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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. The main conclusion of the Great Filter is that there is an inverse correlation between the probability that other life could evolve to the stage in which humanity presently is, and the chances of humanity to survive in the future. This probability threshold, which could lie in the past or following human extinction, might work as a barrier to the evolution of intelligent life, or as a high probability of self-destruction. The main conclusion of this argument is that the more probable it is that other life could evolve to the present stage in which humanity is, the bleaker the future chances of humanity probably are. The idea was first proposed in an online essay titled "The Great Filter – Are We Almost Past It?". Hanson's formulation has received recognition in several published sources discussing the Fermi paradox and its implications.

There is no reliable evidence that aliens have visited Earth; we have observed no intelligent extraterrestrial life with current technology, nor has SETI found any transmissions from other civilizations. To the contrary, we have had great success at explaining the behavior of our planet and solar system, nearby stars, our galaxy, and even other galaxies, via simple "dead" physical processes, rather than the complex purposeful processes of advanced life.

With no evidence of intelligent life in places other than Earth, it appears that the process of starting with a star and ending with "advanced explosive lasting life" must be unlikely.

According to the Great Filter hypothesis, at least one of these steps—if the list were complete—must be improbable. Using anthropic reasoning, Brandon Carter suggested that the filter lies in our past. Meanwhile, the evolution of telescopes that can detect technosignatures at mid-infrared wavelengths could provide insights into the Great Filter. They say that if planets with technosignatures are abundant, then this can increase confidence that the Great Filter is in the past. On the other hand, if finding that life is commonplace while technosignatures are absent, then this would increase the likelihood that the Great Filter lies in the future. Astrophysicist Matt O'Dowd has identified the eukaryogenesis (step 4) as a reasonable candidate for a great filter in the past given the increasing difficulties in finding new useful proteins for prokaryotes. Recently, paleobiologist Olev Vinn has suggested that the great filter may exist between steps 8 and 9 due to inherited behavior patterns (IBP) that initially occur in all intelligent biological organisms. In a specific formulation named the "Berserker hypothesis", a filter exists between steps 8 and 9 in which each civilization is destroyed by a lethal Von Neumann probe created by a more advanced civilization.

They argue that the Great Filter may be abiogenesis, the rise of technological human-level intelligence, or an inability to settle other worlds because of self-destruction or a lack of resources. Astronomer Seth Shostak of the SETI Institute argues that one can postulate a galaxy filled with intelligent extraterrestrial civilizations that have failed to colonize Earth. Although absence of evidence generally is only weak evidence of absence, the absence of extraterrestrial megascale engineering projects, for example, could be attributed to the Great Filter. The lack of perceptible evidence for extraterrestrial civilizations is interpreted by some as suggesting that one of the steps leading to intelligent life is unlikely. The Great Filter – Are We Almost Past It? (1998), Robin Hanson Why Alien Life Would be our Doom - The Great Filter (2018), Kurzgesagt – In a Nutshell

Quick Facts

• The main conclusion of the Great Filter is that there is an inverse correlation between the probability that other life could evolve to the stage in which humanity presently is, and the chances of humanity to survive in the future.
• The Great Filter is one possible resolution of the Fermi paradox.
• The idea was first proposed in an online essay titled "The Great Filter – Are We Almost Past It?".
• This probability threshold, which could lie in the past or following human extinction, might work as a barrier to the evolution of intelligent life, or as a high probability of self-destruction.
• The main conclusion of this argument is that the more probable it is that other life could evolve to the present stage in which humanity is, the bleaker the future chances of humanity probably are.

Source material: Wikipedia - "Great Filter". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.