Most accurate form of radiometric dating
It was all clear when in 1859 Charles Darwin published his "On the Origin of Species".The 'progress' shown by the fossils was a documentation of the grand pattern of evolution through long spans of time.And this gave us the familiar list of divisions in the geologic time scale -- Jurassic, Cretaceous, Tertiary, and so on.Most importantly, it was recognized that each time-unit was characterized by the appearance of particular fossils.They are drawn up mathematically, using lists of morphological (external form) or molecular (gene sequence) characters.What is noteworthy is that modern phylogenetic trees derive no input from stratigraphy, scientific comparisons between tree shape and stratigraphy can be used to confirm the fossil record.The scheme worked all round the world, without fail.The next observation occurred when geologists noted how fossils became more complex through time.
The next step was for geologists began to build up the stratigraphic column.
Any attempt to make a claim about evolution always comes back at some point to the geologic time scale.
But if you are going to be looking at time scales that are that old how do you get the dates?
One fact was soon clear, no dinosaur record could be found to coincide with a human fossil record.
So it was apparent that there was some kind of 'progress' going on.