Not to confuse with simulation theory, but how possible is it that we (humans) were placed/created on Earth by aliens to create an observable simulation of civilization?
Before we had solid evidence for evolution, I would say that it wouldn't be outright implausible - we had no basis for saying we had a long history on this planet and each species seemed sui generis. If we squint we can see that the story of Genesis isn't so far from this idea, albeit none of the writers of Genesis would agree God was merely an merely advanced organism who wanted some entertainment.
However, after the "Modern Synthesis" the idea that people were put here as fully formed organisms flies in the face of mountains of evidence to the contrary. The paleological record and recent advances in "systematics" allows us to trace our lineage back through the phylogenetic tree. We are left with two choices:
- Humans evolved from ancestor species over billions of years.
- The entire crust of the planet was engineered to appear like there was evolution yet it was not the case -- humans are only a few thousand years old.
Therefore, I'd place the likelihood at close to nil that we were placed here fully formed.
A more interesting and plausible hypothesis is that perhaps extraterrestrials leveraged pseudo-panspermian planet seeding approaches to kick-start the process. They would look for planets in the habitable zone with moderately chemo-reactive atmospheres (not totally inert, not highly oxidizing/caustic) and liquid of some sort (maybe it has to be a polar solvent? who knows).
Why they would do this I have no idea, but if we assume that since we exist, then it is likely other species exist as well, and that the universe if very very old, then it's not impossible (although I'd say unlikely given the vast reaches of space) that extraterrestrials were the source of the key molecules needed to kick start abiogenesis on Earth.
If you are asking for a frequentist interpretation, then the likelihood is unknowable until we discover the truth of the situation. Then we will discover that the likelihood was either 1 or 0 all along.
If you are asking for a Bayesian interpretation, the likelihood will depend on what model one uses to represent the prior probability, as well as what information is used to update that probability. For example, under some models (i.e. those that force a zero probability to the likelihood of "aliens") then the likelihood will be zero.
Well, we'd need to do a random sampling of human-like civs, say we settle for N of them because N is a nice number, statistically that is. If n of these civs are alien petri dish cultures, the probability that any random human-like civ is an alien petri dish is n/N.
Since a petri dish culture could not have petri dished itself, IF there are aliens out there, there's at least 1 non-petri dish civ. That is to say, the probability that a civ is not a petri dish cannot be 0.
Since it seems that we all agree that there exists no basis as to how to estimate the probability, I will make a speculation.
Supposedly it is true, then we are living inside something like a "Truman show".
It is reasonable to accept (as a hypothesis) that as we have "full control" over the earth either as observers or as actors, another species became able to do this to a more "wide" perspective and in a similar manner that we have "created" dog species for example and crops by interbreeding and so, somehow they did the same, so in a sense there exists a "global farm" so to speak with multiple layers of manipulation.
So far so good, but we have to address some problems:
If they came here how was this possible, under the assumption that travel on space cannot exceed the speed of light? is this obstacle a matter of perception of reality?
How is that we do not have knowledge of this? perhaps some of us have or had in the past?
Don't any artifacts or hints about this intervention exist? perhaps these are mistaken with something else?