I believe that this is so.
There are many arguments against the presence, potential or actual, of alien beings. Primarily, these consist of essentially philosophic positions, such as "We Are Alone in the Universe", based upon deistic arguments which tend to cite various religious documents as infallible source. Another argument, considerably more scientific but no less dogmatic is the argument which proceeds as follows:
In this Universe, granted, there are many stars, many of them much like ours, many of which would have been formed by the same stellar evolutionary processes which spawned our own Homeworld, of approximately the same age, in stellar-evolutionary time-scale, besides which mere geologic time-scale pales in comparison. It might also be argued that while there are many stars fairly near us which are similar in type, composition, radiance, metallic content and other criteria which would tend to lend credence to the argument of parallel evolution on parallel worlds, our Earth may be quite unusual in that it is accompanied by a very large sister body (Luna), and also, whatever the forces of evolution or deistic interference which gave birth to life itself, we have certainly been subjected to a bombardment of cometary and asteroidal matter which has nearly extinguished this world's life on several occasions. Without the creation of niches by the elimination of dominant species, allowing the proliferation and rapid evolution of new orders of life, intelligence might have never arisen, or alternatively, it might have been established (or nearly so) and wiped out. Our own primacy seems to be rather accidental... and certainly much delayed from the time when intelligent life might have been expected to have been forced from within the ranks of the dinosaurs. The argument against parallel evolution on parallel worlds falls apart if one considers that our Earth has been set back in time by seventy million years by an immense cometary impact at the end of the Cretaceous. Were we to encounter aliens evolved by the same conditions, and at the same rate as were we, we'd have to go back in time some fifty to ninety million years. But, of course, it can be argued that other similar planets formed by similar processes around similar stars forming at the same time as our own sun formed might have had their own parallel setbacks on the evolutionary timetable. This might allow species which would otherwise have had an average of seventy million years to rise from (and to fall back into) the dusts of time to interact, could they but travel here.
But how would they get here?
I maintain that the aliens we see come from our Homeworld.
Several theories immediately come to mind.
The first is commonly categorized in InterNet newsgroups as the "Interdimensional Elves Hypothesis". Certainly legends abound throughout all cultures regarding people generally described as smallish, very fast, with abilities which might be ascribed, under Clarke's Law ("sufficiently advanced technology is indistinguishable from magic") to the supernatural; and with pointed ears sitting high upon the head, and oddly slim and markedly inflexible necks. But such legends can be easily discounted as apocryphal tales dating to early interactions between Celtic tribes and Pictish tribes, but the Picts were notably low-eared, and the Celts who spoke of high-eared peoples with unheard-of skills themselves were often regarded as elven by foreigners such as the Romans who strayed into their lands. At any rate, despite overwhelming evidence which supports theories of an infinitude of parallel realities splitting off at each potential variance of quantum indeterminancy interaction, there is little evidence that travel between these parallel worlds is something which can be easily actualized.
But then again, "you never know".
I personally believe that if one were to deconstruct the mythology of the tales recorded by the Brothers Grimm, in the light of modern homonid paleontological theory, discarding the politically-correct paradigm manipulations of the anthropological left, one might more easily arrive at the conclusion that the Aliens among us are no aliens, but are merely other kinds of human beings, who have always moved among us.
But what of a fusion of the two theories?
There's always been luck, a prime mover in the affiars of Men and indeed of all living things. Luck, and chaos are concepts which can be easily reduced to mathematics generally much less complex and mind-stretching than is the math of quantum mechanics. But all of these, like all of mathematics, interrelate. Could it be that when one has a stroke of luck, one has momentarily crossed into another universe, one in which one's survival was more likely, to then return to one's original frame of reference? But this is mere fruitless conjecture. One could equally argue that there are multiple plenums which tend to converge, toward a common reality to be ultimately shared by all who survive their original worlds. Evolution might indeed be occuring on parallel worlds, along parallel tracks... among wildly divergent people. Perhaps, to continue my mad speculation, the lucks of various individuals have cast those individuals, or small tribes, out of their worlds into the worlds populated by those of another kind, although the convergence might have been of limited, often short, duration.
In mathematics, there is what is known as a convergent series, where most of the elements of several systems which exist independently, because of a multiplicity of shared elements, tend toward very similar solution-sets. Perhaps the multiplicity of parallel worlds is a case similar to the generic concept of the convergent series... perhaps in all of the worlds where hominids rose to primacy, affairs developed towards a common point... and convergency and congruency became equivalent to quantum parallellism, and the worlds began to merge. Doubtless the mathematical community can provide stunning examples of both proofs and contradictions.
What is important is that aliens are here: and as Pogo would say: they is us.
There are clearly ogres walking among us, and vampires, and trolls, and the most frightening of all, there are clearly mortal and deadly Men within the throng. Perhaps those who can surf the wavefronts of quantum indeterminacy, and do so as a matter of reflexive survival, becoming thereby the epitomes of luck, the gods themselves who contend in vain against time alone, are among us even now. The population of Homeworld appears to have exploded far out of proportion to the number of recorded live births. Perhaps the recorders have been less than diligent, or those queried have hidden their increase. Or perhaps, as some have suggested, interstellar visitors have arrived and largely remain disguised as roughly-manlike beings, with the disguises being either rubbery people-suits or perhaps hologram projectors of unknown type.
At any rate, there are many different orders among us, and each we are alien to the other. Some of those who now visit or reside within this confluence of worlds are at odds with the others... we need but look to our various evolutionary histories to easily understand the reasons.
None of us can return whence we came... and most of us cannot seem to live together.
Perhaps we were better off had we actual extraterrestrials with which to contend.
But perhaps we do...
It has been theorized by some that of of the reasons that the most plausible faster-than-light (FTL) drives are equally implausible simply because of the fact that the quantum-tunnelling that would allow wormhole transit (whether or not by "anchored-wormhole" or "unanchored-spatial displacement bubble" a.k.a "warp drive") also tends to tunnel equally through to congruent yet mutually-exclusive Schrodinger Continua. Matter transported through the wormhole tends to arrive in a multiplicity of possible universes, and indeed, it might well be that the most insoluble problem in the mathematics of wormhole transit is the scattering into quantum indeterminacy of all of the particles, virtual and "real", which arrive as a directed wavefront, particularly in the case of anchored wormholes... the wavefront might arrive at the intended physical location, but scattered evenly through all of the universes. But as (see above) luck would have it, the various universes are gathered by a homeostatic tendency toward congruency, and are excluded from the universes where they cannot exist... and quite possibly force gatherings into "plausible universes", where they can exist. This tendency towards order would at first seem to be counter to the forces of entropy, but in a universe primarily entropic, how else can order, or life itself be explained?
It seems almost self-evident, in these terms, that wormhole FTL transit, especially anchored wormhole FTL transit, would tend to "gather" parallel-yet-disparate universes into a convergent plenums.
What would aliens (be they evil humans, extraterrestrials passing-for-human through technologies as yet unknown to mere Earthlings, or Interdimensional Elves) do when they got here? (Note, this is a basic conspiracy-theory page. But insurgency, whether by illegal aliens or extraterrestrial aliens, remains largely the same.)
Take a look at some places in the Washington DC suburbs in Maryland. Take a look at the Bauer Stores, and the facilities at Aspen Hill, all-too-close to Rockville, Maryland, all too close to Washington, DC.
Prepare yourself to be (if I can pull it off) drawn into a scary shared delusional worldview. Well, I sure hope it's delusional... at any rate, I smell possiblities of cracking into the role-playing-game market here...