11 research outputs found
Standardization and quality assurance in skeletal landmark placement and osteometry
Studies revising methodology are essential to the development and standardization of the field of anthropology, especially as the ultimate goal is improved forensic analyses. A series of revisions were made to the Standards for Data Collection Procedures reference manual. This includes changes made to the definitions of several standard measurements ranging from modified landmark placement to variation in the proper orientation of the caliper. The aim of this paper was to compare measurements collected using the different sets of definitions to determine if the measurements would differ significantly. Fifteen measurements were collected from 30 crania and postcrania, first using the original definitions, and then using the modified definitions and/or landmarks. The measurement differences for the 2 sets of definitions were assessed using technical error of measurement and a Kruskal-Wallis test. Results indicate that 8 of the 15 measurements differed significantly when the modified definitions were employed. Therefore, data collected using the different sets of definitions should not be used interchangeably. Forensic practitioners and laboratories making use of the updated reference manual must take into consideration how the current results might influence their standard operating procedures. Furthermore, all databases that currently make use of the original measurements, such as the South African-specific databases used in Fordisc, must be updated to include the modified measurements to stay on par with international data collection standards.http://www.elsevier.com/locate/forsciint2021-03-01hj2020Anatom
Veldt fires in South Africa : implications on osteometry and the biological profile
Presented at the 73rd Annual Scientific Conference of the American Academy of Forensic Sciences, February 15–19,
2021, held virtually.Standard operating procedures for forensic anthropological analyses dictate that thermally
altered remains should not be measured, hindering the creation of a biological
profile. Few studies have addressed estimating biological parameters from burned
remains, with the greatest focus of this research area being on cremated remains.
However, veldt fires are more common than cremation in the South African forensic
context. The aim of this study was to explore the degree of structural changes observed
in domestic pig (Sus scrofa) bones associated with thermal destruction and the potential
impact on the estimation of a biological profile using standard osteometric methods. A
total of 96 pig femora were divided equally into two categories: fresh and dry. Within
each category, equal samples were exposed to different durations of burning, namely,
5, 10, and 20 min. Ten standard femoral anthropological measurements were collected
before and after burning. Technical error of measurement and Wilcoxon signed-rank
tests were used to assess changes in the femoral dimensions before and after burning.
Most measurements were significantly different after burning, with the fresh bones
decreasing in size by up to 7.8% and the dry bones decreasing in size by up to 4.0%. The
magnitude of post-burning
measurement changes for both burn conditions was similar
to, or smaller than has previously been reported for observer measurement errors of
commonly used variables investigated for standard osteometric studies. Veldt fires are
less intense than cremation, thus causing less shrinkage.The National Research Foundation of South Africa.http://wileyonlinelibrary.com/journal/jfoam2024Anatom
Population differences in the postcrania of modern South Africans and the implications for ancestry estimation
The cranium is widely recognized as the most important skeletal element to use when evaluating
population differences and estimating ancestry. However, the cranium is not always intact or available
for analysis, which emphasizes the need for postcranial alternatives. The purpose of this study was to
quantify postcraniometric differences among South Africans that can be used to estimate ancestry.
Thirty-nine standard measurements from 11 postcranial bones were collected from 360 modern black,
white and coloured South Africans; the sex and ancestry distribution were equal. Group differences were
explored with analysis of variance (ANOVA) and Tukey’s honestly significant difference (HSD) test.
Linear and flexible discriminant analysis (LDA and FDA, respectively) were conducted with bone models
as well as numerous multivariate subsets to identify the model and method that yielded the highest
correct classifications. Leave-one-out (LDA) and k-fold (k = 10; FDA) cross-validation with equal priors
were used for all models. ANOVA and Tukey’s HSD results reveal statistically significant differences
between at least two of the three groups for the majority of the variables, with varying degrees of group
overlap. Bone models, which consisted of all measurements per bone, resulted in low accuracies that
ranged from 46% to 63% (LDA) and 41% to 66% (FDA). In contrast, the multivariate subsets, which
consisted of different variable combinations from all elements, achieved accuracies as high as 85% (LDA)
and 87% (FDA). Thus, when using a multivariate approach, the postcranial skeleton can distinguish
among three modern South African groups with high accuracy.National Research Foundation of South Africa (NRF)http://www.elsevier.com/locate/forsciint2016-12-31hb201
Evaluating postcranial macromorphoscopic traits to estimate population variation among modern South Africans
Population overlap and the variation within and among populations have been globally observed but is often difficult to quantify. To achieve this, numerous different methods need to be explored and validated to assist with the creation of an accurate biological profile. The current lack of databases for postcranial macromorphoscopic traits indicates the need to further investigate if the method can be employed repeatably in a forensic context. The current study aimed to assess the prevalence of eleven postcranial macromorphoscopic traits in a South African sample. A total of 271 postcrania of adult black, coloured, and white South Africans were assessed. The intra- and inter-observer agreement ranged from fair to almost perfect except for the accessory transverse foramen of C1, which had poor agreement between observers. Only seven traits differed significantly between at least two of the groups. Univariate and multivariate random forest models were created to test the positive predictive performance of the traits to classify population affinity. The classification accuracies for the univariate models ranged from 33.3% to 53.0% and ranged from 54.6% to 62.1% for the multivariate models. Based on the variable importance, the traits assessing spinous process bifurcation were the most discriminatory variables. The results indicate that the postcranial MMS approach does not outperform current methods employed to estimate population affinity. Further research needs to be done for the method to have practical applicability for medicolegal casework in South Africa.The EU Erasmus+ grant and Bakeng se Afrika.https://www.elsevier.com/locate/forsciinthj2024AnatomyNon
Exploring cranial macromorphoscopic variation and classification accuracy in a South African sample
DATA AVAILABILITY :
The dataset generated/analysed during the current study are available from the corresponding author on reasonable request.To date South African forensic anthropologists are only able to successfully apply a metric approach to estimate population affinity when constructing a biological profile from skeletal remains. While a non-metric, or macromorphoscopic approach exists, limited research has been conducted to explore its use in a South African population. This study aimed to explore 17 cranial macromorphoscopic traits to develop improved methodology for the estimation of population affinity among black, white and coloured South Africans and for the method to be compliant with standards of best practice. The trait frequency distributions revealed substantial group variation and overlap, and not a single trait can be considered characteristic of any one population group. Kruskal-Wallis and Dunn’s tests demonstrated significant population differences for 13 of the 17 traits. Random forest modelling was used to develop classification models to assess the reliability and accuracy of the traits in identifying population affinity. Overall, the model including all traits obtained a classification accuracy of 79% when assessing population affinity, which is comparable to current craniometric methods. The variable importance indicates that all the traits contributed some information to the model, with the inferior nasal margin, nasal bone contour, and nasal aperture shape ranked the most useful for classification. Thus, this study validates the use of macromorphoscopic traits in a South African sample, and the population-specific data from this study can potentially be incorporated into forensic casework and skeletal analyses in South Africa to improve population affinity estimates.Open access funding provided by University of Pretoria.http://link.springer.com/journal/414hj2024AnatomySDG-03:Good heatlh and well-bein
Cranial fluctuating asymmetry and its relationship with non-specific physiological stress indicators in a contemporary South African cadaveric skeletal sample
OBJECTIVES :
Biological anthropologists frequently explore skeletal asymmetry, together with population health and disease. Given the conflicting findings in existing literature, this study aimed to clarify whether an association exists in a South African sample.
MATERIALS :
Dry bone and cranial micro-focus X-ray Computed Tomography (micro-XCT) scans of 115 South African individuals were assessed.
METHODS :
Fluctuating asymmetry (FA) indices were calculated from interlandmark distances, and the frequency of four types of non-specific signs of physiological stress were documented to explore the relationship between FA and disease.
RESULTS :
Black South Africans did not exhibit a high FA index; however, they had the highest prevalence of non-specific signs of physiological stress. However, no significant correlations were detected between FA indices and pathological lesions.
CONCLUSION :
No correlation was observed between FA and populations from different socio-economic backgrounds. However, individuals of lower socio-economic status (SES) demonstrated a greater prevalence of non-specific signs of physiological stress.
SIGNIFICANCE :
This research suggests that skeletal indicators of stress may be a suitable biological marker for assessing differences in SES among population groups, while indicating that levels of cranial FA is an inadequate biological marker.
LIMITATIONS :
Possible limitations may include measurement error, and the lack of information on the life history and medical records of individuals in this sample.
SUGGESTIONS FOR FURTHER RESEARCH :
Future research should include a larger sample with more South African groups, and should evaluate the potential association among age, FA, and expression of skeletal markers of disease.The EU Erasmus+ grant Bakeng se Afrika and the University of Pretoria.https://www.elsevier.com/locate/ijpphj2024AnatomySDG-03:Good heatlh and well-bein
Evaluating the accuracy of cranial indices in ancestry estimation among South African groups
Historically, population differences were quantified using cranial indices. Even though the
application of indices is associated with numerous statistical and methodological problems,
the use of cranial indices to estimate ancestry persists as demonstrated by its inclusion in
several recent papers and conference presentations. The purpose of this study was to classify
207 South African crania and compare the results of five standard cranial indices to linear
discriminant analysis (LDA). New sectioning points were created to contend with low
classification accuracies (40% - 79%) and possible secular trends. Although the accuracies of
the new sectioning points increased (66% - 87%), the accuracies associated with the stepwise
LDA were higher (84%) and could classify the crania into one of the three South African
groups. The results of the study demonstrate that indices cannot compete with multivariate
techniques and should not be used in forensic anthropological analyses for ancestry
estimation.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1556-40292016-09-30hb201
The accuracy of topographical and shape analysis using three-dimensional surface scanning compared to micro-computed tomography
The high number of unidentified bodies recorded in South Africa annually, combined with substantial heterogeneity within the population, necessitates that innovative forensic analysis methods be developed that incorporate variations from South African groups. Although sizeable three-dimensional (3D) scanning modalities exist in osteology and anthropology, developing new advanced methods and techniques involving 3D scanning for real-life forensic applications require that the accessibility, practicality, and, more importantly, accuracy of the methods be taken into consideration. To this end, this study aimed to assess the reliability of 3D surface scanning-based topographical and shape analysis comparison to gold standard micro-focus X-ray computed tomography (micro-XCT) reconstructions for estimating population affinity.
Forty-four adult crania were collected from the Pretoria Bone Collection (PBC), University of Pretoria, South Africa. Two sets of 3D reconstructions were acquired from each cranium, namely micro-XCT scans and 3D surface scans. Three-dimensional reconstructions and landmark datasets were acquired from both scanning modalities and compared using reproducibility testing, geometric discrepancies, and shape analysis.
The minimal geometric discrepancies observed between the reconstructions suggest that both modalities will provide similar shape landmarks datasets and can be used without compromising the accuracy of the analyses at term. The statistical findings showed similar population affinity-related mid-facial shape variations analyzed across both modalities using geometric morphometric methods (GMM).
Incorporating multiple 3D scanning modalities and advanced GMM into the existing biological profile estimation will allow South African forensic anthropologists to analyze shape-related skeletal variation in a more accurate and repeatable way and provide an efficient biological profile in forensic cases.The Bakeng se Afrika grant.https://www.sciencedirect.com/journal/forensic-imaging2024-06-01hj2024AnatomySDG-03:Good heatlh and well-bein
Postcraniometric analysis of ancestry among modern South Africans
The primary role of a physical anthropologist is to provide sufficient information to assist in
the individualisation of unknown skeletal remains. This is often achieved in establishing a
biological profile of the deceased, of which ancestry is an essential aspect. Several successful
osteometric and morphological approaches have been developed to facilitate the estimation of
ancestry from the cranium. However, the cranium is not always available for analysis,
emphasising a need for postcranial alternatives. The postcranial skeleton is frequently
labelled as too variable and unreliable to provide an accurate assessment of ancestry. Yet,
numerous studies utilise the postcrania for sex and stature estimation, where the a priori
knowledge of ancestry results in higher accuracy. Thus, the presence of postcranial
differences among populations when investigating other biological parameters inherently
demonstrates the potential for the estimation of ancestry. The purpose of this study was to
quantify postcranial variation among modern, peer-reported black, white and coloured South
Africans. A series of 39 standard measurements were taken from 11 postcranial bones,
namely the clavicle, scapula, humerus, radius, ulna, sacrum, pelvis, femur, tibia, fibula and
calcaneus. The sample consisted of 360 modern South African individuals (120 black, 120
white, 120 coloured) from the Pretoria Bone and Kirsten Collections housed at the University
of Pretoria and the University of Stellenbosch, respectively. Group differences were explored
with ANOVA and Tukey’s honestly significant difference test (HSD). Group means were
used to create univariate sectioning points for each variable indicated as significant with
ANOVA. Where two of the three groups had similar mean values, the groups were pooled for
the creation of the sectioning points. Multivariate classification models were employed using
linear and flexible discriminant analysis (LDA and FDA, respectively). Classification
accuracies were compared to evaluate which model yielded the best results.
The results demonstrated variable patterns of group overlap. Black and coloured South
Africans displayed similar means for breadth measurements, and black and white South
Africans showed similar means for the maximum length of distal limb elements. The majority
of group variation is attributed to differences in size and robusticity, where white South
Africans are overall larger and more robust than black and coloured South Africans.
Accuracies for the univariate sectioning points ranged from 43% to 87%, with iliac breadth
performing the best. However, the majority of the univariate sectioning points can only
classify individuals into two groups rather than three because of similar group means.
Multivariate bone models created using all measurements per bone resulted in accuracies ranging from 46% to 62% (LDA) and 41% to 66% (FDA). Multivariate subsets consisting of
numerous different measurement combinations from several skeletal elements achieved
accuracies as high as 85% (LDA) and 87% (FDA).
Ultimately the best results were achieved using combinations of different variables
from several skeletal elements. Overall, the multivariate models yielded better results than the
univariate approach, as the inclusion of more variables is generally better for maximising
group differences. Furthermore, FDA achieved higher accuracies than the more traditional
approach of LDA. Despite the significant overlap among the groups, the postcranial skeleton
has proven to be proficient in distinguishing the three groups. Thus, even in a heterogeneous
population, a multivariate postcraniometric approach can be used to estimate ancestry with
high accuracy.Dissertation (MSc)--University of Pretoria, 2015.AnatomyUnrestricte