I think that the big variable in the Fermi / Drake analyses is time. The amount of time that we have produced anything observable to any other civilization is MAYBE 100 years, and our electromagnetic footprint may actually be getting smaller as communication goes from analog to digital and from long wave to very short waves. And, how long has it been since the last above ground A-bomb test?
Worse, there is a component in many of these types of equations that posits that any being that progress enough to be observable is necessarily descended from aggressive predators. So, the number of years that have gone by between us fighting with muscle-propelled sharp and blunt instruments to having the capability to destroy ourselves has been less than a millennium, still a blink of an eye in cosmological time. Some have theorized that any predator-based species will eventually and certainly acquire the means to destroy itself (which ours probably will). So, TWO civilizations existing at the same very short timeframe capable of observing each other would be almost impossible.
OTOH life has been discovered in the strangest, most inhospitable places on Earth; some of it doesn’t even depend on solar power like we do (those creatures that hang around smoker vents in the deep ocean are actually “powered” by the nuclear energy and heat of the Earth’s core).
So, I believe that life is probably fairly common in the Universe - but “intelligent*” life may be rare and fleeting.
*If we are so darned intelligent, why will we probably eventually destroy ourselves?
That’s not really relevant. It only shows life can demonstrate variability; it does nothing to make abiogenesis any easier.
“I think that the big variable in the Fermi / Drake analyses is time.”
Just as valid as any other theory. Same with the ‘aggressive predator’ theory’ making only brief windows of any possible communication possible fairly close together. It’s all based on an example of one.
Freegards
https://en.wikipedia.org/wiki/Great_Oxygenation_Event
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Any intelligent beings within telescope distance would have known that life was here since the The Great Oxygenation Event, 2.5 billion years ago.
https://en.wikipedia.org/wiki/Great_Oxygenation_Event
OTOH life has been discovered in the strangest, most inhospitable places on Earth; some of it doesn’t even depend on solar power like we do (those creatures that hang around smoker vents in the deep ocean are actually “powered” by the nuclear energy and heat of the Earth’s core).
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The Last Universal Common Ancestor is now believed to have inhabited this environment based on genetic study.
But if life is so common, why did this evolutionary step occur only once in 4.5 billion years? After all, there is only one Tree Of Life.
https://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html?_r=0