This is not a sentence for past perfect. Past perfect is used when both the actions were in past and one action is earlier than the the other, then you should use past perefct with the earlier action. BOTH ACTIONS SHOULD HAVE BEEN COMPLETED IN PAST.
The most prominent result of Professor Westonâ€™s archeological research has been the discovery that pharaohs who ruled in the last days of Egypt were buried with fewer artifactsâ€™ than were their earlier counterparts.
The red part is a action started in past but it still true. NOT A PAST ACTION
The blue past is a fact of past. : PAST ACTION
The bold part is just a clause describing the pharos and is not an action.
SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008