These isotopes are present in the following amounts C12 - 98.89%, C13 - 1.11% and C14 - 0.00000000010%.Thus, one carbon 14 atom exists in nature for every 1,000,000,000,000 C12 atoms in living material.Libby and his team intially tested the radiocarbon method on samples from prehistoric Egypt.They chose samples whose age could be independently determined.A sample of acacia wood from the tomb of the pharoah Zoser (or Djoser; 3rd Dynasty, ca. Libby reasoned that since the half-life of C years, they should obtain a C14 concentration of about 50% that which was found in living wood (see Libby, 1949 for further details).The results they obtained indicated this was the case.
Oakley (1979) suggested its development meant an almost complete re-writing of the evolution and cultural emergence of the human species.
The C14 technique has been and continues to be applied and used in many, many different fields including hydrology, atmospheric science, oceanography, geology, palaeoclimatology, archaeology and biomedicine.
There are three principal isotopes of carbon which occur naturally - C12, C13 (both stable) and C14 (unstable or radioactive).
They exist in equilibrium with the C14 concentration of the atmosphere, that is, the numbers of C14 atoms and non-radioactive carbon atoms stays approximately the same over time.
As soon as a plant or animal dies, they cease the metabolic function of carbon uptake; there is no replenishment of radioactive carbon, only decay.