Table Of ContentQuantification of Maxillary Dental Arcade Curvature with Implications for Estimating
Biological Ancestry in Forensic Anthropology
Honors Research Thesis
Presented in Partial Fulfillment of the Requirements for Graduating with Research Distinction in
Anthropology in the Undergraduate Colleges at The Ohio State University
by:
Melissa A. Clark
The Ohio State University
April 2013
Project Advisors: Professors Debbie Guatelli-Steinberg, Mark Hubbe, and Sam Stout,
Department of Anthropology
Abstract
Previous studies suggest that palate shape can be used as an indicator of biological
ancestry in the identification of modern human remains. These studies, which are based on
qualitative analyses conclude that individuals of African, European, and Indigenous American
ancestry tend to have hyperbolic, parabolic, and elliptical-shaped palates, respectively. The
purposes of the present study were to: (1) evaluate interobserver error in ancestry estimation
using the shapes outlined in previous studies and to (2) explore shape variation in the Gullah
African American and Seminole Indigenous populations using a geometric morphometric
analysis of maxillary dental casts. The first phase of this study consisted of a survey in which ten
graduate students with training in osteology were asked to ascribe biological ancestry to twenty-
nine maxillary dental casts from the Gullah and Seminole samples from the Renee M. Menegaz-
Bock Dental Anthropology Collection. The results show that the palate shape is not an effective
indicator of ancestry in these populations. The mean classification accuracy for the survey was
only 27.9% (p-value= 0.5714), indicating that the likelihood of assigning the correct ancestry to
a given cast using palate shape was not much higher than random assignment. In the second part
of the study, Discriminant Function Analysis correctly classified only 72.2% (n=158) of the
sample. Additionally, there were no significant differences in size or curvature between the two
groups. This study is important for the field of forensic anthropology because it demonstrates, for
the first time, that neither qualitative nor quantitative characterization of palate shape is a reliable
means for assessing ancestry.
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Acknowledgements
The author would first like to thank Dr. Debbie Guatelli-Steinberg for her patience,
assistance, availability, and endless enthusiasm. The author would also like to thank Dr. Mark
Hubbe for his statistical expertise, patient instruction, and for the use of the three-dimensional
scanner. She would also like to thank Dr. Sam Stout for his support and suggestions. The author
would like to thank Dr. Debbie Guatelli-Steinberg, Dr. Clark Larsen, and Josh Sadvari for
allowing her access to the Bioarchaeology Laboratory and Renee M. Menegaz-Bock Dental
Anthropology Collection. She would also like to thank Dr. Bart Snapp, Dr. Debbie Guatelli-
Steinberg, Dr. Mark Hubbe, and Dr. Sam Stout for serving on her defense committee. Finally,
she would like to thank Jillian Linn for her assistance and Dr. Jules Angel and Dr. Amelia
Hubbard for their advice and support.
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Table of Contents
Abstract................................................................................................................................2
Acknowledgements..............................................................................................................3
Introduction
Introduction to Forensic Anthropology...................................................................5
History of Forensic Anthropology..........................................................................5
Attribution of Ancestry in Forensic Anthropology.................................................6
Evidentiary Standards and Rationale......................................................................7
Background
Palate Shape and Ancestry Estimation...................................................................11
Geometric Morphometrics.....................................................................................12
Materials.............................................................................................................................13
Methods..............................................................................................................................15
Principal Components Analysis.............................................................................18
Discriminant Function Analysis............................................................................19
Results...............................................................................................................................21
Discussion and Conclusion...............................................................................................29
Appendix I........................................................................................................................31
Appendix II......................................................................................................................33
Appendix III....................................................................................................................37
Appendix IV....................................................................................................................41
Literature Cited................................................................................................................70
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Introduction
Introduction to Forensic Anthropology
Forensic anthropologists make use of methods derived from the fields of archaeology,
osteology, and pathology in the recovery, identification and analysis of human remains (Sapse
and Kobilinsky 2012). In addition, forensic anthropologists are concerned with understanding
probable pre- and postmortem events (Sapse and Kobilinsky 2012). In essence, forensic
anthropologists apply skeletal biology to a medico-legal context. Law enforcement agencies,
coroners, medical examiners, and forensic pathologists may call upon forensic anthropologists
(Steadman 2003) to assist in the recovery and identification of human remains from crime
scenes, mass disasters (Ousley et al. 2009) such as the Oklahoma City bombing and the
September 11th terrorist attacks, and investigations of human rights violations such as those that
took place in Argentina, Rwanda, and the former Yugoslavia (Steadman 2003).
History of Forensic Anthropology
The first time forensic anthropology was used in a criminal investigation was during the
1849 Parkman murder investigation. Anatomists reconstructed the skeleton of the victim and
used the bones to construct a biological profile and identify the decedent. After the conclusion of
WWII, forensic anthropologists were needed to identify and repatriate remains for soldiers killed
in action. To meet this demand, the Central Identification Laboratory in Hawaii (CILHI) was
founded. Despite this, forensic anthropology was not formally recognized as a profession until
1972 when the Physical Anthropology Section was added to the American Academy of Forensic
Sciences (AAFS). Following this addition, the American Board of Forensic Anthropology
(ABFA) was created in 1977 to ensure a standardized level of competence within the profession.
Since then, data have been collected to maintain, revise, and update methods (Byers 2010).
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Attribution of Ancestry in Forensic Anthropology
Forensic anthropologists construct biological profiles to aid in the identification of human
remains. A biological profile consists of sex, ancestry, age, and stature estimations, as well as
individualizing characteristics (e.g., trauma and pathological conditions) (Ousley et al. 2009).
Biological profiles are used to compare unidentified human remains to missing persons reports to
narrow the pool of probable identifications (Konigsberg 2009). Forensic anthropologists are
often criticized by the anthropological community for including ancestry in biological profiles
because it is frequently associated with non-biological race, and, until recently, anthropologists
were using the terms “race” and “ancestry” interchangeably. Race describes an individual as
member of a socially constructed group, and ancestry describes biological human variation that
results from different population origins and histories (Steadman 2003). While “ancestry” is
quickly replacing “race,” it is important to recognize that in order to work effectively with law
enforcement, forensic anthropologists need to orient information in the contemporary cultural
context. Because “race” is still used in the vernacular, it would be inappropriate to use the term
“ancestry” in a missing persons report because doing so may decrease the likelihood of people
coming forward to make a positive identification as “ancestry” may not be a term well-
recognized among potential informants. Furthermore, ancestry and race are largely congruent
(Steadman 2003). It is therefore necessary to adopt, to an extent, the cultural conventions when
assisting in the identification of human remains (Konigsberg 2009).
As a result of genetic changes and microevolution, there are a number of traits that may
be used to estimate ancestry. These include cranial suture patterns (i.e. simple or complex), the
nasal profile (i.e. convex, concave, and/or straight), facial and alveolar prognathism, the angle of
the zygomaxillary suture, the shape of the palatine suture, and the shape of the orbits, mastoid
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process, and mandible (Gill 1998), as well as the shape of the cranial vault and the presence or
absence of Wormian bones (Steadman 2003). Such differences suggest that it is appropriate to
conduct studies that analyze variation to maximize the chances of positive identification in
forensic applications.
One traditional trait used to estimate ancestry is palate shape. Gill (1986) found that
palate shape could be used as an indicator of biological ancestry in the identification of modern
human remains. Qualitative analyses suggest that individuals of African ancestry tend to have a
hyperbolic (i.e. widely arched) palate shape, individuals of European ancestry tend to have a
parabolic (i.e. a medium) palate shape, and people of Indigenous American ancestry tend to have
an elliptical (i.e. narrowly arched) palate shape (Figure 1) (Gill 1986, 1998).
Evidentiary Standards and Rationale
While qualitative analyses provide good foundations for future studies, they are not
sufficient for forensic applications because forensic anthropologists may be required to give legal
testimony as expert witnesses. An expert witness is one who has more knowledge of a particular
subject than the average person and provides testimonial evidence under oath (Meier 1971). The
admissibility of scientific testimonial evidence is determined by several United States Supreme
Court rulings including Frye v. United States (1923), The Federal Rules of Evidence (1975),
Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), and Kumho Tire Company Ltd. v.
Carmichael (1999) (Palmer 2004).
One of the earliest standards for scientific testimonial evidence was the result of Frye v.
United States (1923). A criminal defendant who had been convicted of second-degree murder
appealed his conviction on the grounds that results of a lie detector test presented in the original
trial had been inadmissible because they had not met contemporary standards for expert witness
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testimony. The Supreme Court ruled that “...while courts will go a long way in admitting expert
testimony deduced from a well-recognized scientific principle or discovery, the thing from which
the deduction is made must be sufficiently established to have gained general acceptance in the
particular field to which it belongs” (D.C. Circuit 1923 in Palmer 2004). The conviction was
overturned, and Frye set the precedent of general acceptance by the scientific community for
techniques and methods used in expert witness testimony (National Academy of Sciences 2009).
The next important development in standards for scientific evidence was the adoption of
Rule 702 in The Federal Rules of Evidence in 1975 (Sapse and Kobilinsky 2012). The initial
wording of Rule 702 appeared to allow relevant evidence in expert witness testimony, regardless
of its acceptance within the scientific community, thus making it seem as though it conflicted
with the ruling in Frye v. United States (1923). This apparent opposition would later affect the
ruling in Daubert v. Merrell Dow Pharmaceuticals (1993) (National Academy of Sciences
2009).
In Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), the plaintiffs argued that the
drug Benedictin had caused birth defects when administered to pregnant women. The defendant
argued that the studies introduced as evidence by the plaintiffs were inadmissible because while
relevant, they did not meet Frye’s requirement for general acceptance. The judge ruled that the
admissibility and reliability of scientific evidence was to be determined by the judge rather than
the scientific community, thus weakening the influence of the Frye standard (Palmer 2004).
Furthermore, the judge clarified that Rule 702 superseded Frye and required scientific evidence
to be both relevant and reliable, thus establishing a standard of evidentiary reliability (National
Academy of Sciences 2009). When determining the admissibility of scientific evidence,
presiding judge Justice Blackmun noted that several factors need to be considered. First, judges
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should consider whether or not a technique or theory on which the evidence is based is generally
accepted within the scientific community and whether or not it had been subjected to publication
or peer review. Second, judges should consider whether or not the theory or technique in
question has a standard rate of error and whether or not a given technique has been standardized.
Finally, the judge ruled that in order for judges to allow scientific testimony, the theory or
technique on which it is based must be testable (Palmer 2004).
The decisions in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) and Rule 702
were reaffirmed by the ruling in Kumho Tire Company Ltd. v. Carmichael (1999) (National
Academy of Sciences 2009). The plaintiffs claimed that tires defective in manufacture and
design had caused a number of injury-accidents. The plaintiffs called an expert witness, whose
testimony was ruled to be inadmissible in the Eleventh Circuit Court of Appeals because the
testimony did not meet the criteria set forth by Daubert (Palmer 2004).
Daubert remains the standard for evidence admissibility in the United States federal
jurisdictions, but states are permitted to use the evidentiary standard of their choice for their
independent jurisdictions (National Academy of Sciences 2009). Arkansas, Colorado, Delaware,
Hawaii, Kentucky, Louisiana, Massachusetts, Montana, Nebraska, North Carolina, Oklahoma,
Oregon, Rhode Island, South Dakota, Tennessee, Texas, Vermont, West Virginia, and Wyoming
all follow Daubert, while Alabama, Arizona, California, Florida, Illinois, Kansas, Maryland,
Michigan, Minnesota, Missouri, New Jersey, New York, Pennsylvania, and Washington all
follow Frye. The remaining states apply various other standards (Palmer 2004). Given the above
evidentiary standards and the weight of forensic science in the courtroom, it is necessary that the
reliability of forensic science be maintained. Because of the adversarial nature of the judicial
system and because of the heavy caseloads of lawyers and judges, the scientific community
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needs to continue to ensure the accuracy, reliability, and validity of forensic methods. The
National Academy of Sciences makes several recommendations to maintain the admissibility of
forensic testimony. First, it suggests that studies measuring the accuracy and reliability of
forensic methods do so quantitatively and that these studies be peer reviewed through journal
publications. It is also recommended that studies assessing “human observer bias and sources of
human error in forensic examinations” be encouraged (National Academy of Sciences 2009).
In the first phase of the present study a qualitative method for inferring ancestry that is
currently used in the identification of human remains is tested for its reliability. Participants
experienced in osteology were asked to ascribe biological ancestry to dental casts in the sample
based on Gill’s (1986) criteria. This phase assesses the accuracy of a current qualitative method
by documenting interobserver error. In the second phase of the present study, geometric
morphometric analysis of shape variation in two population samples is explored as a potential
quantitative method for assigning ancestry. The purpose of this second phase is to determine if a
quantitative method, i.e., one that does not rely on subjective assessments of shape, provides a
more accurate means of assigning ancestry than does Gill’s (1986) classification scheme. Both
phases make use of maxillary dental casts from the Renee M. Menegaz-Bock Dental
Anthropology Collection at The Ohio State University. Evaluation of these qualitative and
quantitative methods contributes to our understanding of modern human variation and ensures
that anthropological methods continue to meet the legal standards set forth by Frye v. United
States (1923) (Moenssens 1993), Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) (Page et
al. 2011), and Kumho Tire Company Ltd. v. Carmichael (1999) (Palmer 2004).
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Description:sample. Additionally, there were no significant differences in size or curvature .. According to Hatcher “a principal component can be defined as a.
