How do historians study, divide up, and evaluate the past?

History

Hi there, i need those questions to be answered  as shown below:

SHORT ANSWER–a good paragraph or two

1. How do historians study, divide up, and evaluate the past?
2. How did the original human hunter-gatherer communities become civilized, with what problems and changes to their cultures?
3. What did the Ancient Middle Eastern civilizations contribute to the foundations of Western culture?
4. How did the Greeks and later Hellenistic rulers succeed and fail in politics?
5. How did Rome grow from a city-state to an empire unifying the Mediterranean?
6. How did the new religion of Christianity begin and grow?
7. How did Roman Empire fall in the West, yet last another 1000 years in the East?