Question: Can you idntify how long a body has been there for by looking at the bones ? If no why not ?

Anna Williams answered on 24 Jun 2011:

Hi 10mcrog,
This is a great question!
Forensic anthropologists are often asked how long a body has been there, and really, how we go about answering it depends on the situation.
If it is a buried body, then we can use clues provided by archaeology – we can look at how far down the body was buried, if it was buried under things of known age. For example, if a body is buried under a patio, and there is a water pipe above it that is undisturbed, and that is known to have been put in 5 years ago, then we know that the body was buried more than 5 years ago. We can also look at things that the body is buried with. For example, if the body has a watch and a pair of sunglasses in its pocket, then we know that this is not an archaeological skeleton, and it is relatively recent. Lots of little things like clothes, jewellery etc can be dated quite precisely.

We can also look at the bones themselves. There are small clues given by the way the bone feels and smells. For example, if the skeleton is archaeological (ie from over 70 -100 years ago), it is likely to be dry, flakey and crumbly, and not have any distinct smell. If you smelled it, it would just smell like earth. If a skeleton is much more recent than that, it is likely to feel a bit slimey and greasy, and to have a distinctive, sort of rotting meat smell. This can be very strong if the body is quite recent, but then you’d have other clues, like tendons and skin on that could help you too.

Other than that, we can do radiocarbon dating on the bones, where we take a small sample and send it off to a lab. They look at the amount of a special radioactive type of carbon (carbon-14) it has in it. When someone dies, the amount of carbon 14 in their bones declines rapidly (exponential decay), and so we can look at the amount they would have had when they were alive (atmospheric levels of carbon-14) with the amount they have left in their bones, and work out how long they have been dead. You can find out more at this really good site: http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm