Rodent like teeth, leg structure, better eyes
I believe the answer is: Different scientists use different data for investigation.
I say that because different scientists have different equipment, ideas, and have different methods. I hope I was right and i hope it helped and i wasn't to late to answer this question.
I would say that the Law of Superposition establishes relative dating as between two different sedimentary formations so that the one on top as long as there has been no overturning of beds, would be the younger one ie younger than the formation below it.
