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This is the thing I also always wonder about. Consider that about 60% of a banana's DNA is shared with us. And for cats it's 90%. That's just really stupefying

This is the thing I also always wonder about. Consider that about 60% of a banana's DNA is shared with us. And for cats it's 90%. That's just really stupefying to think about. But the more important point here is that I think it is literally impossible for us to even imagine what life that had no genetic similarity to us would even begin to be like. We just have no basis for comparison whatsoever since we are all so closely related. Though yeah, genetic similarity implying exogenesis would also be an equally interesting result. Would that similarity be organic/natural in nature, or might we just be some species' lab experiment? Perhaps they seeded us with their same genetic origins to discover more about their own evolution and development. This is an experiment I'm certain we'll eventually carry out ourselves. So many interesting possibilities.

jacobush 8y ago
But how quickly did they get started in that case? I mean, the ago of the Earth is quite a nice chunk out of the timeline since the Universe got started.
- TangoTrotFox 8y ago
  200,000 years ago we did not exist as a species. 2500 years ago stabbing each other with iron weapons was literally cutting edge technology. In the past 200 years we have invented: production automobile, airplanes, space flight, launched probes into interstellar space, computers, the internet, ... We have discovered relativity, quantum mechanics, galaxies, ... Assuming we are able to survive, imagine where we'll be in 200k years. Actually you can't. It's just impossible to even begin to try to imagine that. On that scale we'll likely have even begun to experience evolutionary speciation as we settle different regions of space and end up with extended periods of relative isolation. And now consider that this entire timeline is but 400k years. That's not even a blink in the eye of the cosmos.
  - deleted 8y ago
    [deleted]
  - jacobush 8y ago
    It took billions of years before complexity started. We don't even know if that is a long time or a short time. We may be among the first.
    - TangoTrotFox 8y ago
      Absolutely. The point I was making there is that imagine there was another perfect clone of our solar system that was identical in every single way and its timeline was 99.995% identical to ours. Intuitively you'd think that they'd probably be at, more or less, the same point in their development. But that 0.005% is the difference between between glorified monkeys and widespread civilizations launching objects and people into space. And if we add another 0.005% to where we are now, everything we know leads us to believe that the change will be even more extreme since our current technological trajectory remains on a very sharp exponential curve upwards with no reason to expect it to end. As an aside these numbers are also based on the age of the Earth. Looking at the age of the universe would probably be more reasonable and would lead to even more extreme results.
      - jacobush 8y ago
        Hm, fair enough. We just don't know a great many things. :)
saalweachter 8y ago
So there's two high-confidence bets we can make about alien life: (1) They will probably share huge swaths of the basic chemistry and machinery: proteins, sugars, starches, fats, and even more surprising things like cell walls and digestive acid and (something like) DNA. The building blocks of life are basic chemistry, and are some combination of "the simplest possible molecule that can do a thing" and "things that arise naturally from inorganic processes". (2) There will almost certainly be 0% overlap in terrestrial and alien DNA, even assuming aliens use DNA and use the same four amino acids to encode their DNA and even assuming they have identical proteins and cellular structures. This is because the encoding from DNA to proteins is more-or-less arbitrary, and determined by both the exact cellular machinery used to turn DNA into proteins and by our genetic history. Even in our own cellular machinery, different DNA sequences can code for the same protein, so you can encode any individual protein in a bajillion different ways. The only real reason for to different organisms to share any common DNA sequences is because they both derive from a common ancestor. If our DNA and alien DNA overlap in any meaningful way, even with the tiniest of percent, it's basically conclusive proof of exogenesis of some sort. So basically, it is very likely we'll be able to eat aliens (probably no more or less likely than how likely it is you can eat any particular plant or animal on Earth, to be honest), and almost impossible that we could ever hybridize alien and terrestrial plants and animals.
- openasocket 8y ago
  I think it goes further than that, that alien and native lifeforms will probably be toxic to one another. All life on this planet evolved in tandem, and have some of the same basic compounds for life, so there are few toxic interactions between life forms, excluding those evolved for defense (and even then there are exceptions, plenty of plants contain. And even then there are plenty of exceptions. But lifeforms from a completely different evolutionary line may use completely different proteins for basic functions. Even using the same proteins but of the opposite chirality could result in toxic reactions. I think that even if we found alien life that evolved and developed on a planet much like ours, and used the same amino acids, metabolic processes, and cellular structures, the odds are high that contact with them would result in toxic interactions.

jacobush 8y ago

But how quickly did they get started in that case? I mean, the ago of the Earth is quite a nice chunk out of the timeline since the Universe got started.

TangoTrotFox 8y ago
200,000 years ago we did not exist as a species. 2500 years ago stabbing each other with iron weapons was literally cutting edge technology. In the past 200 years we have invented: production automobile, airplanes, space flight, launched probes into interstellar space, computers, the internet, ... We have discovered relativity, quantum mechanics, galaxies, ... Assuming we are able to survive, imagine where we'll be in 200k years. Actually you can't. It's just impossible to even begin to try to imagine that. On that scale we'll likely have even begun to experience evolutionary speciation as we settle different regions of space and end up with extended periods of relative isolation. And now consider that this entire timeline is but 400k years. That's not even a blink in the eye of the cosmos.
- deleted 8y ago
  [deleted]
- jacobush 8y ago
  It took billions of years before complexity started. We don't even know if that is a long time or a short time. We may be among the first.
  - TangoTrotFox 8y ago
    Absolutely. The point I was making there is that imagine there was another perfect clone of our solar system that was identical in every single way and its timeline was 99.995% identical to ours. Intuitively you'd think that they'd probably be at, more or less, the same point in their development. But that 0.005% is the difference between between glorified monkeys and widespread civilizations launching objects and people into space. And if we add another 0.005% to where we are now, everything we know leads us to believe that the change will be even more extreme since our current technological trajectory remains on a very sharp exponential curve upwards with no reason to expect it to end. As an aside these numbers are also based on the age of the Earth. Looking at the age of the universe would probably be more reasonable and would lead to even more extreme results.
    - jacobush 8y ago
      Hm, fair enough. We just don't know a great many things. :)

saalweachter 8y ago

So there's two high-confidence bets we can make about alien life: (1) They will probably share huge swaths of the basic chemistry and machinery: proteins, sugars, starches, fats, and even more surprising things like cell walls and digestive acid and (something like) DNA. The building blocks of life are basic chemistry, and are some combination of "the simplest possible molecule that can do a thing" and "things that arise naturally from inorganic processes". (2) There will almost certainly be 0% overlap in terrestrial and alien DNA, even assuming aliens use DNA and use the same four amino acids to encode their DNA and even assuming they have identical proteins and cellular structures. This is because the encoding from DNA to proteins is more-or-less arbitrary, and determined by both the exact cellular machinery used to turn DNA into proteins and by our genetic history. Even in our own cellular machinery, different DNA sequences can code for the same protein, so you can encode any individual protein in a bajillion different ways. The only real reason for to different organisms to share any common DNA sequences is because they both derive from a common ancestor. If our DNA and alien DNA overlap in any meaningful way, even with the tiniest of percent, it's basically conclusive proof of exogenesis of some sort. So basically, it is very likely we'll be able to eat aliens (probably no more or less likely than how likely it is you can eat any particular plant or animal on Earth, to be honest), and almost impossible that we could ever hybridize alien and terrestrial plants and animals.

openasocket 8y ago
I think it goes further than that, that alien and native lifeforms will probably be toxic to one another. All life on this planet evolved in tandem, and have some of the same basic compounds for life, so there are few toxic interactions between life forms, excluding those evolved for defense (and even then there are exceptions, plenty of plants contain. And even then there are plenty of exceptions. But lifeforms from a completely different evolutionary line may use completely different proteins for basic functions. Even using the same proteins but of the opposite chirality could result in toxic reactions. I think that even if we found alien life that evolved and developed on a planet much like ours, and used the same amino acids, metabolic processes, and cellular structures, the odds are high that contact with them would result in toxic interactions.