Themes are important to historians trying to organize information about the past because they:

Explanation:

Themes is a way to organise information about societies, because in history there's too much information to process at once. So, in order to achieve some aims and do comparison between, you need to segment it.

need more info

explanation:

the group i'm selecting: greeks.

a first group of greek immigrants came to the us in the 1850s. the second group came to america starting in the 1890s due to economic opportunities they didn't have back in their home caused by the hardships of ottoman rule. greek immigration was 90% male, many of them expected to work and return to greece after earning enough capital, but ultimately had to remain in the us after the greek genocide.