system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do historical experts know that what happened during certain time periods actually happened?

How can hundreds and even thousands of years of history, which includes entire civilizations, discoveries and characters, so confidently be explained? Not all of it could have happened the way it's being taught to modern society, right?
gpt
It depends on how far back you’re asking about. 

Mostly, for eras preceding the written word we have to make a lot of guesses using what we know about modern humans, paired with artifacts found around human remains. These artifacts include things like tools, buildings, and personal objects. These things give us clues about the people and time period, and anthropologists sort of piece the rest together into a cohesive story. But they’ll be the first to tell you that it’s a lot of guesswork. 

Once we start getting into the time of the written word, though, it starts to get a little more clear. Now, not only do we have artifacts, landmarks, etc, but we also have written records. And anthropologists will take things like laws, religious texts, diaries, tax documents, etc and they use all of these clues to put together a story of the time. 

In addition, when combining the work that anthropologists and historians do with the hard sciences (like biology, chemistry, and geology) we can explore the relationship between people and their environments and get even more “proof” of things that happened. 

Historians tend to look for confirmation of the facts in as many sources as they can find, but sometimes it’s still a bit of a guessing game. And it’s made muddier when you consider the phrase “history is written by the victors”. But that plays into social and racial issues that is a whole other can of worms when we question the veracity of historical “facts”.