Three of your possibilities are "locations" for the Great Filter, as I read them:

> Intelligent life is far more of an aberration than we realise.

The filter is between "smart mammal" -> "human-level smarts." So there's lots of planets with lions, tigers and bears, but not talking dinos (or whatever).

> Intelligent life is actually very dumb on a macro scale, and falls prey to Malthusian collapse, either by falling into a significant energy gap or by destroying their biosphere.

The filter is between "21st century humanity" and "interplanetary/interstellar civilization." The universe is full of ruined planets, noticable because they've got transuranic elements floating around they shouldn't have.

> Intelligent life tends to succumb to dysgenic fertility, and ceases to be intelligent.

The filter is somewhere between "human-level smarts" and "interplanetary civilization." The universe is full of Morlocks.

We want the filter to be behind us. If it's actually "life is nearly impossible" then we're golden. Life on Mars 'pushes' the possible 'locations' of filter further forward (so life is probably common). If it's multicellular life, that pushes the filter further again, etc.

We're only "golden" until an unfortunate gamma ray blast occurs somewhere nearby and wipes out life on Earth in moments.

The important thing to realize about the Fermi Paradox is that all generalizations about behavior fail automatically as explanatory theories.

It only takes one small group within one species to generate a self-replicating probe, at which point all of the galaxy is visited in a few million years.

A solution to the Fermi Paradox has to explain why that event has never happened despite the fact that some element of our species will do exactly this at some point in the next thousand years. The laws of physics allow it, and our psychology is clearly up for it.

The whole Fermi Paradox thing bugs me too, but in a different way. It assumes we have the capability of detecting the presence of other intelligent life.

The largest radio telescope we have (the 305 meter diameter Arecibo) would need to have it's sensitivity increased by around two orders of magnitude JUST to pick up our TV/FM/AM signals from outside the solar system. If we move into the narrowband signals then, depending on the source-strength, it could pick up signals at up to a few thousand light years... if it happened to be pointed in exactly the right direction at exactly the right time. So, our most sensitive instrument is only capable of measuring a fraction of a percent of a fraction of a percent of the galaxy.

I just straight-up don't believe that we're even remotely approaching the capability of asserting that the galaxy is sterile of higher life that's constantly dumping EM noise... and that's without assuming they've found ways to transmit data that we're ignorant of or that we've seen it and just haven't noticed it.

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The other thing (and I feel a bit like a religious person saying this) is that we have exactly zero basis for asserting that the type of machine you're talking about haven't been here. Given that if one of these machines came here, and stayed, the Earth itself would annihilate all traces of it (especially on the surface) within short order we shouldn't necessarily expect to find evidence of a visit.

Taken to the extreme, you could even reason that all life on Earth could be the product of one of these machines.

Not only is sensitivity an issue, but also frequency range. I feel quite confident that more technologically advanced civilizations will communicate at frequencies we are currently unable to demodulate. It's more efficient. Look how our frequencies have scaled on the order of a hundred years.

> Taken to the extreme, you could even reason that all life on Earth could be the product of one of these machines.

Hah, hilariously ironic. "Where is alien life in the universe? Are we the only ones?" continually bemoan the descendants of the organic probe sent to Earth to populate it with intelligent life.

> It only takes one small group within one species to generate a self-replicating probe

And what would that probe look like?

For it to be a useful to the sending civilization, it needs to go out, replicate, and send information back.

The first two are easy. Send out lots of meteorites with bacteria on them.

The third is not so easy. Creating a self-replicating machine which can then transmit back across interstellar distances or store information in its replication program and then send more of itself out is hard.

Or, you help life evolve and then wait for the results to reach the point where they can send out their own probes and signals...

>>And what would that probe look like?

And more importantly why would anyone send anything to anywhere?

I never understand the argument people make about probes spreading across galaxies. If we assume they are at least as intelligent as we are, then purposelessly wandering in the universe would be least of their goals.

I can understand if probes have military goals. Like for example to evaluate threats to them. But like us here on earth, and with their technology would be carried out at a technical sophistication we have no remote capabilities of detecting currently.

> And more importantly why would anyone send anything to anywhere?

You're assuming everyone is rational. For instance, if I were a future billionaire I'd totally do it... knowing I'd never see even a glimmer of return on the investment... just cause.

Yet how many billionaires on earth do that?

I guess once you have the money you also develop a sense of responsibility about how you wish to spend it. Every thing in the universe, even if we imagine unlimited resources at one's disposal- Every project has its costs. It might be time, energy, or other manual resources. You have to continually trade one for the other based on the goals you have currently.

We are assuming that life forms will just build probes and let them wander for some remote chance of another life form to see it.

It's impossible to judge what one might find valuable. Preserving life as "a thing" might be just as important to future-wealthyperson as fighting Malaria is to a current one.

> A solution to the Fermi Paradox has to explain why that event has never happened

How do you know that it has not? I'm not seriously asserting that it has, mind you. Just noting that there could be a swarm of radio-silent probes in the Kuiper Belt, in which case we would have no clue whatsoever.

It didn't eat us.

One'd expect self replicant things to grow into every available ninche, however irrelevant it is. Thus there's no self replicant thing consuming our galaxy (or there is, but it's incredibly new).

Maybe the first one prevents other intelligent species from arising, and the anthropic principle applies. We're the first, otherwise we wouldn't be here.

Another idea is that basic game theory and physics applies to everyone. It's virtually impossible to defend against attack by objects accelerated near the speed of light. The only way to be safe is to destroy potential threats before they destroy you, and be very very quiet.

Or intelligent life doesn't leave the sort of markers we have been looking for up to now. I don't buy the sim theory at all and think it's a dreadful philosophical cop-out.

> Personally I think we're in a sim and we're about to lose the game

I agree with your last point; however, I believe this is actually a virtual school rather than a "sim".

> Intelligent life tends towards simulation, rather than expansion.

Someone didn't take the Internet away from them when they were young, so they grew addicted to it. Bunch of navel-gazing nerds.

> Intelligent life is actually very dumb on a macro scale, and falls prey to Malthusian collapse, either by falling into a significant energy gap or by destroying their biosphere.

Looking at the Homo "Sapiens" species with a critical eye, I fear this is the most likely explanation.