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> there's a lot that had to go right with the Earth for it to support not just life, but complex, high-energy life, which enables (expensive-in-energy-terms) in

> there's a lot that had to go right with the Earth for it to support not just life, but complex, high-energy life, which enables (expensive-in-energy-terms) intelligence Like what? > It's way more than just being the right size, the right distance from a not-too-dangerous star, and having water. Besides that and having carbon (and nitrogen, I suppose), perhaps some small amounts of other elements, what are you referring to?

krapp 4y ago
If it hadn't been for the K-T event wiping out the dinosaurs and creating a niche for mammals and eventually primates to thrive, we probably wouldn't be here. It doesn't get discussed enough how much of a factor blind stupid luck was in the one example we have of the evolution of intelligence in the universe.
- wizeman 4y ago
  But the question was not whether we would be here. What's to say that in the absence of the K-T event, some dominant dinosaur species wouldn't have eventually evolved their intelligence to our level? Perhaps even earlier? It's not like the K-T event is a prerequisite for "general" intelligence, is it? Perhaps in such an alternative universe where the K-T event didn't happen you'd be a dinosaur posting on Dinohacker News right now.
  - krapp 4y ago
    I don't know, dinosaurs were around for hundreds of millions of years or more, and while they evolved, they never evolved intelligence. It only happened when a catastrophic event disrupted the natural equilibrium. I can't help but wonder if intelligence isn't something that tends to arise under extreme circumstances.
    - potsandpans 4y ago
      there's really no saying. mammals have been around for ~180 million years, so ~112 million before the mass extinction. The dinosaurs were on earth for about 165 million years. Given the relative quickness that intelligence exploded in later hominids, who knows. we could know about some gibbon analog in the dinosaurs right now, that given just a little longer could've made it to human levels of intelligence.
yamtaddle 4y ago
Basically we have a bunch of things going on that cause some graphs to cycle rather than run away, and if you break any of them—which can be as simple as tweaking a value here or there—most of our biosphere's gone. Carbonate-silicate cycle breaking is what's considered the most likely thing to end complex life on Earth, for instance. All it takes to cause that is the Sun getting slightly brighter. In a few hundred million years it'll become increasingly difficult (inefficient) for plants to photosynthesize, reducing energy available to the biosphere, until finally photosynthesis stops completely.
- wizeman 4y ago
  That's very interesting, thanks. So you're saying that in such a scenario, it would be impossible for complex life to exist, even if it looks different from the complex life we have now? I am just wondering whether we are not confusing "complex life as we've seen to exist" with "complex life that can possibly exist". For example, I am wondering whether the Great Oxidation Event is not a counterexample where we had a run-away biological process that caused a mass extinction (which, if it were possible for us to be alive at the time, might have looked like it would be impossible to recover from) but still lead to complex life existing despite oxygen being so toxic (at least from the point of view of the kind of life that existed at the time). I know this is not the best example, as at the time complex life didn't exist yet. But I'm wondering if it wouldn't have been possible for complex life to exist in an oxygen-poor environment. Well, in fact some multicellular species that exist today are anaerobic and therefore do thrive without oxygen, right? Perhaps such anaerobic life would have evolved a lot more if our atmosphere had never been oxygenated. Unfortunately I know nothing about the examples you mentioned, so I can't tell whether they are comparable. Edit: I just read a bit about the carbonate-silicate cycle and I think I know what you mean now. Yes, if surface temperatures were more extreme it would indeed be quite difficult for complex life to exist (at the surface, at least). After all, some limits to the existence of interesting life must surely exist and temperature does seem like an inherent one.
  - yamtaddle 4y ago
    Carbonate-silicate cycle breaking means photosynthesis can't, chemically, happen, not just that its being hotter makes plants less happy. My point isn't that life can't exist otherwise (ocean vents exist—though, you do need an active core for that—and anaerobic life is a thing, as you point out) but that only certain routes, even assuming there are some wildly different paths that might work, will yield enough energy to support complex life. You need a system that's reasonably stable (i.e. tends to prevent a variety of runaway events, turning them into cycles instead) even when life itself is changing the environment. Sometimes life will step in to do that if you get lucky (as in the oxygenation crisis, which you mentioned) but the planet itself needs a bunch of stuff to be just right, too—not just conditions, but processes. I suspect there are lots of planets with some bio-goo on them, maybe even quite a few with things as complex as some insects or crustaceans. I further suspect there are very few (perhaps about as close as one can get to "none" without reaching it) that could support something like (even for generous values of "like") our giant tree of vertebrates. Not enough energy available, or, there is, but the world lacks the processes to stop life's own effects from wrecking the environment and stunting its own potential. Then there's the fact that even complex life doesn't seem to necessarily lead to advanced intelligence and civilization. I mean, look at how long it took humans to develop writing! All that other stuff had gone just right, and intelligence emerged, and we happened to be a tribal species (probably), but we still puttered around for, what, a few hundred thousand years? The dinosaurs had no space program, nor the birds, nor the whales, nor fish, despite existing for tens or hundreds of millions of years—intelligence and the right kind of cooperative pack/tribe behavior to let it flourish seems to be a really rare combo, even when everything else has worked out very well for complex life.

krapp 4y ago

If it hadn't been for the K-T event wiping out the dinosaurs and creating a niche for mammals and eventually primates to thrive, we probably wouldn't be here. It doesn't get discussed enough how much of a factor blind stupid luck was in the one example we have of the evolution of intelligence in the universe.

wizeman 4y ago
But the question was not whether we would be here. What's to say that in the absence of the K-T event, some dominant dinosaur species wouldn't have eventually evolved their intelligence to our level? Perhaps even earlier? It's not like the K-T event is a prerequisite for "general" intelligence, is it? Perhaps in such an alternative universe where the K-T event didn't happen you'd be a dinosaur posting on Dinohacker News right now.
- krapp 4y ago
  I don't know, dinosaurs were around for hundreds of millions of years or more, and while they evolved, they never evolved intelligence. It only happened when a catastrophic event disrupted the natural equilibrium. I can't help but wonder if intelligence isn't something that tends to arise under extreme circumstances.
  - potsandpans 4y ago
    there's really no saying. mammals have been around for ~180 million years, so ~112 million before the mass extinction. The dinosaurs were on earth for about 165 million years. Given the relative quickness that intelligence exploded in later hominids, who knows. we could know about some gibbon analog in the dinosaurs right now, that given just a little longer could've made it to human levels of intelligence.

yamtaddle 4y ago

Basically we have a bunch of things going on that cause some graphs to cycle rather than run away, and if you break any of them—which can be as simple as tweaking a value here or there—most of our biosphere's gone. Carbonate-silicate cycle breaking is what's considered the most likely thing to end complex life on Earth, for instance. All it takes to cause that is the Sun getting slightly brighter. In a few hundred million years it'll become increasingly difficult (inefficient) for plants to photosynthesize, reducing energy available to the biosphere, until finally photosynthesis stops completely.

wizeman 4y ago
That's very interesting, thanks. So you're saying that in such a scenario, it would be impossible for complex life to exist, even if it looks different from the complex life we have now? I am just wondering whether we are not confusing "complex life as we've seen to exist" with "complex life that can possibly exist". For example, I am wondering whether the Great Oxidation Event is not a counterexample where we had a run-away biological process that caused a mass extinction (which, if it were possible for us to be alive at the time, might have looked like it would be impossible to recover from) but still lead to complex life existing despite oxygen being so toxic (at least from the point of view of the kind of life that existed at the time). I know this is not the best example, as at the time complex life didn't exist yet. But I'm wondering if it wouldn't have been possible for complex life to exist in an oxygen-poor environment. Well, in fact some multicellular species that exist today are anaerobic and therefore do thrive without oxygen, right? Perhaps such anaerobic life would have evolved a lot more if our atmosphere had never been oxygenated. Unfortunately I know nothing about the examples you mentioned, so I can't tell whether they are comparable. Edit: I just read a bit about the carbonate-silicate cycle and I think I know what you mean now. Yes, if surface temperatures were more extreme it would indeed be quite difficult for complex life to exist (at the surface, at least). After all, some limits to the existence of interesting life must surely exist and temperature does seem like an inherent one.
- yamtaddle 4y ago
  Carbonate-silicate cycle breaking means photosynthesis can't, chemically, happen, not just that its being hotter makes plants less happy. My point isn't that life can't exist otherwise (ocean vents exist—though, you do need an active core for that—and anaerobic life is a thing, as you point out) but that only certain routes, even assuming there are some wildly different paths that might work, will yield enough energy to support complex life. You need a system that's reasonably stable (i.e. tends to prevent a variety of runaway events, turning them into cycles instead) even when life itself is changing the environment. Sometimes life will step in to do that if you get lucky (as in the oxygenation crisis, which you mentioned) but the planet itself needs a bunch of stuff to be just right, too—not just conditions, but processes. I suspect there are lots of planets with some bio-goo on them, maybe even quite a few with things as complex as some insects or crustaceans. I further suspect there are very few (perhaps about as close as one can get to "none" without reaching it) that could support something like (even for generous values of "like") our giant tree of vertebrates. Not enough energy available, or, there is, but the world lacks the processes to stop life's own effects from wrecking the environment and stunting its own potential. Then there's the fact that even complex life doesn't seem to necessarily lead to advanced intelligence and civilization. I mean, look at how long it took humans to develop writing! All that other stuff had gone just right, and intelligence emerged, and we happened to be a tribal species (probably), but we still puttered around for, what, a few hundred thousand years? The dinosaurs had no space program, nor the birds, nor the whales, nor fish, despite existing for tens or hundreds of millions of years—intelligence and the right kind of cooperative pack/tribe behavior to let it flourish seems to be a really rare combo, even when everything else has worked out very well for complex life.