Anyone doing history knows that all the sources are biased. You have to corroborate evidence and adjust for knowing the context in which the work was produced to determine how reliable it is.

Sure. But there was an era that lasted around 100 years when a photo alone was pretty reliable. Photos and especially videos were at least hard to fake. That era is over. Absolutely anything can be faked cheaply and easily.

Really early photography was so poor compared to modern HD images that obvious fakes fooled "serious" people https://en.wikipedia.org/wiki/Cottingley_Fairies vs Arthur Conan Doyle, for example. But yes, it required more effort, and the effort reduction for fakes offered by AI is extremely powerful.

(There is also the sad business of the 1932 Pulitzer https://www.pulitzer.org/news/statement-walter-duranty )

Photography has always been less reliable than many people thought it was, even without considering photo doctoring. Like statistics, the frame you choose in a photo can completely alter the story it's telling. It might be that entering an era where complete fabrication is easy will make people more resistant to the subtler tricks that have worked well hitherto.

Bill Watterson had a series of strips about this in Calvin and Hobbes in 1992 [0].

> CALVIN: This is what I like about photography. People think cameras always tell the truth.

> CALVIN: They think the camera is a dispassionate machine that records only facts. But really, cameras lie all the time! Select the facts and you manipulate the truth!

> CALVIN: For example, I've cleared off this corner of my bed. Take a picture of me here, but crop out all the mess around me, so it looks like I keep my room tidy.

> HOBBES: Is this even legal?

> CALVIN: Wait, let me comb my hair and put on a tie.

[0] This is the one I quoted, but the one before and after it are related: https://www.gocomics.com/calvinandhobbes/1992/09/17