Auricular surface aging: Worse than expected? A test of the revised method on a documented historic skeletal assemblage

This study presents results and recommendations arising from a blind test of the revised age estimation method for the auricular surface as proposed by Buckberry and Chamberlain ([2002] Am. J. Phys. Anthropol. 119:321-329). Auricular surfaces of 167 individuals from St. Bride's, London, a documented skeletal assemblage spanning the late 17th to early 19th century, were analyzed for the following traits: transverse organization, surface texture appearance, macroporosity, microporosity, and morphological changes to the apex. Composite scores of trait expressions were found to generally correlate with age and to show a positive association with known chronological age (P < 0.01). However, when composite scores were combined to define auricular surface phases, which ultimately assign age estimations, only three distinct developmental stages, compared with seven suggested by Buckberry and Chamberlain ([2002] Am. J. Phys. Anthropol. 119:321-329), could be identified and statistically supported, all showing a considerable degree of individual variation in age. The most well-defined stage in the St. Bride's assemblage was the new stage III, where the majority of individuals were older than 60 years, whereas middle-aged adults displayed a large variation in composite scores. These results provide little hope for a promising application of age-at-death estimation of auricular surface morphology traits with higher resolution, but rather suggest indications of broad stages of life.     

Age estimation from the auricular surface of the ilium: a revised method

A revised method for estimating adult age at death using the auricular surface of the ilium has been developed. It is based on the existing auricular surface aging method of Lovejoy et al. ([1985] Am. J. Phys. Anthropol. 68:15-28), but the revised technique is easier to apply, and has low levels of inter- and intraobserver error. The new method records age-related stages for different features of the auricular surface, which are then combined to provide a composite score from which an estimate of age at death is obtained. Blind tests of the method were carried out on a known-age skeletal collection from Christ Church, Spitalfields, London. These tests showed that the dispersion of age at death for a given morphological stage was large, particularly after the first decade of adult life. Statistical analysis showed that the age-related changes in auricular surface are not significantly different for males and females. The scores from the revised method have a slightly higher correlation with age than do the Suchey-Brooks pubic symphysis stages. Considering the higher survival rates of the auricular surface compared with the pubic symphysis, this method promises to be useful for biological anthropology and forensic science.     

Calcaneal measurement in estimation of stature of South African blacks

Stature (height) is an important factor in establishing the identity of a person in the living as well as in the skeletonized state. When stature is estimated from the bones of the limbs, regression equations, which estimate the ratios of the lengths of bones to the height of the individual, are generated. The majority of bones that were used previously were the long bones. The calcaneus was used for estimating stature only in American whites and blacks (Holland [1995] Am. J. Phys. Anthropol. 96:315-320). The regression equations that he generated were found to be useful for stature estimation in these population groups. Since the calcaneus has not been used for the same purpose in South Africa, the aim of this study was to derive regression equations that will allow this bone to be used for stature estimation in South African blacks. In total, 116 complete skeletons (60 males and 56 females) were selected from the Raymond A. Dart Collection of Human Skeletons, School of Anatomical Sciences, University of the Witwatersrand (Johannesburg, South Africa). The skeletal heights of these sets of skeletons were calculated using the anatomical method of Fully ([1956] Ann. Med. Leg. 35:266-273). Nine parameters of the calcaneus were measured and matched against skeletal heights, using univariate and multivariate regression methods. Regression equations were obtained for estimation of the stature of the South African black population from the calcaneus. The standard error of estimate that was obtained with univariate regression analysis was higher than the corresponding values using multivariate regression analysis. In both cases, the standard errors of estimate compared well with the values obtained for fragmentary long bones by previous authors.     

Stature estimation in ancient Egyptians: a new technique based on anatomical reconstruction of stature

Trotter and Gleser's (Trotter and Gleser: Am J Phys Anthropol 10 (1952) 469-514; Trotter and Gleser: Am J Phys Anthropol 16 (1958) 79-123) long bone formulae for US Blacks or derivations thereof (Robins and Shute: Hum Evol 1 (1986) 313-324) have been previously used to estimate the stature of ancient Egyptians. However, limb length to stature proportions differ between human populations; consequently, the most accurate mathematical stature estimates will be obtained when the population being examined is as similar as possible in proportions to the population used to create the equations. The purpose of this study was to create new stature regression formulae based on direct reconstructions of stature in ancient Egyptians and assess their accuracy in comparison to other stature estimation methods. We also compare Egyptian body proportions to those of modern American Blacks and Whites. Living stature estimates were derived using a revised Fully anatomical method (Raxter et al.: Am J Phys Anthropol 130 (2006) 374-384). Long bone stature regression equations were then derived for each sex. Our results confirm that, although ancient Egyptians are closer in body proportion to modern American Blacks than they are to American Whites, proportions in Blacks and Egyptians are not identical. The newly generated Egyptian-based stature regression formulae have standard errors of estimate of 1.9-4.2 cm. All mean directional differences are less than 0.4% compared to anatomically estimated stature, while results using previous formulae are more variable, with mean directional biases varying between 0.2% and 1.1%, tibial and radial estimates being the most biased. There is no evidence for significant variation in proportions among temporal or social groupings; thus, the new formulae may be broadly applicable to ancient Egyptian remains.     

Technical note: Enhancement of Scott's molar wear scoring method

A method is described for orienting maxillary and mandibular molars in order to standardize the reporting of wear scores on quadrants of the occlusal surfaces (Scott: Am J Phys Anthropol 51 (1979) 213–217). The method, which was developed on an archeological sample from ancient Mendes, Egypt, further requires that quadrant scores be reported individually and sequentially for each tooth, rather than summed, in order to identify more easily differential and directional wear patterns. Intraobserver and interobserver error was found to be negligible when the appropriate diagrams and instructions were consulted. Thus, observer error does not add further to the potential for error associated with Scott's original scoring method. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

A quantitative and qualitative reanalysis of the endocast from the juvenile Paranthropus specimen l338y-6 from Omo, Ethiopia

Based on an analysis of its endocast, Holloway (1981 Am J Phys Anthropol 53:109-118) attributed the juvenile Omo L338y-6 specimen to Australopithecus africanus (i.e., gracile australopithecines) rather than to Paranthropus (Australopithecus) boisei (robust australopithecines) favored by other workers (Rak and Howell [1978] Am J Phys Anthropol 48:345-366). Holloway's attribution was based on the specimen's (1) low cranial capacity, (2) gracile-like meningeal vessels, (3) gracile-like cerebellar hemispheres, and (4) absence of an enlarged occipital/marginal (O/M) sinus system. Recent work, however, has shown that criteria 1 and 2 are not useful for sorting gracile from robust australopithecines (Culotta [1999] Science 284:1109-1111; Falk [1993] Am J Phys Anthropol 92:81-98). In this paper, we test criterion 3 by quantifying the endocranial cerebellar and occipital morphology reproduced on the Omo L338y-6 endocast, and comparing it to seven endocasts from South and East African early hominids. Our preliminary results show that metric analysis of this specimen cannot be used to sort it preferentially with either robust or gracile australopithecines. Finally, we demonstrate that, contrary to previous reports, the Omo L338y-6 endocast reproduces an enlarged left occipital sinus (criterion 4). This observation is consistent with the original attribution of the Omo specimen to robust australopithecines (Rak and Howell [1978] Am J Phys Anthropol 48:345-366). Furthermore, if Omo L338y-6 was a robust australopithecine, this discovery extends the occurrence of an enlarged O/M sinus system to one of the earliest known paranthropines. Am J Phys Anthropol 110:399-406, 1999.     

A blind test of mandibular morphology for sexing mandibles in the first few years of life

Loth and Henneberg ([2001] Am. J. Phys. Anthropol. 115:179-186) proposed that consistent shape differences exist between male and female juvenile mandibles which can be used to predict sex with an accuracy of 81%. A sample of known sex and age from the Spitalfields Collection was examined blind twice and resulted in an overall accuracy of only 64%. The tests also showed that: 1) the method sexed males more reliably than females; and 2) consistency was low.     

Morphology of the pubis and preauricular area in relation to parity and age at death in Macaca mulatta

Some adult human females show bone resorption (pitting) at the dorsal aspect of the pubis and preauricular area of the ilium. The etiology of pelvic bone resorption is attributed alternatively to reproduction and to pelvic anatomy. While most researchers infer that pelvic pitting is related to reproduction, only a few studies are based on women of known parity. Degree of pubic resorption is directly associated with both parity (Suchey et al.: Am. J. Phys. Anthropol. 51:517-539, 1979; Bergfelder and Hermann: J. Hum. Evol. 9:611-613, 1980) and age (Suchey et al.: Am. J. Phys. Anthropol. 51:517-539, 1979). The relationship between parity and degree of resorption of the preauricular area is equivocal, found to be significant by Dunlap (A Study of the Preauricular Sulcus in a Cadaver Population, Ph.D. dissertation, East Lansing, Michigan State University, 1981) but not by Spring et al. (Am. J. Phys. Anthropol. 79:247-252, 1989); both studies report that age is not associated with resorption of the preauricular area. Other mammals evidence public resorption, but the morphology of the preauricular area is less well known. This study addresses the issue on the etiology of pelvic bone resorption using a sample of Macaca mulatta (the free-ranging population from Cayo Santiago) for which parity and age at death are known for all specimens. The following results are reported. Resorption of the pubis is common among females but infrequent among males. Contrary to Rawlins (Am. J. Phys. Anthropol. 42:477-488, 1975), the degree of pubic resorption in female macaques is significantly related to both parity and age at death.(ABSTRACT TRUNCATED AT 250 WORDS)     

Incidence and distribution of postcranial fractures in the prehistoric population of San Pedro de Atacama,northern Chile

Trauma incidence analysis in skeletal populations has been very popular among skeletal biologists during the last two decades. In this context, the work of Lovejoy and Heiple ([1981] Am. J. Phys. Anthropol. 55:529–541) has been quoted as a landmark because their analysis rested on a populational approach, avoiding simple assumptions about cause and etiology. In this study, we apply to the prehistoric population of San Pedro de Atacama, northern Chile, an approach similar to that carried out by Lovejoy and Heiple (1981). The results obtained point to a peak of risk of fractures among old people, estimated age around 45 years. The distribution of fractures by sex and age suggests that the prevailing etiology is related to accidents and not violence. When the frequencies of fractures are compared, the Libben population shows a much higher incidence than the Atacamenean population. It is suggested that this difference can be explained by peculiarities of the subsistence economies of the two populations. Am J Phys Anthropol 109:253–258, 1999. © 1999 Wiley-Liss, Inc.     

Genetic correlations between sides and heritability of asymmetry for nonmetric traits in rhesus macaques on Cayo Santiago

The use of nonmetric traits for estimation of biological distance is a long-standing practice in biological anthropology. Nonmetric traits can be scored using either the individual or the side of the individual as the unit of measure. If sides of the individual are genetically correlated the use of sides would produce redundant genetic information. For this reason, Korey (Am. J. Phys. Anthropol. 53:19-23, 1980) argues for the use of individuals as the unit of measure for nonmetric traits. Ossenberg (Am. J. Phys, Anthropol. 54:471-479, 1981), however, argues that bilateral occurrence of nonmetric traits indicates greater genetic liability for the trait and that therefore the sides are the more biologically correct unit of measure. Genetic correlations for 13 cranial nonmetric traits are estimated for a sample of rhesus macaque skeletons from Cayo Santiago. In addition, heritability of asymmetry is estimated for these 13 traits as a test of Ossenberg's contention that asymmetry is genetically influenced. Significant genetic correlations between sides support Korey's contention that nonmetric traits should be scored by individual. Only two asymmetry heritabilities were significantly different from zero, providing no significant support for Ossenberg's contention that asymmetry is genetically determined. Our results support the theory that asymmetry represents a measure of the ability of an organism to buffer stresses. Therefore, a measure of the heritability of asymmetry is a measure of the heritability of the ability to buffer stresses. This ability does not appear to be heritable in this sample.     

Asymmetry of the os pubis: Implications for the Suchey‐Brooks method

Studies of skeletal development frequently document populational incidences of bilateral asymmetry. Degenerative morphological skeletal changes, attributed to age related and irregular ossification, may also progress asymmetrically, either as the result of asymmetric biomechanical factors expressed over the lifespan, asymmetric expression of physiological processes, or progressive magnification of asymmetry acquired previously during development. This study illustrates the effects of bilateral asymmetry on age at death estimates obtained from human skeletal remains. The Suchey‐Brooks method, which uses the pubic symphyseal face for age estimation (Katz and Suchey, Am J Phys Anthropol 69 1986 427–435), was selected for the study based on its widespread use. Asymmetry in the Suchey‐Brooks symphyseal age phases was found in over 60% of a sample composed of 20th century White male individuals from 18 to 86 years of age (N = 130). However, results suggest that the presence of asymmetry does not compromise the accuracy of the Suchey‐Brooks method if the morphologically older symphyseal face of an asymmetric individual is used to estimate age at death. In addition, weak directional asymmetry and a correlation between age and asymmetry were found. This suggests that a comparison of asymmetry in this area with that in other skeletal areas, where the factors originating and influencing asymmetry are better understood, may be useful in better understanding the biological processes which underlie the age markers used in the Suchey‐Brooks method. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Technical note: a re-evaluation of stature estimation from skeletal length in the grave

Several methods for stature estimation have been proposed over the years. Among these methods is anatomical reconstruction, regression based on long bone lengths, and measuring skeletal vertex - talus length in the grave for individuals buried in a supine position. Recent studies have dealt with the applicability of skeletal length in the grave (Petersen: Int J Osteoarchaeol 15 (2005) 106-114) and anatomical reconstruction (Raxter et al.: Am J Phys Anthropol 130 (2006) 374-384). The results from the latter study calls into question the results of the former study. Therefore an investigation of the potential bias of using skeletal length in the grave as an estimate of living stature has been performed. Twenty Medieval Danish skeletons were measured both in situ and in the laboratory, and the anatomically reconstructed stature (Raxter et al.: Am J Phys Anthropol 130 (2006) 374-384) was compared with the skeletal length in the grave. The results show that 2.5 cm should be added to skeletal length in the grave in order to obtain an unbiased estimate ofliving stature.     

Brief communication: How much larger is the relative volume of area 10 of the prefrontal cortex in humans?

It has long been thought that the prefrontal cerebral cortex has been greatly expanded in the human brain. Semendeferi et al. ([2001] Am. J. Phys. Anthropol. 114:224-241) showed that Brodmann's area 10 is relatively larger in the human compared to pongid brains. The question is: how much larger relatively is it? Using their data, it can be shown that the relative increase for human prefrontal area 10 is only 6% larger. Looking at the data base of neural structures provided by Stephan et al. ([1981] Folia Primatol. (Basel) 35:1-29), it is apparent that 6% is a relatively low residual value from a predicted value based on allometric considerations between total brain weight and any given neural structure. When this small increase is combined with their earlier findings on area 13 of prefrontal cortex (Semendeferi et al. [1997] J. Hum. Evol. 32:375-388), it appears that the prefrontal cortex in humans is not some 200% larger as claimed by some researchers (Deacon [1997] Symbolic Species, New York: W.W. Norton; cf. Holloway [1998] Am Sci 86:184-186), and that the findings of Semendeferi et al. ([2001] Am. J. Phys. Anthropol. 114:224-241) are in agreement with the earlier work (Semendeferi and Damasio [2000] J. Hum. Evol. 38:317-332; Semendeferi et al. [1997] J. Hum. Evol. 32:375-388), showing that the human frontal lobe volume is what would be expected for a primate of its brain size. While the prefrontal cortex may have increased relatively in Homo sapiens, the increase is likely to have been far less than currently believed.     

In vivo bone strain and bone functional adaptation

Mechanistic interpretations of bone cross-sectional shapes are based on the paradigm of shape optimization such that bone offers maximum mechanical resistance with a minimum of material. Recent in vivo strain studies (Demes et al., Am J Phys Anthropol 106 (1998) 87-100, Am J Phys Anthropol 116 (2001) 257-265; Lieberman et al., Am J Phys Anthropol 123 (2004) 156-171) have questioned these interpretations by demonstrating that long bones diaphyses are not necessarily bent in planes in which they offer maximum resistance to bending. Potential limitations of these in vivo studies have been pointed out by Ruff et al. (Am J Phys Anthropol 129 (2006) 484-498). It is demonstrated here that two loading scenarios, asymmetric bending and buckling, would indeed not lead to correct predictions of loads from strain. It is also shown that buckling is of limited relevance for many primate long bones. This challenges a widely held view that circular bone cross sections make loading directions unpredictable for bones which is based on a buckling load model. Asymmetric bending is a potentially confounding factor for bones with directional differences in principal area moments (I(max) > I(min)). Mathematical corrections are available and should be applied to determine the bending axis in such cases. It is concluded that loads can be reliably extrapolated from strains. More strain studies are needed to improve our understanding of the relationships between activities, bone loading regimes associated with them, and the cross-sectional geometry of bones.     

Effect of obesity on the reliability of age-at-death indicators of the pelvis

During medicolegal investigations, forensic anthropologists commonly use morphological changes in the auricular surface of the ilium and the symphyseal face of the pubis to estimate age. However, obesity may impact the reliability of age estimations based on pelvic joints. Over the past several decades, the prevalence of obesity has dramatically increased in the United States (US). Since the rate of progression through age-related stages of weight-bearing joints may be influenced by excessive body mass, it is important that anthropologists understand how obesity affects age-related morphological changes in the skeleton. This study investigates the effects of obesity on the validity of the estimated age-at-death based on the Buckberry–Chamberlin and Suchey–Brooks methods by comparing US adults considered normal BMI (BMI 18.5–24.9) and obese (BMI ≥ 30). The obese group exhibits overall greater bias (overestimation of age) and inaccuracy, less precision, and lower correlations between estimated and known age than the normal BMI group using both methods, although differences in the pubic symphysis are not statistically significant. For the auricular surface the age of transition from one phase to the next is lower and the standard deviations are greater for the obese as compared to normal weight individuals. This study helps to elucidate how obesity affects the rate of age-related skeletal change of the human pelvis, and shows that the pubic symphysis may be a more reliable indicator of age in obese individuals and that greater standard deviations are needed for obese individuals when estimating age-at-death from the pelvis. Am J Phys Anthropol 156:595–605, 2015. © 2014 Wiley Periodicals, Inc.     

Brief communication: A test and correction of the clavicle method of Stout and Paine for histological age estimation of skeletal remains

The histological method developed by Stout and Paine ([1992] Am. J. Phys. Antropol. 87:111–115) for estimating age at death using the clavicle is tested on a known age independent sample from a nineteenth century cemetery near Spitalfriedhof St. Johann in Basel, Switzerland. The mean absolute difference between reported ages and histologically predicted ages is 5.5 years. Mean predicted age for the sample is different from mean reported age. This difference is accounted for by differences in the age distributions between the original autopsy sample used to derive the histological age-predicting formula and the cemetery sample, and an inherent loss of reliability of histological age predictions for the skeletal remains of older individuals. A new formula based upon the combined original autopsy sample of Stout and Paine (1992) and the Swiss cemetery sample is presented. It is recommended that this formula be used when estimating ages for older individuals or archaeological skeletal samples. © 1996 Wiley-Liss, Inc.     

Platyrrhine dental eruption sequences

To determine dental eruption sequences of extant platyrrhines, 367 mandibles and maxillae of informative juvenile specimens from all 16 genera were scored for presence of permanent teeth including three intermediate eruption stages following Harvati (Am J Phys Anthropol 112 (2000) 69-85). The timing of molar eruption relative to that of the anterior dentition is variable in platyrrhines. Aotus is precocious, with all molars erupting in succession before replacement of any deciduous teeth, while Cebus is delayed in M2-3 eruption relative to I1-2. Callitrichines have a distinct tendency toward delayed canine and premolar development. Platyrrhine eruption sequences presented here show some evidence of conformity to Schultz's Rule, with relatively early replacement of deciduous dentition in "slower"-growing animals. The relationship of dental eruption sequences to degree of folivory, body mass, brain mass, and dietary quality is also examined. The early eruption of molars relative to anterior teeth in Pithecia, Chiropotes, and Cacajao, in comparison to genera such as Ateles, Lagothrix, and Alouatta, showing relatively later eruption of the molars, appears to be consistent with current phylogenetic hypotheses. Schultz (Am J Phys Anthropol 19 (1935) 489-581) postulated early relative molar eruption as the primitive dental eruption schedule for primates. The extremely early molar eruption of Aotus versus Callicebus (where both incisors erupt before M2 and M3, with M3 usually last) may lend support to the status of Aotus as a basal taxon. The early relative molar eruption of the fossil platyrrhine species Branisella boliviana is also consistent with this hypothesis (Takai et al.: Am J Phys Anthropol 111 (2000) 263-281).     

Phase II jaw movements and masseter muscle activity during chewing in Papio anubis

It was proposed that the power stroke in primates has two distinct periods of occlusal contact, each with a characteristic motion of the mandibular molars relative to the maxillary molars. The two movements are called phase I and phase II, and they occur sequentially in that order (Kay and Hiiemae [1974] Am J. Phys. Anthropol. 40:227-256, Kay and Hiiemae [1974] Prosimian Biology, Pittsburgh: University of Pittsburgh Press, p. 501-530). Phase I movement is said to be associated with shearing along a series of crests, producing planar phase I facets and crushing on surfaces on the basins of the molars. Phase I terminates in centric occlusion. Phase II movement is said to be associated with grinding along the same surfaces that were used for crushing at the termination of phase I. Hylander et al. ([1987] Am J. Phys. Anthropol. 72:287-312; see also Hiiemae [1984] Food Acquisition and Processing, London: Academic Press, p. 257-281; Hylander and Crompton [1980] Am J. Phys. Anthropol. 52:239-251, [1986] Arch. Oral. Biol. 31:841-848) analyzed data on macaques and suggested that phase II movement may not be nearly as significant for food breakdown as phase I movement simply because, based on the magnitude of mandibular bone strain patterns, adductor muscle and occlusal forces are likely negligible during movement out of centric occlusion. Our goal is to better understand the functional significance of phase II movement within the broader context of masticatory kinematics during the power stroke. We analyze vertical and transverse mandibular motion and relative activity of the masseter and temporalis muscles during phase I and II movements in Papio anubis. We test whether significant muscle activity and, by inference, occlusal force occurs during phase II movement. We find that during phase II movement, there is negligible force developed in the superficial and deep masseter and the anterior and posterior temporalis muscles. Furthermore, mandibular movements are small during phase II compared to phase I. These results suggest that grinding during phase II movement is of minimal importance for food breakdown, and that most food breakdown on phase II facets occurs primarily at the end of phase I movement (i.e., crushing during phase I movement). We note, however, that depending on the orientation of phase I facets, significant grinding also occurs along phase I facets during phase I.