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How likely is it that DNA was created by nature?

In other words, what is the (mathematical) probability that given the timescale and world conditions at that time (approx 4 billion years ago) that nature could have come up with (or evolved) a structure like DNA.

Given that DNA is a complex molecule that has a very elegant system for holding digital information and a very reliable system to copy itself, with seemingly just the right amount of mutation to help evolution. Can we show that it might have happened within the timescales available or does in look like that it would be extremely unlikely?

Another thing that puzzles me is that DNA is a digital information system. When we look at many naturally occurring systems they tend to work in an analogue fashion. What are the probabilities of other types of systems occurring, such as for example, a potential differences caused by different concentrations of molecules used as a basis for information storage?

LUCA - understood to be all life's universal ancestor - a single cell about 3.5 billion years ago (I think). This does not leave a great deal of time to have evolved DNA from when the earth could have had the conditions to allow this. And, presumably DNA would have needed to have been around for quite some time before it managed to evolve LUCA.

Are there any (computer) models that identify these probability issues, what work has been done on this - anyone know? By the way this is a layman's question - I am not a geneticist!

See also

rgds JP


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    Jun 11 2013: Even if we allow for life to ignite somehow; it had to have available fuel/food & the mechanism to utilise it. It had to have an enclosure & protection from the elements. Looking at today's world; the longer we give it, the more likely it is to expire. The whole scenario is wishful thinking.

    • Jun 11 2013: Fuel and food are overlapping magisteria. Do you really think that the sun was not available at the times of the origin of life? Do you think that igneous energy was not available? Thunder? Electrochemical reactions?

      Envelopes are easy to come by, amphipathic molecules easily form spontaneously, and they tend to form micelles and membranes on their own, but I doubt that envelopes would be that necessary when there was no predators.

      Looking at today's world, we notice that organisms with huge populations tend to quickly evolve and better survive. Less abundant ones may get in trouble more often. After all, many organisms have gone extinct in the eons since life started in the planet. That has not stopped remaining species to then radiate into many species and repopulate vacated niches. It's well documented.

      The whole scenario complies with everything we know about physics and chemistry. That you don't like the idea is worse than wishful thinking. It's pure denialism.

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        Jun 13 2013: Hi Entropy,
        " Fuel and food are overlapping magisteria. Do you really think that the sun was not available at the times of the origin of life? Do you think that igneous energy was not available? Thunder? Electrochemical reactions?"

        I am a pretty well evolved mechanism, but I couldn't live on any of these.

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          Jun 13 2013: Is it really appropriate to compare survival now where the world is teaming with life, much of which survives by killing or eating other life, with earlier stages (not very loving).

          Early on there was probably little oxygen until plants developed etc etc.

          A lot of life would be different to now.

          I guess life reflects the environment it lives in. Some bacteria can survive and thrive in super heated water. We can not.

          Life finds a way. Hence antibiotic resistant bacteria.

          So you can not imagine how early life could have survived. Therefore it must be false.

          I suggest not.

          By the way some bacteria are photosynthetic.

          Some bacteria live off iron or sulfur.

          Are you suggesting science is claiming mammals such as your self were one of the early life forms. Only religion does that.
    • Jun 13 2013: What are you talking about Peter? You live out of the Sun's energy.
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        Jun 14 2013: Yes, but only via photosynthesis & a complex food chain. That's not going to work for the first lonely life on the planet. The sun would most likely kill it. Energy is of no use unless you have conversion machinery.

    • Jun 14 2013: But you need photosynthesis and a complex food chain because there's already lots of complexity built up by the interactions between the sources of energy, the substances in our planet, and billions of years of evolution. Things were much simpler at the beginning. By experiments I have seen quite interesting reactions happening by exposing common minerals and gases to sunlight, or to geothermal energy. Several minerals start building up complex structures with the coming and going of sunlight, showing that night/day can make for complex reactions and such kinds of things. One set of complex mineralizations can accommodate organic molecules and catalyze organic reactions, et cetera. Today's life forms are not the best clues about how life started. We have to think a bit out of the box. We still don't know all the ways in which life could start, but I see only advances in the field of abiogenesis. QUite frequently experimentalists find new mixtures and energy sources, and such that build complex organic molecules.

      So, the sun most likely fuelled the process, if not some geothermal energy, and/or other combinations of events.

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        Jun 15 2013: Hi Entropy.
        I totally accept that we can do good stuff in the lab. We may even, eventually, create some form of life. But how does all this expertise being brought to bear help to prove that life can arise without the input of expertise ?
        You have to believe that it happened, & that it happened only once. Other folks believe it happened on other planets as well. Then it had to happen more than once, then why not lots of times on this planet?
        It seems to me that if life can exist on raw sunlight then evolution would have encouraged that ability. That would be much preferable to the rigmarole we have to go through today.
        Anyway, I guess we all have our opinions. Just this one isn't mine.


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