Great Filter

TagLast edit: 19 Mar 2023 20:28 UTC by Diabloto96

The Great Filter is a proposed reframing of the Fermi Paradox, introduced by Robin Hanson in his 1998 essay The Great Filter—Are We Almost Past It?.

The development of space-framing intelligent life requires many steps to occur in sequence, 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, Hanson argues that 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 — a “great filter”.

From Hanson’s 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?

If there is a “Great Filter”, then this 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 AGI, future biotechnology, nanotechnology, or some unknown risk. 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.

This suggests that estimating the location of the Great Filter may be important for helping estimate the magnitude of existential risk. Many efforts have been made in that direction, but much remains uncertain.

If we discovered traces of life on other planets, this would count as evidence for a later Great Filter. Finding that complex life had evolved independently both on Earth and some other nearby planet, would suggest that getting to such a developmental stage was relatively easy. Thus the Great Filter would almost certainly have to be at a later stage.

The study of past mass extinctions and astrobiology can provide ideas for estimating the location of a 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 paper:

… [S]ay 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 — a series of lesser filters, rather than a single “great” one.

Hanson’s follow-up 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

mako yass12 Dec 2020 23:18 UTC
30 points
4 comments1 min readLW link

My cur­rent thoughts on the risks from SETI

Matthew Barnett15 Mar 2022 17:18 UTC
128 points
27 comments10 min readLW link

Repli­cat­ing and ex­tend­ing the grabby aliens model

Tristan Cook23 Apr 2022 0:38 UTC
76 points
20 comments51 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

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

Kaj_Sotala24 Nov 2020 10:36 UTC
83 points
20 comments2 min readLW link

Re­solv­ing the Fermi Para­dox: New Directions

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

Quickly pass­ing through the great filter

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

Robin Han­son’s Grabby Aliens model ex­plained—part 1

Writer22 Sep 2021 18:51 UTC
72 points
30 comments8 min readLW link1 review

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
46 points
28 comments5 min readLW link

Im­pli­ca­tions of the Grabby Aliens Model

harsimony6 Dec 2021 18:34 UTC
2 points
3 comments2 min readLW link

Grabby Aliens could be Good, could be Bad

mako yass7 Mar 2022 1:24 UTC
28 points
10 comments4 min readLW link

[Question] Is Grabby Aliens built on good an­thropic rea­son­ing?

Steven Byrnes17 Mar 2022 14:12 UTC
38 points
29 comments1 min readLW link

Astron­omy, space ex­plo­ra­tion and the Great Filter

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

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

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

UFAI can­not be the Great Filter

Thrasymachus22 Dec 2012 11:26 UTC
61 points
93 comments3 min readLW link

The Great Filter isn’t magic either

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

Don’t Fear The Filter

Scott Alexander29 May 2014 0:45 UTC
11 points
17 comments6 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
80 comments1 min readLW link

Fermi Para­dox: Iron Age Milky Way

Rofel Wodring11 Sep 2022 20:32 UTC
−10 points
9 comments3 min readLW link

An Op­ti­mistic Solu­tion to the Fermi Paradox

Glenn Clayton10 Mar 2024 14:39 UTC
4 points
6 comments13 min readLW link

What if our Galaxy isn’t full of AI be­cause we’re in a Neu­tral Zone be­tween them?

Erlja Jkdf.30 Mar 2023 14:31 UTC
−3 points
0 comments1 min readLW link

[Question] Why don’t peo­ple talk about the Dooms­day Ar­gu­ment more of­ten?

sam31 Mar 2023 17:52 UTC
−1 points
3 comments1 min readLW link

“Op­ti­mists always win!” is the biggest sur­vivor­ship bias

Yunfan Ye20 Nov 2023 8:53 UTC
8 points
0 comments2 min readLW link

Weird ques­tion: could we see dis­tant aliens?

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

Claims & As­sump­tions made in Eter­nity in Six Hours

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

“Cheat­ing Death in Da­m­as­cus” Solu­tion to the Fermi Para­dox

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

AI X-risk is a pos­si­ble solu­tion to the Fermi Paradox

magic9mushroom30 May 2023 17:42 UTC
11 points
20 comments2 min readLW link

Dis­solv­ing the Fermi Para­dox, and what re­flec­tion it provides

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

How in­evitable was mod­ern hu­man civ­i­liza­tion—data

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

Quan­tify­ing an­thropic effects on the Fermi paradox

Lukas Finnveden15 Feb 2019 10:51 UTC
26 points
5 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

[Question] How likely is our view of the cos­mos?

Yitz27 May 2021 16:35 UTC
8 points
3 comments1 min readLW link

Great-Filter Hard-Step Math, Ex­plained Intuitively

Daniel_Eth1 Nov 2021 23:45 UTC
27 points
7 comments16 min readLW link

Robin Han­son’s Grabby Aliens model ex­plained—part 2

Writer9 Nov 2021 17:43 UTC
13 points
4 comments13 min readLW link

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

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