Carbon dating questions
Later, this date was confirmed by two other dating methods (paleomagnetism and fission tracks), and was widely accepted.
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.
Using new samples of feldspar and pumice they ‘reliably dated’ the tuff at 2.61 million years, which agreed nicely.
So Curtis and others redated the KBS tuff using selected pumice and feldspar samples, and obtained an age of 1.82 million years.
This new date agreed with the appearance of the new skull.
Tests by other scientists using paleomagnetism and fission tracks confirmed the lower date.
So by 1980 there was a new, remarkably concordant date for the KBS tuff, and this became the one that was widely accepted.