Final answer:
Older processed pseudogenes are shared by more species because they were present in the last common ancestor, whereas newer pseudogenes may be shared by fewer species due to arising post-divergence. Molecular clocks help estimate the divergence times, supporting the method of using mutation accumulation to age pseudogenes.
Step-by-step explanation:
The age of processed pseudogenes can be estimated by looking at the number of mutations they have accumulated over time. Older pseudogenes tend to have more mutations because they have been around for a longer time, and therefore they are likely to be shared by more species. This is because these older pseudogenes would have been present in the last common ancestor of these species, and hence they can confirm evolutionary relationships. In contrast, newer pseudogenes may be shared by fewer species as they would have arisen after the divergence of species from their common ancestor. The usage of molecular clocks based on DNA sequences allows scientists to estimate the time when different species diverged from their common ancestor, thus supporting this method of estimating pseudogene age.