I imagine aliens would use sexual activity as a form of communication.
All the facehuggers were doing was saying "Hi!"
Honestly, I think they are “we”, or at the very least our cousins, far removed. I think our history is replete with strange and similar occurrences and with the advent, not only of modern media and digital technology, but of globe spanning information networks with personal access, I believe that only now are we starting to have the ability to truly sort out some signal from all the noise.
I think the reality of time around us and the nature of how it truly functions is not as homogenous as we would like to believe. As was beautifully illustrated in the film “Interstellar”, albeit in extreme fashion, I think that “time” as we understand it has a direct correlation with gravity, and I think that, just as with any liquid or solid medium there exist unequal pressures, and bow shocks will emerge where those unequal pressures intersect.
I think that Earth is not homogenous in its mass distribution and that scientifically observable gravitational anomalies can and do exist in our world as a result of those unequal mass distributions. As a result, “time” itself as we experience it may not be smooth and equal as we’d like to think. It may have as much variation as the clouds and storms on Jupiter do, but perhaps on a scale that is mostly unnoticeable to us unless extraordinary circumstances arise. Like plate tectonics; the plates are always in motion acting in opposition to adjacent plates, but so slowly and on such a massive scale that us tiny humans are mostly oblivious to it, unless something happens to quake or erupt.
If, perhaps, the passage of Time behaved similarly to those massive plates then perhaps what may have begun smooth and equal is now all wrinkled up or folded-up and in on itself where those distinct regions of different time rates intersect.
I think that just as we ignore the time delays in conversations with each other until they start lagging beyond a second or so, perhaps these rifts and wrinkles go mostly unnoticed by us. Perhaps we traverse these time rifts and wrinkles as easily as we board or exit an escalator. I think reports of “ghosts” or “time slips”, if they likewise exist, may be evidence of these bizarre but subtle little eddies and turbulences in spacetime.
I think once you are able to master a level of technology whereby you can create a little pocket of space time that you can slip your craft of choice into, like a Joey in a pouch, that perhaps your effective footprint in spacetime can be reduced to point at which you could, intentionally or unintentionally, traverse these rifts and folds between regions.
Perhaps those inequalities may be tiny, but also somehow cumulative. If you or I were on a road trip and we suddenly found ourselves somewhere that’s lagging behind our home turf by 10,000 years, how do you think the locals would react us and our Winnebago? And how well would we interact with those fine cave and hunter/gatherer folk if we tried to stop and ask for directions? Would we even choose to interact if we could help it?