Adaptationism and the anthropoid postcranium: selection does not govern the length of the radial neck.

The length of the radial neck has been assumed to vary in living and extinct primates in accordance with its role as a moment arm during flexion by the m. biceps brachii. We here use a simple developmental approach to investigate whether or not this trait does, in fact, vary in such a manner. We find, instead, that virtually all variation in radial neck length is explicable as a simple correlate of overall body size, and that there is no evidence to conclude that selection has separately modified radial neck length in response to differing locomotor patterns. Further implications for the interpretation of mammalian skeletal morphology are briefly discussed.

Fetal age: methods of estimation and effects of pathology.

Accurate identification of fetal age is important in a wide variety of circumstances. Seventeen anthropometric and radiographic measurements were taken on fetuses between 15 and 42 weeks of gestational age, both with and without pathologic conditions. A full evaluation including radiographic, karyotypic, gross anatomic, and histologic examination of the fetus and placenta identified 72 individuals as nondysmorphic with no signs of chronic uterovascular insufficiency. These specimens served as the control group. Based on least-squares regressions of this group, age-estimation equations were calculated for all variables. Six models were adequately described by linear equations; the remaining 11 required a quadratic term. Based on standard error of the estimate (S(y:x)), skeletal measures proved the most accurate age estimators. Pathologic conditions were shown to have an influence on age estimation indicated by high levels of inaccuracy and, in some instances, significant bias.

Pattern and process of growth of the abnormal human fetus.

Identifying patterns of fetal growth alteration benefits both the clinician and the researcher. Twenty-four measurements in three variable sets (anthropometric measures, organ weights, and long-bone measures from radiographs) were taken on fetuses both with and without pathological conditions that are suspected to result in growth alteration. In addition, radiographs of each case were examined for the presence or absence of ossification centers. Based on least-squares regressions of the normal group, we calculated standardized residuals for the affected group to identify patterns of growth alteration. A large sample of fetuses between 15 and 42 weeks of gestational age with a variety of pathological conditions is described and evaluated for growth alterations. Symmetric and asymmetric growth alteration was detected in a small part of the sample and was predominantly isolated to fetuses in the late third trimester. Although patterns of growth alteration have been suggested as a means for noninvasive diagnoses of syndromes (such as trisomy 21), no consistent patterns are discernible in the current group. The sample provides a unique opportunity to evaluate fetal growth in terms of the interaction between genetic and environmental influences.

Response of bone and enamel formation to nutritional supplementation and morbidity among malnourished Guatemalan children.

The effects of changes in nutritional and health status upon bone and enamel development are examined in a sample of 63 rural Guatemalan children (24 females, 39 males). The number of ossified hand-wrist centers at 3 years and the number of linear enamel hypoplasias (LEH) in approximately 0-3 year zones of developing teeth were used to monitor the response of bone mineralization and enamel matrix formation to illness and nutritional supplementation. Numbers of ossified centers and LEH were compared across sex, supplementation, and morbidity groups. Enamel matrix secretion responded positively to increased supplementation. Children who received less than 34.25 kcal/day in supplement had more LEH than those who received more supplement. No differences in ossification status were found between supplementation groups. These data suggest that enamel formation may be more sensitive to changes in nutritional status than is bone mineralization. Disruptions of bone and enamel formation were both associated with frequent illness. Children who were ill more than 3.6% of the time had more LEH and fewer ossified hand-wrist centers than children who were less frequently ill. Conclusions regarding relative environmental sensitivity must take into account the specific aspects of dental and skeletal development examined.

Independent test of the fourth rib aging technique.

The sternal surface of the 4th rib has been suggested as a useful predictor of adult age-at-death (Iscan et al.: Journal of Forensic Sciences 29:1094-1104, 1984; American Journal of Physical Anthropology 65:147-156, 1984). We tested its ability to do so in two tests. In the first, we developed a method of seriation and target age assignment for the 4th rib so that inaccuracy and bias of the method could be assessed by decade. We found that the 4th rib shows characteristic changes in morphology with age and can be included in multifactorial age estimates. In the second test, we applied the phase method developed by Iscan et al. (Journal of Forensic Sciences 29:1094-1104, 1984). The results of our three judges were generally similar to those reported by Iscan and Loth (Journal of Forensic Sciences 31:122-132, 1986). Measures of race differences in 4th rib morphology were included in both tests. Americans of African descent (black) showed a non-significant trend for the rib changes to be delayed compared to Americans of European descent (white). This is in contrast to the work of Iscan et al., which predicted that blacks would show a tendency toward accelerated rib changes compared to whites, especially after the early 30s (phases 5-7) (Iscan et al.: Journal of Forensic Sciences 32(2):452-466, 1987).

Test of the multifactorial aging method using skeletons with known ages-at-death from the Grant Collection.

The multifactorial aging method has been shown to be a highly reliable method of skeletal aging because it incorporates age information from as many age indicators as are available for each skeleton (Lovejoy et al.; Am. J. Phys. Anthropol. 68:1-14, 1985). The present study was a blind test to assess its accuracy on a skeletal sample composed of 55 individuals with verified death certificates (Grant Collection, University of Toronto). Three authors (C.O.L., M.E.B., and K.F.R.), with no access to the death certificate ages, independently seriated and aged the sample using three to four criteria: auricular surface, pubic symphysis, and radiographs of the proximal femur and clavicle. Summary ages were then calculated for each individual in the sample. The authors' independent summary age estimates showed strong correlations with one another (r = 0.84-0.89). Multifactorial age estimates correlated better with real age than did those from any single indicator used. The mean error (averaging 8.7 years) for summary age was at least 1 year less than that for any single indicator. Average bias ranged from -0.7 (underage) to 1.4 (overage) years. These results indicate that utilization of several age indicators, weighted according to their reliability, helps control for variation in the changes that occur with age in any single morphological indicator. This method may therefore be considered one of the most accurate available for the determination of skeletal age-at-death, particularly for paleodemographic analysis.

Standardized residuals as a means for detection of growth alteration in the pathologic human fetus.

This paper introduces and discusses the use of standardized residuals as a technique for comparing the growth of normal and pathologic human fetuses. Anthropometric measures, radiographic measures, and organ weights were regressed on known gestational age of second- and third-trimester fetuses. Standardized residuals were calculated for a group of potentially growth-impaired fetuses. Use of residuals aids in identification of patterns of growth alteration in specific pathologies. Most important, studying the response of developing organ systems to a variety of insults may elucidate mechanisms of growth regulation in the fetus. We emphasize the special quality of the multivariate measures of the core sample of fetuses from the Akron Children's Hospital collection.

Further evidence on relative dental maturation and somatic developmental rate in hominoids.

New data on hominoid dental development are presented. Individual bivariate pairings of all mandibular teeth were made for African apes and humans. Data were analyzed with a full linear regression model. No statistically significant differences were found among apes, although a consistent pattern of earlier incisal development was observed in Pan relative to Gorilla. This is concordant with an earlier fusion of the premaxillary:maxillary suture in Pan. Only one tooth pair differed significantly by sex among apes. Two biologically distinct human samples (Libben and Hamann-Todd), although assessed differently (extraction and radiography) yielded virtually identical results. Humans differ from apes only by earlier relative calcification of their anterior teeth. This can be viewed as a consequence of reduced facial prognathism and a shift in hominid canine function.

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.

Hypothesis: a selective advantage for cystic fibrosis heterozygotes.

European populations have both a particularly long history of pulmonary tuberculosis and extremely high frequencies of cystic fibrosis (CF). While carriers of the recessive gene are asymptomatic for CF disease, their fibroblasts produce excessive amounts of hyaluronic acid, whose role in successful isolation of virulent pathogens appears to be especially adaptive in host resistance to the human strain of Mycobacterium tuberculosis. CF heterozygosity may have been an adaptation to a disease environment once dominated by this infection.

Multifactorial determination of skeletal age at death: a method and blind tests of its accuracy.

Traditional methods of estimating skeletal age at death have relied solely on the pubic symphyseal face or on this indicator combined with others in nonsystematic ways. A multifactorial method is presented that uses a principal components weighting of five indicators (public symphyseal face, auricular surface, radiographs of proximal femur, dental wear, and suture closure). This method has been tested by completely blind assessment of age in two samples from the Todd collection carefully screened for accuracy of stated age at death. Results show a marked superiority of the multifactorial method over any single indicator with respect to both bias and accuracy. This represents the first truly blind test of an age-at-death indicator or system, as the test populations were independent of the system(s) being tested, and the age, sex, and ethnogeographic origin of the individuals being assessed (as well as the compositions of the test samples with respect to these variables) were completely unknown until the tests were completed. Implications for paleodemography are discussed.

Chronological metamorphosis of the auricular surface of the ilium: a new method for the determination of adult skeletal age at death.

A new method for the determination of adult skeletal age at death based upon chronological changes in the auricular surface of the ilium is presented. Formal stages have been constructed following extensive tests and refinements in observations made of such changes. Two completely "blind" tests were conducted to assess the accuracy and bias of the new method. Results show that the system is equally accurate to pubic symphyseal aging (although somewhat more difficult to apply), and also carries the advantages of a higher preservation rate for the auricular surface in archaeological populations and continued age-related change beyond the fifth decade.

A revised method of age determination using the os pubis, with a review and tests of accuracy of other current methods of pubic symphyseal aging.

All current standardized methods of age determination using the os pubis were tested by blind assessment of a skeletal sample with documented ages (from the Todd collection; N = 96). No demographic data (sex, age, race, age composition) were known to the assessors prior to completion of the test. Results showed the Todd method to be more reliable than more recent component techniques and that all systems tended to underage. Therefore, modifications were made of the Todd system to eliminate this and other deficiencies, and a second test using a new sample was conducted (N = 109). The age distribution determined by the revised Todd method did not significantly differ from the actual age distribution of the second sample. Error due to race was nonsignificant. Biological stages of pubic metamorphosis are described and possible evolutionary specializations of the hominid symphysis are discussed. Revised standards for age determination are presented.

Ectocranial suture closure: a revised method for the determination of skeletal age at death based on the lateral-anterior sutures.

A new method for estimation of age-at-death based on the degree of suture closure is presented. The method employs simple ectocranial scoring of specific sites on the external table. Composite scores for two groups of sutures, lateral-anterior and vault systems, which are used to provide estimates of age-at-death, have been developed from a sample of 236 crania from the Hamann-Todd Collection. A variety of tests show that the lateral-anterior sutures are superior to the sutures of the vault, that ectocranial is superior to endocranial observation, and that age estimates are independent of race and sex. It is concluded that suture closure can provide valuable estimates of age-at-death in both archaeological and forensic contexts when used in conjunction with other skeletal age indicators.

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.

Components of longevity: developmental and genetic responses to differential childhood mortality.

Childhood disease may have far-reaching effects on adult longevity in high-mortality populations. It was earlier reported from demographic analysis of 19th century New England communities that survivors of high-fatality childhood epidemics lived significantly longer than their unstressed counter-parts. As part of a broader survey of agricultural families of western Massachusetts, these data indicate that elevated child mortality is associated with an increase in the average age at death of survivors. This paper examines this selection process and the problem of heritable longevity using cohort data selected from historical epidemics. A series of tests of the selection hypothesis in which an attempt is made to control demographic covariates suggest that widespread childhood infectious disease strengthens survivors in a developmental manner. Whether such episodes also eliminate less fit individuals according to a simple selection model could not be determined. The influence of family formation variables on child loss, and behavioral (fertility) responses to childhood epidemics in these communities are also considered.

Paleodemography of the libben site, Ottawa county, ohio.

The Libben site, a Late Woodland ossuary and occupation site from the Great Black Swamp of northern Ohio has yielded a well-preserved skeletal sample of 1327 articulated individuals. The outstanding preservation and completeness of the site and the utilization of an exhaustive aging methodology make this the largest and most comprehensively censused North American prehistoric cemetery. Survivorship data indicate a robust, successful population. Life expectancy at birth was 20 years. Among adults, male mortality was consistently higher than female, a condition possibly related to high interpersonal and intergroup aggression. Infant mortality was generally low, and a general hypothesis concerning the elevation of infant mortality and the simultaneous depression of adult mortality among aboriginal peoples after European contact is suggested.