Thursday, September 22, 2005

A tooth for a tooth

How old am I? Oh, never mind. But if you want to know how old a person is, and they won't tell you, ask for a tooth. According to a report in the September 15 issue of Nature, tooth enamel can indicate a person's age to within a year or so.

Here's why. Several nations tested nuclear bombs in the atmosphere during the period 1955-63. The amount of radioactive carbon-14 in the atmosphere shot up dramatically, peaking with the signing of the Test Ban Treaty in 1963. Since then it has been decreasing exponentially as the atoms decay or are incorporated into plants. and animals that feed on plants. The amount of C-14 in the human body closely parallels that in the atmosphere at any given time. Tooth enamel is formed at specific times in childhood and, unlike other parts of the body, remains stable. Measure the amount of C-14 in tooth enamel and you have a reliable indicator of age.

But I'm safe. Or rather the best you can say is that I was born before 1943, twelve years before the onset of nuclear testing. The final formation of dental enamel is for wisdom teeth at age 12.

As for the rest of you young pups, consider that you are carrying around in your teeth atoms that were produced in nuclear explosion -- maybe somewhere in Nevada or Siberia, half a century ago -- little souvenirs of a dark chapter of human history, reminders of the way even your chompers are part of something bigger and more fragile than yourselves.