So more or less they use fossils to date rocks, and rocks to date fossils?<quoted text>
The geological time scale is something that was deduced from the evidence. In particular, that many processes take millions of years was well-established before Darwin wrote any of his books. It is also supported by radiometric dating (NOT carbon dating---carbon dating only works for things less than about 100,000 years old--very young for geological processes).
The geological time scale informs us of how long various stages of evolution took, but it is not dependent on the evidence of evolution, nor is the evidence for evolution directly dependent on the geological time scale. The two *do* inform each other, though.
I should also point out that the geological time scale, which involves actual dates and times is different than the geologic column, which tells the *order* of events, but does not give the timing of those events. So, we can look at various human ancestors and know the order of their appearance even in the cases where we do not have good dates for the different species. The geologic column was well-established long before the dates of the events in that column were figured out.
And if they date the rocks by the fossils, how can they then turn around and talk about the patterns of evolutionary change through time in the fossil record?
I was reading an artical on this, and that was a question it asked.
Just curious to hear someones input on it.