Materials that originally came from living things, such as wood and natural fibres, can be dated by measuring the amount of carbon-14 they contain.For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings. The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.Plant eating animals (herbivores and omnivores) get their carbon by eating plants.
Common materials for radiocarbon dating are: The radiocarbon formed in the upper atmosphere is mostly in the form of carbon dioxide. Because the carbon present in a plant comes from the atmosphere in this way, the radio of radiocarbon to stable carbon in the plant is virtually the same as that in the atmosphere.
Once an organism dies, it stops taking in carbon-14.
The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.
Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive.
By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.