All living things absorb both types of carbon; but once it dies, it will stop absorbing.
This rate of decay, thankfully, is constant, and can be easily measured in terms of ‘half-life’.
It has been summed up most succinctly in the words of American neuroscience Professor Bruce Brew: that samples of moss could be brought back to life after being frozen in ice. That carbon dating deemed the moss to have been frozen for over 1,500 years.
Now, if this carbon dating agrees with other evolutionary methods of determining age, the team could have a real discovery on their hands.
Example: wood found in a grave of known age by historically reliable documents is the standard for that time for the C14 content.
This standard content of C14 can then be used for wood not associated with a historically documented date.