Secular Change and Allometry in the Long Limb Bones of Americans from the Mid 1700s through the 1970s

Secular change has long been of interest to researchers in fields ranging from human growth to human identification. In addition to changes in size, changes in limb bone proportions may also have occurred. Secular change in size and limb bone length proportion was investigated in five U.S. skeletal samples (Total N =2700) with dates of birth ranging from mid 1700 to 1970s. The six long bones are measured for maximum lengths, and stature is known for a approximately 2000 individuals. The goals of this study include 1) examining any changes in the long bones and stature of white and black males and females, and 2) examining the allometric relationships of the six long bones for these sex/race groups across time, and 3) examining any geographical differences in size and shape in a subsample. In order to test for secular change in stature and bone lengths, regression is employed with each of the variables regressed onto year of birth. The second analysis involves the examination of allometric secular change. Size (geometric mean) and shape (X/size) were employed in a principal components analysis. The principal components of shape were then regressed onto year of birth for each sex/race group. Using Trotter\u27s WWII sample, geographic differences are examined by using size and shape in principal components analysis and multivariate analysis of variance. Results indicate that white males exhibit secular change in stature, all long bones, and most of their proportional relationships. Black males exhibit change in stature and all long bones except the humerus. Both male groups exhibit change in the proportional relationship of arm to leg bones with legs getting longer while arms get shorter. White females show the same secular change in size and bone lengths as black males, while black females only exhibit change in stature. Results of the geographical analysis indicate that white males vary significantly by region in both size and shape, but black males do not. Of the five regions employed and examined, the Northeast yields the smallest males while the West has the largest. Environmental improvements in the U.S. have lead to secular increases in size and bone lengths. Males exhibit a greater plastic response to these environmental changes, whereas females are more stable. Whites exhibit greater response than do blacks possibly due to harsher environmental conditions endured by blacks historically

Secular Changes in the Postcranial Skeleton of American Whites

Secular change in height has been extensively investigated, but size and shape of the postcranial skeleton much less so. The availability of large, documented collections of nineteenth- and twentieth-century skeletons makes it possible to examine changes in skeletal structure over the past 150 years. We examined secular changes in long bone lengths and proportions, their allometric relationship to stature, and cross- sectional properties of long bone shafts. Bone measurements and stature were organized into 10-year birth cohorts, ranging from 1840 to 1989. Variation among cohorts was tested by one-way ANOVA, and secular trend was examined visually by plotting mean measurements by birth decade. Allometry was examined by regressing log bone lengths onto log stature, using least squares regression. Allometry was also examined using the geometric mean of log bone lengths as the size variable. All bone lengths and stature showed positive secular change. Stature and the distal long bones showed the most pronounced changes. Proportions also changed, as revealed by the brachial and crural indices. Both indices increased, but the brachial index change was the most pronounced. Allometric relationships suggest that brachial index changes result from positive allometry of the radius and negative allometry of the humerus. Similar but less marked allometric relationships were found in the tibia and femur. Long bone shaft properties changed in the following ways: femur midshafts and tibia shafts at the nutrient foramen became more mediolaterally narrowed, and the femur became more mediolaterally thickened at the subtrochanteric level, approaching platymeria. All major long bones became more gracile. These remarkable changes in the postcranial skeleton are a response to the unparalleled changes in the environment in which modern Americans now live. Changes in growth resulting from plentiful and secure nutrition, reduced disease load, and marked reduction in bone loading from reduced activity levels are mainly responsible

The Remarkable Change in Euro-American Cranial Shape and Size

Secular changes in stature, weight, or other components of the body that can be obtained from historical records have been extensively studied. Cranial change has been central to anthropology for more than a century, but the focus has normally been on change measured in centuries or millennia. Cranial change measured in decades, normally considered to result from plastic response to the environment, has been less studied. This article reports on change in cranial vault dimensions in white Americans. Variables were glabello-occipital length (GOL), basion-bregma height (BBH), basion-nasion length (BNL), maximum cranial breadth (XCB), and biauricular breadth (AUB). Cranial size was calculated as the geometric mean of these variables, and shape dimensions were calculated as described by Darroch and Mosimann (1985). Cranial module and cranial capacity were also calculated. Samples consisted of 1,112 males and 668 females complete for those variables. Samples were organized into 10-year birth cohorts, with birth years ranging from 1820 to 1990. One-way ANOVA was used to test for variation among cohorts. The pattern of secular change was examined graphically and was compared with quality-of-life and environmental indicators, including stature, infant mortality, calories per person, and relative number of immigrants. All variables showed significant secular change, but BBH, XCB, and BNL responded most strongly. Over the past 170 years, crania became relatively higher, narrower, and larger with longer cranial bases. Both sexes changed, but female change was less pronounced than male change. The cranial variables tracked secular changes in stature, most prominently BNL. The highest correlation between a cranial variable and quality-of-life indicator was BBH and infant mortality. We are not able to identify specific causes of secular changes in cranial morphology. However, given that modern Americans have introduced themselves into a novel environment never before experienced by human populations, we consider it unlikely that it is pure plasticity. In addition to possible plastic responses, it is likely that selection, acting through the dramatic changes in infant mortality, is also involved

Error quantification of osteometric data in forensic anthropology

Abstract This study evaluates the reliability of osteometric data commonly used in forensic case analyses, with specific reference to the measurements in Data Collection Procedures 2.0 (DCP 2.0). Four observers took a set of 99 measurements four times on a sample of 50 skeletons (each measurement was taken 200 times by each observer). Two-way mixed ANOVAs and repeated measures ANOVAs with pairwise comparisons were used to examine interobserver (between-subjects) and intraobserver (within-subjects) variability. Relative technical error of measurement (TEM) was calculated for measurements with significant ANOVA results to examine the error among a single observer repeating a measurement multiple times (e.g. repeatability or intraobserver error), as well as the variability between multiple observers (interobserver error). Two general trends emerged from these analyses: (1) maximum lengths and breadths have the lowest error across the board (TEM < 0.5), and (2) maximum and minimum diameters at midshaft are more reliable than their positionally-dependent counterparts (i.e. sagittal, vertical, transverse, dorso-volar). Therefore, maxima and minima are specified for all midshaft measurements in DCP 2.0. Twenty-two measurements were flagged for excessive variability (either interobserver, intraobserver, or both); 15 of these measurements were part of the standard set of measurements in Data Collection Procedures for Forensic Skeletal Material, 3rd edition. Each measurement was examined carefully to determine the likely source of the error (e.g. data input, instrumentation, observer’s method, or measurement definition). For several measurements (e.g. anterior sacral breadth, distal epiphyseal breadth of the tibia) only one observer differed significantly from the remaining observers, indicating a likely problem with the measurement definition as interpreted by that observer; these definitions were clarified in DCP 2.0 to eliminate this confusion. Other measurements were taken from landmarks that are difficult to locate consistently (e.g. pubis length, ischium length); these measurements were omitted from DCP 2.0. This manual is available for free download online (https://fac.utk.edu/wp-content/uploads/2016/03/DCP20_webversion.pdf), along with an accompanying instructional video (https://www.youtube.com/watch?v=BtkLFl3vim4)

Data for validation of osteometric methods in forensic anthropology

Abstract Many techniques in forensic anthropology employ osteometric data, although little work has been done to investigate the intrinsic error in these measurements. These data were collected to quantify the reliability of osteometric data used in forensic anthropology research and case analyses. Osteometric data (n =99 measurements) were collected on a random sample of William M. Bass Donated Collection skeletons (n = 50 skeletons). Four observers measured the left elements of 50 skeletons. After the complete dataset of 99 measurements was collected on each of the 50 skeletons, each observer repeated the process for a total of four rounds. The raw data is available on Mendeley Data (DCP Osteometric Data, Version 1. DOI: 10.17632/6xwhzs2w38.1). An example of the data analyses performed to evaluate and quantify observer error is provided for the variable GOL (maximum cranial length); these analyses were performed on each of the 99 measurements. Two-way mixed ANOVAs and repeated measures ANOVAs with pairwise comparisons were run to examine intraobserver and interobserver error, and relative and absolute technical error of measurement (TEM) was calculated to quantify the observer variation. This data analysis supported the dissemination of a free laboratory manual of revised osteometric definitions (Data Collection Procedures 2.0, pdf available at https://fac.utk.edu/wp-content/uploads/2016/03/DCP20_webversion.pdf) and an accompanying instructional video (https://www.youtube.com/watch?v=BtkLFl3vim4). This manual is versioned and updatable as new information becomes available. Similar validations of scientific data used in forensic methods would support the ongoing effort to establish valid and reliable methods and protocols for proficiency testing, training, and certification