What do you call the method that scientist did to find explanation and to answer the problems such as this?

such as human origins, or the past and contemporary spread and treatment of infectious disease, or globalization, requires synthesizing information from all four subfields. Anthropologists are highly...

by performing experiments, they answer their problem's answers.

By looking at a calender.

The Scientific Method

You are probably looking for the word hypothesis, which is a question which can be formally tested. The explanation is usually contained in the data/results or conclusion of an experiment.