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 guess would be self-replicating biological organisms capable of significant rates of mutation.
But then my preferred solution to the paradox as a whole is basically the “nobody tries” idea.
I don’t think there’s tremendous reason to try to make ones-self detectable at long distances. It’s an expenditure of non-trivial resources for an uncertain result. Since there isn’t really any robustly sound logic for making the attempt outside of dramatized sci fi stories, I imagine a vanishingly small percentage of occurrences of intelligent life would make a serious, high-powered attempt at any point.
I don’t really subscribe to the theory, but I think the idea that alien races are all like “go to SPACE? Why the fuck would we do that?? It sucks up there!” is definitely the funniest solution to the Fermi paradox.