Exactly what it says on the tin. Are there any stories where Humans were an ancient precursor civilization in Equestria?

Whether they're extinct by modern Equestria is irrelevant, either way is fine.

Well, most of the stories I can name that have that basically spoils a lot of stuff because they have that.

Diaries of a Madman. Good read. Dark as hell.

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Links?

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To Be Remembered
Scribbler Productions did a radio play of it a few years ago and it's really good.

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https://www.fimfiction.net/story/45860/diaries-of-a-madman
It's very long. Have fun.

Anthropology (not sure if that's how it's spelled)

I think I have two listed on my shelves that fit the bill:

Redemption - https://www.fimfiction.net/story/3326/redemption
Tales of the Oppressed - https://www.fimfiction.net/story/172088/tales-of-the-oppressed

I think ther used to be some of the most popular stories during the fandom peak

https://www.fimfiction.net/story/1438/the-luna-project

The Dragonverse series of fics I'm working on has that as a premise, but the "episode" where they first go into detail about it hasn't been started yet. The Group's series bible mentions it, though. The ancient precursors (called the "Orions" by the modern inhabitants) eventually got into a war with dragons after ten thousand years of living in peace, and almost exterminated the dragons, only to have to flee into space when a new breed of dragon proved too strong for them, leaving the Orion starbeast behind so the new dragons wouldn't chase them to avenge their fallen ancestors.

(The Dragonverse flips dragons and ponies, grants Dragons their own tribes, and flips genders, too. It also has quite a few things to make it truly different, such as all the villains being smarter than their Prime universe counterparts.)

(Some "Orions" failed to escape and had to go into hiding, so they will play some role.)

there's this: https://www.fimfiction.net/story/412080/infamous-a-new-beginning
I've written humanity to be an extinct species that existed millions of years before the creatures that roam Equus now.

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Anthropology

Even in death we fight https://www.fimfiction.net/story/361525/1/fall-of-equestria-even-in-death-we-fight/forever-and-ever

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Humani Victoria

dam. there was one I read some years ago, it was explaining why Diamond Dog gather gems.

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