If life was actually seeded here, how might that have happened? By accident....or (hushed whisper) deliberately? Well, the idea of accidental seeding has been explored in considerable detail by a surprising number of non-mainstream thinkers and even by a few credentialed scientists (British astronomer Fred Hoyle being perhaps the most notable). The "accidental seeding" theory is called panspermia, and the idea behind it is that bacterial life came to Earth on comets or asteroids arriving from planets where it had existed before they exploded and sent pieces hurtling through space to collide some millennia later with our just-forming planet.
A variation of this theory is called directed panspermia, which replaces comets and asteroids with capsules launched by alien civilizations to traverse space for millennia and deliberately home in on our just-forming planet. However, the idea of conscious direction from any source beyond the confines of Earth is as abhorrent to science as ever, so directed panspermia has received little better than polite derision from the establishment. But for as blatantly as undirected panspermia defies the scientific tenet that all of life begins and ends within the confines of Earth, it is marginally acceptable as an alternative possibility. There have even been serious, ongoing attempts to try to determine if the raw materials for life might be found in comets.
The point to note here is that no one wants to step up to the plate and suggest the obvious, which is that some entity or entities from somewhere beyond our solar system came here when it was barely formed and for whatever reason decided to seed it with two kinds of prokaryotes, the hardiest forms of bacteria we are aware of and, for all we know, are creatures purposefully designed to be capable of flourishing in absolutely any environment in the universe. (Understand that prokaryotes exist today just as they did 4.0 billion years ago...unchanged, indestructible, microscopic terminators with the unique ability to turn any hell into a heaven. But more about that in a moment.)
If we take the suggested leap and accept the notion of directed-at-the-scene panspermia, we are then confronted with a plethora of follow-up questions. Were all of the planets seeded, or just Earth? Why Earth? Why when it was a seething cauldron? Why not a couple billion years later, when it was cooled off? Good questions all, and many more like them can be construed. But they all lead away from the fundamental issue of why anyone or (to be fair) anything would want to bring life here in the first place, whether to the proto-Earth or to any other protoplanet? And this brings us to the kicker, a question few of us are comfortable contemplating: Is Earth being deliberately terraformed?
Well, so what? What if we are just bit players in a cosmic movie that has been filming for 4.0 billion years? As long as we are left alone to do our work and live our lives in relative peace, where is the harm in it?
Is this fantastic notion really possible? Is it even remotely plausible? Consider the facts as we know them to be, not what we are misled into believing by those we trust to correctly inform us. The simple truth is that life came to our planet when it (Earth) had no business hosting anything but a galactic-level marshmallow roast. The life forms that were brought, the two prokaryotes, just happen to be the simplest and most durable creatures we are aware of. And, most important of all, they have the unique ability to produce oxygen as a result of their metabolic processes.
Why oxygen? Why is that important? Because without an oxygen-based atmosphere life as we currently know it is impossible. Of course, anaerobic organisms live perfectly well without it, but they would not make good neighbors or dinner companions. No, oxygen is essential for complex life as we know it, and quite possibly is necessary for higher life forms everywhere. If that is the case, if oxygen is the key ingredient for life throughout the universe, then from a terraformer's perspective bringing a load of prokaryotes to this solar system 4.0 billion years ago begins to make a lot of sense.
Let's put ourselves in their shoes (or whatever they wear) for a moment. They are a few million or even a few billion years into their life cycle as a species.
