals were to identify potential differences in relative tibia growth and evaluate the extent to which such differences were concordant with demographic and epidemiological characteristics of the two groups. Methods used were designed to minimize the shortcomings of unknown age and sex of the skeleton, small sample sizes, and population differences in adult size attained. Results showed that Bt-5 preadolescent growth performance and health status in general were superior to those of the Libben group. Modifications in the rate and timing of Libben tibia growth occurred early and were primarily restricted to the weaning period. It is suggested that high levels of infectious disease experienced in the first years of life at Libben played a substantial role in the etiology of early long bone growth retardation, a greater prevalence of iron deficiency anemia in the childhood years, and elevated levels of subadult morbidity and mortality compared to Bt-5. Paleodemographic, paleoepidemiological, and modern comparative population data that support these inferences are discussed. No evidence of chronic malnutrition owing to dietary inadequacy was observed for either group. Alternatively, higher population density and greater degree of sedentism alone may have been responsible for elevated disease loads at Libben compared to low levels that were observed for the seasonally mobile semisedentary Bt-5 hunter-gatherers.

Multifactorial determination of skeletal age at death: a method and blind tests of its accuracy.

Traditional methods of estimating skeletal age at death have relied solely on the pubic symphyseal face or on this indicator combined with others in nonsystematic ways. A multifactorial method is presented that uses a principal components weighting of five indicators (public symphyseal face, auricular surface, radiographs of proximal femur, dental wear, and suture closure). This method has been tested by completely blind assessment of age in two samples from the Todd collection carefully screened for accuracy of stated age at death. Results show a marked superiority of the multifactorial method over any single indicator with respect to both bias and accuracy. This represents the first truly blind test of an age-at-death indicator or system, as the test populations were independent of the system(s) being tested, and the age, sex, and ethnogeographic origin of the individuals being assessed (as well as the compositions of the test samples with respect to these variables) were completely unknown until the tests were completed. Implications for paleodemography are discussed.

Chronological metamorphosis of the auricular surface of the ilium: a new method for the determination of adult skeletal age at death.

A new method for the determination of adult skeletal age at death based upon chronological changes in the auricular surface of the ilium is presented. Formal stages have been constructed following extensive tests and refinements in observations made of such changes. Two completely "blind" tests were conducted to assess the accuracy and bias of the new method. Results show that the system is equally accurate to pubic symphyseal aging (although somewhat more difficult to apply), and also carries the advantages of a higher preservation rate for the auricular surface in archaeological populations and continued age-related change beyond the fifth decade.

A revised method of age determination using the os pubis, with a review and tests of accuracy of other current methods of pubic symphyseal aging.

All current standardized methods of age determination using the os pubis were tested by blind assessment of a skeletal sample with documented ages (from the Todd collection; N = 96). No demographic data (sex, age, race, age composition) were known to the assessors prior to completion of the test. Results showed the Todd method to be more reliable than more recent component techniques and that all systems tended to underage. Therefore, modifications were made of the Todd system to eliminate this and other deficiencies, and a second test using a new sample was conducted (N = 109). The age distribution determined by the revised Todd method did not significantly differ from the actual age distribution of the second sample. Error due to race was nonsignificant. Biological stages of pubic metamorphosis are described and possible evolutionary specializations of the hominid symphysis are discussed. Revised standards for age determination are presented.

Accuracy and direction of error in the sexing of the skeleton: implications for paleodemography.

Determinations of sex by subjective assessment of the skulls from a skeletal series of known sex were compared to fully independent assessments based on pelves of the same specimens. Within-sex correlations of cranial and pelvic morphologies measured on an android-gynecoid scale were smaller than expected. Subjective assessment by means of the skull compared favorably to that of the linear discriminant functions of Giles and Elliot; however, the direction of error was similar for both procedures. Of course, estimations based on the pelves were generally superior to both in terms of frequency and overall bias of error. The bias of sex estimation for paleodemographic purposes is contingent upon completeness of skeletal remains.

Anatomical, physiological, and epidemiological correlates of the aging process: a confirmation of multifactorial age determination in the Libben skeletal population.

Paleodemographic analyses based on estimates of skeletal age at death consistently report high levels of young adult mortality with few individuals living in excess of 50 years. Critics assert these data indicate systematic underaging of adults and justifiably remark that criteria for estimating skeletal age at death may be unreliable, age determinations are too frequently based on one or two criteria alone, and adult paleodemographic age profiles often mimic the age distribution of the modern population from which an age indicator's standards were originally derived. This study reports a series of tests based on well-documented biological aging phenomena that can be used to investigate potential effects of systematic underaging in adults, assuming the skeletal population is of sufficient size to permit such tests. These include patterns of third decade sternal clavicular epiphyseal fusion, multiple age and sex criteria associated with cortical bone dynamics, and fractures known to occur throughout the entire adult ages range. These phenomena are examined here for the Libben site skeletal population where adult age at death was determined by the multifactorial summary age technique. None of the biological criteria reported here were used in the Libben summary age analysis and thus serve as an independent test of accuracy in age determination. In addition, the summary age method has recently been applied to a series of modern skeletons of known age (Todd samples 1 and 2). Age standards for criteria employed with Libben and Todd 1 were identical. Since Todd 1 displayed underaging in older adults, a second Libben age distribution adjusted for Todd 1 bias was generated for comparison. A third Libben adult survivorship profile based on a Coale and Demeny West level 3 mortality experience, considered by some to be a more realistic model for skeletal populations, was produced for comparison. For all criteria examined, original Libben summary ages provided superior concordance with known patterns of biological aging in human populations. While Libben ages adjusted for Todd 1 bias were slightly better in the third decade, both Todd 1 adjusted and Coale and Demeny West level 3 age distributions produced unrealistic patterns of biological aging for individuals greater than 35 years. Implications of these results are discussed.

Part Two: The role of constitutional factors, diet, and infectious disease in the etiology of porotic hyperostosis and periosteal reactions in prehistoric infants and children.

Abstract A model of analysis incorporating methodological improvements and epidemiological refinements has been employed to investigate the etiology of porotic hyperostosis and periosteal reactions in infants and children from the Libben Site, a Late Woodland ossuary and occupation site from Ottawa County, Ohio. Results of the age-specific intrapopulational analysis of porotic hyperostosis demonstrate that the skeletal lesion strongly fits the age-specific distribution of hypochromic microcytic iron-deficiency anemia in infants and children. The data indicate that the lesion is a response to nutritional stress. Similarly, our findings show that the age-specific distribution of periosteal reactions strongly coincides with, and appears to be a response to, infectious disease as it occurs in infants and children. More importantly, survivorship and growth data indicate that porotic hyperostosis and periosteal reactions are strongly associated with patterns of infant and child morbidity and mortality, and therefore appear to play an important role in selection and fitness at Libben. Based upon the age-specific patterns and associations observed for porotic hyperostosis and periosteal reactions in the Libben infants and children, it is suggested that: 1. the current methodological procedure of partitioning skeletal populations into broad age categories can significantly distort important age-specific pathophysiological relationships; 2. skeletal lesions should be classified according to their physical quality (i.e., remodeled and unremodeled) to provide an estimate of both the morbidity and mortality associated with the age-specific distribution of a particular skeletal lesion; 3. porotic hyperostosis may be a valuable indicator of nutritional stress which can be employed to evaluate the nutritional status of prehistoric human populations; 4. the pathogenesis of porotic hyperostosis can best be understood in terms of the synergistic interactions between constitutional factors, diet, and infectious disease.