The emergence of a new species from a parent species occurs due to a combination of geographical and genetic barriers. The effects of these barriers on different parent species vary widely; therefore, the emergence of new species should be distributed randomly over time. However, paleontologists have discovered a pattern in which extremely large and disparate groups of new species occasionally appear all at once.

Which of the following, if true, provides the best starting point for an explanation of the emergence of many new species at the same time?

(A) Parent species with few physiological differences among their members are less likely to evolve into a new species.
(B) Biologists use different evidence to identify the emergence of new species today than paleontologists use to identify such events that occurred in the past.
(C) Some new species develop exclusively because of geographical barriers between different groups of a parent species.
(D) Periodically, global disasters create sudden geographical divisions within many species' habitats which send subgroups of these species down different genetic paths.
(E) In some cases, one parent species will give rise to multiple new species that all possess a trait formerly unique to the parent species