UNCLAIMED - Analytical Chemist Discusses Isotope Oxgen Analysis Results

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UNCLAIMED – a feature-length documentary
While serving a humanitarian mission in Southeast Asia decades after serving 27 months in Vietnam with the 11th Armored Cavalry Regiment ("Blackhorse Regiment"), a war-torn Vietnam vet discovers a mysterious man claiming to be an American MIA. The documentary Unclaimed reveals a tale of brotherhood, redemption and the struggle to prove a lost identity.

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Lesley Chesson, Analytical Chemist with the Ehleringer Lab, University of Utah, and IsoForensics, Inc. discusses isotope oxgen analysis results
Outtake from documentary Unclaimed, Summer 2012

As discussed widely on youtube and on our Facebook page, oxygen isotope analysis was indeed conducted on a molar extracted by the man claiming to be John H. Robertson. The isotopic oxygen ratios of teeth represent the ratios of the region in which an individual was born and raised. The decision to conduct the test on the tooth extracted during filming was made at a time in filming when it appeared there would be no opportunity for DNA testing, before John H. Robertson's immediate family (the Holley family) had been found.

Read more here:

1. Oxygen isotope analysis by Carol Chenery, British Geological Survey
http://www.wessexarch.co.uk/book/expo...

Excerpt: Oxygen isotope analysis of dental enamel can assist in determining a persons place of origin.

Tooth enamel stores a chemical record of their owners' childhood living environment, such as local climate and geology. Each tooth opens a window of information covering the short time of tooth enamel formation. The mineral apatite that makes up the structure of our teeth and bones is the main component of tooth enamel. Its chemical composition is primarily calcium, phosphorous and oxygen with trace amounts of other elements including strontium and lead. Of these elements the isotopes of oxygen and strontium are the strongest independent indicators we have of the local natural environment.

Nearly all of the oxygen that goes into the formation of tooth and bone comes from the water we drink and virtually all the water we drink is ultimately derived from precipitation as rain or snow.

The element oxygen has 3 different forms called isotopes, which are chemically the same, but have slightly different physical properties due to a small difference in their weight.

The oxygen isotopes ratio of the water you drink depends on the source of the water in precipitation, the distance from the coast, latitude and altitude and the local temperature of precipitation. For our purposes we are interested in the ratio of heavy (oxygen 18) to light (oxygen 16) isotopes. Drinking water in warm climates has more heavy isotopes (higher ratio) and in cold climates has more light isotopes (lower ratio). We can compare the oxygen isotopes ratio in teeth with that of drinking water from different regions and determine where a person might have lived, at the time their teeth formed.


2. Isotope Analysis
http://en.wikipedia.org/wiki/Isotope_...

Excerpt: Isotopic oxygen is incorporated into the body primarily through ingestion at which point it is used in the formation of, for archaeological purposes, bones and teeth. The oxygen is incorporated into the hydroxylcarbonic apatite of bone and tooth enamel.

Bone is continually remodelled throughout the lifetime of an individual. Although the rate of turnover of isotopic oxygen in hydroxyapatite is not fully known, it is assumed to be similar to that of collagen; approximately 10 years. Consequently, should an individual remain in a region for 10 years or longer, the isotopic oxygen ratios in the bone hydroxyapatite would reflect the oxygen ratios present in that region.

Teeth are not subject to continual remodelling and so their isotopic oxygen ratios remain constant from the time of formation. The isotopic oxygen ratios, then, of teeth represent the ratios of the region in which the individual was born and raised. Where deciduous teeth are present, it is also possible to determine the age at which a child was weaned. Breast milk production draws upon the body water of the mother, which has higher levels of 18O due to the preferential loss of 16O through sweat, urine, and expired water vapour.

While teeth are more resistant to chemical and physical changes over time, both are subject to post-depositional diagenesis. As such, isotopic analysis makes use of the more resistant phosphate groups, rather than the less abundant hydroxyl group or the more likely diagenetic carbonate groups present.