There’s an interesting exposition of the reason why claims of alien (extra-terrestrial) contact with this planet is extremely unlikely.
I most agree with it: the distances, the length of time it would take technology to develop that would make interstellar travel possible, the sheer luck that would be needed to stumble upon another civilization.
In fact I would go further, I think there’s a chance civilizations discover something like limited control of anti-matter, which it only takes a single nutter to detonate, taking out an entire solar system. We call them “supernovas.” We assume they’re all natural phenomena. If the technology to travel between stars is as powerful but takes longer than the development of a self-extermination bomb, the latter will be developed first by a death cult (easier to make an UNCONTROLLED explosion than a controlled one). Therefore no two interstellar civilizations will ever meet. The upside of this is that this will always be fiction.
But that’s where I have to draw the line.
The simple problem is, we’re not sure what extraterrestrial life would look like. Consider an ant. How would it describe Manhattan to another ant? Now try the other direction: what do we know about how life would evolve in the atmosphere of a gas giant? Would we recognise life forms based on silicone if we saw them? Until 30 years ago, it was assumed that most stars don’t have planets. Why? Because at the time none outside this solar system had been identified. But until about the same time it was assumed that “nothing can live in sulphuric acid.” Wrong.
Claims of alien contact and counter claims of no alien contact suffer from the same problem. We don’t really know what we’re looking for looks like. A bit like looking for something different in a haystack without knowing it’s a needle.
If there has been a close encounter with a primitive society on Earth, this is the one I’d bet on. Creating gigantic pictures of animals that can only be seen from above and only really spotted in the 1930s. I’m more than 99.99% sure they aren’t meant to be seen beings in flying saucers. And there is no doubt that local technology was capable of making them. But no one has been looking at the sky systematically for 50,000 years.
Speaking of which, there’s a lunar eclipse to try and catch in a few minutes.