Carbon dating to determine the age of fossil remains
FOSSIL In this section we will explore the use of carbon dating to determine the age of fossil remains.
Carbon is a key element in biologically important molecules. During the lifetime of an organism, carbon is brought into the cell from the environment in the form of either carbon dioxide or carbon-based food molecules such as glucose; then used to build biologically important molecules such as sugars, proteins, fats, and nucleic acids. These molecules are subsequently incorporated into the cells and tissues that make up living things. Therefore, organisms from a single-celled bacteria to the largest of the dinosaurs leave behind carbon-based remains.
Carbon dating is based upon the decay of 14C, a radioactive isotope of carbon with a relatively long half-life (5700 years). While 12C is the most abundant carbon isotope, there is a close to constant ratio of 12C to 14C in the environment, and hence in the molecules, cells, and tissues of living organisms. This constant ratio is maintained until the death of an organism, when 14C stops being replenished. At this point, the overall amount of 14C in the organism begins to decay exponentially. Therefore, by knowing the amount of 14C in fossil remains, you can determine how long ago an organism died by examining the departure of the observed 12C to 14C ratio from the expected ratio for a living organism.