Juvenile Body Mass Estimation from the Femur Using Postmortem Computed Tomography Data.

Skeletal estimation methods to reconstruct the juvenile biological profile are largely limited to those estimating age and, to a lesser extent, sex. While body mass is not generally estimated as part of the biological profile in forensic investigations, this is a logical candidate for inclusion in the forensic biological profile, as it has long been of interest in paleoanthropology and several methods to estimate juvenile body mass currently exist. To explore the performance of body mass estimation for juveniles, the authors tested the accuracy and precision of previously published panel regression formulae using two femoral measurements: the breadth of the distal metaphysis and the cross-sectional polar moment of inertia (J). The test sample consisted of measurements of 94 individuals from birth to 12.5 years of age, taken from postmortem computed tomography scans housed at the Office of the Medical Investigator, New Mexico, USA. Results indicate that body mass estimates are more accurate when estimated from cross-sectional than from metaphyseal measures. Both formulae, however, consistently underestimated weight, and the magnitude of the underestimation increased exponentially with age. This suggests that, contrary to what others have argued, body mass estimation is complicated by population variation in body composition. This study reinforces the importance of documenting and investigating the ontogeny of human variation. The global increase in medical imaging in clinical settings can be leveraged to obtain skeletal data for juveniles from a wide range of ontogenic environments, marking an exciting time for the study of human variation.

Lack of biological mortality bias in the timing of dental formation in contemporary children: Implications for the study of past populations.

OBJECTIVES: Biological mortality bias is the idea that individuals who perish (non-survivors) are biologically distinct from those who survive (survivors). If biological mortality bias is large enough, bioarchaeological studies of nonsurvivors (skeletal samples) cannot accurately represent the experiences of the survivors of that population. This effect is particularly problematic for the study of juvenile individuals, as growth is particularly sensitive to environmental insults. In this study, we test whether biological mortality bias exists in one dimension of growth, namely dental development. MATERIALS AND METHODS: Postmortem computed tomography scans of 206 children aged 12 years and younger at death were collected from two institutions in the United States and Australia. The sample was separated into children dying from natural causes as proxies for non-survivors and from accidental causes as proxies for survivors. Differences in the timing of dental development were assessed using sequential logistic regressions between dental formation stages and residual analysis of dental minus chronological age. RESULTS: No consistent delay in age of attainment of dental stages was documented between survivors and non-survivors. Delays between survivors and non-survivors in dental relative to chronological age were greatest for infants, and were greater for females than for males. DISCUSSION: Lack of biological mortality bias in dental development reinforces confidence in juvenile age estimates and therefore in skeletal growth profiles and growth studies. As dental development is known to be less environmentally sensitive than skeletal growth and development, further studies should examine biological mortality bias in long bone length.

Does age estimated from teeth forming in different early life periods show differential discrepancy with known age?

OBJECTIVES: The aim of this study is to explore growth discrepancies in the dentition of impoverished children and examine how dental development is impacted by environmental influences throughout childhood, thereby identifying which teeth are more sensitive to the effects of biocultural factors and are consequently less useful to predict age. METHODS: Length measurements of developing teeth (deciduous and permanent) were taken from individuals of known age and sex (n = 61) from the Certosa collection, a 19th century skeletal assemblage representing Italian children of low socioeconomic status. Discrepancies between age estimates based on tooth length and chronological age were calculated, and the accuracy and precision of age prediction between earlier forming teeth and later forming teeth were compared. RESULTS: Deciduous teeth produced more precise dental age estimates (mean age discrepancy -0.092 years), while discrepancies between chronological age and age based on developing permanent dentition were larger (-0.628 years). The difference between these discrepancies in age estimates for deciduous and permanent teeth was significant (p < 0.001), indicating that age prediction from deciduous tooth length is more accurate than age predicted using permanent tooth length. CONCLUSION: An increasing variation and delay in tooth length for age reflects increasing susceptibility to biocultural factors, which impacts tooth growth during the course of childhood. Teeth whose development occurs earlier in life are less variable in their growth and provide more accurate estimations of age as a result.

Comment on 'Krapina atlases suggest a high prevalence of anatomical variations in the first cervical vertebra of Neanderthals'.

A review of the observation of an anterior cleft on the atlas of a Neanderthal from Krapina.

Age estimation in three distinct east Asian population groups using southern Han Chinese dental reference dataset.

BACKGROUND: Dental age estimation can assist in the identification of victims following natural disasters and it can also help to solve birth date disputes in individuals involved in criminal activities. A reference dataset (RDS) has been developed from the dental development of 2306 subjects of southern Han Chinese origin and subsequently validated. This study aimed to test the applicability of the southern Han Chinese dental maturation RDS on three distinct East Asian population groups. METHODS: A total of 953 dental panoramic radiographs of subjects aged 2 to 24 years were obtained from Philippines, Thailand and Japan. The staging of dental development was conducted according to Anglo-Canadian classification system. The dental age (DA) was calculated using six methods; one un-weighted average and five weighted average (n-tds, sd-tds, se-tds, 1/sd-tds, 1/se-tds) methods based on the scores of the southern Han Chinese RDS. Statistical significance was set at p < 0.05 and the variation between chronological age (CA) and DA was evaluated using paired t-test and Bland & Altman scatter plots. RESULTS: From six dental age calculations, all methods of DA accurately estimated the age of Japanese and few methods in Filipino subjects (n-tds, 1/sd-tds, 1/se-tds). There was consistent overestimation of age for all the methods for Thai females (p < 0.05). CONCLUSIONS: The southern Han Chinese dental reference dataset was shown to be most accurate for Japanese, followed by Thai males and it was particularly ineffective for Filipinos and Thai females.

Age estimation of immature human skeletal remains from the metaphyseal and epiphyseal widths of the long bones in the post-natal period.

OBJECTIVES: This study provides regression and classical calibration models for the estimation of age from the dimensions of the metaphyses and epiphyses of the six long bones. METHODS: A sample of 148 known sex and age individuals (56 females and 92 males), aged between birth and 12 years of age, selected from Portuguese and English skeletal collections. Age estimation models were obtained separately for each sex and for the sexes combined, for the entire sample and for the sample divided into two subsamples at the age of 2 years. RESULTS: The best performing epiphysis is the proximal epiphysis of the tibia. For the metaphyses, the distal metaphysis of the tibia and the proximal metaphysis of the femur are best for individuals below and above 2 years of age, respectively. Growth of the metaphyses is similar to that of the diaphysis. Results suggest that age can be as accurately estimated from the width of the metaphyses and epiphyses as from the length of the diaphyses, or as from the length of the deciduous and permanent teeth. CONCLUSIONS: These models may be useful for fragmentary material in both archaeological and forensic contexts. However, due to the background of the samples, the models would be most applicable to individuals exposed to adverse environmental conditions during growth and development. Metaphyseal and epiphyseal widths may be less affected by ecological conditions than diaphyseal length.

Age estimation of immature human skeletal remains from the dimensions of the girdle bones in the postnatal period.

OBJECTIVES: This study provides classical calibration regression formulae for age estimation from the dimensions of unfused shoulder and pelvic girdle bones. MATERIALS AND METHODS: Age estimation models were derived from a sample of 160 known age and sex individuals (63 females and 97 males) aged birth to 12 years, selected from Portuguese and English skeletal collections. The sample was divided into two age groups at the age of 2 years, and formulae were obtained for the sexes separately and combined. RESULTS: Measurements of the pelvis provide more precise age estimates than the shoulder. In the younger age group, the height and width of the ilium, and the height of the glenoid yield the most precise age estimates. In the older age group, the length of the clavicle provides the most precise estimates, followed by measurements of the pubis and ischium. DISCUSSION: In the younger individuals (<2 years), age estimates based on measurements of the pelvic girdle seem to be as or more precise than those based on the length of long bones. In older individuals (≥2 years), estimates based on the measurements of the girdles are less precise than those based on the length of long bones. These age estimation formulae may be useful for fragmentary and incomplete material in archaeological and forensic contexts. The formulae are suitable for a variety of archeological populations living under adverse conditions. These conditions are similar to some "developing" countries, and hence the formulae may also be applicable to modern forensic remains from such environments.

Shape, size, and maturity trajectories of the human ilium.

Morphological traits of the ilium have consistently been more successful for juvenile sex determination than have techniques applied to other skeletal elements, however relatively little is known about the ontogeny and maturation of size and shape dimorphism in the ilium. We use a geometric morphometric approach to quantitatively separate the ontogeny of size and shape of the ilium, and analyze interpopulation differences in the onset, rate and patterning of sexual dimorphism. We captured the shape of three traits for a total of 191 ilia from Lisbon (Portugal) and London (UK) samples of known age and sex (0-17 years). Our results indicate that a) there is a clear dissociation between the ontogeny of size and shape in males and females, b) the ontogeny of size and shape are each defined by non-linear trajectories that differ between the sexes, c) there are interpopulation differences in ontogenetic shape trajectories, which point to population-specific patterning in the attainment of sexual dimorphism, and d) the rate of shape maturation and size maturation is typically higher for females than males. Male and female shape differences in the ilium are brought about by trajectory divergence. Differences in size and shape maturation between the sexes suggest that maturity may confound our ability to discriminate between the sexes by introducing variation not accounted for in age-based groupings. The accuracy of sex determination methods using the ilium may be improved by the use of different traits for particular age groups, to capture the ontogenetic development of shape in both sexes.

Age estimation of immature human skeletal remains from the diaphyseal length of the long bones in the postnatal period.

Age at death in immature human skeletal remains has been estimated from the diaphyseal length of the long bones, but few studies have actually been designed specifically for the purpose of age estimation and those which have, show important caveats. This study uses regression and classical calibration to model the relationship between age and diaphyseal length of the six long bones, in a sample of 184 known sex and age individuals (72 females and 112 males), younger than 13 years of age, selected from Portuguese and English skeletal collections. Age estimation models based on classical calibration were obtained for each of the six long bones, and separately for each sex and for the sexes combined, and also for the entire sample and when it is subdivided into two subsamples at the age of 2 years. Comparisons between inverse and classical calibration show there is a systematic bias in age estimations obtained from inverse calibration. In the classical calibration models, the length of the femur provides the most accurate estimates of age. Age estimates are more accurate for the male subsample and for individuals under the age of 2 years. These results and a test of previously published methods caution against inverse calibration as a technique for developing age estimation methods even from the immature skeleton. Age estimation methods developed using cemetery collections of identified human skeletons should not be uncritically applied to present-day populations from the same region since many populations have experienced dramatic secular trends in growth and adult height over the last century.

Chronology of fusion of the primary and secondary ossification centers in the human sacrum and age estimation in child and adolescent skeletons.

Little is known about fusion times of the primary and secondary centers of ossification in the sacrum, particularly from dry bone observations. In this study, the timing of union of these centers was studied in a sample of modern Portuguese skeletons (90 females and 101 males) between the ages of 0 and 30 years, taken from the Lisbon documented skeletal collection. A three-stage scheme was used to assess fusion status between ossification centers as unfused, partially fused and completely fused. Posterior probability tables of age, given a certain stage of fusion, were calculated for most anatomical locations studied using both reference and uniform priors. Partial union of primary centers of ossification was observed from 1 to 8 years of age and partial union of secondary centers of ossification was observed from 15 to 21 years of age. The first primary centers of ossification to complete fusion are the neural arch with the centrum of the fifth sacral vertebrae and the last are the costal element with the centrum of the first sacral vertebra. The annular and sacroiliac epiphyses are the first, among the secondary centers of ossification observed, to complete fusion, after which the lateral margin fuses. This study offers information on timing of fusion of diverse locations in the developing sacrum useful for age estimation of complete or fragmented immature human skeletal remains and fills an important gap in the literature, by adding to previously published times of fusion of primary and secondary ossification centers in this sample.

Age at death and linear enamel hypoplasias: testing the effects of childhood stress and adult socioeconomic circumstances in premature mortality.

OBJECTIVE: The aim of this study was to test the association between linear enamel hypolasias and adult socioeconomic circumstances with age at death in a modern skeletal sample of known age. Specifically, this study wishes to test whether there is a relationship between early life stressors, environmental quality in adult life and premature mortality. METHODS: The presence/absence of LEH and the number of LEH episodes were recorded in 113 adult males from the Lisbon identified skeletal collection. The association between LEH and age was quantified using linear regression and binary logistic regression models, calculating crude and adjusted linear regression coefficients and odds ratios. The models were adjusted for year of birth, socioeconomic and migration status, and cause of death. RESULTS: The presence and number of LEH were related to premature mortality. Individuals expressing at least one enamel defect survived 9.0 years less or were 2.5 times more likely to die before 53 years of age compared to individuals with no LEH. However, when controlling for the confounding factors considered, the association between LEH and age became nonsignificant. CONCLUSIONS: The results indicate that although early life stressors, identified as LEH, seem strongly associated with premature mortality, adulthood socioeconomic circumstances accounts for most of the decreased longevity. This suggests that either macroscopically identified LEH in the permanent canine do not measure stressors early in life, or that a cumulative adversity model is a more adequate explanation.

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.

Metatarsal fusion pattern and developmental morphology of the Olduvai Hominid 8 foot: Evidence of adolescence.

The morphology of the Olduvai Hominid (OH) 8 foot and the sequence of metatarsal epiphyseal fusion in modern humans and chimpanzees support the hypothesis that OH 8 belonged to an individual of approximately the same relative age as the OH 7 subadult, the holotype of Homo habilis. Modern humans and chimpanzees exhibit a variety of metatarsal epiphyseal fusion patterns, including one identical to that observed in OH 8 in which metatarsal 1 fuses before metatarsals 2-5. More than the metatarsal fusion sequence, however, the principal evidence of the youthful age of OH 8 lies in the morphology of metatarsals 1, 2, and 3. Because both OH 8 and OH 7 come from the same stratum at the FLK NN type site, the most parsimonious explanation of the OH 8 and OH 7 data is that this material belonged to the same individual, as originally proposed by Louis Leakey. The proposition that OH 8 belonged to an adult is unsupported by morphology, including radiographic evidence, and the fusion sequences in human and chimpanzee skeletal material reported here and in the literature.

Age estimation from stages of epiphyseal union in the presacral vertebrae.

The presacral vertebrae have various secondary centers of ossification, whose timing of fusion can be used for age estimation of human skeletal remains up to the middle to the latter third decade. However, detailed information about the age at which these secondary centers of ossification fuse has been lacking. In this study, the timing of epiphyseal union in presacral vertebrae was studied in a sample of modern Portuguese skeletons (57 females and 47 males) between the ages of 9 and 30, taken from the Lisbon documented skeletal collection. A detailed photographic record of these epiphyses and the age ranges for the different stages of epiphyseal union are provided. Partial union of epiphyses was observed from 11 to 27 years of age. In general, centers of ossification begin to fuse first in the cervical and lumbar vertebrae, followed by centers of ossification in the thoracic region. The first center of ossification to complete fusion is usually that of the mammillary process in lumbar vertebrae. This is usually followed by that of the transverse process, spinous transverse process, and annular ring, regardless of vertebra type. There were no statistically significant sex differences in timing of fusion, but there was a trend toward early maturation in females for some vertebra or epiphyses. Bilateral epiphyses did not show statistically significant differences in timing of fusion. This study offers information on timing of fusion of diverse epiphyseal locations useful for age estimation of complete or fragmented human skeletal remains.

Socioeconomic differences in permanent teeth mineralization of Portuguese girls and boys from Porto, Portugal.

Purpose: Socioeconomic differences in dental maturation can be used to examine the impact of environmental factors on dental maturation. The purpose of this study is to assess socioeconomic differences in dental maturation of the seven permanent mandibular teeth (I1-M2). Methods: A total of 2114 panoramic radiographs of Portuguese children, adolescents and young adults were studied. The sample was divided into a high socioeconomic status (SES) (n = 925), and a low SES group (n = 1189). Ages ranged between 5 and 26 years. Demirjian's stages were used to assess the maturation of the seven mandibular teeth on the left side. Median-age of attainment of each stage and each tooth was calculated and compared between groups using binary logistic regression. Results: Low SES girls showed a consistent advancement in dental maturation across the entire dentition. Low SES boys, however, showed more often a delayed maturation relative to their high SES counterparts, but this pattern was not consistent and a clear socioeconomic difference seems to be absent in boys. Conclusions: While this study was not able to further explore the causes of the dental advancement in girls, it is hypothesized that it might be related to a higher prevalence of overweight/obesity, and possibly caries, in low SES girls, compared to the SES difference in prevalence in boys.

Testing the cross-applicability of juvenile sex estimation from diaphyseal dimensions.

Sex estimation is a crucial component of the biological profile. Stull et al. (2017) have proposed a promising juvenile sex estimation method using long bone measurements taken from a South African sample, providing relatively high classification accuracies and made easy to use via the KidStats web-based app. In this study, we test the models developed by Stull et al. (2017) on an external historic population from Lisbon, Portugal, in order to determine whether the models can be reliably applied to archeological and forensic populations outside of the original population sample. The study sample consisted of 102 individuals (45 females and 57 males) aged under 13 years at death from the Lisbon identified skeletal collection. Measurements from these individuals were used to test the flexible discriminant analysis (FDA) models given by Stull et al. (2017). Allocation accuracies were calculated for boys and girls and children over and under 2 years separately and combined. Our findings show that the models developed by Stull et al. (2017) yield poor accuracy when applied to our external population and thus can potentially be misapplied on archeological skeletal remains or forensic remains of unknown origin. A number of statistical issues may explain why models fail to be transportable or even generalizable, namely multicollinearity, model overfitting and overly optimist bootstrapped cross-validation rates. It is also likely that population differences in size and sexual size dimorphism also affected the applicability of the models. We emphasize the importance of externally validating prediction models, particularly if they are intended to be applied across populations. Our study addresses Stull and co-worker's request for further validation of the method on populations outside of South Africa, as the models cannot be confidently applied in the field until it has been externally validated.

Age estimation of immature human skeletal remains from mandibular and cranial bone dimensions in the postnatal period.

Age estimation is one of the crucial first steps in the identification of human skeletal remains in both forensic and archeological contexts. In the postnatal period, age is traditionally estimated from dental development or skeletal growth, typically long bone diaphyseal length. However, in many occasions other methods are required. This study provides alternative means of estimating age of juvenile remains from the size of several cranial bones and the mandible. A sample of 185 identified juvenile skeletons between birth and 13 years of age from two European collections were used (Lisbon and Spitalfields). Measurements of the frontal, occipital-lateralis, occipital-basilaris, occipital-squamous, zygomatic, maxilla, and mandible were used to calculate classical calibration regression formulae for the sexes combined. The sample was divided into three age groups birth-2 years, 2-6 years, and 2-12.9 years, depending on bone and its growth trajectory. For all the bones, measurements of the youngest age groups yielded the most precise age estimates. The vault bones on average yielded the best performing models, with the frontal bone having the most precise of all. The mandible performed on par with the best performing cranial bones, particularly in individuals under the age of 2 years. This study provides one of the most comprehensive approaches to juvenile age estimation based on bones of the skull, providing a resource that potentially can help estimate age of juvenile skeletons from a variety of circumstances.

Secular change in the timing of dental root maturation in Portuguese boys and girls.

OBJECTIVES: In this study, we compare root formation in a modern sample of living Portuguese children (n = 521), between 6 and 18 years of age, with that of a similar sample of known sex and age Portuguese child skeletons (n = 114), who lived half a century earlier, to assess secular change in dental maturation. METHODS: The roots of seven developing permanent mandibular teeth were assessed for their maturation in both samples. The median age-of-attainment of root stages was calculated using logistic regression and compared between the samples. The potential influence of mortality bias in root development of the skeletal sample was tested. RESULTS: No mortality bias effect was detected. We find that the dentition of modern Portuguese boys and girls mature on average 1.22 years and 1.47 years earlier, respectively, compared to their counterparts born one half a century before. Our results also suggest that an earlier timing of attainment of root formation maturational stages was not accompanied by a change in the overall duration of root formation. CONCLUSIONS: We demonstrate a clear and consistent acceleration in dental root maturation due to secular changes and show that the plasticity in dental development in response to environmental factors is greater than previously thought.

Historical, demographic, curatorial and legal aspects of the BoneMedLeg human skeletal reference collection (Porto, Portugal).

The BoneMedLeg research project was developed to address current research concerns related to the use of skeletal reference collections for forensic purposes. These concerns were partly addressed by amassing a new reference collection which incorporates unclaimed human remains sourced from two municipal cemeteries in the city of Porto, Portugal. Amassed between 2012 and 2014 the collection was developed with permission from and in partnership with the Municipality of Porto, in a manner that is similar to that of other skeletal reference collections in Portugal. Traditionally, municipalities have bequeathed human remains that are cleared from temporary primary and secondary burial plots at local cemeteries and deemed unclaimed, to museums and universities for research purposes. The BoneMedLeg collection currently includes a total of 95 individuals, of which only 81 are fully identified (38 males and 43 females), with ages ranging from 21 days to 94 years, and a mean age of about 62 years. Years of death range from 1969 to 2003, and years of birth from 1891 to 1969. Only about half of the individuals are documented as to cause of death, which includes a considerable diversity of etiologies, from oncological to cardiovascular system disorders, and also traumatic injuries. The collection is more representative of an unskilled working class and aged population, due to one of the main sourced cemeteries disproportionately serving more socioeconomic disadvantaged communities and reflecting the demographics of the city over the past 40 years. In addition to describing the history and curatorial process of the collection in detail, this paper also discusses its broad legal framework and potential biases in its profile and composition which can inform and help plan future research projects.