Since the magnetic field progressively changes with time in a predictable way Whenever possible, paleoanthropologists collect as many dating samples from an ancient human occupation site as possible and employ a variety of chronometric dating methods.
In this way, the confidence level of the dating is significantly increased.
Radioactive elements were incorporated into the Earth when the Solar System formed.
Specifically, the electrons of quartz, feldspar, diamond, or calcite crystals can become displaced from their normal positions in atoms and trapped in imperfections in the crystal lattice of the clay molecules.
As a result, all of the argon-40 in a volcanic rock sample is assumed to date from that time.
When a fossil is sandwiched between two such volcanic deposits, their potassium-argon dates provide a minimum and maximum age.
The methods that are used depend on the presumed age of the site from which they were excavated.
For instance, if a site is believed to be over 100,000 years old, dendrochronology and radiocarbon dating could not be used.
Although, organic materials as old as 100,000 years potentially can be dated with AMS, dates older than 60,000 years are still rare.