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.     

Bone resorption of the pubis and preauricular area in humans and nonhuman mammals

Some innominates of adult human females show areas of bone resorption on the dorsal aspect of the pubic corpus and preauricular area of the ilium. For both sites, many studies have shown a positive association between degree of resorption and parity. The present study tested hypotheses concerning resorption of the pubis and preauricular area. Samples of innominates from three prehistoric Amerindian populations were used. Within each population, only a minority of females, in general, showed resorption more severe than that which characterized males. The severity of resorption of the pubis was not significantly associated with that of the preauricular area. Pitting of the pubis, but not of the preauricular area, was significantly correlated with age-at-death in each sample of Amerindian females. Also, sacral angulation was not significantly associated with resorption of the preauricular area. Observations on resorption of the pubis and preauricular area in samples of Pan troglodytes and Gorilla gorilla are reported. In previous studies on resorption of the pubis and preauricular area in the human innominate, the proposed etiologies involve ligamentous hyperplasia and joint trauma. However, a number of studies on resorption of the pubis in the nonhuman mammalian innominate have been overlooked by anthropologists. These latter studies demonstrate that estrogen alone can induce resorption of the mammalian pubis by stimulating the synthesis of osteoclastic enzymes. Partial resorption of the pubis may be obstetrically advantageous in some mammals, as resorption would delay or inhibit synostosis of the interpubic joint. The relationship between estrogen and the preauricular area is an issue that requires further research.     

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.     

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.     

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.     

Age-at-death estimation in an Italian historical sample: A test of the Suchey-Brooks and transition analysis methods

A growing body of research is demonstrating increased accuracy in aging from a relatively new method, transition analysis. Although transition analysis was developed for paleodemographic research, a majority of subsequent studies have been in the forensic arena, with very little work in bioarchaeological contexts. Using the Suchey‐Brooks pubic symphysis phases, scored on a target sample of historic Italians from the island of Sardinia, we compare accuracy of aging between transition analysis combined with a Bayesian approach and the standard Suchey‐Brooks age ranges. Because of the difficulty in identifying a reasonable informative prior for bioarchaeological samples, we also compared results of both an informative prior and a uniform prior for age estimation. Published ages‐of‐transition for the Terry Collection and Balkan genocide victims were used in conjunction with parameters generated from Gompertz hazard models derived from the priors. The ages‐of‐transition and hazard parameters were utilized to calculate the highest posterior density regions, otherwise known as “coverages” or age ranges, for each Suchey‐Brooks phase. Each prior, along with the parameters, were input into cumulative binomial tests. The results indicate that the Bayesian approach outperformed the Suchey‐Brooks technique alone. The Terry Collection surpassed the Balkans as a reasonable sample from which to derive transition analysis parameters. This discrepancy between populations is due to different within phase age‐at‐death distributions that reflect differences in aging between the populations. These results indicate bioarchaeologists should strive to apply a Bayesian analysis when aging historic and archaeological populations by employing an informative prior. Am J Phys Anthropol 149:259–265, 2012. © 2012 Wiley Periodicals, Inc.     

Reliability of age at death in the Hamann-Todd collection: validity of subselection procedures used in blind tests of the summary age technique

The blind test procedures used by Lovejoy et al., (Am. J. Phys. Anthropol. 68:1-14, 1985a) have been criticized because they used the Hamann-Todd collection as their known-age population. It has been suggested that variation within this sample was reduced by selection procedures designed to ensure accuracy of age at death. Powerful statistical tests for differences in dispersion of ages for pubic symphyseal stages were applied to comparisons between their core sample (N = 238) and those of a large autopsy-room collection used to develop the Suchey-Brooks System (N = 530). The variances in ages of the selected Hamann-Todd Sample are not reduced. The careful subselection of specimens has resulted in a valid statistical core sample for use in the development of aging methodologies.     

Energy expenditure of bipedal walking is higher than that of quadrupedal walking in Japanese macaques

The authors previously compared energetic costs of bipedal and quadrupedal walking in bipedally trained macaques used for traditional Japanese monkey performances (Nakatsukasa et al. 2004 Am. J. Phys. Anthropol. 124:248-256). These macaques used inverted pendulum mechanics during bipedal walking, which resulted in an efficient exchange of potential and kinetic energy. Nonetheless, energy expenditure during bipedal walking was significantly higher than that of quadrupedal walking. In Nakatsukasa et al. (2004 Am. J. Phys. Anthropol. 124:248-256), locomotor costs were measured before subjects reached a steady state due to technical limitations. The present investigation reports sequential changes of energy consumption during 15 min of walking in two trained macaques, using carbon dioxide production as a proxy of energy consumption, as in Nakatsukasa et al. (2004 Am. J. Phys. Anthropol. 124:248-256). Although a limited number of sessions were conducted, carbon dioxide production was consistently greater during bipedal walking, with the exception of some irregularity during the first minute. Carbon dioxide production gradually decreased after 1 min, and both subjects reached a steady state within 10 min. Energy expenditure during bipedalism relative to quadrupedalism differed between the two subjects. It was considerably higher (140% of the quadrupedal walking cost) in one subject who walked with more bent-knee, bent-hip gaits. This high cost strongly suggests that ordinary macaques, who adopt further bent-knee, bent-hip gaits, consume a far greater magnitude of energy during bipedal walking.     

Gombe chimpanzee sex differences in the pelvis and observations of pubic and preauricular areas

The skeletons of Gombe chimpanzees provide an opportunity for analysis of bony tissue with reference to known sex and parity in combination with observations on other life history variables and behavior. Measurements of the pelvic bones show a mosaic of sex differences. Well-defined resorption areas on the dorsomedial aspect of the pubis and the preauricular area of the ilium have been associated with sex and parity in humans and other species. However, these are not present in either females or males in this chimpanzee skeletal series.     

Test of revised method of age estimation from the auricular surface of the ilium

The objective of this paper is to test a revised method of age estimation based on the morphology of the auricular surface recently proposed by Buckberry and Chamberlain ([2002] Am. J. Phys. Anthropol. 119:231-239). The study sample consists of 309 individuals of known sex, age, and race from the Terry and Huntington Collections. Auricular surfaces were scored using the revised technique to determine whether it is equally applicable to both sexes as well as blacks and whites. The auricular surfaces of the same individuals were also scored using the original method of auricular surface scoring developed by Lovejoy et al. ([1985] Am. J. Phys. Anthropol. 68:15-28) to determine whether the revised technique is comparable to the original method in terms of accuracy. Results show that the revised method is equally applicable to males and females as well as blacks and whites. The revised method is less accurate than the original method for individuals between 20-49 years of age, but more accurate for individuals between 50-69 years of age.     

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.     

Is the genetic structure of Gran Chaco populations unique? Interregional perspectives on native South American mitochondrial DNA variation

This study reevaluates the hypothesis in Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203) that Gran Chaco peoples demonstrate a unique pattern of genetic diversity due to a distinct regional population history. Specifically, they found populations in the central part of the Gran Chaco, or Central Chaco, to have higher within- and lower between-population mitochondrial DNA (mtDNA) haplogroup frequency variation compared to populations in other South American regions. To test this hypothesis of regional uniqueness, we applied analytical and simulation methods to mtDNA first hypervariable (HVI) region sequence data from a broad set of comparative South and Central American population samples. Contrary to the results of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203), we found that the Gran Chaco's regional within-population diversity is about average among regions, and populations are highly differentiated from each other. When we limited the scale of analysis to the Central Chaco, a more localized subregion of the Gran Chaco, our results fell more in line with the original findings of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203). Still, we conclude that neither the Gran Chaco regional pattern, nor the Central Chaco subregional pattern, is unique within South America. Nonetheless, the Central Chaco pattern accords well with the area's history, including pre-European contact lifeways and the documented historical use of the area as an interregional crossroads. However, we cannot exclude post-European contact disruption of traditional mating networks as an equally plausible explanation for the observed diversity pattern. Finally, these results additionally inform broader models of South American genetic diversity. While other researchers proposed an east-west continental division in patterns of genetic variation (e.g., Fuselli et al. 2003 Mol. Biol. Evol. 20:1682-1691), we found that in the geographically intermediate Central Chaco, a strict east-west divide in genetic variation breaks down. We suggest that future genetic characterizations of the continent, and subsequent interpretations of evolutionary history, involve a broad regional sampling of South American populations.     

Adult females and pubic bone growth

Previous research (Tague [1994] Am. J. Phys. Anthropol. 95:27–40) has shown an age effect in pubic bone length among adult women. Tague found that in three prehistoric Native American skeletal samples, women aged 18–24 had a significantly shorter linea terminalis than did women aged 25 and older. The purpose of this research is to determine whether such a difference can be discerned in other female skeletal samples. Three female skeletal samples were used in this analysis: 75 African-American and 42 European-American females aged 18–39 from the Hamann-Todd Collection (collected between 1893 and 1938; Iscan, 1990) and 99 African-American females aged 18–39 from the Terry Collection (collected between 1914 and 1965; Cobb, 1933; Iscan, 1990). Several chord measurements of pubic bone length along the linea terminalis were analyzed by one-tailed t-tests of the separate samples subdivided into two age groups: 18–24 and 25–39 years. Of 15 comparisons between age groups, none differed significantly by age group within each sample. It is concluded that the observed significant difference in pubic bone length in the Native American female skeletal samples cannot be replicated in other samples and that there is no age effect on pubic bone length in the samples tested in this analysis. Tague's findings reflect either the occurrence of late menarche in prehistoric populations or differential survivorship. Am J Phys Anthropol 106:323–328, 1998. © 1998 Wiley-Liss, Inc.     

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.     

Improved DNA extraction from ancient bones using silica-based spin columns

We describe a simple method for extracting polymerase chain reaction-amplifiable DNA from ancient bones without the use of organic solvents. Bone powders are digested with proteinase K, and the DNA is purified directly using silica-based spin columns (QIAquick™, QIAGEN). The efficiency of this protocol is demonstrated using human bone samples ranging in age from 15 to 5,000 years old. Am J Phys Anthropol 105:539–543, 1998. © 1998 Wiley-Liss, Inc.     

The influence of body size on adult skeletal age estimation methods

Accurate age estimations are essential to archaeological and forensic analyses. However, reliability for adult skeletal age estimations is poor, especially for individuals over the age of 40 years. This is the first study to show that body size influences skeletal age estimation. The ??can et al., Lovejoy et al., Buckberry and Chamberlain, and Suchey‐Brooks age methods were tested on 764 adult skeletons from the Hamann‐Todd and William Bass Collections. Statures ranged from 1.30 to 1.93 m and body masses ranged from 24.0 to 99.8 kg. Transition analysis was used to evaluate the differences in the age estimations. For all four methods, the smallest individuals have the lowest ages at transition and the largest individuals have the highest ages at transition. Short and light individuals are consistently underaged, while tall and heavy individuals are consistently overaged. When femoral length and femoral head diameter are compared with the log‐age model, results show the same trend as the known stature and body mass measurements. The skeletal remains of underweight individuals have fewer age markers while those of obese individuals have increased surface degeneration and osteophytic lipping. Tissue type and mechanical loading have been shown to affect bone turnover rates, and may explain the differing patterns of skeletal aging. From an archaeological perspective, the underaging of light, short individuals suggests the need to revisit the current research consensus on the young mortality rates of past populations. From a forensic perspective, understanding the influence of body size will impact efforts to identify victims of mass disasters, genocides, and homicides. Am J Phys Anthropol 156:35–57, 2015 © 2014 Wiley Periodicals, Inc.     

Fossil hominin ulnae and the forelimb of Paranthropus

The discovery of Pan in the Middle Pleistocene deposits of the Kapthurin Formation of the Tugen Hills (McBrearty and Jablonski: Nature 437 (2005) 105-108) inspires new interest in the search for other chimpanzee fossils in the East African Rift Valley. Craniodental evidence of an eastward excursion of chimpanzee populations in the Plio-Pleistocene goes undetected in other hominin sites, but one enigmatic postcranial fossil, the Olduvai Hominid 36 ulna, has many chimp-like features. Analyses by Aiello et al. (Aiello et al.: Am J Phys Anthropol 109 (1999) 89-110) reveal that it is similar to extant Pan in some respects, but it also has unique traits not seen in other hominoid species. They refer it to Paranthropus boisei. In this study, we reassess the affinities of OH 36 using a different data set that includes more recently discovered hominin fossils including those attributed to Paranthropus. Despite its superficial resemblance to modern Pan, our results agree with those of Aiello et al. (Aiello et al.: Am J Phys Anthropol 109 (1999) 89-110) that OH 36 is distinctly different from modern chimpanzees. By default, it is reasonable to assign this specimen to P. boisei, but it is not at all similar to other ulnae referred to this genus. Ulnae attributed to Paranthropus from South Africa, Kenya, and Ethiopia are morphologically more heterogeneous than those within species of large-bodied Hominoidea. Although there are many apparent shared derived traits justifying a monophyletic Paranthropus clade, most if not all of these traits are related to a single functional complex (hypermastication) that may have evolved in parallel and thereby constituting a paraphyletic group of species.     

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.     

Brief Communication: Shape analysis of the MT 1 proximal articular surface in fossil hominins and shod and unshod Homo

As a follow-up study to Proctor et al. (Am J Phys Anthropol 135 (2008) 216-224), this study quantifies the first metatarsal proximal articular surface using three-dimensional morphometrics to test for differences in articular surface shape between habitually shod and habitually unshod humans. In addition, differences in shape between Homo, Pan, Gorilla, and Hylobates are compared to the fossil hominin specimens A. L. 333-54, Stw 562, Stw 573 ("Little Foot"), OH 8, SKX 5017, and SK 1813. No difference in surface shape was found between habitually shod and habitually unshod humans. There is a clear quantitative division in articular surface shape between humans and apes that is more pronounced than a previous study by Proctor et al. (Am J Phys Anthropol 135 (2008) 216-224), due to additional landmarks present in this study. The specimen OH 8 is indistinguishable from modern Homo. The fossils A. L. 333-54, Stw 562, and Stw 573 are intermediate in shape between humans and apes. The specimens SKX 5017 and SK 1813 have a more apelike articular surface. When combined with other characteristics, this trait suggests that Paranthropus used a degree of abduction during locomotion that was much less than that in extant apes, but greater than that in Australopithecus, allowing for some small degree of grasping ability.