Early human carbon dating
Unfortunately the ratio of carbon-12 to carbon-14 has yet to reach a state of equilibrium in our atmosphere; there is more carbon-14 in the air today than there was thousands of years ago. In order for carbon dating to be accurate, we must know what the ratio of carbon-12 to carbon-14 was in the environment in which our specimen lived during its lifetime.It has resulted in artificially high levels of carbon-14 in plants and animals living in the past 60 years.
After an organism dies, its level of carbon-14 gradually declines at a predictable pace, with a half-life of about 5,730 years.Carbon-14 has a half-life of 5,730 ± 40 years—, half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years.Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon.Sidebar to the article Applying Carbon-14 Dating to Recent Human Remains by Philip Bulman with Danielle Mc Leod-Henning Standard carbon-14 testing, as used by archaeologists, is based on the natural process of radioactive carbon formation that results from cosmic ray bombardment of nitrogen in the earth's upper atmosphere.The radioactive carbon is taken from the atmosphere and incorporated into plant tissues by plant photosynthesis.
A large increase in atmospheric carbon-14 occurred when the United States and several other countries tested nuclear weapons aboveground during the 1950s and 1960s (see Figure 1).