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A) Some level of residual radiation or lack of complex chemicals might have delayed life ~2 billion years. B) Proto-life might indeed have evolved 2 billion ea

A) Some level of residual radiation or lack of complex chemicals might have delayed life ~2 billion years. B) Proto-life might indeed have evolved 2 billion earlier than earth and have been brought to earth by asteroids. Which is to say it took ~2 billion years for a primordial soup to become single-celled organisms (with viruses being an intermediate stage). C) If life evolves "everywhere", then the odds are we are "typical life" (axiom of mediocrity), so the odds are for whatever reason life was ~2 billion later than some estimates.

deleted 6y ago
[deleted]
Reelin 6y ago
Dinosaurs existed in the Triassic ~250 Mya. Following multiple extinction events primates showed up something like ~80 Mya. Australopithecus only dates to something like 3 Mya, Homo habilis to only ~2 Mya, and humans to a mere ~0.3 Mya. 250 vs 3 (or even 80) is a huge difference, and it's unreasonable to assume that all planets would experience extinction events at anywhere near the same rates. To put it in terms of your axiom of mediocrity, it looks like the "typical" timeline we followed has a lot of wiggle room so why don't we see anyone else?
- joe_the_user 6y ago
  To put it in terms of your axiom of mediocrity, it looks like the "typical" timeline we followed has a lot of wiggle room so why don't we see anyone else? Arguably, on a log scale, the total complexity of organisms is increasing fairly regularly. Extinction events may just be ways the increased complexity manifests. Further, there might be wiggle room but maybe our current explosion in scientific knowledge doesn't yet put near the jumping off point. The sci-fi paradigm is imagining galaxy colonization as akin to the colonization of islands and continents around the world by sea faring but the scales aren't comparable, the effort isn't comparable, etc.
  - mannykannot 6y ago
    I am trying to figure out how extinction events caused by a meteorite impact, massive volcanism or global glaciation could be manifestations of increased complexity. Are you are saying that worlds populated only by simple organisms are effectively immune from mass extinctions? Even if that were so (which I doubt), it would seem to be irrelevant to the Fermi 'paradox', which concerns the non-arrival, here, of complex organisms or their machines.
    - joe_the_user 6y ago
      "I am trying to figure out how extinction events caused by a meteorite impact, massive volcanism or global glaciation could be manifestations of increased complexity." A multitude of organism evolve over time, with more complex organism appearing in little ecological niches not occupied by existing species. When an extinction event occurs, the entire ecology changes and the most fit, complex and well adapted organism now can fill many more niches. Are you are saying that worlds populated only by simple organisms are effectively immune from mass extinctions? No, nothing of the sort.
      - mannykannot 6y ago
        Mass extinctions roll the dice on complexity. They redefine the yardstick against which fitness is measured, at least temporarily (but long enough to have a lasting effect.) If the KT meteorite were somewhat larger, it might have bombed Earth back to the Archean. On the other hand, this is one aspect of the Fermi puzzle where we do have more than one example - and they suggest that mass extinction events alone are not sufficient to answer it.
  - Reelin 6y ago
    I dunno, dinosaurs seem pretty biologically complex to me. We've got examples of just about all the features you'd come across today (possibly even venom). I suppose if we take intelligence as a sort of measure of overall complexity it could work, the obvious issue being that we can only make the roughest of estimates for it.
mannykannot 6y ago
One can always posit possible causes, but is there evidence for any of them? For example, is there evidence that, two billion years before the origin of life on Earth, radiation levels throughout the galaxy were such as to prevent the same thing happening anywhere, or that nowhere in the galaxy could there have been the chemistry which was vital for the emergence of life on Earth?
- joe_the_user 6y ago
  Anything to do with the Fermi paradox is going to be very broad speculation. We're discussing the probability of X thing happening when have exactly one instance available.
  - marcosdumay 6y ago
    Yet, here we are without even a reasonable speculative explanation. Your #1 is against all the evidence we have. And we have quite a bit of it. Your #2 is a well discussed possibility, but we have evidence of life evolving on Earth from very simple creatures. So placing a severe ceiling on the complexity of that panspermy subject, and removing most of the power from that hypothesis. Granted that it's still a possibility, but we know that nearly all of our evolution happened here on Earth, on roughly the same time that was available for those very simple organism to appear. Your #3 is literally begging the question.

deleted 6y ago

[deleted]

Reelin 6y ago

Dinosaurs existed in the Triassic ~250 Mya. Following multiple extinction events primates showed up something like ~80 Mya. Australopithecus only dates to something like 3 Mya, Homo habilis to only ~2 Mya, and humans to a mere ~0.3 Mya. 250 vs 3 (or even 80) is a huge difference, and it's unreasonable to assume that all planets would experience extinction events at anywhere near the same rates. To put it in terms of your axiom of mediocrity, it looks like the "typical" timeline we followed has a lot of wiggle room so why don't we see anyone else?

joe_the_user 6y ago
To put it in terms of your axiom of mediocrity, it looks like the "typical" timeline we followed has a lot of wiggle room so why don't we see anyone else? Arguably, on a log scale, the total complexity of organisms is increasing fairly regularly. Extinction events may just be ways the increased complexity manifests. Further, there might be wiggle room but maybe our current explosion in scientific knowledge doesn't yet put near the jumping off point. The sci-fi paradigm is imagining galaxy colonization as akin to the colonization of islands and continents around the world by sea faring but the scales aren't comparable, the effort isn't comparable, etc.
- mannykannot 6y ago
  I am trying to figure out how extinction events caused by a meteorite impact, massive volcanism or global glaciation could be manifestations of increased complexity. Are you are saying that worlds populated only by simple organisms are effectively immune from mass extinctions? Even if that were so (which I doubt), it would seem to be irrelevant to the Fermi 'paradox', which concerns the non-arrival, here, of complex organisms or their machines.
  - joe_the_user 6y ago
    "I am trying to figure out how extinction events caused by a meteorite impact, massive volcanism or global glaciation could be manifestations of increased complexity." A multitude of organism evolve over time, with more complex organism appearing in little ecological niches not occupied by existing species. When an extinction event occurs, the entire ecology changes and the most fit, complex and well adapted organism now can fill many more niches. Are you are saying that worlds populated only by simple organisms are effectively immune from mass extinctions? No, nothing of the sort.
    - mannykannot 6y ago
      Mass extinctions roll the dice on complexity. They redefine the yardstick against which fitness is measured, at least temporarily (but long enough to have a lasting effect.) If the KT meteorite were somewhat larger, it might have bombed Earth back to the Archean. On the other hand, this is one aspect of the Fermi puzzle where we do have more than one example - and they suggest that mass extinction events alone are not sufficient to answer it.
- Reelin 6y ago
  I dunno, dinosaurs seem pretty biologically complex to me. We've got examples of just about all the features you'd come across today (possibly even venom). I suppose if we take intelligence as a sort of measure of overall complexity it could work, the obvious issue being that we can only make the roughest of estimates for it.

mannykannot 6y ago

One can always posit possible causes, but is there evidence for any of them? For example, is there evidence that, two billion years before the origin of life on Earth, radiation levels throughout the galaxy were such as to prevent the same thing happening anywhere, or that nowhere in the galaxy could there have been the chemistry which was vital for the emergence of life on Earth?

joe_the_user 6y ago
Anything to do with the Fermi paradox is going to be very broad speculation. We're discussing the probability of X thing happening when have exactly one instance available.
- marcosdumay 6y ago
  Yet, here we are without even a reasonable speculative explanation. Your #1 is against all the evidence we have. And we have quite a bit of it. Your #2 is a well discussed possibility, but we have evidence of life evolving on Earth from very simple creatures. So placing a severe ceiling on the complexity of that panspermy subject, and removing most of the power from that hypothesis. Granted that it's still a possibility, but we know that nearly all of our evolution happened here on Earth, on roughly the same time that was available for those very simple organism to appear. Your #3 is literally begging the question.