However, if these substances are heated (such as when pottery is fired in a kiln or stones are dropped in a fire) this releases these trapped electrons and resets the 'clock' to zero.The object will then begin to trap electrons again.Heating these crystals (such as when a pottery vessel is fired or when rocks are heated) empties the stored energy, after which time the mineral begins absorbing energy again.
Since the world is much older than this, most objects are already saturated.
In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.
Thermoluminesence (TL) and Optically Stimulated Luminesence (OSL) are related techniques which measure when objects were last heated (TL) or when buried deposits were last exposed to light (OSL).
If they are then buried beneath later deposits, they begin to trap electrons again and can be dated by similar methods (OSL).
by Tas Walker Darwin considered the Australian Aborigines as primitive and not much evolved from the ‘anthropoid apes’.