Even if we consider the possibility that the Oromo didn’t use the structures as tombs, the argument is still flawed in its assumption that the Oromo culture influenced the Swahili culture (and not the other way around). It is the structure, not the use, of the buildings that we care about.

This is descriptively inaccurate. The argument does not indicate that one event occurred earlier than another event. We know that the Swahili tombs are from the 14th and 15th centuries, but we have no idea when the Oromo people built their structures.

This is descriptively inaccurate. The premises don’t actually support a much broader conclusion––the premises don’t even support the conclusion that the historian provided.

The historian actually does demonstrate that it wasn’t a third civilization that inspired the structures. The historian says that the tombs were found in the Swahili and Oromo civilizations, but that they were unknown among any other people with whom the Swahili civilization had contact.

This is the flaw. The stimulus does not say anything about when the Oromo created their tombs. From the information given, it could totally be the case that the Swahili civilization built their tombs first, and the Oromo culture was influenced by the Swahili culture.