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.     

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.     

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).     

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.     

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.     

Determination of age at death in human skeletal remains: A comparison of two techniques

Reliable palaeodemographic reconstruction is dependent upon accurate determination of age at death in human skeletal remains. Two methods, Todd (Todd, 1920, 1921) and Suchey-Brooks (Katz & Suchey, 1986), which use morphological changes of theos pubis as an indicator of age at death, were applied to a sample of Central California Indians. Life tables were constructed and the two data sets were compared. Differences between the two data sets were evident when life expectancies, mean ages, and survivorship curves were compared. Because both methods were developed using male samples, only the male data were considered valid. In a comparison between the two male data sets it became apparent that the differences lie in the upper decades depending upon which method was used. In an attempt to rectify the difference in age ranges between the two methods, a conversion of Todd phases into equivalent Suchey-Brooks phases (Katz & Suchey, 1986) was employed. Applications and limitations of both methods are discussed and it is suggested that the Suchey-Brooks method is to be perferred.     

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.     

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.     

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.     

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.     

Age at death determination by means of femoral frequency of secondary osteons

A statistical model for the estimation of the age at death is defined and tested to evaluate its performance. It is characterized by the probability of the femoral frequency of secondary osteons for any given age, that we compute by means of 28 scheletons of Italian subjects. In a standard case we obtain good evalutations of the methods, while in practice it can be used according to the objectives of the particular investigation. Moreover other surveys could easily be added to our data in order to obtain a more powerfool tool.     

Effects of field size when using Kerley's histological method for determination of age at death

The field size at which a bone is read affects the results obtained when using Kerley's histological method for age estimation, even after applying the recommended correction factor. Whereas there is no tendency for any one of three field sizes tested to consistently underestimate or overestimate age, a field size closest to that used by Kerley in his original study had significantly lower variances for its age estimates, and thus provides greater reliability. This particular field size yields more precise estimates because it is sampling a pattern and number of structures more similar to that of Kerley. Correction factors cannot equalize the counts of osteons and osteon fragments because of spatial variations in the distributions of these histological structures. A field size similar to that used by Kerley in gathering the data from which he developed his regression equations must be used to assure that the same pattern and number of structures is being sampled. For this reason, we suggest a field size as close to 2.06 mm² as possible be used when employing Kerley's method.     

Mathematical hazard models of mortality: an alternative to model life tables

A five-parameter competing hazard model of the age pattern of mortality is described, and methods of fitting it to survivorship, death rate, and age structure data are developed and presented. The methods are then applied to published life table and census data to construct life tables for a Late Woodland population, a Christian period Nubian population, and the Yanomama. The advantage of this approach over the use of model life tables is that the hazard model facilitates life-table construction without imposing a particular age pattern of mortality on the data. This development makes it possible to use anthropological data to extend the study of human variation in mortality patterns to small populations.     

Flexible parametric modeling of survival from age at death data: A mixed linear regression framework

Many long-lived vertebrate species are under threat in the Anthropocene, but their conservation is hampered by a lack of demographic information to assess population long-term viability. When longitudinal studies (e.g., Capture-Mark-Recapture design) are not feasible, the only available data may be cross-sectional, for example, stranding for marine mammals. Survival analysis deals with age at death (i.e., time to event) data and allows to estimate survivorship and hazard rates assuming that the cross-sectional sample is representative. Accommodating a bathtub-shaped hazard, as expected in wild populations, was historically difficult and required specific models. We identified a simple linear regression model with individual frailty that can fit a bathtub-shaped hazard, take into account covariates, allow goodness-of-fit assessments and give accurate estimates of survivorship in realistic settings. We first conducted a Monte Carlo study and simulated age at death data to assess the accuracy of estimates with respect to sample size. Secondly, we applied this framework on a handful of case studies from published studies on marine mammals, a group with many threatened and data-deficient species. We found that our framework is flexible and accurate to estimate survivorship with a sample size of 300 . This approach is promising for obtaining important demographic information on data-poor species.     

Life and death in ancient populations: Bones of contention in paleodemography

In a recent articleBocquet-Appel & Masset (1985) renew their criticism of paleodemography and criticizeVan Gerven & Armelagos' (1983) defense of paleodemographic methods. In the present analysis we respond toBocquet-Appel andMasset's criticisms ofVan Gerven andArmelagos and then address the question of whether paleodemographic methods are capable of producing plausible results based on what is known about contemporary human populations. This is done by expanding the life tables previously analysed byVan Gerven and co-workers for the Medieval Christian site of Kulubnarti in Nubia'sBatn el Hajar. The expanded results are then compared to data obtained from contemporary human populations as well as interpreted in light of Nubian culture history.     

A comparison of two methods for the microscopic determination of age at death.

The precision and accuracy of the Kerley and Ahlqvist-Damsten microscopic methods of age determination are compared. Both methods were applied to the same sample of 40 femoral thin sections of documented age at death. The results indicate that (1) both methods can be used with equal precision, as suggested by comparable observer errors; and (2) the Kerley method produces overall more accurate age estimates. The low previously published standard error of the Ahlqvist-Damsten method (6.71 years) apparently results from the uneven age distribution and small size (20) of their sample.     

Technical note: calculation of age at formation of radiopaque transverse lines

A simple method for determining the age of an individual at the time of radiopaque transverse (Harris) line formation is presented. To use this method, only two measurements are required: total bone length and distance of line to nearest bone end; these are put into formulae that calculate the percent of total bone growth when the line appeared. The result of this calculation is compared with tables of percent bone growth per year (one to 16 years in females and one to 18 years in males) to arrive at estimations of age at line formation. Since these tables are presented for the femur, tibia, humerus, and radius, this technique can be used on any one of the major long bones exhibiting lines.