Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Anthropology

Major Professor

Erin H. Kimmerele, Ph.D.

Committee Member

Heide Castañeda, Ph.D.

Committee Member

Robert H. Tykot, Ph.D.

Committee Member

George D. Kamenov, Ph.D.

Committee Member

Zachary Atlas, Ph.D.

Keywords

ecological anthropology, migration, radiogenic isotopes, Stable Isotopes, trace elements and REE

Abstract

The biochemistry of human tissues can provide information for geoprofiling (geographic birthplace or migration patterns) of an unidentified decedent. Utilizing isotope analyses (both stable and radiogenic) from teeth, bone, nails, and/or hair reveals specific isotopic information that correlates to diverse geographic regions reflecting an individual’s birthplace and migration patterns. Isotope analysis of enamel and bone has been employed in bioarchaeology for decades to reconstruct the diet, health, and migration patterns of past populations. Isotope ratios measured from enamel can then be compared to isotope ratios measured from bone of the individual to track patterns of migration. The enamel from the first adult molar elucidates the isotope ratios from birth to approximately three and half years of age, while the isotope ratios of specific bones will elucidate the geographic residency location for approximately the last 10 to 20 years of the decedent. After the enamel on the tooth crown has completely developed, it will no longer remodel or self-repair, and the geochemical isotope signature is locked into the enamel tissue. Living in one location for 10 to 20 years constitutes as an extended period, because previous research has documented amount of time for certain bones to completely remodel depends on the morphology and composition (trabecular vs. compact bone). If an individual lived in one geographic location for an extended period during their childhood, then moved to a distinctively different geographic location and lived in that second location for 10 to 20 years, that amount of time should allow for the bone to remodel and turnover with the geochemical signature of the more current location.

However, the application of isotope analysis is a relatively new investigative tool when applied to the identification of unidentified decedents in the medicolegal system in cases where the decedent has been discovered as a non-local resident or an immigrant, assisting authorities to contact an international consultant or other agencies to facilitate identifying the decedent. Multiple isotopic systems are measured and collected to georeference an unidentified decedent. Standard protocol for the USF-Florida Institute of Forensic Anthropology and Applied Science (IFAAS) and the University of Florida Geological Sciences (UFGS) utilize specific radiogenic isotopes that include strontium (87/86Sr) and lead isotopes (206/204Pb, 207/204Pb, 208/204Pb), along with stable isotopes oxygen (δ18 O) and carbon (δ13C) for current and cold casework. Isotope analysis has been utilized for geoprofiling to aid in the identification of unidentified decedents in Florida, which has assisted the numerous medicolegal agencies. Multiple data points from individual teeth, including stable isotopes (δ18O, δ13C), and radiogenic isotopic data (87/86Sr, 206/204Pb, 207/204Pb, 208/204Pb) are utilized to cultivate a more complete georeferencing guide. There were 70 individuals who donated their teeth for this research, primarily from the USA but a fair number of individuals were international. The aim of this research is to identify the baseline isotope ranges for Florida residents to assist with geoprofiling unidentified decedents discovered in Florida. The isotope results from this research will support the following hypotheses: H0: The 87/86Sr ratios for individuals born and raised in Florida for an extended period (20+ years) will not exhibit statistically significant values compared to other residents living in the USA or people from other regions of the world. H1: The predicted 87/86Sr ratios for individuals born and raised in Florida for an extended period (20+ years) will exhibit values approximately 0.70700 to 0.70800. H0: The 206/204Pb, 207/204Pb, 208/204Pb ratios for individuals born and raised in Florida for an extended period (20+ years) will not exhibit statistically significant values compared to other residents living in the USA or people from other regions of the world. H2: The predicted 206/204Pb, 207/204Pb, 208/204Pb ratios for individuals born and raised in Florida for an extended period (20+ years) will exhibit values will cluster closely to USA residents. H0: The δ18O ratios for individuals born and raised in Florida for an extended period (20+ years) will not exhibit statistically significant values compared to other residents living in the USA or people from other regions of the world. H3: The predicted δ18O ratios for individuals born and raised in Florida for an extended period (20+ years) will exhibit values will be more enriched compared to other regions among USA residents. H0: The δ13C ratios for individuals born and raised in Florida for an extended period (20+ years) will not exhibit statistically significant values compared to other residents living in the USA or people from other regions of the world. H4: The predicted δ13C ratios for individuals born and raised in Florida for an extended period (20+ years) will exhibit values that are closer to a C4 diet, consistent with the C4 diet of USA residents. H0: Identification of specific trace element or rare earth elements (REE) concentrations for individuals born and raised in Florida for an extended period (20+ years) will not exhibit statistically significant values compared to other residents living in the USA or people from other regions of the world. H5: Identification of specific trace element or rare earth element (REE) concentrations for individuals born and raised in Florida for an extended period (20+ years) will exhibit values that are closely related to USA residents but are statistically significant from residents who have lived outside of the USA. Parametric T-tests, descriptive statistics and ANOVA (Scheffe Post Hoc) tests will be utilized to identify if there are any statistically significant differences between the isotope values between local and non-locals (Florida resident versus non-Florida resident) and between the average variation of individuals with stable versus complex residential histories. Complex residential histories can be individuals who have had to move around a lot during their early childhood through their late teenage years, especially for US military families or if the family immigrated to the USA during their juvenile years. The first permanent molar will develop from birth to three and a half years old, while the third molar develops from 11 to 16 years old. Bivariate plot graphs with the stable and radiogenic isotope ratios will also be used to visualize isotope variation and “cultural clustering” among the populations. Cultural clustering specifically refers to the δ13C ratios that an individual or group exhibits related to their diet, and that also correlates to cultural behaviors, decisions, and consumption of the culture’s staple crop. An example is North and Central America consumes mostly corn based products which is considered a C4 plant diet, and corn is a major staple crop for both North and Central America. The utilization of bivariate plot graphs with δ13C and 87/86Sr ratios help visualize the how North and Central America populations group or cluster together versus other cultures and geographic regions, such as Europe or Asia. Principal component analysis (PCA) will be utilized to investigate which trace element results by simplifying the “complexity of high-dimensional data” while retaining possible patterns or trends among the multiple trace elements collected from each donor tooth. K-cluster analysis will be used in conjunction with PCA to identify if the selected trace elements would group individuals into regional geographic cohort to aid with geoprofiling unidentified decedents. Specific trace elements that are not bioregulated for homeostasis by the body, will likely be a better indicator for georeferencing and complement the isotope values linked to the Florida baseline.

Results for enamel and/or tooth root (n=82) for donated teeth from individuals who were born in the USA and international countries were collected from a local dentist clinic in Tampa, Florida during 2018 to 2020. Individuals born in Florida and/or lived in Florida through their early childhood exhibit an average strontium isotope ratio of 0.70894 ± 0.00205. Lead isotope values collected have fallen into the expected US ratios: 206/204Pb ~ 18.4 to 19.1, 207/204Pb ~ 15.6 to 15.7, and 208/204 Pb ~ 38.1 to 38.8. Oxygen isotope (δ18 O) values are more positive compared to other regions of the USA. The δ13C values measured consistently indicate a typical diet in the USA, however there were values for individuals that were more positive than expected, possibly reflecting cultural practices and dietary choices. The results from this research will impact the forensic science community by revealing isotope values for modern populations in terms of assisting with identification. However, this research and the results are valuable for academic sectors for future studies in human diet and health, migration, environmental sciences, and how anthropogenic changes can change isotope values or trace element concentrations within the human body.

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