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Thread: Snowball Earth and evolution

  1. #1
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    Snowball Earth and evolution

    Did snowball Earth trigger the formation of multicellular life? It does seem that complex life emerged from under the ice of Snowball Earth, but it is interesting to wonder why. Was there an advantage to grouping together, simply because being bigger retains heat? Did the development of complex organs enable more efficient food consumption?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

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    I suspect the melting snowball provided opportunities for life. In modern ocean environments warm seas are diverse, while cold seas have low diversity but large biomass, so quite possibly a frozen world will not drive evolution.

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    But there were hundreds of millions of years before the snowball when life did not evolve. What was it about the period after the snowball that forced life to evolve?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    Quote Originally Posted by parallaxicality View Post
    But there were hundreds of millions of years before the snowball when life did not evolve....
    I seem to be horribly uninformed. What's this 'snowball' you're talking about? I understand you're talking about the time when earth life transitioned from only single-celled forms to single and multicelled forms. Yes, it's remarkable that single-cell life appeared pretty quickly (when the earth was hot) and then persisted alone on earth for the first 3 billion years! We think 65 million years back to the dinosaurs is a long time. 3 billion is running 65 million over and over 46 times! It might have been achingly slow, but I think there was some pretty important biological evolution going on.

    Of course, when you start going multicellular, things really take off.
    Everyone is entitled to his own opinion, but not his own facts.

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    I seem to be horribly uninformed. What's this 'snowball' you're talking about?
    Here's the wikipedia article on snowball earth:

    http://en.wikipedia.org/wiki/Snowball_Earth

    We know very little about that time period when "snowball earth" may have occured. There was extensive glaciation at times 850-630 million years ago, but we currently can't be sure if it was global in nature with glaciation in the tropics resulting in a snowball earth. We also know very little about the rate of change in life and if and how this rate changed during or around the period when snowball earth may have occured. Discussions about the effects of snowball earth on evolution are very speculative.

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    Quote Originally Posted by parallaxicality View Post
    But there were hundreds of millions of years before the snowball when life did not evolve. What was it about the period after the snowball that forced life to evolve?
    May be increase in oxygen level, evolution of the eye ...etc.

    http://en.wikipedia.org/wiki/Cambrian_explosion

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    Quote Originally Posted by canopuss View Post
    May be increase in oxygen level, evolution of the eye ...etc.

    http://en.wikipedia.org/wiki/Cambrian_explosion
    If we assume a decrease of life forms during the glaciation event it would be consistent to have a radiation of new life forms , after.

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    Who says life wasn't evolving before your 'snowball'?
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    Quote Originally Posted by parallaxicality View Post
    Did snowball Earth trigger the formation of multicellular life? It does seem that complex life emerged from under the ice of Snowball Earth, but it is interesting to wonder why. Was there an advantage to grouping together, simply because being bigger retains heat? Did the development of complex organs enable more efficient food consumption?
    I think the retention of heat question can be answered, from a heat transfer standpoint, as "not enough at that scale to drive evolution." Microscopic organisms, or even small macroscopic ones, like most insects, simply cannot generate enough metabolic heat to maintain equilibrium temperatures much above ambient, especially if they're in watery environment.

    I know that Kasting has published articles about the "snowball Earth," e.g. Kasting & Pollard (beware; the link is to a pdf).

  10. #10
    Quote Originally Posted by Ronald Brak View Post
    Here's the wikipedia article on snowball earth:

    http://en.wikipedia.org/wiki/Snowball_Earth

    We know very little about that time period when "snowball earth" may have occured. There was extensive glaciation at times 850-630 million years ago, but we currently can't be sure if it was global in nature with glaciation in the tropics resulting in a snowball earth.
    Quote Originally Posted by wikipedia
    Budyko found that if ice sheets advanced far enough out of the polar regions a feedback ensued where the increased reflectiveness (albedo) of the ice led to further cooling and the formation of more ice until the entire Earth was covered in ice and stabilized in a new ice-covered equilibrium.[6] While Budyko's model showed that this ice-albedo stability could happen, he concluded that it had never happened, because his model offered no way to escape from such a scenario.
    Budyko did not think it had ever happened and my understanding is that most scientists do not think there has ever been global glaciation.

    Budyko's model showed that the Earth could not escape from this because the ice would reflect too much light back into space. There is speculation that greenhouse gases from volcaloes could seep through the ice and eventually heat the Earth enough to melt the ice, but that is a bit iffy and could only happen when the Earth was young and there was a lot more volcanism than there is now.

    Bottom line: If scientists are not even convinced that there ever was global glaciation, much less agreed on when it occured, then it seems rather speculative to discuss its effect on evolution.

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    Quote Originally Posted by parallaxicality View Post
    Did snowball Earth trigger the formation of multicellular life? It does seem that complex life emerged from under the ice of Snowball Earth, but it is interesting to wonder why. Was there an advantage to grouping together, simply because being bigger retains heat? Did the development of complex organs enable more efficient food consumption?
    My understanding is that the evolution of multi-cellular life was enabled by the increased concentration of oxygen in the atmosphere. All life on earth was microbial for at least the first three billion years. Algae convert carbon dioxide into oxygen, and they gradually transformed the poisonous air of the early planet into an atmosphere that could support complex life.

    Linking this to the snowball earth hypothesis of around 800 million years ago is interesting, in that it suggests a period before the Cambrian Explosion of 540 MY ago in which microbes transitioned into the multicellular Cambrian organisms such as those in the Burgess Shale.

    Isn't the problem with snowball earth that it would be self-reinforcing, with reflection of light causing earth to get ever colder? It seems to conflict with the gaia homeostasis hypothesis which suggests that life must have maintained liquid water on the surface of earth at all times.

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    Quote Originally Posted by Robert Tulip View Post
    My understanding is that the evolution of multi-cellular life was enabled by the increased concentration of oxygen in the atmosphere. All life on earth was microbial for at least the first three billion years. Algae convert carbon dioxide into oxygen, and they gradually transformed the poisonous air of the early planet into an atmosphere that could support complex life.

    Linking this to the snowball earth hypothesis of around 800 million years ago is interesting, in that it suggests a period before the Cambrian Explosion of 540 MY ago in which microbes transitioned into the multicellular Cambrian organisms such as those in the Burgess Shale.
    You're referring to the Ediacaran Period ...

    (also previously: Vendian; Precambrian Z)


    Isn't the problem with snowball earth that it would be self-reinforcing, with reflection of light causing earth to get ever colder?
    not for an idea that uses extensive volcanism to both initiate and end the process ...

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    Perhaps it might be due to a combination of events.

    The cold period may see a variety of colonies collect near thermal vents for both sustenance and heat. Evolution has only prepared life forms for the single cell. However, then a giant impact, normally suggested for extinctions, causes a shock wave that penetrates to the crowded thermal vent and smashes cells into each other. The cells were not yet prepared to digest the new forms forced inside their cell walls and they have to find a way to deal with the new topology. Multicellular life represents a frustrating failure to find a solution out of the new thorny geometry.

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