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Now we know that nuclear war and biorisk are not the Great Filter: AI is so close and so clearly possible that a future Great Filter (if it is indeed a future one) can be explained only by AI.
But AI as a Great Filter is a bad explanation – grabby aliens are still possible under AI. Some chance of a filter remains in the form of a chaotic singularity, AI wars, or sudden AI halting. Thus, the Great Filter is in the past.
I think it was never plausible that more than 99% of alien civilizations wipe themselves out with engineered pandemics before they start spreading to the stars. As Scott argues, the Great Filter needs to explain why none of the ~10^18 planets in our past lightcone developed an interstellar civilization that could have colonized us, so something like pandemics are not nearly big enough risk to be plausible filter.
2avturchin
If AI would be 100 years from 2014, but the progress in biotech, cheap nukes, drones etc continues, there was a possibility of large global system crisis which can be different in different civilizations but almost inevitably result in collapse.