Aliens are not going to think like us. They are going to think nothing like us. Logic and mathematics might be the only common ground we have at all.
even if logic and mathematics are the only common ground (although I would expect physics and chemistry to be in the mix as well) it doesn't take a genius to work out that a planet has a finite amount of living space and isn't the most stable of places to live (99% of all species that have ever lived on Earth have been made extinct due to everything from meteor impacts through volcanic activity to climactic change) and will know that their only hope for species survival is to put some of their eggs in a different basket (colonise another planet)
Looking for evidence of gods (which is what the difference of several thousand or heaven forbid million or billion years amounts to) is ludicrous on its face, and if that isn't immediately obvious to you, then I don't really know what to tell you.
no-one is looking for evidence of gods, but if a technologically primitive civilisation of our past was visited by an advanced civilisation from another star system, the accounts of that meeting (from the primitive view point) would read pretty much like most of the early religious texts.
if it is ludicrous to look for the origins of the myths and legends then, by that logic, it is also ludicrous to research our past in any way.
it is ludicrous to say that if we were visited there would be some evidence and the dismiss out of hand any and everything that could be that evidence.
even the creation described in Genesis could be interpreted as alien intervention given that ET could clone himself (create man in his own image) then take another tissue sample, remove the Y chromosome and replace it with a duplicated X chromosome to give male and female of the species.
NOTE I am not saying that this is what happened, but I find it interesting that several thousand years ago technologically primitive man described something that has only recently been found to be possible.
this doesn't mean that everything in all ancient texts should be taken as 100% true (owing to translation errors and a game of chinese whispers stretching over millenia) but as some historians and archaeologists have discovered, many myths and legends have some basis in fact.
the Illiad and the Odyssy talk of a city/state called Troy and an archaeologist followed the directions and found the remains of a city in the right place. this could be a coincidence or it could be that there was a Trojan war and the stories were basically true with some embelishments added through retelling. take WW2 as an example. we know it happened and that there are many interesting and exciting things that did happen, but the popular image we have of WW2 today is from films like Saving Private Ryan where the setting and the main events are real but the personal story is fictitious. just because there was no Private Ryan doesn't make WW2 fiction.
another interesting find made after following the directions from a myth was that when the course plotted in the story of Jason and the Argonauts is followed it leads to an area where fleeces are thrown into a river to collect gold dust then hung on a tree to dry. much of the story is embellishment but there is a grain of truth behind it.
the question this raises is are there similar grains of truth in any other myths, legends or religious texts?
if we follow this question to its conclusion we get the question what inspired so many ancient peoples around the world to write accounts of visitors from the stars?
if those accounts have some factual basis then the chances are that we have been visited but the evidence we have for it is being overlooked due to a polarisation regarding those texts (those that follow them as religious texts don't want a mundane explanation of the events described and those that don't believe class them as superstition and unworthy of research) and the embellishments and mistakes added over the years.
