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Thread: How long does multicellular life have left?

  1. #1
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    How long does multicellular life have left?

    According to the wikipedia timeline of the far future, in 500 - 600 million years C3 photosynthesis will cease and approximately 99 percent of present photosynthetic species will die. In 800 - 900 million years C4 photosynthesis will no longer be possible, and eventually all multicellular life dies out. Is this an accurate prediction? Does eukaryotic life have 500 - 900 million years left to live? Will humanity last near that long?

  2. #2
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    Quote Originally Posted by cjackson View Post
    According to the wikipedia timeline of the far future, in 500 - 600 million years C3 photosynthesis will cease and approximately 99 percent of present photosynthetic species will die. In 800 - 900 million years C4 photosynthesis will no longer be possible, and eventually all multicellular life dies out. Is this an accurate prediction? Does eukaryotic life have 500 - 900 million years left to live? Will humanity last near that long?
    I think the answer is "yes, but..." Because that is due to the expansion of the sun. However, if by that time we have established colonies either on planets that are further away from the sun or as artificial habitats, life could be sustained there. And even without the sun, we could get light either from nuclear fission or nuclear fusion. If it's fusion, there is a LOT of hydrogen out there, so life could outlast the sun. The last question about whether humanity could last that long is IMO an easier one. I would say probably not, but who knows. After all, predictions are difficult, especially about the future.
    As above, so below

  3. #3
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    Quote Originally Posted by cjackson View Post
    According to the wikipedia timeline of the far future, in 500 - 600 million years C3 photosynthesis will cease and approximately 99 percent of present photosynthetic species will die. In 800 - 900 million years C4 photosynthesis will no longer be possible, and eventually all multicellular life dies out. Is this an accurate prediction?
    There’s an interesting site that I lost track of that discussed a number of the standard assumptions and effects if assumptions are changed. For instance, the assumption that the hydrosphere will remain essentially the same, but there is an argument that much of the water will move to the interior in a billion years. This should mean less water to add to a greenhouse effect, so the planet would remain reasonably cool for longer. There were other things discussed that woud affect temperature and how long C4 photosynthesis could continue. The upshot, it could be a fair bit longer than a billion years.

    Will humanity last near that long?
    I doubt it. Nearly all complex life evolved in the last 500 million years. It seems unlikely to me that humans would remain recognizably human over that time, even if something resulting from us survives that long.

    I’ve seen two arguments for how it might be possible: (1) If human civilization continues over megayears and genetic engineering is used to fix our genes so they remain the same and never change, (2) If other entities (different species, robots, whatever) keep a copy of our genome and revive us from time to time.

    I see the idea of humanity lasting that long a bit sad. I would hope to see something of us still there, with thoughts and desires, maybe something like us but more intelligent and with the rough edges worn off, but not necessarily something we would recognize as human.

    One thing though - if an advanced civilization exists then, a sunshade could keep Earth comfortable until the sun becomes too extreme a red giant. There are also other possibilities assuming really advanced technology, like moving the planet over time, or mixing the sun’s hydrogen to extend its time on the main sequence. I make no claims about the feasibility of these things.

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    And also, I should have added, there is also a possibility (given the time span, not remote at all) that the Earth would undergo a sterilizing event, for example a collision with a large asteroid, and that life (life period, not just multicellular life) would disappear. Depending on whether we have colonized other worlds, life might go on (though even then, depending on the nature of the event it might not).
    As above, so below

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    I only need about 40 years....
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  6. #6
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    Quote Originally Posted by cjackson View Post
    According to the wikipedia timeline of the far future, in 500 - 600 million years C3 photosynthesis will cease and approximately 99 percent of present photosynthetic species will die. In 800 - 900 million years C4 photosynthesis will no longer be possible, and eventually all multicellular life dies out. Is this an accurate prediction?
    No way to know how accurate it will be but to wait. I volunteer to stay alive and observe.

    Will humanity last near that long?
    We have a thread on that topic.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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