: Historically, when predicting the ancestry of human skeletal remains, forensic anthropologists have not fully considered the variation within human populations, but instead have relied on a ...typological, experience‐based approach. Unfortunately, reliance on observer experience has produced a method that is as much an art as it is a science. This research focuses on the frequency distribution and inter‐trait correlations of 11 common morphoscopic traits to demonstrate that the experience‐based approach to ancestry prediction is indeed an art that is unscientific, because it is unreplicable, unreliable, and invalid. Ten of 11 traits examined had frequency distributions with significant differences (p < 0.001) between groups, but the range in variation of these traits far exceeds previous assumptions. Such within group variation clearly demonstrates that extreme trait expressions are not reliable for estimating ancestry through visual observation alone, but instead that these traits should be analyzed within a statistical framework.
The macromorphoscopic databank Hefner, Joseph T.
American journal of physical anthropology,
August 2018, 2018-08-00, 20180801, Letnik:
166, Številka:
4
Journal Article
Recenzirano
The development of identification standards in forensic anthropology requires large and appropriate reference samples comprising individuals with modern birth years. Recent advances in ...macromorphoscopic trait data collection and analysis have created a need for reference data for classification models and biological distance analyses. The Macromorphoscopic Databank (N ∼ 7,397) serves that function, making publicly available trait scores for a large sample (n = 2,363) of modern American populations and world‐wide groups of various geographic origins (n = 1,790). In addition, the MaMD stores reference data for a large sample (n = 3,244) of pre‐, proto‐ and historic Amerindian data, useful for biodistance studies and finer‐levels of analysis during NAGPRA‐related investigations and repatriations. In developing this database, particular attention was given to the level of classification needed during the estimation of ancestry in a forensic context. To fill the knowledge gap that currently exists in the analysis of these data, the following overview outlines many of the issues and their potential solutions. Developing valuable tools that are useful to other practitioners is the purpose of growing a databank. As the Macromorphoscopic Databank develops through data collection efforts and contributions from the field, its utility as a research and teaching tool will also mature, in turn creating a vital resource for forensic anthropologists for future generations.
Ancestry assessments using cranial morphoscopic traits currently rely on subjective trait lists and observer experience rather than empirical support. The trait list approach, which is untested, ...unverified, and in many respects unrefined, is relied upon because of tradition and subjective experience. Our objective was to examine the utility of frequently cited morphoscopic traits and to explore eleven appropriate and novel methods for classifying an unknown cranium into one of several reference groups. Based on these results, artificial neural networks (aNNs), OSSA, support vector machines, and random forest models showed mean classification accuracies of at least 85%. The aNNs had the highest overall classification rate (87.8%), and random forests show the smallest difference between the highest (90.4%) and lowest (76.5%) classification accuracies. The results of this research demonstrate that morphoscopic traits can be successfully used to assess ancestry without relying only on the experience of the observer.
Ancestry estimation methods using macromorphoscopic (MMS) traits commonly focus exclusively on cranial morphology. The objective of this study was to demonstrate the value of postcranial MMS traits, ...highlighting a combined cranial/postcranial trait approach to ancestry estimation using quadratic discriminant function and a variety of machine learning classification models including artificial neural networks (aNN), random forest models, and support vector machine. Eight cranial and eleven postcranial MMS traits were collected from the Terry and Bass Skeletal Collections (American Black = 81; American White = 173). Our classification models using cranial and postcranial traits correctly classified 88–92% of the sample, improving classification accuracies by nearly fifteen percent over models relying exclusively on cranial data. These same results demonstrate the importance of a multivariate statistical framework incorporating cranial and postcranial data and the nearly unlimited potential of machine learning models to improve the accuracy of ancestry estimates over traditional methods of analysis. To facilitate implementation in casework, one of the more robust models (aNN) is incorporated into a web‐based application, ComboMaMD Analytical, to facilitate cranial and postcranial MMS traits analysis for ancestry estimation.
Objectives
Probit has not been applied to ancestry estimation in forensic anthropology. The goals of this study were to: (1) evaluate the performance of probit analysis as a classification tool for ...ancestry estimation using ordinal data and (2) expand our current understanding of human cranial variation for an understudied population.
Methods
Multivariate probit models were used to classify the ancestral affiliation of Filipino crania using morphoscopic traits. Ancestral reference populations represented Africa, Asia, and Europe in a three‐group model, with the addition of Hispanics in a four‐group model. Posterior probabilities across these groups were interpreted as admixture proportions of an individual. Model performance was also evaluated for individuals with missing data.
Results
The overall correct classification rates for the three‐group and four‐group models were 72.1% and 68.6%, respectively. Filipinos classified as Asian 52.9% of the time using three ancestral reference groups and 48.6% using four groups. A large portion of Filipinos also classified as African. There were no significant differences in classification trends or accuracy rates between complete crania and crania with at least one missing variable.
Conclusions
Multivariate probit models using morphoscopic traits perform well when populations are represented in both training and test samples. Probit can also accommodate individuals with missing data. Classifying Filipinos showed only moderate success. Filipinos are more phenotypically similar to Africans than the other Asian samples used here, but still affiliate most closely as Asian. Ancestry methods would benefit from including Filipinos as a reference sample given the additional variation they provide to the continental category of Asian.
A skeletal assessment of ancestry relies on morphoscopic traits and skeletal measurements. Using a sample of American Black (n = 38), American White (n = 39), and Southwest Hispanics (n = 72), the ...present study investigates whether these data provide similar biological information and combines both data types into a single classification using a random forest model (RFM). Our results indicate that both data types provide similar information concerning the relationships among population groups. Also, by combining both in an RFM, the correct allocation of ancestry for an unknown cranium increases. The distribution of cross‐validated grouped cases correctly classified using discriminant analyses and RFMs ranges between 75.4% (discriminant function analysis, morphoscopic data only) and 89.6% (RFM). Unlike the traditional, experience‐based approach using morphoscopic traits, the inclusion of both data types in a single analysis is a quantifiable approach accounting for more variation within and between groups, reducing misclassification rates, and capturing aspects of cranial shape, size, and morphology.
As the hardest tissue in the body, teeth have the potential to offer a wealth of biological information to the forensic anthropologist, which can include the assessment of ancestry. Using a large ...data set of dental measurements, the efficacy of mesiodistal and buccolingual tooth dimensions to discriminate between broad, geographically based groups is explored. A general pattern is identified: African populations have the largest teeth, Asians possess teeth of intermediate size, and Europeans have the smallest teeth. In a discriminant function analysis using crown measurements of all teeth (mandibular and maxillary and excluding the third molar), individuals were correctly classified in 71.3% of cases. When the sex of the individual is known, classification is improved up to 88.1% in females and 71.9% of males (cross‐validated). Based on these results, we argue that dental metrics can be regularly employed as part of the development of the biological profile.
Dental morphology is becoming increasingly visible in forensic anthropology as part of the estimation of ancestry. As methods are developed based on these data, it is important to understand the role ...of observer error in data collection and method application. In this study, 10 observers collected dental morphological data on 19 traits on the same set of nine plaques. Various measures of interrater reliability were calculated to assess observer error. Data were then input into one of three ancestry estimation methods based on dental morphology to understand the role of observer error in these methods. Results show low rater reliability for all dental morphological traits when all 10 observers are compared. Rater reliability increases when only experienced observers are compared and traits are dichotomized. Further, differences in trait scores by observers resulted in disparate estimations of ancestry in each of the methods. While observer error appears to be an issue in dental morphological methods of ancestry estimation, these problems can be addressed. An argument is made for advanced training in dental anthropology in laboratories and in graduate programs. Further, methods need to test for and employ traits with high rater agreement.
We investigate whether hazards of death from plague and physiological stress at a fourteenth-century plague cemetery (Royal Mint, London) differed between populations using N = 49 adults whose ...affiliation was established using macromorphoscopic traits. Compared to a nonplague cemetery (N = 96), there was a greater proportion of people of estimated African affiliation in the plague burials. Cox proportional hazards analysis revealed higher hazards of death from plague for those with estimated African affiliation. There were higher rates of linear enamel hypoplasia in those with estimated African affiliation, but this finding is not statistically significant. These results provide the first evidence that hazards of plague death were higher for people of estimated African affiliation compared to other affiliations, possibly because of existing inequalities, in addition to migration (free or forced) outcomes. These findings may reflect premodern structural racism’s devastating effects.
Investigamos si los riesgos de la muerte resultando de la peste y estrés fisiológico en un cementerio de la peste del siglo XIV (Royal Mint, Londres) son diferente entre poblaciones de adultos (N = 49) quienes afiliación estuvieron establecido utilizando rasgos macromorfoscópicos. En comparación con un cementerio no asociado con la peste (N = 96), había una proporción más grande de gente estimado tener afiliación africana en los entierros asociados con la peste. Análisis de riesgos proporcional de Cox indicaron que había un riesgo de muerte de la plaga más alto por individuos estimados tener afiliación africana. Había índices más grandes de hipoplasia de esmalte dental en individuos de afiliación africana, pero el nivel estadístico no fue significativo. Los resultados demuestran la primera evidencia que los riesgos de la muerte de la peste fueron más altos por gente de afiliación africana en comparación a otras afinidades, posiblemente como resultado de disparidades sociales en combinación con los efectos de migración (libre o forzada). Los resultados se pueden reflejar las consecuencias devastadoras del racismo estructural premoderno.
Highlights • Cranial macromorphoscopic trait variation is explored in a sample from Colombia. • US-based ancestry assessment methods can classify unknown individuals from Colombia. • Colombian ...phylogeographic social distinctions are not usefully discernible. • Pooled Colombian samples are more useful in the assessment of ancestry at this time. • Artificial neural networks may be useful for ancestry assessment in some cases
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