The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
https://en.wikipedia.org/wiki/Great_Filter
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, “If life is so easy, someone from somewhere must have come calling by now.”
https://en.wikipedia.org/wiki/Fermi_paradox
Personally I think it’s photosynthesis. Life itself developed and spread but photosynthesis started an inevitable chain of ever-greater and more-efficient life. I think a random chain of mutations that turns carbon-based proto-life into something that can harvest light energy is wildly unlikely, even after the wildly unlikely event of life beginning in the first place.
I have no data to back that up, just a guess.
My suspicion is that it’s abiogenesis, but it’s only a suspicion that I can’t have any certainty of
Nah, I’m willing to bet there is actual physical life in our very own solar system (apart from all life on Earth, of course). Europa’s oceans for example have a decently high probability of hosting microbial life.
Of course, discovering primitive life all around us would be a bad sign the great filter is still ahead of us instead of behind us…
Definitely the simplest answer and aligns so far with out observations.