Bomb Tests Aid Tooth Dating

Forensic scientists have a new tool for determining the age of unidentified human remains, thanks to the above-ground nuclear bomb tests that took place from 1955 to 1963. Before 1955, the amount of carbon-14 in the atmosphere was relatively constant, but atmospheric concentration of the radioactive isotope spiked dramatically with nuclear bomb tests and has been steadily declining since above-ground testing stopped. Because tooth enamel for individual teeth forms at distinct times during childhood and contains a small amount of carbon, Kirsty L. Spalding, Jonas Frisén, and coworkers from Sweden's Karolinska Institute reasoned that they could correlate atmospheric and enamel C-14 concentration to determine the age of an individual tooth, and therefore, the age of the person that the tooth belonged to (Nature 2005, 437, 333). Spalding's group tested the technique on 22 people and accurately determined their ages within 1.6 years. That result is far more precise than those obtained with current methods used to determine age, which have a five- to 10-year margin of error.