The eyes have it:

Scientists can ascertain date of birth by looking into the lens of the eye

Researchers have discovered that the lens of the eye can reveal the date of birth of a human being. This can be determined by measuring the level of the carbon isotope C-14 in the lens of the eye. The technique provides a useful tool for forensic scientists with which to date an unidentified body and may also have further implications for health science research.

Source : http://healthsciences.ku.dk/newslist/eyelens/