  The measurement of the ratio of 228Th vs 228Ra, two isotopes from the natural
radioactivity, is an ancient, but not entirely reliable, method of dating
biological materials. It has been applied for the dating of fishes with
mitigated results in many cases. It has been also experimented with mixed
success in forensics cases where the question of how long a person whose bones
were found was dead. Here too, the precision of the results is not
satisfactory. Other applications concern age dating oil and gas waste waters
spills. Our goal, while based on the same measurement of the ratio of the two
radiosiotopes, is different. We aim at assessing the age of an animal at the
date of its death, in particular for the animals intended for human
consumption. The measurement technique relies on gamma spectrometry of the
bones of 228Th and 228Ra stemming from ingested food and from the environment.
A strong incentive to our research is fraudulent sales of meat with falsified
identification. For instance, mutton sold as lamb, which is more expensive.
Depending on the country of origin, this is complicated by varying legal
definitions of the animal category, which renders controls for imported meat
difficult. Preliminary measurements with retail samples of approximate
identification validate the procedure. Further and more precise inquiries in a
collaborative work with the French Ministry's Anti-Fraud Agency (equivalent of
the U.S. Food and Drug Administration) are on their way.
