clipped from www.telegraph.co.uk

The age measurement method comes as an unusual byproduct of atomic weapons tests that took place in the atmosphere half a century ago. The carbon isotope that the explosions produced has declined year by year, providing a kind of watch to determine a victim's birth dates by looking into the lens of the eye

by measuring the amount of the carbon isotope C-14 trapped in the eye lens

scientists

establish

when a person was born

The reason that the isotope level can be used this way is that it is incorporated into the body in the first two years of life to build tiny transparent proteins

known as lens crystallines, remain essentially unchanged for the rest of our lives and is the only tissue in the human body apart from dental enamel to remain unchanged throughout life

By comparing the yearly record of the content of the C-14 in the atmosphere with the content of C-14 in the lens crystallines of the eye, scientists can accurately date a person's year of birth - providing they are born after 1950