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Radiocarbon Dating of the Human Eye Lens Crystallines

Radiocarbon Dating of the Human Eye Lens Crystallines. Katie Axwik, Broc Glover, Jory Schlitt. Background. Previously, enamel has been used primarily to determine the age of victims (accurate to within 1.6 years)

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Radiocarbon Dating of the Human Eye Lens Crystallines

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  1. Radiocarbon Dating of the Human Eye Lens Crystallines Katie Axwik, Broc Glover, Jory Schlitt

  2. Background • Previously, enamel has been used primarily to determine the age of victims (accurate to within 1.6 years) • It has recently been found that there is another biological protein that forms early in life and remains constant ie. has no carbon turnover throughout life Eye lens crystallines

  3. Why should we use this method? a) Can be used in conjunction with enamel testing to improve the accuracy of age predictions b) Situations that require an alternative technique to determine age of individual • In 2009, model Jasmine Fiore was murdered by husband Ryan Jenkins- she had been beaten, teeth pulled, and fingers cut off • Criminal organizations sometimes removes the teeth and fingers to prevent identification of their victims

  4. Formation of the Eye Lens • Human lens grows rapidly in the embryo and during the first postnatal year • Growth slows between ages 1-10 • Growth reaches a much slower, nearly linear rate throughout life • Although the eye lens is soft and subject to deformations throughout life, the lens crystalline is never subject to turnover or remodeling once formed

  5. “Such a lifelong permanence of human tissue has hitherto only been described for dental enamel”

  6. Utilization of Carbon from the Environment • Human tissue derives its 14C content from the atmospheric CO2 • Carbon is used in the formation of the eye lens • Lens capsule completely encloses the lens and there are no blood vessels, therefore no remodeling of fibers nor removal of degraded lens fibers • 14C content of the lens proteins therefore reflects the atmospheric content of 14C at the time when the lens crystallines were formed because there is no significant carbon turnover throughout life

  7. After World War II, there was extensive nuclear testing done above ground, creating a spike in the amount of 14C in the atmosphere • Testing was banned in 1963 and there has been a steady decline in the amount of 14C in the atmosphere ever since

  8. Using this universally accepted standard, the authors found that it is possible to determine the age of an individual from the 14C content of their eye lens

  9. Mathematical Model based on assumption that the lens crystallines have been formed as a single event at the year of birth “Delay” (R) of approximately one year from the time the plant incorporated the CO2 to the time it was ingested by the human

  10. CASE STUDY Lynnerup N et al (2010) Ascertaining year of birth/age at death in forensic cases: A review of conventional methods and methods allowing for absolute chronology. Forensic Science International. 201: 74-78 • In 2007 the corpses of three newborn babies were found in a deep-freezer in a family home in Germany • The babies were removed by the police and taken to the local forensic medical facility. • The autopsy revealed that all the babies were mature and alive with respiration at birth. • The German judicial authorities assessed the manner of death to be manslaughter in all three cases • Subsequent investigation of the inquiry authorities centered on the mother

  11. Methods: • As they were newborn, there was no enamel to study • All six lens nuclei, as well as the nails, were sent to radiocarbon dating (Aarhus AMS Dating Centre, Denmark), where • the carbon was extracted in the form of CO2 by combustion. The • CO2 was converted to graphite, and the concentration of 14C (i.e. • the 14C/12C ratio) was measured with high accuracy by accelerator • mass spectrometry (AMS). The data were calibrated using the • program OxCal 4.0 [42], i.e. basically they were converted to • calendar dates by comparing the measured 14C values with a plot • showing the atmospheric 14C concentration as a function of time

  12. Conclusion • There is a need for alternative methods to determine the age of individuals, particularly in homicide cases • The global 14C levels spiked dramatically with nuclear testing, but have dropped off steadily since this practice was stopped • Because the human eye lens develops shortly before and after birth, the 14C level is indicative of the year an individual was born • The human eye lens can be used for accurate age prediction due to yearly changes in 14C ratios.

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