Taken

In folklore, the Elves take a normal baby and leave a changeling in its stead. This is noticed when the child turns-out to be strange-- withdrawn, addled, fey, or otherwise undesirable.

This is typical of Humans-- they get it wrong. Why would the Elves want normal babies? In fact, the baby is not exchanged, but changed by the mysterious "elvish influence", from Human to Elf, which makes it an alien among Humans, so of course it doesn't seem like everyone else. And the change isn't necessarily made all at once, to a baby in a cradle. Often, nothing is noticeably strange until the onset of puberty, when there is suddenly much more to influence. But influence can be effective into the mature years-- that "mid-life crisis"?

And where it used to be "taken by the Elves", it has become "taken by Aliens", which is just Humans updating their wrongness-- in the world of nuclear warfare and all the other wonders of science and technology, natural beings like Elves no longer signify, but futuristic space-craft carrying humanoids do, so...

But as in the olden days, most of those "taken" are just confused people and/or liars. In reality, those benefiting from elvish influence keep that to themselves, and since no-one believes in Elves anymore, no one sees an Elf-changeling; instead, it's a person with autism or some other modern syndrome. However, changelings can spot each other pretty readily, and they often make their true identity obvious to their fellows in various improvised ways. The thing is-- many changelings don't know what they are, from how they are, if they haven't been told, but they know it's something, and they're on the look-out for others like themselves.

So, if you haven't been told, I'll tell you here-- yes, you are probably an Elf-changeling, and even if, strictly speaking, you are not, it doesn't matter-- if you are elvish, you are, to all intents and purposes, an Elf. But it's not so much a matter of identity-- ultimately, elvish is as elvish does, and, to some extent, you can choose elvishness. In fact, you must choose it, and work at it, because, surrounded by Humans and the world they have made, you are heavily influenced (corrupted) by them. And until you have become well and truly an Elf, it can be a hard road for you to travel. Sooner or later, though, you encounter others of your sort-- not always the blessing it might seem, so take care-- there are Elves and Elves (and faked Elves). But don't go traumatic-- trust yourself. Remember-- self-possessed self-reliance will get you through most things, generally. You need to get your direction from within-- the outer stuff will sort itself out with a little applied intelligence. As an Elf, you are an agent of change, perhaps a secret agent. Though you may in time fall-in with other Elves, you will never be a herd-animal, and much relies on your inner access to things that the Herd knows nothing about-- so you had better get down to that, before anything else, and you'll be fine. And someday, you yourself will have developed the inner substance which can influence those you come upon with themselves a latent bent toward elvishness, helping them along.

Until then, fellow, Go Deep! And use what you have brought back from there to work in the real world for the coming of the Edhli-menning!