Great Filter

TagLast edit: 1 Oct 2020 18:30 UTC by Ruby

The Great Filter is a proposed explanation for the Fermi Paradox. The development of intelligent life requires many steps, such as the emergence of single-celled life and the transition from unicellular to multicellular life forms. Since we have not observed intelligent life beyond our planet, there seems to be a developmental step that is so difficult and unlikely that it “filters out” nearly all civilizations before they can reach a space-faring stage. Robin Hanson coined the term in his 1998 essay The Great Filter—Are We Almost Past It?.

From that essay:

Humanity seems to have a bright future, i.e., a non-trivial chance of expanding to fill the universe with lasting life. But the fact that space near us seems dead now tells us that any given piece of dead matter faces an astronomically low chance of begating such a future. There thus exists a great filter between death and expanding lasting life, and humanity faces the ominous question: how far along this filter are we?

Should we worry?

The Great Filter might be a step in our evolutionary past, in which case our civilization has already passed it. But the hard step might also be ahead of us: surviving the creation of nuclear bombs, AGI, biotechnology, nanotechnology or an asteroid impact 1. In that case, we should be worried, as the Great Filter seems to have been successful in stopping the development of every other civilization so far. Estimating the location of the Great Filter is thus important for helping estimate the magnitude of existential risk. Many efforts have been made in that direction, but much remains uncertain.

Traces of life on other planets are evidence for a later Great Filter2. If we were to find that complex life had evolved independently both on Earth and some other planet, it would suggest that getting to such a developmental stage was relatively easy. Thus the Great Filter would have to be at a later stage.

The study of past mass extinctions and astrobiology can provide ideas for estimating the location of the Great Filter. However, there are many difficulties involved. For instance, the time that it takes to pass a step doesn’t reveal much about how easy or hard that step was. Robin Hanson gives the following example in his seminal paper:

“…say you have one hour to pick five locks by trial and error, locks with 1,2,3,4, and 5 dials of ten numbers, so that the expected time to pick each lock is .01,.1, 1, 10, and 100 hours respectively. Then just looking at those rare cases when you do pick all five locks in the hour, the average time to pick the first two locks would be .0096 and .075 hours respectively, close to the usual expected times of .01 and .1 hours. The average time to pick the third lock, however, would be .20 hours, and the average time for the other two locks, and the average time left over at the end, would be .24 hours. That is, conditional on success, all the hard steps, no matter how hard, take about the same time, while easy steps take about their usual time.”


In a subsequent paper, Hanson constructs a simulation of the distribution of the hard steps, which suggests that there should be about four to seven hard steps, uniformly distributed in our past. It also suggests that there has been at least one hard step since the evolution of hominids, and that the best extinction model that fits all these requirements is William Schopf’s model. Taking evolutionary arguments for AGI and observation selection effects together, Bostrom and Shulman argue that Hanson’s results can help estimate the difficulty of creating AGI.

Blog posts

External links

See also

The Fermi Para­dox has not been dis­solved—James Fodor

MakoYass12 Dec 2020 23:18 UTC
30 points
4 comments1 min readLW link

Astron­omy, space ex­plo­ra­tion and the Great Filter

JoshuaZ19 Apr 2015 19:26 UTC
36 points
68 comments20 min readLW link

The Oc­to­pus, the Dolphin and Us: a Great Filter tale

Stuart_Armstrong3 Sep 2014 21:37 UTC
73 points
236 comments3 min readLW link

UFAI can­not be the Great Filter

Thrasymachus22 Dec 2012 11:26 UTC
59 points
92 comments3 min readLW link

Don’t Fear The Filter

Scott Alexander29 May 2014 0:45 UTC
7 points
17 comments6 min readLW link

The Great Filter isn’t magic either

Stuart_Armstrong27 Sep 2017 17:04 UTC
13 points
6 comments3 min readLW link

The es­say “In­ter­stel­lar Com­mu­ni­ca­tion Us­ing Microbes: Im­pli­ca­tions for SETI” has im­pli­ca­tions for The Great Filter.

MakerOfErrors22 Dec 2017 6:05 UTC
16 points
4 comments2 min readLW link

The Great Filter is early, or AI is hard

Stuart_Armstrong29 Aug 2014 16:17 UTC
32 points
76 comments1 min readLW link

Late Great Filter Is Not Bad News

Wei_Dai4 Apr 2010 4:17 UTC
19 points
82 comments3 min readLW link

Planets in the hab­it­able zone, the Drake Equa­tion, and the Great Filter

JoshuaZ1 Oct 2011 2:44 UTC
16 points
64 comments1 min readLW link

Quickly pass­ing through the great filter

James_Miller6 Jul 2014 18:50 UTC
20 points
51 comments4 min readLW link

An em­piri­cal test of an­thropic prin­ci­ple /​ great filter reasoning

James_Miller24 Mar 2010 18:44 UTC
13 points
42 comments2 min readLW link

The Fermi Para­dox: What did Sand­berg, Drexler and Ord Really Dis­solve?

shminux8 Jul 2018 21:18 UTC
45 points
28 comments5 min readLW link

Sny­der-Beat­tie, Sand­berg, Drexler & Bon­sall (2020): The Timing of Evolu­tion­ary Tran­si­tions Suggests In­tel­li­gent Life Is Rare

Kaj_Sotala24 Nov 2020 10:36 UTC
79 points
15 comments2 min readLW link

Re­solv­ing the Fermi Para­dox: New Directions

jacob_cannell18 Apr 2015 6:00 UTC
20 points
59 comments9 min readLW link

Weird ques­tion: could we see dis­tant aliens?

paulfchristiano20 Apr 2018 6:40 UTC
31 points
78 comments3 min readLW link

Why it took so long to do the Fermi calcu­la­tion right?

Jan_Kulveit2 Jul 2018 20:29 UTC
73 points
20 comments1 min readLW link

Claims & As­sump­tions made in Eter­nity in Six Hours

Ruby8 May 2019 23:11 UTC
48 points
7 comments3 min readLW link

“Cheat­ing Death in Da­m­as­cus” Solu­tion to the Fermi Para­dox

avturchin30 Jun 2018 12:00 UTC
12 points
5 comments3 min readLW link

Dis­solv­ing the Fermi Para­dox, and what re­flec­tion it provides

Jan_Kulveit30 Jun 2018 16:35 UTC
25 points
22 comments1 min readLW link

How in­evitable was mod­ern hu­man civ­i­liza­tion—data

taw20 Aug 2009 21:42 UTC
32 points
104 comments3 min readLW link

Quan­tify­ing an­thropic effects on the Fermi paradox

Lanrian15 Feb 2019 10:51 UTC
25 points
4 comments41 min readLW link

Dis­solv­ing the Fermi Para­dox (Ap­plied Bayesi­anism)

shin_getter3 Jul 2017 9:44 UTC
16 points
10 comments1 min readLW link

Astro­biol­ogy, Astron­omy, and the Fermi Para­dox II: Space & Time Revisited

CellBioGuy10 Mar 2016 5:19 UTC
35 points
35 comments1 min readLW link
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