We've recovered air trapped in ice cores up to 2 million years old. Odds are if there had been an advanced ancient civilization of any size (and an advanced on

We've recovered air trapped in ice cores up to 2 million years old. Odds are if there had been an advanced ancient civilization of any size (and an advanced one is going to tend to be large) and for any length of time, they'd have done quite a bit of lead smelting (lead's really useful and super-easy to smelt... shame it's poisonous), and we'd see it in the ice core record. Let alone something like fossil fuel use. Plus probably dozens of other markers of iron-age industry or later, that I don't know about. I very much doubt any very-ancient humans/hominids got past Bronze Age tech, at best. If I had to place a bet on it, I'd bet against them having gotten past stone-age tech at all. I think we'd see evidence of it.