As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.
Which illustrates that, contrary to popular belief, the dating methods are not the primary way that ages are decided. Their results are always ‘interpreted’ to agree with other factors, such as the evolutionary interpretation of geology and fossils.
Over time, potassium-40 changes, or decays, into a different material, called argon-40.
By comparing the ratio of potassium to argon, scientists gauge how long this natural clock has been ticking.
Then Richard Leakey found a skull (called KNM-ER 1470) the KBS tuff, a skull that looked far too modern to be 3 million years old.
So Curtis and others redated the KBS tuff using selected pumice and feldspar samples, and obtained an age of 1.82 million years.
The Laetoli footprints are rare treasures in the record of human ancestry.