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.     

太行山猕猴髋骨异速增长和性别判定研究

目的是了解太行山猕猴髋骨性差特征及异速增长模式。太行山猕猴髋骨标本66例(雄21例,雌45例)。选择髋骨4个比值变量。数据分析采用SPSS 20.0。组间均值比较采用单因素方差分析。性别判别分析采用逐步判别法。结果表明:成年太行山猕猴大部分髋骨变量性差显著(P0.05)。根据髋骨变量的异速增长分析可以得到3种模式。回归模型检验有统计学意义(P<0.01)。用少量髋骨变量可以有效地识别性别,性别正确判别率是87.0%。结论:髋骨变量的性差与异速增长模式主要与雌性髋骨变量青春期异速增长有关,髋骨的形态特征是猕猴运动功能与生殖功能交互作用的结果。     

Expanding the evolutionary explanations for sex differences in the human skeleton

While the anatomy and physiology of human reproduction differ between the sexes, the effects of hormones on skeletal growth do not. Human bone growth depends on estrogen. Greater estrogen produced by ovaries causes bones in female bodies to fuse before males' resulting in sex differences in adult height and mass. Female pelves expand more than males' due to estrogen and relaxin produced and employed by the tissues of the pelvic region and potentially also due to greater internal space occupied by female gonads and genitals. Evolutionary explanations for skeletal sex differences (aka sexual dimorphism) that focus too narrowly on big competitive men and broad birthing women must account for the adaptive biology of skeletal growth and its dependence on the developmental physiology of reproduction. In this case, dichotomizing evolution into proximate‐ultimate categories may be impeding the progress of human evolutionary science, as well as enabling the popular misunderstanding and abuse of it.     

Age and sex biases in the preservation of human skeletal remains

Inaccuracies introduced through biases in preservation are a major source of error in paleodemographic reconstructions. Although it is generally assumed that such biases exist, little is known about their magnitude. To investigate this problem, we studied age and sex differences in the preservation of skeletal remains from Mission La Purisima and a prehistoric cemetery (Ca-Ven-110). Comparison of mortality profiles obtained through analysis of skeletal remains and burial records from the mission indicates that biases in preservation can be very significant in poorly preserved skeletal collections. The Purisima burial records show that most of the people interred in the cemetery were either infants or elderly adults. The skeletal remains, in contrast, are predominantly those of young adults. The burial records and skeletal collection produced comparable sex ratios. These results show that age biases in preservation are much more important than sex biases. This conclusion is supported by data on the completeness of the skeletons from La Purisima and Ca-Ven-110. At both sites, the remains of young adults were better preserved than those of children or elderly adults, and the completeness of male and female skeletons was comparable.     

Parturition and pelvic changes

A detailed analysis of the female bony pelvis in relation to parity status was made. A total of 198 complete pelves were inspected for five features considered to be associated with pregnancy and parturition. During final analysis two features were eliminated. Three remaining features - dorsal pubic pitting, pre-auricular grooves, and grooves located at the site of interosseous ligament insertion were found to be significantly related to partirution. Other findings of interest were: (1) pits and grooves acquired through pregnancy and parturition appear to become obliterated in old age, (2) the preauricular groove is the most sensitive indicator of pregnancy and parturition, (3) moderate-large pitting in the dorsal pubic region rarely occurs in nulliparous females, and (4) it is doubtful that more precise statements than "no children" and "one or more children" can be made on the basis of skeletal remains alone.     

Variation in pelvic size between males and females

Selection intensity and phenotypic variability are inversely related. It has been hypothesized that, owing to opposing selection pressures on pelvic morphology in females between efficiency in locomotion and obstetric adequacy, female pelvic morphology is less variable than that in males. The hypothesis was supported based on data derived from observational methods of sexing pelves (Meindl et al., 1985). The hypothesis was tested in the present study based on a metrical analysis of the true pelvis. The results show that there are no sexual differences in pelvic variability. Consequently, while males and females are equally variable in the dimensions of the true pelvis, the visual cues that osteologists use to sex pelves are more variable in males.     

Bone mineral density correlates with fracture load in experimental side impacts of the pelvis

Pelvic fractures resulting from automotive side impacts are associated with high mortality and morbidity, as well as substantial economic costs. Previous experimental studies have produced varying results regarding the tolerance of the pelvis to lateral force and compression. While bone mineral density (BMD) has been shown to correlate with fracture loads in the proximal femur, no such correlation has been established for the pelvis. Presently, we studied the relationships between total hip BMD and impact response parameters in lateral impacts of twelve isolated human pelves. The results indicated that total hip BMD significantly correlated with fracture force, Fmax, and maximum ring compression, Cmax, of the fractured pelves. These findings are evidence that BMD may be useful in assessing the risk of pelvic fracture in automotive side impacts. Poor correlation was observed between total hip BMD and maximum viscous response, (VC)max, energy at fracture, Epeak, and time to fracture, tpeak. Mean Fmax and calculated tolerances for Cmax and (VC)max were lower than those established in previous studies using full cadavers, likely a result of our removal of soft tissues from the pelves prior to impact.     

Obstetric dimensions of the true pelvis in a medieval population from Sudanese Nubia.

Functional analysis of the true pelvis (defined as that portion lying below and including the pelvic brim) was undertaken on a sample of 36 females from the Medieval site of Kulubnarti in Sudanese Nubia. Standard obstetric measurements were taken and compared to four additional prehistoric skeletal samples and to modern American standards for the same obstetric dimensions. Relative to the other prehistoric populations, the Kulubnarti pelves are smaller in most dimensions and, when compared to modern American standards, from one-third to one-half would be diagnosed as contracted in one or more planes. Given the meager, fluctuating resources of these Medieval Nubians' harsh desert environment, pelvic size reduction is a likely result of body size reduction as one biological response to nutritional stress (Mittler and Van Gerven, 1989; Moore et al., 1986; Van Gerven et al., 1981). It is argued, however, that size reduction created a high potential for either maternal-neonatal morbidity and mortality due to fetopelvic disproportion or neonatal loss due to low birth weight. In either case, it is suggested that the Kulubnarti population paid a significant biological price for this aspect of size reduction.     

Elastic and viscoelastic properties of the human pubic symphysis joint: effects of lateral impact joint loading

The human pelvis is susceptible to severe injury in vehicle side impacts owing to its close proximity to the intruding door and unnatural loading through the greater trochanter. Whereas fractures of the pelvic bones are diagnosed with routine radiographs (x-rays) and computerized tomography (CT scans), non-displaced damage to the soft tissues of pubic symphysis joints may go undetected. If present, trauma-induced joint laxity may cause pelvic instability, which has been associated with pelvic pain in non-traumatic cases. In this study, mechanical properties of cadaveric pubic symphysis joints from twelve normal and eight laterally impacted pelves were compared. Axial stiffness and creep responses of these isolated symphyses were measured in tension and compression (perpendicular to the joint). Bending stiffness was determined in four primary directions followed by a tension-to-failure test. Loading rate and direction correlated significantly (p<0.05) with stiffness and tensile strength of the unimpacted joints, more so than donor age or gender. The impacted joints had significantly lower stiffness in tension (p <0.04), compression (p<0.003), and posterior bending (p<0.03), and more creep under a compressive step load (p<0.008) than the unimpacted specimens. Tensile strength was reduced following impact, however, not significantly. We concluded that the symphysis joints from the impacted pelves had greater laxity, which may correlate with post-traumatic pelvic pain in some motor vehicle crash occupants.     

Protection of obstetric dimensions in a small-bodied human sample

In human females, the bony pelvis must find a balance between being small (narrow) for efficient bipedal locomotion, and being large to accommodate a relatively large newborn. It has been shown that within a given population, taller/larger-bodied women have larger pelvic canals. This study investigates whether in a population where small body size is the norm, pelvic geometry (size and shape), on average, shows accommodation to protect the obstetric canal. Osteometric data were collected from the pelves, femora, and clavicles (body size indicators) of adult skeletons representing a range of adult body size. Samples include Holocene Later Stone Age (LSA) foragers from southern Africa (n = 28 females, 31 males), Portuguese from the Coimbra-identified skeletal collection (CISC) (n = 40 females, 40 males) and European-Americans from the Hamann-Todd osteological collection (H-T) (n = 40 females, 40 males). Patterns of sexual dimorphism are similar in the samples. Univariate and multivariate analyses of raw and Mosimann shape-variables indicate that compared to the CISC and H-T females, the LSA females have relatively large midplane and outlet canal planes (particularly posterior and A-P lengths). The LSA males also follow this pattern, although with absolutely smaller pelves in multivariate space. The CISC females, who have equally small stature, but larger body mass, do not show the same type of pelvic canal size and shape accommodation. The results suggest that adaptive allometric modeling in at least some small-bodied populations protects the obstetric canal. These findings support the use of population-specific attributes in the clinical evaluation of obstetric risk.     

Measuring the human pelvis: A comparison of direct and radiographic techniques using a modern United States–based sample

Seven measurements were taken on a sample of 50 human cadaveric pelves, all white Texans born in the 20th century. Two separate methodologies were used to obtain these data: radiographs and direct measurements. These two methodologies were compared and contrasted, with the relative advantages and disadvantages of each explored. Results indicate that significant differences exist between the two methodologies. Pelvic height, breadth of symphysis, sacro-iliac breadth (P = 0.0001) and anterior upper spinal breadth (P = 0.0002) were larger when measured directly. Pelvic breadth, transverse diameter of the pelvic brim, and height of the ilium did not significantly differ between methodologies (P = 0.2037, P = 0.5253, P = 0.1752). Due to secular changes and inherent intrapopulational variation, taking measurements either directly from modern cadaveric specimens or radiographically on living volunteers in a limited geographic or socioeconomic grouping, rather than from skeletal collections or archived radiographs, may be more appropriate for providing data for current anthropometric applications. Am J Phys Anthropol 103:471–479, 1997. © 1997 Wiley-Liss, Inc.     

Methods for estimating missing human skeletal element osteometric dimensions employed in the revised fully technique for estimating stature

One of the greatest limitations to the application of the revised Fully anatomical stature estimation method is the inability to measure some of the skeletal elements required in its calculation. These element dimensions cannot be obtained due to taphonomic factors, incomplete excavation, or disease processes, and result in missing data. This study examines methods of imputing these missing dimensions using observable Fully measurements from the skeleton and the accuracy of incorporating these missing element estimations into anatomical stature reconstruction. These are further assessed against stature estimations obtained from mathematical regression formulae for the lower limb bones (femur and tibia). Two thousand seven hundred and seventeen North and South American indigenous skeletons were measured, and subsets of these with observable Fully dimensions were used to simulate missing elements and create estimation methods and equations. Comparisons were made directly between anatomically reconstructed statures and mathematically derived statures, as well as with anatomically derived statures with imputed missing dimensions. These analyses demonstrate that, while mathematical stature estimations are more accurate, anatomical statures incorporating missing dimensions are not appreciably less accurate and are more precise. The anatomical stature estimation method using imputed missing dimensions is supported. Missing element estimation, however, is limited to the vertebral column (only when lumbar vertebrae are present) and to talocalcaneal height (only when femora and tibiae are present). Crania, entire vertebral columns, and femoral or tibial lengths cannot be reliably estimated. Further discussion of the applicability of these methods is discussed.     

Differential Renal Function Study—An Aid in Preoperative Evaluation of Hypertensive Patients

Non-occlusive ureteral catheters were placed bilaterally in the renal pelves of 30 patients known to have hypertension. Samples of urine were collected under conditions of normal hydration, of urea-PAH-saline diuresis and, in some cases, mannitol diuresis. The samples were analyzed for indications of impaired flow of blood to the kidneys. Aortograms were obtained in all cases.This placement of non-occlusive catheters up into the renal pelves was felt to have caused only minimal disturbance of renal function, and was not accompanied by ureteral edema with the concomitant complications caused by occlusive catheters. Under conditions of normal hydration, leakage was insignificant.Of the 20 patients in whom urea-PAH-saline infusion revealed an ischemic pattern, 19 had an ischemic pattern under conditions of normal hydration. Since in the one exception an aortographic examination did not show a surgically reparable renal lesion, it may be inferred that the use of urea-PAH-saline diuresis is not essential in the preoperative evaluation of hypertensive renal disease.Correlation of the results of differential renal function studies and aortographic findings was possible in 19 of the 30 patients. Lack of correlation in the remaining 11 patients emphasized the importance of obtaining both types of study.Aortographic examination combined with differential renal function studies, using small ureteral catheters under conditions of normal hydration, should give the urologist a practical and yet accurate method of determining differential renal blood flow. If desired, further verification could be obtained by administering contrast medium and performing serial measurements of urine density.     

Environmental effects on skeletal versus dental development: Using a documented subadult skeletal sample to test a basic assumption in human osteological research

This study examines the relationship between measures of skeletal and dental development and socioeconomic factors in a 20th century documented skeletal sample of children from Portugal. The skeletons are of known sex and chronological age, and include other biographic data, such as cause of death. Growth in the length of the long bone is used as a measure of skeletal growth, and schedules of tooth formation are used as a measure of dental development. These two measures of physiological age were compared to chronological age, to assess growth and developmental status. Socioeconomic indicators were obtained from the supporting documentation, and include the occupation of the father and the place of residence, which were used to build a socioeconomic classification based on two groups, one of low and the other of high socioeconomic status. Growth and development status was then compared in these two groups. Results show that socioeconomic differences are much more pronounced in skeletal growth than in dental development. This largely supports the assertion that dental development is buffered against environmental factors relative to skeletal development. However, in this study, skeletal maturation could not be assessed, and findings indicate that dental development can show significant delays at the lower end of the socioeconomic gradient.     

Changes in osteoarthritis associated with the development of a maritime economy among southern California Indians

The severity of osteoarthritis was studied in human skeletal remains from archaeological sites in the Santa Barbara Channel area of southern California. These remains were analyzed to better understand changes in activity patterns associated with the economic shift from hunting and gathering to intensive fishing and craft specialization that occurred in this area. The joints of 967 burials from seven archaeological sites occupied between 3500 B.C. and the time of European contact were scored for osteoarthritis. These data show that the rate at which people developed osteoarthritis increased through time. This suggests that the adaptive shift toward more intensive exploitation of the marine environment resulted in an increase in the time people spent in strenuous physical activity. The increase in osteoarthritis affected males to a greater extent than females. One interpretation of this is that the work load of men increased with the economic importance of fishing.     

Sarcolemmal ATP-sensitive potassium channels modulate skeletal muscle function under low-intensity workloads

ATP-sensitive potassium (K_ATP) channels have the unique ability to adjust membrane excitability and functions in accordance with the metabolic status of the cell. Skeletal muscles are primary sites of activity-related energy consumption and have K_ATP channels expressed in very high density. Previously, we demonstrated that transgenic mice with skeletal muscle–specific disruption of K_ATP channel function consume more energy than wild-type littermates. However, how K_ATP channel activation modulates skeletal muscle resting and action potentials under physiological conditions, particularly low-intensity workloads, and how this can be translated to muscle energy expenditure are yet to be determined. Here, we developed a technique that allows evaluation of skeletal muscle excitability in situ, with minimal disruption of the physiological environment. Isometric twitching of the tibialis anterior muscle at 1 Hz was used as a model of low-intensity physical activity in mice with normal and genetically disrupted K_ATP channel function. This workload was sufficient to induce K_ATP channel opening, resulting in membrane hyperpolarization as well as reduction in action potential overshoot and duration. Loss of K_ATP channel function resulted in increased calcium release and aggravated activity-induced heat production. Thus, this study identifies low-intensity workload as a trigger for opening skeletal muscle K_ATP channels and establishes that this coupling is important for regulation of myocyte function and thermogenesis. These mechanisms may provide a foundation for novel strategies to combat metabolic derangements when energy conservation or dissipation is required.     

Purinergic receptors expressed in human skeletal muscle fibres

Purinergic receptors are present in most tissues and thought to be involved in various signalling pathways, including neural signalling, cell metabolism and local regulation of the microcirculation in skeletal muscles. The present study aims to determine the distribution and intracellular content of purinergic receptors in skeletal muscle fibres in patients with type 2 diabetes and age-matched controls. Muscle biopsies from vastus lateralis were obtained from six type 2 diabetic patients and seven age-matched controls. Purinergic receptors were analysed using light and confocal microscopy in immunolabelled transverse sections of muscle biopsies. The receptors P2Y(4), P2Y(11) and likely P2X(1) were present intracellularly or in the plasma membrane of muscle fibres and were thus selected for further detailed morphological analysis. P2X(1) receptors were expressed in intracellular vesicles and sarcolemma. P2Y(4) receptors were present in sarcolemma. P2Y(11) receptors were abundantly and diffusely expressed intracellularly and were more explicitly expressed in type I than in type II fibres, whereas P2X(1) and P2Y(4) showed no fibre-type specificity. Both diabetic patients and healthy controls showed similar distribution of receptors. The current study demonstrates that purinergic receptors are located intracellularly in human skeletal muscle fibres. The similar cellular localization of receptors in healthy and diabetic subjects suggests that diabetes is not associated with an altered distribution of purinergic receptors in skeletal muscle fibres. We speculate that the intracellular localization of purinergic receptors may reflect a role in regulation of muscle metabolism; further studies are nevertheless needed to determine the function of the purinergic system in skeletal muscle cells.     

Born to run; the story of the PEPCK-Cmus mouse

In order to study the role of the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK-C) in skeletal muscle, PEPCK-Cmus mice were created by introducing the cDNA for the enzyme, linked to the human alpha-skeletal actin gene promoter, into their germ line. Two founder lines generated by this procedure were bred together, creating a line of mice that have 9.0 units/g skeletal muscle of PEPCK-C, as compared to 0.080 units/g in muscle from control animals. The mice were more active than controls in their cages and could run for up to 5 km, at a speed of 20 m/min without stopping (control mice run for 0.2 km at the same speed). Male PEPCK-Cmus mice are extremely aggressive, as well as hyperactive. During strenuous exercise, they use fatty acids as a fuel more efficiently than do controls and produce far less lactate than do control animals, perhaps due to the greatly increased number of mitochondria in their skeletal muscle. PEPCK-Cmus mice also store up to five-times more triglyceride in their skeletal muscle, but have only marginal amounts of triglyceride in their adipose tissue depots, despite eating 60% more than controls. The concentration of leptin and insulin the blood of 8-12 months of PEPCK-Cmus mice is far lower than noted in the blood of control animals of the same age. These mice live longer than controls and the females remain reproductively active for as long as 35 months. The possible reasons for the profound alteration in activity and longevity caused the introduction of a simple metabolic enzyme into the skeletal muscle of the mice will be discussed.