To get the evolutionary rate, you need either fossil record or other dated events, or samples from different time periods. Phylogenetic trees can give you estimates of the relative rates, even if you do not have a time element to work out the absolute rate.

Plotting the bias depends on which type of bias you are interested in.

Assuming there is a molecular clock, keep in mind that fossils will only provide a minimum age of origin so all molecular extrapolations are also minimums and so the evolutionary rate is also contingent (presumably it is a maximum is older ages will spread the rate out over a longer period).