Scientists have now found a way to use radiocarbon dating on the eyes of dead people to determine their approximate year of birth, providing a useful tool for forensic scientists wanting to establish the age of an unidentified body. The details are pretty interesting.
Radiocarbon dating is currently used to date biological archeological finds that are up to 60,000 years old. Carbon-14 is a radioactive isotope that occurs naturally in the atmosphere and is not dangerous to us because it occurs in very small amounts and decays at a very slow rate into nitrogen. "Carbon is one of the principal organic elements, and constantly moves in and out of the food chain. The same is true for the tiny quantity of C-14 in the atmosphere. As long as an organism is part of the food chain, the amount of C-14 in its cells will remain constant and stay at the same level as the C-14 atmospheric content. When the organism dies, however, the quantity of C-14 will slowly but surely drop over the course of thousands of years, while it transforms into nitrogen." This drop in C-14 levels can be measured over time to determine the approximate date of death with some accuracy. So, how is it that we can now determine the date of birth using deceased human eyes?
Here's where it gets interesting. Human eyes are made of transparent proteins that behave like crystals, "allowing light to pass through the eye so we can see." These proteins, called crystallins, are formed in the first two years of life and after that remain relatively unchanged for the remainder of our lives. As the crystallins form, they absorb C-14 from the atmosphere and food stuffs. Now, "from the end of World War II and up until about 1960, the superpowers of the Cold War era conducted nuclear tests, detonating bombs into the atmosphere. These detonations have affected the content of radioactive trace materials in the air and created what scientists refer to as the C-14 bomb pulse. From the first nuclear detonation until the ban on nuclear testing was evoked, the quantity of C-14 in the atmosphere doubled. Since 1960, it has only slowly decreased to natural levels." Because the increased levels of radioactive trace materials in the atmosphere were closely monitored, we have complete records of levels over the years. Matching the amount of C-14 from a human eye sample at the time of death (which has remained unchanged since about age 2) to the amount of C-14 in the atmosphere at a certain time should tell us age of the decedent.
Also, it should be noted that "Bomb Pulse" would be a good band name.
Public Library of Science. "The Eyes Have It: Researchers Can Now Determine When A Human Was Born By Looking Into The Eyes Of The Dead." ScienceDaily 30 January 2008. 31 January 2008