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What seems to me obvious if one looks at: a) the age of the universe b) the age of the earth c) the age of life on earth d) the age of aware-enough-to-look-at-s

by themgt 10y ago

What seems to me obvious if one looks at: a) the age of the universe b) the age of the earth c) the age of life on earth d) the age of aware-enough-to-look-at-stars-and-wonder-about-aliens life on earth Is that life itself is relatively "easy" and is likely to be common. It seems more likely to me that the crucial "filter(s)" are for a species of lifeforms to cross the boundary into a global, technological civilization. There appear to be very unique, perhaps somewhat accidental set of circumstances that led to homo sapiens crossing that rubicon that aren't just evolution doing a "dial intelligence to 11", but more about an ability for intelligent individuals to share and store their thoughts and build shared abstractions and culture over periods much longer than individual lifetimes (e.g. capability for complex vocalizations and extremely precise control with hands and fingers; not living in water)

marcosdumay 10y ago
> Is that life itself is relatively "easy" and is likely to be common. It's either that, or life is so hard that it can only appear during a short time-span.
jseliger 10y ago
Is that life itself is relatively "easy" and is likely to be common. Life appears common, but multicellular life appears to be extremely uncommon and appears to have evolved only once on earth, at least according to Nick Lane's excellent (though inadvertently depressing) book The Vital Question: Energy, Evolution, and the Origins of Complex Life (https://www.amazon.com/Vital-Question-Evolution-Origins-Complex/dp/0393088812?ie=UTF8&camp=1789&creative=390957&linkCode=as2&tag=thstsst-20 https://www.amazon.com/Vital-Question-Evolution-Origins-Comp...). I can't gauge the accuracy of his claims but the book does not appear to have been rebutted, at least from what I've found. Given all the discussion about biology on this thread I'm surprised no one else has mentioned it.
- derekp7 10y ago
  Also, as far as we know, single-celled life also evolved exactly once. This is one thing I haven't seen a good answer for -- if life came about so early, that would indicate that it is easy. But since it occurred only once, that would indicate that it is hard. The common explanation is that once life evolved and began to spread, that it would prevent other life from appearing by out-competing it. But there is plenty of raw materials and sunlight to go around, so I don't buy that explanation. The only thing that seems to fit, is that life is hard to evolve, but has extra-terrestrial origin. If that is the case then life should exist (at least in bacterial form) wherever a suitable habitat is found.
dTal 10y ago
I like this style of analysis, but I disagree with your conclusion. There's a few intermediate levels I'd also put in there, each of them a filter in their own way. There's whatever fueled the Cambrian explosion of diverse animal lifeforms (some say "multicellular life" but I'm not sure about that as multicellularity has evolved independently "at least 46 times" according to Wiki) - this took billions of years so we can classify that as "hard". Then there's "intelligent enough to solve problems and be self-aware" - dog level intelligence. This is relatively common on Earth, so we can call that "easy". Then, as you say, there's "culture and language" (language implying at least a certain level of abstract thought), which are not unique to humans (other primates, corvids, orcas, and elephants spring to mind) but is quite rare. Still, it's evolved several times independently (and there were pack hunters even among dinosaurs that may have qualified), so perhaps we can file that under "not numerically common, but inevitable given time". Then, at last, there's "technological" - it's not at all clear what the qualitative adaptation is there, though I would suspect some sort of runaway sexual selection fixated on abstract thought beyond what is strictly required for survival. That's kind of a freak event, but on the other hand sexual selection as a whole isn't that rare and it fixates on all kinds of things. And of course, it happened a few hundred million years after the Cambrian explosion, and maybe only a few tens of millions of years after evolution got far enough to give us culture and language etc. So maybe this is also a "give it time" kind of thing. A plausible stat would be 1% of cultured, language-using species ending up technological. Not super common, but neither a unicorn event. We just happen to be the first. Now bearing in mind that the lifespan of a star like ours is roughly 10 billion years, it seems to me like overwhelmingly the hardest thing in all this is making the jump from just slime growing on everything, to little animals running around eating each other, before the star dies. That jump took billions of years for us, and everything after that has happened stupendously quickly by comparison. My personal opinion for the "great filter"? A combination of "life-bearing planets are rare", "animals are rare", and "technological civilizations don't make it to space for reasons unknown" (either lack of will or more likely self destruction).

by themgt 10y ago

marcosdumay 10y ago

> Is that life itself is relatively "easy" and is likely to be common. It's either that, or life is so hard that it can only appear during a short time-span.

jseliger 10y ago

Is that life itself is relatively "easy" and is likely to be common. Life appears common, but multicellular life appears to be extremely uncommon and appears to have evolved only once on earth, at least according to Nick Lane's excellent (though inadvertently depressing) book The Vital Question: Energy, Evolution, and the Origins of Complex Life (https://www.amazon.com/Vital-Question-Evolution-Origins-Complex/dp/0393088812?ie=UTF8&camp=1789&creative=390957&linkCode=as2&tag=thstsst-20 https://www.amazon.com/Vital-Question-Evolution-Origins-Comp...). I can't gauge the accuracy of his claims but the book does not appear to have been rebutted, at least from what I've found. Given all the discussion about biology on this thread I'm surprised no one else has mentioned it.

derekp7 10y ago
Also, as far as we know, single-celled life also evolved exactly once. This is one thing I haven't seen a good answer for -- if life came about so early, that would indicate that it is easy. But since it occurred only once, that would indicate that it is hard. The common explanation is that once life evolved and began to spread, that it would prevent other life from appearing by out-competing it. But there is plenty of raw materials and sunlight to go around, so I don't buy that explanation. The only thing that seems to fit, is that life is hard to evolve, but has extra-terrestrial origin. If that is the case then life should exist (at least in bacterial form) wherever a suitable habitat is found.

dTal 10y ago

I like this style of analysis, but I disagree with your conclusion. There's a few intermediate levels I'd also put in there, each of them a filter in their own way. There's whatever fueled the Cambrian explosion of diverse animal lifeforms (some say "multicellular life" but I'm not sure about that as multicellularity has evolved independently "at least 46 times" according to Wiki) - this took billions of years so we can classify that as "hard". Then there's "intelligent enough to solve problems and be self-aware" - dog level intelligence. This is relatively common on Earth, so we can call that "easy". Then, as you say, there's "culture and language" (language implying at least a certain level of abstract thought), which are not unique to humans (other primates, corvids, orcas, and elephants spring to mind) but is quite rare. Still, it's evolved several times independently (and there were pack hunters even among dinosaurs that may have qualified), so perhaps we can file that under "not numerically common, but inevitable given time". Then, at last, there's "technological" - it's not at all clear what the qualitative adaptation is there, though I would suspect some sort of runaway sexual selection fixated on abstract thought beyond what is strictly required for survival. That's kind of a freak event, but on the other hand sexual selection as a whole isn't that rare and it fixates on all kinds of things. And of course, it happened a few hundred million years after the Cambrian explosion, and maybe only a few tens of millions of years after evolution got far enough to give us culture and language etc. So maybe this is also a "give it time" kind of thing. A plausible stat would be 1% of cultured, language-using species ending up technological. Not super common, but neither a unicorn event. We just happen to be the first. Now bearing in mind that the lifespan of a star like ours is roughly 10 billion years, it seems to me like overwhelmingly the hardest thing in all this is making the jump from just slime growing on everything, to little animals running around eating each other, before the star dies. That jump took billions of years for us, and everything after that has happened stupendously quickly by comparison. My personal opinion for the "great filter"? A combination of "life-bearing planets are rare", "animals are rare", and "technological civilizations don't make it to space for reasons unknown" (either lack of will or more likely self destruction).