Expert: Ralph Salier - 11/22/2008

Question
How accurate is the radiocarbon dating of early animals bones?Is the plus or minus 120 years accurate?Thanks!

Answer
Hi Randy.  

Radiocarbon dating of any thing but charcoal has limitations.  However, in the last few months I have read  that for more recent materials, they have been able to detect the higher levels of C14 caused by the A bomb testing of the early 1950s and 1960's in the bones of people born during this time.  The +/- 120 years sounds like a very broad time frame and I don't know where this came from.  It is highly dependent on the atmospheric content of C14 which can change from year to year based on  the number of fires burning in different parts of the world as this adds to the C14 in the air.  

The amount of C14 changes from year to year for this and other reasons including the amount of and type of particle coming from the sun.  A number of charts have been created over time which are used to "determine" the date based on the C14 content of the sample.  In addition, if the sample is more then 10 thousand years old, the amount of C14 has decreased by 75% in the sample and thus becomes very hard to get a good dating.  (this is due to the half life of C14).  

So how early are the bones? if they are less then 10K years old, then a date can be determined to a degree. The date spread may be larger of smaller then the 120 years based on the data available.  If the sample is less then 5K years old the the date may be much more accurate.