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.
Over the second half-life, of the atoms remaining decay, which leaves of the original quantity, and so on.
One half-life is the amount of time required for of the original atoms in a sample to decay.
It is also based on the fact that background radiation causes electrons to dislodge from their normal positions in atoms and become trapped in the crystalline lattice of the material.
When odd numbers of electrons are separated, there is a measurable change in the magnetic field (or spin) of the atoms.
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.