The whole thing depends on what you choose to call "our Age".

What was it in RJ's mind, really? We don't know.

We know his fictional world make abstraction of much of real world science, a bit the same way the creationists do. There's no big bang, the Sun is eternal.

So where did RJ drew the line between reality and fiction exactly? What did he chose to accept as "real" and what did he choose to reject for fictional purpose? What of our past is part of what he called "Our Age"? We have some clues: Most legends come from the early Age, and the end of the previous ones. Myths go further, to the dawn of the previous Age and beyond. So our legends and myths are clues.

He had Thom in EOTW speak of Ages where men ran with animals, and Ages in which the world was covered in Ice. That seems to indicate that, just like characters in the Third Age, and though unlike them we don't share their world view about the Pattern or Ages, we still have many facts/legends/myths from the past Age, and all sort of scientific theories and little more about the Age before that. "Our Age" seems to begin with the dawn of civilization, and end in some imaginary nuclear holocaust that RJ stopped talking about after book 1, as communist Russia broke apart in the meantime, and it was some years before the new geopolitics cleared up. The Age where humans ran with animals (and shamans walked Dreams) would be pre history and extended into primitive civilizationsbefore fading, both of which incidentally has given us several key elements of later mythology (from moon goddesses to cyclical time to animal totems and so on). The Age before would be the last Ice Age, and beyond that, in RJ's concept, there's an Age we know nothing, and which isn't at all what we believe our past beyond the Ice Age to have been.

There's also the matter of the earth being wholly different in the Third Age to what it is in "our Age". It isn't impossible the continents were ours in the AOL before the Breaking, but it's possible the theorical cataclysm that ended our Age changed them too, and if it was nuclear indeed, it may have wiped out almost everything, and left pretty much a clean slate for humanity to start again at the dawn of the AOL (which was either a very, very long Age, or a very short one. The peaceful state achieved could indicate the AOL civilization was stable for millenia before Shai'tan, while channelling could suggest humanity rebuilt itself up from almost nothing to the pinnacle of the AOL in a very short time as well, short enough to remember the lessons about war from the previous Age).

As for the Portal Stones... nothing confirms they're from the Age before the AOL. There could be a very simple explanation: they were buried during our Age and a few more, and only the AOL people found them.

Of course, between the Ogier and the Finns, nothing makes science-fiction-ish theories like having the Portal Stones brough by Aliens toward the end of our Age ridiculous. My feeling is still that they were the creations of the Finns. It's confirmed now they made the gateways (the doorways) to their world - them, not the Aes Sedai - and RJ confirmed previously they could travel to the Mirror Worlds somehow(he said they could put someone in one such, and empty one, if someone wasn't careful how he asked to be made "King of the World".) So they seem to have the knowledge, and they can also guess at the strength of angreal and such... and can feed on someone's connection to the True Source, like a gholam. We'll never know the full details of their relationship to the One Power, but it seems they can make objects that human qualify, perhaps wrongly, as "ter'angreal". It seems almost certain they made the original Foxhead medallion, which Elayne can reproduce, if imperfectly.

The Finns also spoke of themselves as "Ancients" - and they sure seem to know the "numbers of chaos"!! So my pet theory is that the Finns found the human world through their Portal Stones, and built Ghenjei as a permanent doorway, and later the two doorways for humans after they made a bargain with them. We can believe pretty much what we want, I'm pretty sure RJ intended to leave those ancient mysteries untouched and unexplained, or otherwise this would ruin the mythos, to give us "ancient" information not a single character has. I think it's the same reason why he always refrained from saying too much about the "mystery Ages" - a wise decision as many other works of fiction (Lost, Star Wars etc.) have proven over and over. If we're told too much, all the bolts and screws and gaping logical holes will show, and this would undermine the "realism" of the worldbuilding a lot, and by extension, the series itself.