Every living thing on earth contains the element carbon.When an organism dies, be it a plant or an animal, the carbon acquired during its lifetime begins to decay at a steady, predictable rate, releasing carbon-14, a radioactive isotope with a half-life of 5,730 years.By measuring the amount of carbon-14 left in the organism, scientists can estimate how long ago the organism died. In recent years, scientists have refined methods for radiocarbon dating.Accelerated mass spectrometry, or AMS, is more precise than standard radiocarbon dating and can be performed on smaller samples.The SUERC results showed a 95% probability that the bone samples dated from around AD1430-1460, and over in Oxford the results both came out at around AD1412-1449, again with a 95% confidence. Radiocarbon dating of marine organisms can be out by up to several hundred years, and this effect can occur to a lesser degree in terrestrial life where sea-food forms part of the diet.The mass spectrometry of the Greyfriars bone samples reveals that the individual in question had a high-protein diet including a significant proportion of seafood.Isotopes participate in the same chemical reactions but often at differing rates.
A calibrated radiocarbon date is one that has been calibrated to the tree-ring record to adjust for variations in the concentration of atmospheric C-14 over time. During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon).However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue. Along with hydrogen, nitrogen, oxygen, phosphorus, and sulfur, carbon is a building block of biochemical molecules ranging from fats, proteins, and carbohydrates to active substances such as hormones.All carbon atoms have a nucleus containing six protons.