What information might the geographer be able to convey more clearly than the economic historian

Since a geographer is the scientist whose field of study is geography, the study of Earth's natural environment as well as human society, an information that a geographer might be able to convey more clearly than the economic historian would be the patterns of how human beings migrated over time as a result of the climate change and environment which made them to move. 

On the other hand, economic historians are responsible with the study of economies or economic phenomena of the past.

julius caesar turned the roman republic into the roman empire by coming in and taking the "dictator" role during the time of a civil war (elites vs lower classes) winning battles and reputation, then declaring him dictator for life

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25. twelve tables

26. having important positions chosen by lot