Radiocarbon Dating Background:
Radiocarbon dating, also known as carbon-14 dating, is a scientific method many archeologists use to determine the age of organic materials—some as old as 60,000 years– accurately. This technique, first developed in the late 1940s at the University of Chicago by Willard Libby, is based on the decay of the carbon-14 isotope. Radiocarbon dating has been used for historical studies as well as atmospheric science and triggered archaeology’s “radiocarbon revolution.” Carbon dating has also helped us reveal our bodily functions, understand the climate of the Earth, and track the sun’s activity and the Earth’s magnetic fields. It was also instrumental in the discovery of human-caused climate change, as scientists use it to track the sources of carbon in the atmosphere over time.
Isotopes:
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. Isotopes can generally be divided into two categories– radioactive and stable. Radioactive isotopes tend to decay over time, a property that archeologists use to date soils and rocks. Stable isotopes on the other hand have a stable nucleus and so do not decay. Their abundance stays the same over time which makes it very useful for archeologists.
Radiocarbon Dating Explained:
When cosmic rays reach Earth’s upper atmosphere, physical and chemical interactions cause the formation of the radioactive isotope carbon-14. The living organisms on Earth absorb this isotope into their tissue. The carbon-14 then slowly changes into other atoms once the organism dies. Scientists use this concept to measure how much carbon-14 remains and use it to estimate how long an organism has been dead. In the 1940s, Libby and fellow chemists measured carbon-14 by developing a technique to purify a sample so it only emits carbon-14. By the 1970s a new method using a particle accelerator that counts the atoms of carbon-14 started becoming used.
Functions of Isotope Analysis:
Like carbon dating, isotopes are present all around the world, and each substance has different isotope ratios. Over the years the isotopes in the food we eat and the water we drink begin to incorporate into our body tissues and our skeleton. By measuring the different ratios of isotopes in bones and teeth archeologists can find details about an individual's diet and environment they grew up in. The ratios of isotopes are measured using an analytical instrument called isotope-ratio-mass-spectrometers(IRMS) and while archeologists use a variety of stable isotopes the most commonly used ones are carbon, nitrogen, oxygen, and strontium.
Radiocarbon dating and isotope analysis are two important methods archeologists use to date items they find and learn more about the diet and habitat of species that may now be extinct. However, it is important to note that these methods are also useful outside of archeology in fields like ecology, forensic science, atmospheric sciences, etc.
References
Koppes, Steve, and Louise Lerner. “Carbon-14 Dating, Explained.” University of Chicago News, 2023, news.uchicago.edu/explainer/what-is-carbon-14-dating#:~:text=Radiocarbon%20dating%2C%20or%20carbon%2D14,of%20the%20carbon%2D14%20isotope.
“What Is Stable Isotope Analysis?” FutureLearn, University of Reading, 25 Oct. 2022, www.futurelearn.com/info/courses/archaeology/0/steps/15267#:~:text=By%20measuring%20the%20ratios%20of,environment%20they%20grew%20up%20in.
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