Absolute chronometric dating techniques
This is the critical time period during techniques humans evolved from radiometric ape ancestors.
Despite this limitation, paleoanthropologists have found dating by association with polar reversals to be a helpful additional method of tracking the evolution of our fossil ancestors in regions such as East Africa where there has been frequent volcanic activity leaving clear thermoremnant magnetic evidence.The time between reversals has ranged between less than 100,000 to tens of millions of years with an average of about 300,000 years. It takes 1,000-8,000 years for one to be completed. It is thought that as a reversal approaches, the earth's magnetic field weakens.It has been gradually weakening for the last 250 years.It is based on the fact that amino acids (the building blocks of all proteins) exist in two mirror image forms, both of which otherwise have the same chemical structures.The L-amino acid molecule form has an extension to the left, while the D-amino acid form has an extension to the right.
Fortunately, there are other methods available to researchers.