The Great Filter
by MikeGeneHere is an interesting article:
From these two facts it follows that the evolutionary path to life-forms capable of space colonization leads through a "Great Filter," which can be thought of as a probability barrier. (I borrow this term from Robin Hanson, an economist at George Mason University.) The filter consists of one or more evolutionary transitions or steps that must be traversed at great odds in order for an Earth-like planet to produce a civilization capable of exploring distant solar systems. You start with billions and billions of potential germination points for life, and you end up with a sum total of zero extraterrestrial civilizations that we can observe. The Great Filter must therefore be sufficiently powerful–which is to say, passing the critical points must be sufficiently improbable–that even with many billions of rolls of the dice, one ends up with nothing: no aliens, no spacecraft, no signals. At least, none that we can detect in our neck of the woods.
Now, just where might this Great Filter be located? There are two possibilities: It might be behind us, somewhere in our distant past. Or it might be ahead of us, somewhere in the decades, centuries, or millennia to come. Let us ponder these possibilities in turn.
Where Are They?
Why I hope the search for extraterrestrial life finds nothing.
May 8th, 2008 at 11:23 pm |
Very interesting. Here's one fact he mentions.
Comment by nobody — May 8, 2008 @ 11:23 pm
May 8th, 2008 at 11:47 pm |
Maybe I should clarify.
Abiogenesis is the Great Filter.
Comment by nobody — May 8, 2008 @ 11:47 pm
May 9th, 2008 at 12:09 am |
Interesting stuff. And I notice that's Nick Bostrom, whose simulation hypothesis I was reading about recently.
I've heard of this before though. We seem awfully alone in this very big universe. Guess we have our work cut out for us.
Comment by nullasalus — May 9, 2008 @ 12:09 am
May 9th, 2008 at 4:38 am |
I think the article is interesting but purely one-sided. But then again I have (had) an interest in the UFO phenomenon for a decade, which the author seems to dismiss in a single sentence with some hand-waving. Even if a tiny minority of UFO reports are extraterrestrial probes, his point is proven wrong.
Ah well.
Comment by Jean — May 9, 2008 @ 4:38 am
May 9th, 2008 at 10:13 am |
If the rocks didn't even survive, then it's unlikely any evidence of life would have survived. Life may have started and been destroyed several times as the Earth continued to accrete through bombardment.
It's hard to set dates to this transition. But anything on the order of billions of years can have cosmological significance. On the other hand, as MikeGene might point out, once we have colonial eukaryotes, life is somewhat front-loaded for everything that follows.
Bostrom's analogy is a reworking of the Drake Equation combined with Fermi's rhetorical question, "Where are they?" If abiogenesis and resultant evoltion are likely (
fl > >), then the lifespan of technological civilizations may be shorter (L < <).Comment by Zachriel — May 9, 2008 @ 10:13 am
May 9th, 2008 at 4:51 pm |
Zachriel pointed out recently that SETI justifies its search by noting that after the Earth cooled down to the point where carbonaceous life could exist, life appeared relatively quickly, thus suggesting that abiogenesis was probable. Bostrom doesn't seem to address that. But even if abiogenesis didn't happen, and life of Earth was designed by a human-like designer, then we could expect that we aren't the only planet that has been seeded with life.
What Bostrom doesn't seem to consider is that planets may have been seeded at roughly the same time. This means that if other technological civilizations are emerging on other planets, then they may doing so at about the same time as we are. And since we have only been producing radio signals for a hundred years, and only listening for fifty, it's quite possible that the signals haven't traveled far enough to be heard by other planets.
Comment by Bilbo — May 9, 2008 @ 4:51 pm
May 9th, 2008 at 5:25 pm |
Bilbo,
Well, abiogenesis doesn't preclude design. In fact, even a designer would have conceivably had to work out an intervention where life came from non-life.
Just wanted to toss that into the ring as well.
Even if they were all seeded at the same time, I suppose that doesn't show that they would all evolve at the same rates. Different environments, different situations, different results. On the other hand, maybe someone could make the argument that even a widespread seeding (by a designer or not) wouldn't automatically mean widespread intelligence. Maybe intelligent life has another filter on it.
It's all pretty interesting, though. We do seem awfully alone. And people forget that, once upon a time, it was assumed we'd find at least complex life on just about every planet in our solar system.
Comment by nullasalus — May 9, 2008 @ 5:25 pm
May 9th, 2008 at 5:44 pm |
Who knows, fairies may have even lived here.
Comment by kornbelt888 — May 9, 2008 @ 5:44 pm
May 9th, 2008 at 6:36 pm |
nullasalus:
The jury is still out on that. (is there any non-complex life?)
Szathmary E., Ganti T., Pocs T., Horvath A., Kereszturi A., Berzci Sz. and Sik A. (2007), Life in the dark dune spots of Mars: a testable hypothesis - in Planetary Systems and the Origin of Life, ed. Ralph Pudritz, Paul Higgs, Jonathan Stone, Cambridge Astrobiology Series III., Cambridge University Press
Szathmary makes a good case that Mars may harbor microbial life. I've seen him lecture on it, and I came away thinking that the odds are not so bad. We'll see when a mission to Mars will take samples from the dark dune spots.
Comment by Raevmo — May 9, 2008 @ 6:36 pm
May 9th, 2008 at 6:48 pm |
Raevmo,
I think for the purposes considered, complex would be far beyond microbial. If microbial is common but anything beyond that is rare or (with one exception, of course) unheard of, same basic situation.
Comment by nullasalus — May 9, 2008 @ 6:48 pm
May 9th, 2008 at 6:57 pm |
nullasalus:
But if there is microbial life on other planets, and unrelated to life on earth (it could have dispersed from earth after all), wouldn't that shed a little doubt on the idea that life was designed and front-loaded to evolve into complex life? Why would the Designer plant the seeds of life on Mars if there was no chance for it to evolve into intelligent life? Assuming of course that the Designer knew all too well that conditions on Mars would prohibit such evolution.
Comment by Raevmo — May 9, 2008 @ 6:57 pm
May 9th, 2008 at 7:06 pm |
There is a significant caveat to overcome before
reaching conclusions about the Great Filter. From Craig Venter (the genome guy):
Comment by MikeGene — May 9, 2008 @ 7:06 pm
May 9th, 2008 at 7:12 pm |
Raevmo,
Designer? I thought we were talking about Bostrom's filters and the probability of intelligent life.
But even going that route - you could ask the same question if you dial it back enough years on earth. "Nothing here but microbes. If some designer wanted intelligent life, why isn't there any on earth?" Or if complex life was all over the place, "Well, how special can it be if it's common?" If they were very similar, why did the designer bother recreating the same damn thing? If they were very different, why did the designer keep changing the plans?
I don't think any of the given situations make design more/less likely. It just shuffles the questions that will likely be asked. If situation X, why? If situation Y, why?
Comment by nullasalus — May 9, 2008 @ 7:12 pm
May 9th, 2008 at 7:33 pm |
nullasalus:
Excuse me, but I thought bringing up a designer is not entirely off topic on an ID blog.
Yeah, but remember that earth is a very privileged planet. It was clear from the start that earth - unlike mars - had the right conditions for intelligent life to evolve. So why bother planting life on mars if it was clear (as it must have been to the Designer) that it had no chance to evolve into something more interesting? I suppose one answer might be that if life on earth were destroyed by some freak accident (unforeseen by the Designer), mars might serve as a secondary seeder of life on earth.
Comment by Raevmo — May 9, 2008 @ 7:33 pm
May 9th, 2008 at 7:42 pm |
Raevmo,
I'm not telling you off. I'm just expressing some surprise. I don't think Bostrom touches on a designer in the article. Now, his simulation theory..
Well, keep in mind that I'm friendly to ID, but I'm in my own category in all likelihood. So I don't see a designer hedging bets for a freak accident. I don't see any surprises from a designer perspective. I don't even rule out abiogenesis; to me, that's one more tool a designer would use.
But again, how do we know it won't evolve into something interesting - especially once humans arrive there? Maybe they're there for us to study, or be used as a tool. Maybe part of the front loading was the conditions of earth. I can think of a lot of uses, none of which demand complex life right now. (And again, time's another consideration. If we were sentient observers at the right point in earth history, we could have mounted an argument of 'No life here, certainly no intelligent life, so what's the point?' Enough time passed to answer that objection.)
Comment by nullasalus — May 9, 2008 @ 7:42 pm
May 9th, 2008 at 7:52 pm |
Raevmo,
It all depends on the way that the designer planted life. Denton thinks that there is something like a natural law that generates life any time the conditions are right. So if microbial life is common it would be evidence for his kind of ID.
If on the other hand if alien microbial life is completely different from life on earth, not based on carbon or no DNA for example Denton’s law would seem less probable IMHO.
Whatever we find it will be fascinating stuff from an ID perspective and Darwinists will claim it was predicted all along.
Peace
Comment by fifth monarchy man — May 9, 2008 @ 7:52 pm
May 9th, 2008 at 7:57 pm |
nullasalus:
Very good points indeed. It's good fun to make up creative just-so stories, isn't it? I don't mean this in a negative way at all, it really is fun to imagine such scenarios.
Comment by Raevmo — May 9, 2008 @ 7:57 pm
May 9th, 2008 at 8:05 pm |
fmm:
Perhaps. But only if Denton would be more specific about the "right conditions". Otherwise it's too easy to say that the conditions must have been right, or there wouldn't have been life.
Indeed it will be fascinating, but why do you think Darwinists will make such a claim?
Comment by Raevmo — May 9, 2008 @ 8:05 pm
May 9th, 2008 at 8:17 pm |
Raevmo,
I don't take it as negative. Who knows what we're going to find out in space? The unknown is an essential aspect of life. We'll get answers, one way or the other.
Fmm,
Indeed. The possibilities are staggering, and interesting - as limited as human design. (Which is to say, few limits at all.)
Comment by nullasalus — May 9, 2008 @ 8:17 pm
May 9th, 2008 at 9:15 pm |
Would you say that any eventual finding about life on other planets would make Neo-Darwinism less likely?
Comment by fifth monarchy man — May 9, 2008 @ 9:15 pm
May 10th, 2008 at 12:02 am |
MikeGene Says:
I didn't know we had that much exchange of material with Mars. On top of that, we've probably contaminated Mars with microbes that hitchhiked on Russian and American spacecraft. If our space program survives, I expect we will eventually find life over there. I also expect that life to be DNA-based.
Comment by nobody — May 10, 2008 @ 12:02 am
May 10th, 2008 at 9:43 am |
Neo-Darwinism is a rather old theory, but I suppose you mean the modern Theory of Evolution. Life, if discovered, would almost certainly have evolved over time, and would probably add considerably to abiogenetic theory. The discovery of life on other planets would cause a reevaluation of many scientific theories. That's what happens.
Comment by Zachriel — May 10, 2008 @ 9:43 am