Why is it useful for historians to base certain studies on the analysis of historical themes

The same themes apply to people living in very different times and places.

Explanation:

Students of history think about timeframes, or periods of time, by considering what are the most impactful events of a period. Every period in history makes a picture of the world or a locale during that specific period of time. By observing historical themes, you can actually see how the same thing might happen to different people and how many mistakes are repeated through the course of time.

disease was the number one killer of native peoples. they had had little exposure to the diseases of europe. this led to some villages being almost completely wiped out and some tribes destroyed.