Relative dating techniques in archaeology
In 1949, American chemist Willard Libby, who worked on the development of the atomic bomb, published the first set of radiocarbon dates.
So every living thing has a certain amount of radiocarbon within them.
Limitations and calibration: When Libby was first determining radiocarbon dates, he found that before 1000 BC his dates were earlier than calendar dates.
He had assumed that amounts of Carbon-14 in the atmosphere had remained constant through time.
Plankton absorbs, Carbon-14 from the ocean much like terrestrial plants absorb Carbon-14 from the air.
Since plankton is the foundation of the marine food chain, Carbon-14 is spread throughout aquatic life.