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.     

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.     

Testing the value of skeletal samples in demographic research: a comparison with vital registration samples

Critics of paleodemography have suggested that the science is so fraught with error that its demise must be close at hand. Among the problems suggested as unsolvable are representativeness of skeletal samples and inaccuray of skeletal aging techniques. A historical skeletal sample with supportive vital registration might afford the opportunity to test the validity of such criticism or at least to examine the extent of the above problems. In 1984, a skeletal sample of 296 individuals was excavated from a 19th century American poorhouse cemetery. Age at death was determined by macroscopic multivariate examination. Mortality records of 247 individuals who died during four years of the poorhouse's operation provide data for demographic comparisons with the skeletal sample. A comparison of life tables generated from each sample demostrates that there are no significant differences in the age at death structure, life expectancy (at birth: 30.7 in the mortality records and 32.6 from the skeletal sample), or survivorship between the two samples. Skeletal aging techniques can, therefore, provide a demographic picture that is similar in accuracy to that presented by vital registration records.     

Reconstruction of paleodemographic characteristics from skeletal age at death distributions: perspectives from Hitotsubashi, Japan

This is a demographic exploration of the city of Edo, which reveals the changes that accompanied its urbanization and analyzes the skeletal remains of 207 individuals from a specific site in Tokyo (Hitotsubashi), using several paleodemographic approaches. A comparison of the three methods employed herein suggests that the Bayesian and maximum likelihood estimation techniques provide more plausible mortality patterns than the direct method of age estimation because the direct method of age estimation relies on published age intervals for the auricular surface and that would account for the underestimation of old people relative to the other two methods. Analyses using these new approaches indicate a short life span tendency for the people of Hitotsubashi. Although we cannot rule out methodological problems of adult-age estimation, one plausible interpretation of that life expectancy is an inadequate food supply and a poor public health situation. This study suggests that, in Tokugawa Japan, urbanization might have imposed health risks, increasing the risk of mortality. Analysis of demographic data from Hitotsubashi has refined our understanding on the impact of urbanization on the Edo period, and presents new perspectives on paleodemography in Japan.     

Radiographic changes in the clavicle and proximal femur and their use in the determination of skeletal age at death

Visually seriated radiographs of the proximal femur, proximal humerus, clavicle, and calcaneus from 130 individuals from the Hamann-Todd collection were examined as indicators of skeletal age at death. The clavicle demonstrated the most consistent relationship to age in both sexes. The same radiographs were also seriated by size-normalized optical density as a means of establishing relative radiolucency. In this context, visual seriation proved superior. The four sites studied showed strong divergence in response to age. Since each was sampling bone response from the same individual, it is concluded that bone loss is highly site specific. This demonstrates the individual character of specific skeletal sites. Visual inspection of clavicular radiographs, seriated on a populational basis, provides age estimates that are comparable to anatomical age indicators and provides independent estimates of skeletal age when included in the summary age method (1985: Am. J. Phys. Anthropol. 68:1–14).     

Tooth crown size differences between age groups: A possible new indicator of stress in skeletal samples

Juveniles and adults from a prehistoric Amerindian skeletal series from Tennessee are compared for differences in the means and variances of the buccolingual dimensions of their permanent teeth. While there are no significant differences in variance, it is found that juveniles exhibit significantly smaller mandibular canines, first premolars, and first molars. The results are similar to those of a previous examination of an Amerindian skeletal collection from South Dakota. There is evidence to suggest that teeth may fail to develop to their maximum genetic size potential when there is interference from exogenous chronic stressors such as malnutrition or disease. Archeological and biological evidence demonstrates that both the Tennessee and South Dakota series represent groups that suffered considerably from environmental stressors. It is suggested that those persons who suffered most were more likely to die prematurely, thus explaining why juvenile skeletons tend to have smaller teeth. The conclusion is that the examination of age variation in crown size can be a useful supplement to other osteological indicators of stress in skeletal collections. The factor of sex ratio and the implications of the results for other kinds of dental metric studies are discussed.     

Dental wear in the Libben population: Its functional pattern and role in the determination of adult skeletal age at death

Modal patterns of occlusal attrition are presented for the Libben population based on a sample of 332 adult dentitions. Maxillas and mandibles were reviewed independently by seriation prior to assessment of complete dentitions. The Spearman rank order coefficient for upper and lower dentitions was.96. Wear patterns are very similar to those reported by Murphy (1959a: Am. J. Phys. Anthropol. 17:167–178) for Australian aborigines. There were no significant sexual differences in wear rate. Dental wear is concluded to be a highly reliable and important indicator of adult age at death for skeletal populations if seriation procedures are employed.     

The short die young: the interrelationship between stature and longevity-evidence from skeletal remains

It has long been observed that tall people display longer life spans. The current data were employed to verify this association within the bioarchaeological context. To this end, stature and its association with age-at-death were analyzed in a pooled sample of 2,923 skeletons. Height was estimated from proxy indicators based on the maximum length of the humerus, radius, femur, and tibia. Stature estimation followed the procedure outlined by Pearson ([1899] Philos. Trans. R. Soc. Lond. [A] 192:169-244), incorporating minor modifications by R?sing ([ 1988] Handbuch der vergleichenden Biologie des Menschen; Stuttgart: Gustave Fischer, p 586-600). Individual age estimates were classified into three mutually exclusive age groups: 20-39 years (591 males, 667 females), 40-59 years (876 males, 499 females), and 60+ years (171 males, 119 females). The results document that both sexes display a statistically significant inverse relationship between adult height and age-at-death (males, P < 0.01; females, P < 0.05). Taking an epidemiological approach, the risk model implies that the estimated odds of survival beyond age 40 improve by approximately 16% for 1 SD in bone length. However, not all bones may be equally adept at displaying the association. The radius failed to support the positive association between stature and longevity, which may be indicative of a relatively greater contribution of environmental factor to radius length. Overall, the relationship between body height and longevity is not causal but coincidental: mitigated by diverse environmental factors such as nutrition, socioeconomic stressors, and disease load.     

Ectocranial suture closure: a revised method for the determination of skeletal age at death based on the lateral-anterior sutures

A new method for estimation of age-at-death based on the degree of suture closure is presented. The method employs simple ectocranial scoring of specific sites on the external table. Composite scores for two groups of sutures, lateral-anterior and vault systems, which are used to provide estimates of age-at-death, have been developed from a sample of 236 crania from the Hamann-Todd Collection. A variety of tests show that the lateral-anterior sutures are superior to the sutures of the vault, that ectocranial is superior to endocranial observation, and that age estimates are independent of race and sex. It is concluded that suture closure can provide valuable estimates of age-at-death in both archaeological and forensic contexts when used in conjunction with other skeletal age indicators.     

Small rodent population fluctuations: The effects of age structure and seasonality

Despite more than 50 years of effort, the causes and mechanisms of small rodent population fluctuations remain unknown. The two major questions are as follows: (1) what is the cause of population decline and (2) what is the cause of cyclicity and its geographical variation? At present, no hypothesis can provide answers to both these questions. Recently, progress has been made by Boonstra (1994), who proposed the senescence hypothesis to explain the cause of cyclic decline in population numbers. Here, we tested the main prediction that voles in decline are older than in other phases of the cycle, by analysing changes in age structure in a fluctuating population of the bank vole (Clethrionomys glareolus). The results generally support this prediction; however, the differences in absolute age seem to be too small to explain the occurrence of senescent animals exclusively in declines. We propose a new model to explain changes in age structure and the mechanisms behind the decline and geographic variation in cyclicity. It is based on the idea that voles are oldest in declines, developed independently of Boonstra. However, it differs in three respects: (1) it is more general and thereby applicable to the whole cycle; (2) density-dependent changes in age structure are based on the bimodality in a female's age at first reproduction; and (3) it stresses developmental rather than physiological changes in the quality of decline of animals as being relevant to the rate of senescence. We propose that seasonality of the environment is a principal candidate to explain geographical variation in cyclicity. We present substantial theoretical and empirical evidence to indicate that in more seasonal environments with shortened vegetation periods, population dynamics is inevitably less stable due to increased variation in two critical parameters – age at first reproduction and the length of the breeding season – which determine population growth rates. Any external perturbation may then easily destabilize population numbers. The general applicability of the seasonality-senescence hypothesis to other mammalian species decreases with declining r and increasing life span. The hypothesis is falsifiable, and testable predictions are provided.     

The role of GDF11 in aging and skeletal muscle,cardiac and bone homeostasis

GDF11 is a secreted factor in the TGFß family of cytokines. Its nearest neighbor evolutionarily is myostatin, a factor discovered as being a negative regulator of skeletal muscle growth. High profile studies several years ago suggested that GDF11 declines with age, and that restoration of systemic GDF11 to ‘youthful’ levels is beneficial for several age-related conditions. Particularly surprising was a report that supplementation of GDF11 aided skeletal muscle regeneration, as its homolog, myostatin, has the opposite role. Given this apparent contradiction in functionality, multiple independent labs sought to discern differences between the two factors and better elucidate age-related changes in circulating GDF11, with most failing to reproduce the initial finding of declining GDF11 levels, and, importantly, all subsequent studies examining the effects of GDF11 on skeletal muscle described an inhibitory effect on regeneration – and that higher doses induce skeletal muscle atrophy and cachexia. There have also been several studies examining the effect of GDF11 and/or the downstream ActRII pathway on cardiac function, along with several interesting reports on bone. A review of the GDF11 literature, as it relates in particular to aging and skeletal muscle, cardiac and bone biology, is presented.     

Assessing the influence of occupational and physical activity on the rate of degenerative change of the pubic symphysis in Portuguese males from the 19th to 20th century

Among the many factors suggested as potential sources of variation in the rate of ageing of the pubic symphysis is occupational/physical activity, but this has yet to be demonstrated. This study's main goal is to determine whether occupational/physical activity influences the aging process in the pubic symphysis. We analyzed a sample of 161 males (18-96 years) from two Portuguese identified skeletal collections, where age-related features were recorded in the pubic symphysis as absent/present. The sample was divided in two groups according to the occupation of the individuals (manual and non-manual) and in two groups according to the femoral robusticity index (robust and gracile). The manual and robust groups represent individuals with more physically demanding occupations while the non-manual and gracile groups represent less physically demanding occupations. The possible influence of occupational/physical activity on the rate of ageing was evaluated by comparing the transition age for each age-related feature, between the two groups, using logistic regression. Only the ligamentous outgrowths on the ventral beveling showed a statistically significant younger age in the robust group, indicating a possible faster rate or early timing of change in the individuals with a more physically demanding activity compared with their gracile counterparts. Thus, these results do not provide significant support to the hypothesis that individuals with a greater demanding occupation or physical activity show greater pubic symphysis degeneration. Further testing of this hypothesis in other samples with individuals from known occupation is required.     

Brief communication: infracranial maturation in the skeletal collection from Coimbra, Portugal: new aging standards for epiphyseal union

Age at death of a single skeletal individual or a group is essential information in archaeological, paleoanthropological, and forensic contexts. Dental remains are the most commonly used age indicators, but when the dentition is not available, or too few teeth are present for an accurate age assessment, other age indicators such as skeletal maturation must be used. Of particular utility in this regard is the fusion of the epiphyses of the infracranial skeleton. Here we present new aging standards based on the infracranial maturation of individuals from the known age and sex collection from Coimbra, Portugal. We scored infracranial epiphyseal fusion and spheno-occipital synchondrosis closure (64 loci of ossification in total) on 137 skeletons from individuals between 7 and 29 years old. We further discuss developmental differences between the sexes and similarities and differences between the Coimbra documented collection and other published aging standards.     

Epiphyseal union at the innominate and lower limb in a modern Portuguese skeletal sample, and age estimation in adolescent and young adult male and female skeletons

This study documents the timing of epiphyseal union at the innominate, femur, tibia, and fibula in a sample of modern Portuguese skeletons. The sample was taken from the Lisbon documented skeletal collection and it is comprised of 57 females and 49 males between the ages of 9 and 25. Individuals are mostly representative of the middle-to-low socioeconomic segment of the early 20th century Lisbon population. A total of 18 anatomical locations were examined for epiphyseal union using a three-stage scheme: 1) no union; 2) partial union; and 3) completed union, all traces of fusion having disappeared. Results show that females are ahead of males by 1-2 years and provide similar age ranges for the stages of union than previous studies. Some variations between studies can be explained by methodological differences between dry bone and radiographic observations. However, a review of the literature indicates that socioeconomic status of a given population seems to be of decisive importance to the rate of ossification and most of the differences in skeletal maturation across studies and populations can probably be ascribed to different levels of social and economic development of the societies in which the individuals lived. Although the effects of socioeconomic status in skeletal maturation are greater during childhood than in adolescence, as to make the timing of epiphyseal union a reliable estimate of age at death, they are not negligible and age estimates should take into account the likely socioeconomic status of the individual, whose remains are under examination.     

Skeletal age determination based on the os pubis: A comparison of the Acsádi-Nemeskéri and Suchey-Brooks methods

After reviewing various systems of age determination based on analysis of the pubic bone, the discussion concentrates on the collection and preparation of an extensive autopsy sample (n=1225) of pubic bones from modern individuals with legal documentation of age at death (death and/or birth certificates). TheSuchey-Brooks method derived from this sample is described. TheAcsádi-Nemeskéri system is evaluated in terms of the documented collection and it is seen that their five stage method focuses only on the early and late morphological changes. The intermediate stages, in which the ventral rampart is in process of completion, are not described. Their suggested age ranges do not correspond with the documented modern sample. Based on these limitations of theAcsádi-Nemeskéri method, applications of theSuchey-Brooks system are discussed.     

Use of the frontal bone in age determination of Labeo horie (Pisces,Cyprinidae) in Jebel Aulia Reservoir,Sudan

In spite of the exuberance of recent approaches to age determination of fish, many ecologists are convinced that the most valid method is age reading from permanent marks or growth rings laid on skeletal parts. Of the known structures used, only the vertebrae are suitable and readable for a large variety of species and sizes. Examination of different skeletal structures of Labeo horie, a Cyprinid collected from Jebel Aulia reservoir, revealed that the frontal bone carried well-defined growth rings. The validity of these rings was checked against other direct and indirect methods of age determination. Results proved to be statistically valid, and the frontal bone offers an additional device of age determination of L. horie.     

Proteasomal activity in skeletal muscle: A matter of assay design, muscle type, and age

The ubiquitin-proteasome system (UPS) is a major degradation system for regulatory and misfolded proteins. UPS function has been implicated to exert a central role in the pathogenesis of various human diseases. Because biochemical analyses are often hampered by the amount of available diseased tissue, we report on the establishment and validation of a luminescence-based proteasomal activity assay applicable to 5-mg quantities of skeletal muscle. We demonstrate that the specific proteasomal activity differs in individual muscle groups and decreases with aging. These findings warrant the use of appropriate controls and a careful interpretation of results in mammalian skeletal muscle pathologies.