Cold War Provides Helpful New Forensic Tool

One of the most important questions in forensic science is to determine the age of remains. This can be difficult, because currently employed methods can have associated errors ranging between five to ten years. However, a promising new forensic tool seems to have emerged from the fallout of nuclear bomb testing.
According to a report published this week in the journal Nature, carbon isotopes generated from atmospheric atomic bomb testing trapped in tooth enamel may provide a more precise method for determining a deceased individual’s age than other forensic methods can.
The above-ground nuclear tests that occurred between 1955 and 1963 dramatically increased the amount of the isotope carbon-14 in the atmosphere. The levels rapidly equalized around the globe, even though the explosions occurred at only a few locations, and entered plants in the food chain through photosynthesis. By eating plants, and animals that feed on plants, human absorb carbon-14 and exhibit levels of the benign, traceable isotope that are similar to atmospheric concentrations. What is more, carbon-14 decays with a half-life of 5,730 years, a phenomenon that scientists can exploit as a way to determine the ages of objects that contain the isotope.
For the new study, Jonas Frisen of the Medical Nobel Institute in Stockholm, Sweden, and his colleagues analyzed the carbon content of tooth enamel. Because teeth do not exhibit any turnover during a person’s life, the scientists can determine when a tooth formed by comparing its carbon-14 content to past atmospheric levels. In addition, adult teeth form during a distinct period of childhood development around age 12, so this information can be translated into the age of an individual.
The team tried the new approach on teeth recovered from 22 individuals and found that it gave a remarkably precise estimate for their ages. In all cases, the result projected by carbon-14 dating was within 1.6 years of the correct age.
Of course, this particular approach can only precisely identify the age individuals born after 1943 because they would be the first group to have adult teeth by 1955, when the nuclear testing first occurred. But because exposure to carbon-14 through diet or local conditions may vary around the world, the authors caution that “the method will need to be verified on a larger scale, and perhaps on a wider geographical range, of cases before it can be applied to forensic work.”
Read the abstract of this study…