Requirements for the origin of life on Earth

  1. Hi,

    I'm a physicist with a layman's interest in biology. I was just wondering what the physical requirements for the origin of life on Earth are expected to be. So, for example, pressure range, temperature range, chemicals needed etc. If this has an answer, how confident is the community, or are there many competing hypotheses?

    You can tell me if it's valid or not, but the discussion may be limited to life which began on, i.e. not from a meteor or whatever.

    *Idk if this would be more appropriate in the biology, chemistry or physics section* so, i guess it can be moved to either (if that's how it works).

    Cheers,

    InsertName.
     
  2. jcsd
  3. Pythagorean

    Pythagorean 4,623
    Gold Member

  4. Evo

    Staff: Mentor

    You might enjoy this video on abiogenesis by Dr. Jack Szostack. He explains it quite simply.



    https://www.youtube.com/watch?v=U6QYDdgP9eg
     
    Last edited by a moderator: Sep 25, 2014
  5. Thanks for the replies! It already sounds more interesting than I imagined...
     
  6. But what are the physical requirements? May I suggest a few?

    1. Temperature conducive for a vibrant carbon chemistry (not to hot, not too cold)

    2. The presence of carbon, hydrogen, oxygen, nitrogen, and a few others,

    3. Some mechanism to concentrate the chemical species to facilite the chemistry at a sufficiently high rate,

    4. An energy source to faciliate the production of high-energy bonds to counter-act the second law,

    5. At least some periods of relative planetary stability (time to chemically evolve).

    So if I take those five, put them in a bottle and shake vigorously, will I produce life?
     
    Last edited: May 9, 2012
  7. Pythagorean

    Pythagorean 4,623
    Gold Member

    That more or less the Miller Urey experiment I linked above. It didn't produce life, but it does produce a lot of amino acids, which are a first step!
     
  8. Well wait a minute, I'm confussed, someone help me. If that's more or less the Miller-Urey experiement and that experiment did NOT produce life then either it takes more than those five or your suggestion the experiment reflected those five is not correct.
     
  9. Pythagorean

    Pythagorean 4,623
    Gold Member

    Abiogenesis is still an open topic. We don't know the exact conditions that started life. But showing that a bunch of free-floating elements can self-organize into amino acids (the building blocks of life) under the right conditions means we're on the right track: that we have met many (not all) of the condition with the Miller Urey experiment.
     
  10. Not elements. Molecules. And they have to find (living) attractors don't they? That takes apparently a great deal of time if unassisted. Maybe I should have added a sixth:

    6. There has to exist dynamic attractors representing the stable states of life (ala Rene Thom) and the chemistry has to be given a sufficient amount of time to find them if unassisted.

    Miller-Urey was not nearly enough time.
     
    Last edited: May 9, 2012
  11. Pythagorean

    Pythagorean 4,623
    Gold Member

    You're right, molecules is more accurate.

    I agree there needs to be a driver on the system and the system would likely then fall to something like an attractor (not necissarily an attractor... it could be a chaotic repellor right? Then the chaotic dynamics are a transient state that will eventually end.)

    It is most likely an itinerant system. Trajectories fall through several "attractor ruins" or "chaotic saddles", experiencing a variety of Lyapunov exponents at each symbolic region of phase space.

    The video Evo posted gives one example of a structured driver (heating vents in a large body of water).
     
  12. As the OP asked for physical requirements, I'd like to add:

    7. The planet has to be a size capable of supporting an atmosphere conducive to a vibrant carbon chemistry (not too heavy, not too light) which means probably a planet orbiting a particular type of sun at a particular range of distance. See "Habitable Zone":
    http://en.wikipedia.org/wiki/Habitable_zone

    and that leads to an eighth one:

    8. The presence of water.

    And all my requirements are for carbon-based life. There have been suggestions for other life forms but an argument can be made that carbon is ideally suited for life and no other element would work including silicon.
     
    Last edited: May 10, 2012
  13. Has anyone run the Miller-Urey experiment for long periods of time? If so, who, and were there more complex molecules produced than Miller-Urey?
     
  14. Pythagorean

    Pythagorean 4,623
    Gold Member

    Yes, I don't know, yes.

    The Miller Urey wiki brings it up
     
  15. We know only about a certain kind of life here on Earth. It is possible to look around the Earth and see zones where there is no life.

    The Earth was different when life began. It is quite likely that sulphur took the role that oxygen now has. The very oldest life forms are like that.

    I've never studied the range of conditions but it is more than you'd think. There are bacteria that live in boiling water. There is an ecology that lives at the bottom of the ocean next to hot water vents that go up to 150 C, but I'm not sure. Worms live in glacial ice in Iceland. Bacteria can live in the stomach, which has a pH of zero or something like that. I have read that there are lots of bacteria 4km down in the earth, which is hard to believe but could be.l

    Organic life uses only about eleven of the elements. Hydrogen carbon nitrogen and oxygen are by far the most important. Sodium, chlorine, and potassium for electrolytes. Sulphur, calcium for bones, and iron for oxygen transport. It would very likely be possible to make do with less or with substitutes.
     
  16. The Miller-Urey experiment was hugely important because it demonstrated that laboratory investigation of abiogenesis was a practical possibility. The experimental results are largely irrelevant. They had the wrong starting conditions. Only a couple of the amino acids produced are used in organisms. There was no preferred chirality. And so on. Conceptually brilliant, practically - now - irrelevant.
     
  17. D H

    Staff: Mentor

    If by oxygen you mean diatomic oxygen, that is incorrect. It's bass ackwards, in fact. The diatomic oxygen in our atmosphere and dissolved in the oceans appeared about a billion years after the origin of life. It was created by life rather than being necessary for the origin of life.
     
  18. There is little indication that jackmell was referring to oxygen gas. His named elemental requirements were for CHON, which he gave in the conventional order. I took his intention as very clearly referring to elemental oxygen as a necessary requirement of organisms, at least as we know them.
     
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