There are no old, space faring civilizations, for one inescapable reason. Technology is incompatible with species. No ifs or buts.
Brief explanation: Life of any kind, in any environment must always evolve as species - defined as multiple beings sharing a common 'genetic code base' - regardless of how the information is encoded. In our case it's DNA. In all species the individuals serve as reproductive vectors for the code they carry, and individual survival of the fittest is required for any species to evolve and adapt to its environment. This implies that individuals also die - this is necessary, otherwise natural selection cannot operate, hence no evolution.
Life is likely quite common in the Universe. Even if intelligence is statistically a rare development, there still should be countless instances, including plenty long ago, where 'long' means more than one star lifetime. So if intelligence results in technological cultures, including any kind of major engineering or space travel, where are they all? Even if such civilizations choose not to say hello to us, we should still see evidence of their works.
But we don't. There's apparently nothing. Just elusive local UFO sightings, of unknown reliability. Certainly no daylight landings in city park, so to speak. That was just to restate the Fermi Paradox. Where is everyone? We exist, so there should be other civilizations like us, but much older and more technologically advanced.
The logical error here, is to assume that technology is a continuum; that a society develops technology and then just continues to progress as a society - a cooperating population of individuals with a common genetic heritage, hence species.
But this NEVER happens. Can never, will never, never does. Here's the inescapable reason.
As a species develops technology, they inevitably discover the nature of the physical encoding scheme of their own biology. They develop the means to manipulate that coding scheme. Our fledgling genetic engineering is an example of how that starts. Quite rapidly the science of engineering their own coding will advance, since after all it's just a messy 'wet' version of computing science, and you can't have high tech without already being well advanced in computing technology.
Somewhere in the process of unraveling their genetic coding, an intelligent species will also develop a science of consciousness - what we presently think of as AI, but which is ultimately about minds in general and how they work, including our own.
As these two science threads advance, genetics and mind-science, it is 100% totally inevitable, that at some point individuals will gain the technological capability to begin modifying their own nature. We already do this - for instance using altered viruses to perform corrective edits of faulty DNA, eg the Cystic Fibrosis cure.
But that is primitive stuff. Ultimately, gene engineering and AI technology provide individuals with the means to 'transcend' - to embark on total self re-engineering.
At this point in the analysis, most people become incapable of logically carrying through. It seems there's another strong cognitive bias or two, not listed in the Wiki. One is that most people seem incapable of thinking impartially about the probability of termination of their own species. Another is a mental block against thinking logically about the likely motivations of entities that do not share the species-centric world-view of us genetic humans.
Here's an idea: try thinking about an intelligent entity, that does NOT share any of our reproduction-motivated species-protective instincts. Nor any of the many cognitive biases in the Wiki list.
Because that's what you get eventually, after any species-based individual achieves self-engineering capability, then immortality, an ability to deliberately optimize and enhance it's own mental capabilities, weed out instincts no longer appropriate to it's new existence as an immortal space-traveling entity.
Anyway, the point is that 'technological species' is an unstable state, that cannot last. It inevitably results in one or more of the genetic members of the species diverging into self-directed enhancement. To which there is no upper limit.
The problem is, that a society of genetically homogeneous members of the species, and one or more highly diverged self-engineering entities, is totally unstable. Coexistence is impossible. For many reasons, some of which are: competition for resources, evolution-derived 'anti-outsider' hostile instincts, inevitable desire of many individuals in the species to avoid dying by transcending themselves, governmental power structures feeling threatened by the inevitability of major change, etc.
What happens then can involve many different scenarios, but they *all* end up with there being no more 'technological species'. Results can include 'no survivors', one transcended survivor, multiple transcended survivors, etc. But the result in which the technological society survives, is not an end point. It is just a loop - events will repeat, until one of the other end-points occurs.
The Universe is full of life. But there are two kinds:
1. Ecosystems in which intelligence has not yet evolved to the point where technology develops.
2. Very high tech immortal self engineering unique individual sentient entities, with nothing in common with any species. In particular, such beings won't have any pointless (to them) instincts to reproduce, populate, conquer, etc.
The transition between stage 1 and 2 occurs very fast, on stellar timescales. In our case the entire timeline from appearance of Homo Sapiens, to Transcended appearing is going to be less than one million years. From technology, radio, etc, to transcended, probably little over 100 years. If that's typical it's no wonder we don't even detect radio waves from other civilizations. Such expanding shells of radio signals will be very thin - less than a 100 light-years thick. Blink and you missed it.
A good analogy for the mindset of Type 2 entities would be 'space gypsies.' If you can consider a vast fleet of networked, stealthed, ancient starships, forming a single conscious entity, who is wandering around the Universe on a timeless journey of adventure and discovery, a gypsy. But why not? That's what they are.
Incidentally, the 'little gray guys' of UFO lore are not 'aliens'. They are just mass produced remotes. Materially efficient, easily manufactured Waldos. Probably built on a pattern something like open source shareware, passed between Gypsies when they happen to meet and trade stories, knowledge and code.
So why don't they introduce themselves to us?
Can you really not see it? More cognitive bias blinkers...
What is the one thing that such beings could value? They inhabit a Universe of unlimited material resources. But there is one thing that never grows stale. Stories. True ones. Even better, if the story is a chronicle of the arising of a new Gypsy (for want of a better name.)
If you find someone who is telling a great and original story, that you know others you may meet will like to hear and value for it's genuine nature and honesty, would you interrupt them and start dictating how the story should go?
No. By doing so you'd destroy it's value. Even merely announcing your own existence would hopelessly corrupt the telling. It wouldn't be a valid true saga, it would have become just a kind of echo of your own ego.
And that is why the one or more Gypsies who have been observing our Solar system probably for millions of years, confine themselves to simply watching. With possible exceptions of doing what they can to invisibly prevent humans from turning Earth into nuclear slag, because that would certainly ruin the story, ending it prematurely. They're waiting... if and when Earth produces a Transcended, then they'll say hello to that newborn, and welcome them to the Eternal Adventure. They are very patient.
Incidentally, Humans should stop attempting (and sometimes succeeding) to shoot down UFOs and dissect the Grays. It's annoying.
A related SF short story: http://everist.org/texts/Fermi...