No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Ancestry Estimation in Asian and Asian- Derived Populations Using Dental Morphology
Abstract
The use of dental morphology to estimate ancestry has become more prevalent within forensic anthropology, and several new methods have been published (e.g., Edgar 2005, 2013; Irish 2015; Scott et al. 2018). While these methods represent great advances,
they are lacking in modern Asian reference samples. As such, they may be unable to adequately differentiate Asian individuals from those who express similar dental morphology (i.e., Hispanics and Native Americans). This study explores dental morphological population variation of various skeletal samples in an effort to suggest areas of improvement for methods of ancestry estimation.
Biological distance analyses were conducted on dental morphological data from a Mexican skeletal collection housed at the Universidad Nacional Autónoma de México in Mexico City (n = 88), Hispanic dental casts housed at the University of New Mexico in Albuquerque (n = 71), a Japanese skeletal sample at Chiba University in Chiba, Japan (n = 96), and a comparative global data set collected by T. Hanihara. Clear patterns emerge that align with the Sinodont/Sundadont dental variation, where Native American samples cluster with East Asian samples (Sinodont) and Southeast Asian groups cluster with Melanesia, Papua New Guinea, and Australia (Sundadont). The two Hispanic samples are found to be distinct from these Asian samples and cluster with Macro-European
and West African samples. These results highlight the complexity of Asian and Asian-derived populations and underscore the need for appropriate references samples
in method creation.
ResearchGate has not been able to resolve any citations for this publication.
The use of crown and root morphology to estimate population relationships has a long history in dental anthropology. Over the past two decades, methods employing dental morphology within forensic anthropology have been formalized with the incorporation of statistical models. This paper presents a new web-based application (rASUDAS) that estimates the ancestry of unknown individuals based on their suite of tooth crown and root traits. The application utilizes 21 independent traits that were scored following the Arizona State University Dental Anthropology System (ASUDAS). The reference sample represents approximately 30,000 individuals from seven biogeographic regions. A naive Bayes classifier algorithm was created in the R open source programming language to assign posterior probabilities for individual group assignment. To test the application, 150 individuals were selected from the C. G. Turner II database with the proviso that an individual had to be scored for a minimum of 12 of the 21 traits. In a seven-group analysis, the model correctly assigned individuals to groups 51.8% of the time. In a four-group analysis, classification accuracy improved to 66.7%. With three groups, accuracy was at 72.7%. It is still necessary to validate the program using forensic cases and to augment the reference sample with modern skeletal data. However, results from the beta version of rASUDAS are presented as proof of concept on the potential of dental morphology in ancestry estimation in forensic contexts.
The mean measure of divergence is a dissimilarity measure between groups of individuals described by dichotomous variables. It is well suited to datasets with many missing values, and it is generally used to compute distance matrices and represent phenograms. Although often used in biological anthropology and archaeozoology, this method suffers from a lack of implementation in common statistical software. A package for the R statistical software, AnthropMMD, is presented here. Offering a dynamic graphical user interface, it is the first one dedicated to Smith's mean measure of divergence. The package also provides facilities for graphical representations and the crucial step of trait selection, so that the entire analysis can be performed through the graphical user interface. Its use is demonstrated using an artificial dataset, and the impact of trait selection is discussed. Finally, AnthropMMD is compared to three other free tools available for calculating the mean measure of divergence, and is proven to be consistent with them.
The Mean Measure of Divergence (MMD) is a formula that converts a battery of trait frequencies into a numerical value such that the more dissimilar two samples are, the greater the value. This measure of phenetic distance was developed by the statistician Cedric A. B. Smith and has become popular among dental anthropologists and osteologists for estimating the dissimilarity among groups in order to help reconstruct populations’ movements and structure over time and space. The purpose of the present study is to present the correct formulae and procedures for the MMD given that (1) numerous errors have entered into the literature concerning the formulae themselves, (2) improvements have been described that should be incorporated, and (3) various misunderstandings and misinterpretations have developed that need clarification.
The kappa statistic is frequently used to test interrater reliability. The importance of rater reliability lies in the fact that it represents the extent to which the data collected in the study are correct representations of the variables measured. Measurement of the extent to which data collectors (raters) assign the same score to the same variable is called interrater reliability. While there have been a variety of methods to measure interrater reliability, traditionally it was measured as percent agreement, calculated as the number of agreement scores divided by the total number of scores. In 1960, Jacob Cohen critiqued use of percent agreement due to its inability to account for chance agreement. He introduced the Cohen's kappa, developed to account for the possibility that raters actually guess on at least some variables due to uncertainty. Like most correlation statistics, the kappa can range from -1 to +1. While the kappa is one of the most commonly used statistics to test interrater reliability, it has limitations. Judgments about what level of kappa should be acceptable for health research are questioned. Cohen's suggested interpretation may be too lenient for health related studies because it implies that a score as low as 0.41 might be acceptable. Kappa and percent agreement are compared, and levels for both kappa and percent agreement that should be demanded in healthcare studies are suggested.
Health and socioeconomic disparities tend to be experienced along racial and ethnic lines, but investigators are not sure how individuals are assigned to groups, or how consistent this process is. To address these issues, 1,919 orthodontic patient records were examined by at least two observers who estimated each individual's race and the characteristics that influenced each estimate. Agreement regarding race is high for African and European Americans, but not as high for Asian, Hispanic, and Native Americans. The indicator observers most often agreed upon as important in estimating group membership is name, especially for Asian and Hispanic Americans. The observers, who were almost all European American, most often agreed that skin color is an important indicator of race only when they also agreed the subject was European American. This suggests that in a diverse community, light skin color is associated with a particular group, while a range of darker shades can be associated with members of any other group. This research supports comparable studies showing that race estimations in medical records are likely reliable for African and European Americans, but are less so for other groups. Further, these results show that skin color is not consistently the primary indicator of an individual's race, but that other characteristics such as facial features add significant information.
A newly defined nonmetrical tooth crown characteristic, the distal accessory ridge of the upper and lower canines, is described and classified on a six grade scale. An analysis of seven Southwest U.S. Indian and two American white samples shows that this crown trait is sexually dimorphic in terms of frequency and degree of expression. A significant degree of association between the ridge on the upper and lower canines was found in seven of eight samples. Although there are only limited population data available, frequencies for the lower canine distal accessory ridge are significantly higher in Southwest Indians (53.9%) than in American whites (22.04%) or Asiatic Indians (23.0%).
Two common ideas promulgated in the literature on dental morphology are that (1) shovel-shaped incisors characterize Asiatic populations, and (2) Carabelli's trait characterizes European populations. While there is extensive support for the first idea, the latter notion is not as unequivocal as generally presented. Observations on Carabelli's trait in 1,943 individuals from 10 samples show that European groups have the highest trait frequencies, but they are closely approximated by African samples. If there is a dichotomy in Carabelli's trait variation, it is between Asiatic and Asiatic-derived groups with low trait frequencies (25-60%) and European and African populations with high trait frequencies (70-90%). Asiatic Indians fall between these two groupings and American Indians are somewhat exceptional in showing high trait frequencies but few pronounced forms of trait expression.
This guide to scoring crown and root traits in human dentitions substantially builds on a seminal 1991 work by Turner, Nichol, and Scott. It provides detailed descriptions and multiple illustrations of each crown and root trait to help guide researchers to make consistent observations on trait expression, greatly reducing observer error. The book also reflects exciting new developments driven by technology that have significant ramifications for dental anthropology, particularly the recent development of a web-based application that computes the probability that an individual belongs to a particular genogeographic grouping based on combinations of crown and root traits; as such, the utility of these variables is expanded to forensic anthropology. This book is ideal for researchers and graduate students in the fields of dental, physical, and forensic anthropology and will serve as a methodological guide for many years to come.
This study evaluates population variation of eight cranial morphoscopic traits using samples of known southwest Hispanics (n = 72), Guatemalans (n = 106), American Blacks (n = 146), and American Whites (n = 218). We applied the support vector machine (SVM) method to build a prediction model based on a subsample (20%) of the data; the remainder of the data was used as a test sample. The SVM approach effectively differentiated between the four groups with correct classification rates between 72% (Guatemalan group) and 94% (American Black group). However, when the Guatemalan and southwest Hispanic samples were pooled, the same model correctly classified all groups with a higher degree of accuracy (American Black = 96%; American White = 77%; and the pooled Hispanic sample = 91%). This study also identified significant differences between the two Hispanic groups in six of the eight traits using univariate statistical tests. These results speak to the unique population histories of these samples and the current use of the term "Hispanic" within forensic anthropology. Finally, we argue that the SVM can be used as a classification model for ancestry estimation in a forensic context and as a diagnostic tool may broaden the application of morphoscopic trait data for the assessment of ancestry.
© 2015 American Academy of Forensic Sciences.
The use of dental morphological characteristics to estimate the ancestry of skeletal remains commonly includes few traits, combines dental traits with other skeletal characteristics, and is nonstatistical. Here, discriminant function equations for estimating whether an unknown person was African American or European American, or Hispanic American are presented. Equations were developed from observations of 29 dental traits in 509 individuals. These equations were then applied to the original sample and a test sample (n = 40). Correct assignment rates for estimating African or European American versus Hispanic American range from 66.7 to 89.3%. Correct assignment of African Americans versus European Americans is 71.4 to 100%. Correct geographic assignment of Hispanics from South Florida or New Mexico range from 46.2 to 72.7%. Various discriminant equations using combinations of characteristics are provided. Coupled with the error estimates, these equations offer an important step in the use of dental morphology in contemporary, post-Daubert forensic science.
The ancestory of Koller's subline of the C57BL strain is not known. A study of the minor skeletal variants in this subHne showed that it differs from the other ten sublines of C57BL more than they difier from each other. It appears to have separated from. the rest before the genotypes of the sublines had been fixed by inbreeding. There is enough evidence to show that it is indeed a branch of C57BL strain.
The rate of divergence of the sublines of C57BL is surprisingly high. It is reconsidered whether the whole of this divergence can be explained by recent mutations or whether residual heterozygosis has also played a part in it.
The eight diagnostic morphological traits of the Sundadont and Sinodont divisions of the Mongoloid dental complex are identified. Intra-and intergroup variation for these crown and root features is plotted. The univariate frequency distributions provide useful evidence for several suggestions about East Asian prehistory, dental microevolution, and intergroup relationships. The case for local evolution of Sundadonty is strengthened by finding Australian teeth to be very similar to this pattern. Australian Aboriginal teeth are also generally like those of Jomonese and some Ainus, suggesting that members of the late Pleistocene Sundaland population could have initially colonized Sahulland as well as the continental shelf of East Asia northward to Hokkaido.
The term "Hispanic" groups people from Central and South America and the Caribbean, combining disparate cultures, languages, and ancestry, and masking biological differences. Historical and current admixture patterns within these populations and with indigenous and European-, African-, and/or Asian- derived populations complicate the biological picture. Although "Hispanic" has little biological meaning, it is used widely in epidemiology, disease management, and forensics as a biologically significant group. An interdisciplinary approach combining historical, cultural, and biological data can characterize regional and temporal differences between Hispanic populations. We examined biological distances with a population of central New Mexico Hispanics, as a case study of the local specificity of population history. We collected dental morphological trait frequencies from samples of recent Albuquerque-area Hispanic Americans and several ancestral and contemporary groups. To explore regional admixture patterns we calculated biological distances using the modified Mahalanobis D(2) statistic. Our results indicate that Albuquerque Hispanics are more similar to their European and African ancestral groups than to Native Americans in New Mexico. Additionally, their affinity to Native Americans is greater with prehistoric rather than contemporary samples. We argue that these results reflect a local rather than pan-Hispanic admixture pattern; they underscore that populations are better understood at the local and regional levels. It is undesirable to make sweeping biological generalizations for groups known to be geographically and genetically disparate. This research is part of a growing trend in biological research concerning Hispanics and other groups-an emphasis on local samples, informed by historical, cultural, and biological factors.
The effect of gene flow on Hispanic populations from different geographic regions of the United States was analyzed using six autosomal DNA markers (LDLR, GYPA, HBGG, D7S8, GC, and HLA-DQA). By region of sampling, the Hispanic populations showed different ancestry contributions, from a trihybrid structure with European, Native American, and African contributions (California, Nevada, Florida, New Jersey, and Virginia) to a dihybrid structure with European and American contributions (Southwest population) or European and African contributions (Pennsylvania and Southeast population). These findings allowed us to define two regional groups, the West and the East. In the former, Native American contributions ranged from 35.58% to 57.87%; in the East region the values ranged from 0% to 21.27%. An African influence was similar in both regions, ranging from 0% to 17.11%, with a tendency of increasing in the East region. These data reflect the different origins of the Hispanic populations that led to the present ones. In the West, Hispanics are mostly of Mexican origin, and in the East, they are predominantly of Cuban and Puerto Rican origin.
Historically, forensic anthropology has concentrated on race determination using skeletal morphological variation. Conversely, dental anthropology has been concerned with worldwide patterns of dental morphological variation. This paper represents a synthesis of the goals of forensic anthropology with the methods of dental anthropology. Dentitions of modem African Americans (n = 110) and European Americans (n = 155) were observed using methods based on the Arizona State University dental morphology standards. Of 136 characters observed, eight were found with frequencies that were very different between the groups. Based on these eight characteristics, probability tables were created for determining an individual's social race, using both Bayesian prediction and logistic regression. These tables are applicable for determining the probability that an unknown individual can be categorized as African American or European American. This method was tested on 40 individuals known to belong in one of these two ancestral groups. Correct assignment of race was made in 90% of cases.
The patterns of inter- and intra-regional variation among 12 major geographical groups from around the world were investigated based on 15 nonmetric dental traits. The R-matrix method was applied using a pooled within-group variance-covariance matrix estimated with the maximum likelihood method (tetrachoric correlation matrix) and the threshold value for each trait estimated by univariate probit analysis. Using average heritability rates that range from 0.40 to 1.00, the inter-regional variation represented by Fst falls between 7.19% and 16.23% of the total variance. This range of variation is compatible with those obtained by genetic, craniometric, and odontometric data. Subsaharan Africans show the largest intra-regional diversity among the groups compared. The degree of intra-regional variation shows, moreover, rough clinalities from subsaharan Africa to peripheral regions. The relationship between regional variation and geographic distance from subsaharan Africa supports serial bottlenecks and the founder effect of ancient populations originating in Africa. The variation of East/Northeast Asians is relatively large, suggesting a complex population history such as possible earlier divergence and multiple migrations from outside sources. The present findings are in agreement with both the recent African model for the origin of anatomically modern humans and the current scenario for human migration history suggested by genetic analyses.
Due to the increasing number of Southwest Hispanics in the United States, as well as the overwhelming number of foreign nationals that die every year trying to enter the United States along the southern United States border with Mexico, new methods for classifying individuals have been established at the Pima County Office of the Medical Examiner in Tucson, Arizona (PCOME). For each of the past 5 years, the PCOME has investigated a record number of deaths associated with these border crossings. The overwhelming majority of the identified decedents are Mexican Nationals. However, approximately 25% of these undocumented border crossers have yet to be identified, making it clear that improved methods for human identification are greatly needed. The first goal of this paper is to delineate the suite of skeletal nonmetric traits utilized in assessing Southwest Hispanic ancestry at the PCOME. This suite of nonmetric traits has proven to be an effective component in establishing the "biological profile" of unknown individuals in these cases. The second goal of this paper is to introduce methods used at the PCOME to establish the "cultural profile" of individuals in these cases. The "cultural profile" is a set of identification criteria that include: the geographic context of recovery, personal effects, dental health, and cultural accoutrements. Establishing the "cultural profile" in these cases is essential in identifying individuals as foreign nationals who have died trying to cross the border.
Non-Metric and Metric Dental Assessment of Ancestry in Contemporary Mexican Individuals: An Aid to Identifying Undocumented Border Crossers
- R George
George R. Non-Metric and Metric Dental Assessment of Ancestry
in Contemporary Mexican Individuals: An Aid to Identifying
Undocumented Border Crossers [MA thesis]. Chico: California State University; 2015.
Human Dental Development, Morphology, and Pathology: A Tribute to Albert A. Dahlberg. Anthropological Papers No. 54
- T Hanihara
Hanihara T. Metric and nonmetric dental variations of major human
populations. In: Lukacs JR, ed. Human Dental Development,
Morphology, and Pathology: A Tribute to Albert A. Dahlberg.
Anthropological Papers No. 54. Eugene: University of Oregon
Press; 1998:173-200.
Overview of race and Hispanic origin
- K R Humes
- N A Jones
- R R Ramirez
Humes KR, Jones NA, Ramirez RR. Overview of race and Hispanic origin: 2010. 2010 Census Briefs. Washington, DC:
U.S. Department of Commerce, U.S. Census Bureau; 2011.
Dental nonmetric variation around the world: Using key traits in populations to estimate ancestry in individuals
- J D Irish
Irish JD. Dental nonmetric variation around the world: Using key
traits in populations to estimate ancestry in individuals. In:
Berg GE, Ta'ala SC, eds. Biological Affinity in Forensic Identification of Human Skeletal Remains: Beyond Black and
White. Boca Raton, FL: CRC Press; 2015:165-190.
Skeletal Attribution of Race: Methods for Forensic Anthropology. Maxwell Museum of Anthropological Papers No
- S Rhine
Rhine S. Non-metric skull racing. In: Gill GW, Rhine S, eds. Skeletal Attribution of Race: Methods for Forensic Anthropology.
Maxwell Museum of Anthropological Papers No. 4. Albuquerque: University of New Mexico; 1990:9-20.
Biological Distance Analysis: Forensic and Bio archaeol o gi cal Perspectives
- G R Scott
- R Schomberg
Scott GR, Schomberg R. A baffling convergence: Tooth crown and
root traits in Europe and New Guinea. In: Pilloud MA, Hefner
JT, eds. Biological Distance Analysis: Forensic and Bio archaeol o gi cal Perspectives. San Diego: Elsevier; 2016: 411-424.