Final answer:
Processed pseudogenes are useful for testing Darwin's theory of descent with modification because they accumulate mutations at a constant rate and can help examine phylogenetic relationships among organisms.
Step-by-step explanation:
Processed pseudogenes can be useful for testing Darwin's theory of descent with modification because they accumulate mutations at a constant rate, and thus older processed pseudogenes should be shared by a greater variety of species. This allows for the examination of phylogenetic relationships among organisms and helps to support the concept of common ancestry. By comparing the presence and sequence of processed pseudogenes in different species, scientists can identify the mutations that have occurred over time and trace the evolutionary history of organisms.