Age of fossils was previously determined by radioactive elements. More precise recent method which has led to revision of evolutionary period is
Electron spin resonance and fossil DNA
Electron Spin Resonance or ESR and fossil DNA provide more precise method for determining the age of fossils. This method measures the amount of unpaired electrons in crystalline structures that were previously exposed to natural radiation. The age of substance can be determined by measuring the dosage of radiation since the time of its formation. ESR dating is used instead of Radiocarbon dating because ESR dating can date newly formed materials or previously heated rock.