Sex Determination of the Atlas in 3 Modern Population Groups VICTORIA SWENSON M.A.
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Sex Determination of the Atlas in 3 Modern Population Groups VICTORIA SWENSON M.A. DEPARTMENT OF ANTHROPOLOGY, THE UNIVERSITY OF MONTANA, MISSOULA, MT Abstract Marino (1997) developed a method for estimating sex from eight measurements of the superior and inferior articular surfaces and vertebral foramen of the atlas from individuals of European and African descent from the Terry and Hamann-Todd collections. This study applies Marino’s method to post-1950s individuals who are self-classified as Hispanic, Caucasian, and, African-American. Eight measurements were taken from the superior and inferior articular surfaces of the atlas and vertebral foramen area as defined by, Marino (1997). The measurements taken from this study were analyzed using Statistical Package for the Social Sciences (SPSS) to establish a discriminant function that distinguishes sex from Caucasians, African Americans, and Hispanics. The cross-validated accuracy of sex determination from the atlas yields the following: African American 89.1%, Caucasian 87.5%, and Hispanic 86.7%. This method concludes that the weight load of the cranium affects the size of the atlas which then results in significant accuracy of sex determination. Introduction Discussion : Measurements LSFL Length of the Left Superior Facet LSFR Length of the Right Superior Facet WSFL Width of the Left Superior Facet WSFR Width of the Right Superior Facet LIFL Length of the Left Inferior Facet LIFR Length of the Right inferior Facet WILF Width of the Left Inferior Facet WIRF Width of the Inferior Right Facet MXDS Maximum distance between Superior Facets MXDI Maximum distance between Inferior Facets LVF Length of the Vertebral Foramen WFV Width of the Vertebral Foramen Results References When unidentified human skeletal remains are found, forensic anthropologists develop a biological profile to determine ancestry, sex, age, and stature. Determining the sex of a skeleton narrows the probability of identification by 50% (Loth and Iscan 2000; and Robinson and Bidmos 2009). Humans, unlike most other nonhuman primates, exhibit little sexual dimorphism, and there are some differences based on two biological differences between males and females: size and architecture (Byers, 2008).The two most important elements for sex determination are the pelvis and the skull (Holland, 1985; and Marino, 1993). However when these bones are not present or are too damaged, other elements are needed for analysis (Holland, 1985; Marino, 1993; Sutherland and Suchey, 1991). “Because the atlas, is in essence, a block under pressure, its articular surfaces-superior and inferior-will possess measureable differences between heavier and lighter loads. It is these differences that allow this bone to be used as a race and sex discriminator” (1993:9). As Marino (1993) states the weight of the skull increases the size of occipital condyles, which in turn will increase the superior facets of the atlas. Marino (1993 and 1997) developed a method for estimating sex from eight measurements of the superior and inferior articular surfaces and vertebral foramen of the atlas from individuals of European and African descent from the Terry and Hamann-Todd collections. Based on observations by Marino (1993) it is logical to hypothesize that there are measureable statistical sex differences in the atlas. Acknowledgemen ts: I sincerely thank my committee chair and advisor, Dr. Randall Skelton. I am extremely thankful for Mr. Eugene Marino for my inspiration and helping me expand his prior research into my thesis topic. I would like to also thank the extreme generosity of Dr. Bruce Anderson from the Pima Co. Coroner’s Office for his advice, guidance, and use of their specimens. I am also grateful for Dr. Dawnie Steadman, from the William Bass Donated Skeletal Collection at the University of Tennessee, and Dr. Heather Edgar from the Maxwell Museum of Anthropology at the University of New Mexico for allowing access to their donated collections. Materials and Methods: The samples for this study are composed of males and females from the William Bass Donated Skeletal Collection, at the University of Tennessee, Knoxville, TN, the Pima County Medical Examiner’s Office, Pima County Arizona, and the Maxwell Museum’s Donated Skeletal Collection, at the University of New Mexico, Albuquerque, NM. The William Bass and Maxwell Museum collections comprise of donated skeletal specimens. Seven of the eight measurements developed and defined by Marino were taken from the right superior and inferior surfaces. The maximum width as measured along the long axis of the anterior fovea (right to left) was substituted for the maximum width of the vertebral foramen. This measurement was substituted because it appeared visually significant. The results from this study suggests that a statistical examination of the first cervical vertebra is useful in sex estimation, and these results are consistent with Marino’s (1993; and 1995) sex estimation of the atlas. The discriminant analysis yields an accuracy of sex determination in the following: African American 89.1%, Caucasian 87.5%, and Hispanic 86.7%. Byers (2008) states that the differences between males and females are size and architecture. The skull used as an indicator of sex is fairly accurate. Byers states “the most basic difference (in the skull), is size and rugosity (2008: 191). Males are larger and are more robust where as females are smaller and more gracile (Byers, 2008). This also holds true with distinguishing between males and females using the atlas. This method suggests that the weight load of the cranium affects the size of the atlas which then results in significant accuracy of sex determination. Thus a male’s cranium is larger than a female’s which will result in larger features of the first cervical vertebrae. This study has been applied to two historic archaeological collections, two modern skeletal collections, and finally a sample of Unidentified Border Crossers at the Pima Co. Medical Examiner’s Office. Both studies have shown that the discriminant analysis can be applied to fragmentary elements as well. However, I like Marino, conclude that “before any reliance is placed on this technique within forensic applications, more work with larger and more geographically and temporally diverse populations should be conducted” (1995:132; and 1997: 1116). Aiello, L. and Dean, C. 1990. An Introduction to Human Evolutionary Anatomy. Academic Press, Harcourt Brace Jovanovich, Publishers Byers, S.N. 2008. Introduction to Forensic Anthropology. Boston: Pearson. Holland, T.D. 1985 Sex Determination by Multiple- Regression Analysis of the cranial base. Unpublished Masters thesis, Department of Anthropology, University of Missouri, Columbia. Loth, SR. and Iscan M.Y. 2000. Sex Determination, in: Encyclopedia of Forensic Sciences, Academic Press, San Diego, CA. 252-260. Marino, E.A. 1993. Sex and Race Estimation Using the First Cervical Vertebra. Unpublished Masters thesis, Department of Anthropology, University of Missouri, Columbia. Marino, E.A. 1997. A Pilot study using the first cervical vertebra as an indicator of race. Journal of forensic sciences; 42(6):1114-1118. Robinson, M.S. and Bidmos, M.A. 2009. The Skull and Humerus in the Determination of Sex: Reliability of discriminant function equations. Forensic Science International ; 186:86 e1-5. Sutherland, L.D. and Suchey J.M. 1991. Use of the Ventral Arc in Pubic Sex Determination. Journal of Forensic Sciences 26(2): 501-511 Classification from stepwise method of the sex discriminant analysis – African Americans Classification from stepwise method of the sex discriminant analysis - Caucasians Classifiction from stepwise method of the sex discriminant anaylsis- Hispanic Classification from stepwise method of the sex discriminant analysis – All three groups Key: - Discriminating Measurement for Sex in African Americans - Discriminating Measurements for Sex in Caucasians - Discriminating Measurements for Sex in Hispanics - Discriminating Measurements for Sex in 10% 5 % 86% Skeletal Collections: N = 214 Pima Co. Medical Examiner's Office Maxwell Museum Skeletal Collection William Bass Skeletal Collection 33% 59% 8% Sex: N = 214 Female Male Unknown
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Sex Determination of the Atlas in 3 Modern Population Groups VICTORIA SWENSON M.A. DEPARTMENT OF ANTHROPOLOGY, THE UNIVERSITY OF MONTANA, MISSOULA, MT. Abstract. - PowerPoint PPT Presentation
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Sex Determination of the Atlas in 3 Modern Population GroupsVICTORIA SWENSON M.A.
DEPARTMENT OF ANTHROPOLOGY, THE UNIVERSITY OF MONTANA, MISSOULA, MT
AbstractMarino (1997) developed a method for estimating sex from eight measurements of the superior and inferior articular surfaces and vertebral foramen of the atlas from individuals of European and African descent from the Terry and Hamann-Todd collections. This study applies Marino’s method to post-1950s individuals who are self-classified as Hispanic, Caucasian, and, African-American. Eight measurements were taken from the superior and inferior articular surfaces of the atlas and vertebral foramen area as defined by, Marino (1997). The measurements taken from this study were analyzed using Statistical Package for the Social Sciences (SPSS) to establish a discriminant function that distinguishes sex from Caucasians, African Americans, and Hispanics. The cross-validated accuracy of sex determination from the atlas yields the following: African American 89.1%, Caucasian 87.5%, and Hispanic 86.7%. This method concludes that the weight load of the cranium affects the size of the atlas which then results in significant accuracy of sex determination.
Introduction Discussion:
Measurements
LSFLLength of the Left
Superior Facet
LSFRLength of the Right
Superior Facet
WSFLWidth of the Left
Superior Facet
WSFRWidth of the Right
Superior Facet
LIFLLength of the Left
Inferior Facet
LIFRLength of the Right
inferior Facet
WILFWidth of the Left
Inferior Facet
WIRFWidth of the Inferior
Right Facet
MXDSMaximum
distance between Superior Facets
MXDIMaximum distance
between Inferior Facets
LVFLength of the
Vertebral Foramen
WFVWidth of the Vertebral
Foramen
Results
References
When unidentified human skeletal remains are found, forensic anthropologists develop a biological profile to determine ancestry, sex, age, and stature. Determining the sex of a skeleton narrows the probability of identification by 50% (Loth and Iscan 2000; and Robinson and Bidmos 2009). Humans, unlike most other nonhuman primates, exhibit little sexual dimorphism, and there are some differences based on two biological differences between males and females: size and architecture (Byers, 2008).The two most important elements for sex determination are the pelvis and the skull (Holland, 1985; and Marino, 1993). However when these bones are not present or are too damaged, other elements are needed for analysis (Holland, 1985; Marino, 1993; Sutherland and Suchey, 1991). “Because the atlas, is in essence, a block under pressure, its articular surfaces-superior and inferior-will possess measureable differences between heavier and lighter loads. It is these differences that allow this bone to be used as a race and sex discriminator” (1993:9). As Marino (1993) states the weight of the skull increases the size of occipital condyles, which in turn will increase the superior facets of the atlas. Marino (1993 and 1997) developed a method for estimating sex from eight measurements of the superior and inferior articular surfaces and vertebral foramen of the atlas from individuals of European and African descent from the Terry and Hamann-Todd collections. Based on observations by Marino (1993) it is logical to hypothesize that there are measureable statistical sex differences in the atlas.
Acknowledgements:I sincerely thank my committee chair and advisor, Dr. Randall Skelton. I am extremely thankful for Mr. Eugene Marino for my inspiration and helping me expand his prior research into my thesis topic. I would like to also thank the extreme generosity of Dr. Bruce Anderson from the Pima Co. Coroner’s Office for his advice, guidance, and use of their specimens. I am also grateful for Dr. Dawnie Steadman, from the William Bass Donated Skeletal Collection at the University of Tennessee, and Dr. Heather Edgar from the Maxwell Museum of Anthropology at the University of New Mexico for allowing access to their donated collections.
Materials and Methods:The samples for this study are composed of males and females from the William Bass Donated Skeletal Collection, at the University of Tennessee, Knoxville, TN, the Pima County Medical Examiner’s Office, Pima County Arizona, and the Maxwell Museum’s Donated Skeletal Collection, at the University of New Mexico, Albuquerque, NM. The William Bass and Maxwell Museum collections comprise of donated skeletal specimens.
Seven of the eight measurements developed and defined by Marino were taken from the right superior and inferior surfaces. The maximum width as measured along the long axis of the anterior fovea (right to left) was substituted for the maximum width of the vertebral foramen. This measurement was substituted because it appeared visually significant.
The results from this study suggests that a statistical examination of the first cervical vertebra is useful in sex estimation, and these results are consistent with Marino’s (1993; and 1995) sex estimation of the atlas. The discriminant analysis yields an accuracy of sex determination in the following: African American 89.1%, Caucasian 87.5%, and Hispanic 86.7%. Byers (2008) states that the differences between males and females are size and architecture. The skull used as an indicator of sex is fairly accurate. Byers states “the most basic difference (in the skull), is size and rugosity (2008: 191). Males are larger and are more robust where as females are smaller and more gracile (Byers, 2008). This also holds true with distinguishing between males and females using the atlas. This method suggests that the weight load of the cranium affects the size of the atlas which then results in significant accuracy of sex determination. Thus a male’s cranium is larger than a female’s which will result in larger features of the first cervical vertebrae.
This study has been applied to two historic archaeological collections, two modern skeletal collections, and finally a sample of Unidentified Border Crossers at the Pima Co. Medical Examiner’s Office. Both studies have shown that the discriminant analysis can be applied to fragmentary elements as well. However, I like Marino, conclude that “before any reliance is placed on this technique within forensic applications, more work with larger and more geographically and temporally diverse populations should be conducted” (1995:132; and 1997: 1116).
Aiello, L. and Dean, C. 1990. An Introduction to Human Evolutionary Anatomy. Academic Press, Harcourt Brace Jovanovich, Publishers
Byers, S.N. 2008. Introduction to Forensic Anthropology. Boston: Pearson.
Holland, T.D. 1985 Sex Determination by Multiple-Regression Analysis of the cranial base. Unpublished Masters thesis, Department of Anthropology, University of Missouri, Columbia.
Loth, SR. and Iscan M.Y. 2000. Sex Determination, in: Encyclopedia of Forensic Sciences, Academic Press, San Diego, CA. 252-260.
Marino, E.A. 1993. Sex and Race Estimation Using the First Cervical Vertebra. Unpublished Masters thesis, Department of Anthropology, University of Missouri, Columbia.
Marino, E.A. 1997. A Pilot study using the first cervical vertebra as an indicator of race. Journal of forensic sciences; 42(6):1114-1118.
Robinson, M.S. and Bidmos, M.A. 2009. The Skull and Humerus in the Determination of Sex: Reliability of discriminant function equations. Forensic Science International; 186:86 e1-5.
Sutherland, L.D. and Suchey J.M. 1991. Use of the Ventral Arc in Pubic Sex Determination. Journal of Forensic Sciences 26(2): 501-511
Classification from stepwise method of the sex discriminant analysis – African Americans
Classification from stepwise method of the sex discriminant analysis - Caucasians
Classifiction from stepwise method of the sex discriminant anaylsis- Hispanic
Classification from stepwise method of the sex discriminant analysis – All three groups
Key: - Discriminating Measurement for Sex in African Americans - Discriminating Measurements for Sex in Caucasians - Discriminating Measurements for Sex in Hispanics - Discriminating Measurements for Sex in All groups
10% 5%
86%
Skeletal Collections: N = 214
Pima Co. Medical Examiner's OfficeMaxwell Museum Skeletal CollectionWilliam Bass Skeletal Collection
33%
59%
8%
Sex: N = 214
FemaleMaleUnknown
