Archeology {Cognitech and Nanotech}
Archeologists study human cultures through the recovery, documentation, analysis and interpretation of material remains and environmental data, including architecture, artifacts, features, biological artifacts, and landscapes. In Sufficiently Advanced, they have over twelve thousand years of history to study, multiple worlds and cultures many of them technological. Because of this, and more sophisticated techniques, it is quite a bit different from the days of "highly educated ditch diggers" at least among the more advanced civilizations.
Site selection, the recovery, documentation, analysis and interpretation of archeological artifacts (including paleological ones) are all specialized tasks. Many archeologists also have familiarity with Metatech research and engineering.
Historian {Cognitech}
History is the study of past, focused on human activity and leading up to the present day. More exactly, history is the field of research producing a continuous narrative and a systematic analysis of past events and their relation to humanity.
With more than six thousand years of well-documented history (and many more of poorly documented history), historians have quite a bit before them. By the standards of their era, proper documentation, with life logs and the like, only really began in the mid 21st century. Also, with the Tao of History and the popularity of meticulously researched and detailed re-enactments and drama, a historian can make a good living especially if he or she can communicate their discoveries to the lay audience.
The difference from archeology is that historians tend to take the broad view, using the findings of archeologists.
Historians study both extinct and active cultures, examining their records and trying to understand them. In many ways they are specialized versions of Metatech Engineers, looking at how previous civilizations worked.