Ever since the beginning of recorded time, humanity has pondered on that age-old chestnut, "Where did we come from and how did life originate on this wondrous planet of ours?" This has, of course led to as many theories as there have been people to think about it with very few agreeing on anything except the fact that no-one yet has a firm answer. Whole schools of thought and great religions nave come and gone without being able to put a finger on it for one obvious reason. That being that no-one was actually there at the time.
Countless religions claim that their various deities created the universe and all that is within it (including our world and us) at a whim or in a dream or whatever. All very poetic and full of mystery, but really explaining nothing. The problem we here at Stalag Invisible find with all these theories is that they all tend to be either:
Then, of course, we have our rationalists, who with Dr. Miller's "primordal atmosphere and a spark-plug in a jam-jar" experiment claimed to show that life evolved as a result of chemical reactions in our nascent biosphere. Anyway, Dr. Miller's experiment doesn't satisfactorily explain why one of the first dominant form of life to evolve (plants) totally altered our atmosphere instead of evolving to adapt to it. Surely, given our understanding of natural selection, it would have been more logical for the life-forms that evolved to adapt to the then existing atmosphere.
We here at Invisible Palace take a much broader view on this great topic. For instance, we accept that there is "intelligent" life elsewhere in this galaxy of ours and the rest of the universe at large. Not only that, but we accept that there are most likely other species who got to where we are today long ago as well as others who are just "crawling out of caves and down from tress" so to speak. At this point, we diverge...
Consider a space-faring species in this galaxy. They would have a far-flung civilization with their craft plying the highways and byways of space taking goods, passengers and cargo from here to there as the case would most likely be. Oh yes, they would have their great visionaries guiding them forth, their great heroes doing great deeds. But what about the ordinary schmucks who do the day-to-day donkey work? Yes, the grunts who actually do all the work to get their great space craft from A to B and back again? The ones who do all the essential work that grand plans can't even get off the ground without? Theirs is an unglamorous and often boring lot. Meaning that unless they were mindless robots, they'd need releif and entertainment.
Consider a group of such "deck-hands" on a long journey, bored senseless with tedium. On one of their journeys, the pass by a newly-formed solar-system with some as-yet lifeless planets. So, for a bit of diversion, they take a short side-trip down to one of them. And, like the slobby inconsiderate campers that they are, leave behind a pile of rubbish and their equivalent of a mountain of empty beercans, etc., etc. These beings must have been from a biosphere which contained oxygen in fair quantities. As with most piles of rubbish, it soon began to fester, rot, decompose, etc. The remaining life-forms which survived, found themselves in an environment without any competion and filled it up as rapidly as they could, altering our atmosphere along the way.
4 billion or so years later and, hey presto, here I am at the word-processor writing about it. This magnificent theory also explains why all the aliens in the films breathe oxygen and speak english and their women have such formidable breasts. The reason being is that they all evolved from rubbish-piles left on once-barren planets billions of years ago by the same long-lost galactic civilization!
We here at Invisible Megacorp are now directing our top scientific research teams to locating the original touch-down site. Furthermore, we are also busily examining all stars in the local arm of our galaxy for simliar oxygenated planets to which we will broadcast endless repeats of the "I Love Lucy" show, the Antiques Roadshow and Russ Abbott.