cst commonsense

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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

  • Jun 11 2013: In terms of probability: 1. In terms of likelihood: 100%. DNA was built by natural processes. I know this because there's plenty of DNA in nature.

    There's nothing too particular about something natural being a "digital" system. All that "digital" means is that there's no continuums, but, rather, complete blocks of stuff. In DNA it is four kinds of molecules in the chain. But we have found that at the uttermost level, the whole of reality is "digital" since stuff exist in quanta. Precise pieces of matter/energy, rather than continuums. The very idea of atoms shows a level where we should expect things to be digital. There's no continuum between a hydrogen molecule and a water molecule, et cetera.

    If our planet is 4.5 billion years old, and the first apparent fossils are 3.5 billion years ago, there's lots of time available. I don't know about you, but to me even hundreds of millions of years is a huge amount of time.

    In order to properly calculate the probabilities we would have to know how many different conditions existed back then, what kinds of conditions, and a huge et cetera. I don't think that such is an easy task. Whatever the possibility to calculate those probabilities, it is true that we are here, therefore that DNA would form was possible. Not only that, science shows that chemistry and physics pose no barrier for it to happen. It's a matter of figuring out possible conditions for such things to happen. Given advances in origin-of-life research, I think that we will end up with many viable and very convincing scenarios, but we will have a very hard time deciding if any of those were the ones happening that far ago.

    P.S. By the way. Common sense alone is not enough to decide on these issues. Scientific information and understanding are necessary. Remember that common sense is built on everyday situations that can often mislead our understanding when talking about unfamiliar situations and scales.
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      Jun 13 2013: Hi entropy, I agree with most of your points, except your first one. Its a bit like saying I know god made the universe because I see the universe all around.

      The universe is so complex. Even the basic stuff like atoms interacting, or what is going on in an atom. Often our brains seem to struggle, but we are good at assuming and dealing with agency. So a god did it seems to reasonate even when there is no evidence.

      A lot of these arguments seem to be life and the universe is so complex it just could happen naturally. Yet they are comfortable with assuming some elusive being existed that created the universe and life. It really is kind of odd when you think of it.

      And oddly they are comfortable with complex natural processes that are more familiar going on all around them, like weather, the formation of babies, like all the chemical and nuclear reactions going on (the sun).

      Whatever happens in natural that is complex and hard to grasp seems to pale in comparison when you think how much would be involved in planning and creating all this. Better define this being as smart and powerful.
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    Jun 12 2013: I am not sure if the time element in your question is geological time or evolutionary time. The odds of something as complex as a DNA may look pretty low in a given span of time but if you consider the huge number of evolutionary reiterations possible under huge number of environmental stressors, it will appear that it is nothing miraculous for a complex system like DNA to come up. In fact it will appear highly probable.
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    Jun 11 2013: Here are some sources on the evolution of DNA.


    I think that once you've read through them you'll find the explanation reasonable.

    And here are some websites and download links for different kinds of evolution simulators.


    Oh, and to answer your title, It's very likely.
  • Jun 11 2013: Technically your question is asking about something that has already occurred, so the answer is 100%

    If you meant to ask about the odds of DNA being produced in the presumed environment of early Earth, that would be a very different question. The answer to that question would be, that probability is unknowable because we do not have enough information. From what we do know about the geological development of Earth, it is extremely unlikely that we will find evidence of the origins of DNA.

    We do not know for a fact that DNA developed from less complex compounds here on Earth. There is no evidence to support the possibility that DNA was delivered to Earth by an asteroid or comet, but it is a possibility.

    Due to the continuous changes caused by nature, it is most likely that we will never have an accurate understanding of the origin of life on this planet. Lack of knowledge is not evidence of anything.
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      Jun 11 2013: ....
      A Billion has 9 zeros, a Trillion has 12 zeros
      There are about 300 Trillion cells in your body flying in close formation. That makes ......er lots & lots to have gotten there act together over a few Billion years of evolution.
      Believe it if you like.

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          Jun 11 2013: Yes, we know a bit about DNA. But aren't all these cells subtly different from one another as they build eyes, brains, bones, teeth, & many kinds of flesh etc.
          I get the feeling we are looking up at the bottom rung of a veeeeeeeerryy long ladder.
          What I find weird is that most people have no interest whatsoever in this subject.

      • Jun 13 2013: Nah, those cells did not come together, they formed by a process of division and differentiation, not by flying around until they found each other after billions of years. How much do you think it helps you understand science if you picture something that you knew much better in that equivocal way instead.
  • Jun 11 2013: Imagine someone coming form another planet and asking: "How likely is for humans to have developed this level of technology by themselves?"... any of us would just laugh, because we know we didn't went to sleep one day as cavemen and woke up the next day civilized and modern, it was a process that took 10,000 years or so. It is the same with DNA, it did not form from one day to the other, it took millions of years to form piece by piece, not all at once, and just like human technology the first steps where extremely slow, but as more and more elements were available the more likely it was for them to assemble themselves into more complex building blocks, which speed up the process gradually but steadily, until the present day.
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      Jun 11 2013: “we didn't went to sleep one day as cavemen and woke up the next day civilized and modern”

      Just a point of correction: Actually early prehistoric humans/cavemen did have a civilized social society, the old myth of cavemen being ape like has been disproven. Although our tools, education, language has greatly evolved, humans way of thinking seems to closely match modern humans. I’m guessing if a modern new born was taken back in time a raised by a prehistoric family, he likely fit right in, and vice-versa.
      • Jun 11 2013: I do appreciate you remark, I will take that into account for any further discussion, however you forgot to rephrase my idea in the proper therms. Since you are meaning correcting me, I think to rephrase my idea with the correct words it is the polite thing to do in these cases.
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      Jun 13 2013: But the cells needed to develop somewhere.
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    Jun 13 2013: From one of my provided sources.

    "How Could DNA Have Evolved?

    While there is no direct fossil evidence for the evolution of DNA (because of its size and fragility), scientists have theorized on its origins based on verified laboratory evidence. One theory goes like this: DNA began as a simple self-replicating peptide, possibly containing no more than 32 amino acids, which formed naturally (and somewhat easily) in the early oceans of Earth.

    Once self-replication had been achieved, the forces of Natural Selection took over. For example, those molecules which were protected from the elements survived longer and reproduced more. So, any molecules which found themselves with a lipid bubble (which also forms naturally) would have a better chance of reproducing. After many incremental steps, the lipid bubbles eventually became cell membranes, and the molecules DNA."
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    Jun 13 2013: Funny how you used the word created. Even when talking about natural process or nature you are still thinking in terms of creation. Doesn't creation imply a creator?
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    Jun 13 2013: Did any non-believers check my sources in the previous post? Any questions on that or are you now in tune with those ideas?
    • Jun 13 2013: Your first question is ambiguous. What do you mean by "non-believers"?
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    Jun 12 2013: I doubt you can make a reasonable predictions without all sorts of questionable assumptions.

    If there was just a 10% probability of your parents meeting and having a child (you), and each of their parents meeting, and each of their parents meeting, then the probability of just 3 generations of your ancestors meeting to result in your potential birth is 1 in 10,000,000. This ignores all the potential genetic outcomes from 2 specific parents. Yet here you are.

    The probability of the specific water molecules being in this glass of water is infinitesimal. Yet here they are.

    The probability of a particular oxygen atom hooking up with 2 specific hydrogen atoms is even lower. Yet we are surrounded by water molecules.

    Low probability, but so what?

    I suggest complex DNA didn't just form as is. There was probably a progression from a simple self replicating molecule, to something like RNA etc.

    Life and the universe is old and complex. WE don't have all the answers, especially around the origins of life. However, we do see DNA consistent with descent.

    I'm not sure assuming a god started life, or a committee of other dimensional beings, or a super alien from a previous big bang or other unsupported and unexplained claim really helps.
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    Jun 11 2013: Mount Rushmore could be created by natural forces over time. The recognizable images of yet-to-be-born historical figures could be formed by erosion, wind, temperature variations, aging, etc. Anybody believe that? Mt. Rushmore is easy compared to DNA which has an unfathomably high information storage capacity. One microgram of DNA could store as much data as a million CD’s! The code is staggeringly sophisticated using letters and words with the meaning of the words being unrelated to the chemical properties of the letters. No man-made coding system in existence, no matter how sophisticated, can compare to the complexity of the DNA code. Just as discovered remnants of an ancient clay pot speak of a designer and a maker, so does DNA. Gradualism offers a zero probability for random, spontaneous generation of life on earth, or, as we call it, DNA. DNA is a message. All messages originate in a Mind!
    • Jun 11 2013: I doubt it. For such thing to be possible you would need mounts that could reproduce, and mechanisms that would allow only mounts looking more and more like Mount Rushmore to successfully reproduce. But mounts don't reproduce and we know of no natural mechanism that would select for yet-to-exist images of people and allow such mounts to reproduce and mix their successful features.
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        Jun 11 2013: You advance to the bonus round!
        • Jun 12 2013: So did you understand the roles of reproduction, variability, and selection? My guess is that the only thing you took from my comment was "I doubt it." That made you happy and therefore you ignored the rest and how it evidences the main mistake(s) in comparing Mt Rushmore with evolution.
    • Jun 12 2013: Oh I forgot your second part. DNA is much easier than a Mount Rushmore. DNA exists in reproducing organisms. Organisms can be subjects of selection by natural mechanisms. Therefore it can get as complex as time allows.

      P.S. "Gradualism" is not the only natural process that gets us more complex DNAs, we also have duplications, insertions, recombinations, et cetera. Remember: our understanding of evolution has changed since Darwin!
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        Jun 12 2013: Oh? You folks don't need billions of years for a room full of monkeys to type Shakespeare's complete works? It can be done in how much time now? So, you still owe me a list of Darwin's errors which you new folks have evolved away from. Can I get that list from you? Seriously, Entropy, are you saying there is a better chance for DNA to occur spontaneously, without any control, than for the weather to carve Mt. Rushmore? You're losing me buddy.
    • Jun 12 2013: Edward,

      For you to understand why it is easier for DNA to evolve than for the weather to make a Mount Rushmore, you have to understand the points I was making about reproduction and selection. They relate to that, in case you did not notice. It would be great and I would appreciate it if you tried to understand my comments a bit better.

      As per Darwin's "errors," I have listed plenty of changes on evolutionary theory since Darwin, but you seem not to read what I write, or forget next minute, or maybe you haven't tried to understand them as in the above where I clearly explained why the weather would not carve a Mount Rushmore as easily as DNA would evolve complexity. We talked about genetics and all the fields that came with incorporating knowledge of genetics into evolutionary theory. The fields are huge compared to anything that Darwin wrote or even imagined. Then, I told you about molecular biology. I said that Darwin did not know about that. From mol biol we've got neutral and nearly neutral theories. Enormous fields of research too that dwarf Darwin's books by amount and insight. Now I told you about things other than gradualism. WIll you ask again for lists next time? Will you ignore again that population genetics is huge? That mol biology has given us insights never imagined by Darwin? Everything I said?
    • Jun 12 2013: It would be impossible for a room full of monkeys to type the works of Shakespeare in any amount of time without the typing materials being able to reproduce only after selecting those more similar to shakespeare's works. If there was a way for typing materials to be selected and then only successful ones reproduce and recombine we would have the works of Shakespeare in much less time. But that's not how typing works.

      Do you really think that I talked about Mount Rushmore above and about reproduction and selection for no reason? I was trying to show why your metaphors fail. They have nothing in common with evolutionary processes. Typing monkeys are creationist cartoon that don't help anybody understand how evolution works. They are rhetorical devices aimed at hiding the science from the gullible so that the gullible will have an easy way for rejecting evolution out of defeating a straw-man. But it is not evolution that you are rejecting that way Edward. You're fighting a straw man and nothing more.
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        Jun 12 2013: Thank you for condescending to make your opinions clear to me. I am sorry if you do not find my awe and respect for those opinions to be at satisfactory levels. I do hope you don't put too much stock in my opinion of your opinions. Gradualism is not a straw man. Gradualism is essential for your theory to hang on. If the Universe is not 14 billion-years-old your theory begins to leak. You really need astronomical amounts of time for your theory to hold together. If a Creationist soldier struck a fatal blow to Gradualism his Generals would decorate him, they would certainly not reprimand him for attacking a straw man. The flaws you detect in my conduct are really not important in this post. The topic asks if DNA could have been spontaneously generated in the natural order. My answer is no. Your answer is yes. We disgree. That happens. Be well.
    • Jun 12 2013: Sorry Edward, but I do not expect you to have awe and respect for my "opinions" or for my explanations. I did, however, expect you to have the respect of listening to an interlocutor who did pay attention to you, but who was rather flabbergasted to find that you did not pay any attention to him. At least not by any appearance.

      The universe is a bit less than to 14 billion years old. Sorry. Gradualism is a straw-man depending on how it's defined. Creationists are quite good at defining it so that it burns quickly, while leaving evolutionary theory intact. If "creationist soldiers" burn such straw-men their generals do indeed decorate them. I have watched them erect the straw-men, burn them, and then have generals declare victory and celebrate. Of course, why would the generals reprimand the soldiers who burnt the straw-men? They taught their soldiers to do exactly that. The problem with all those burnt straw-men is that scientists don't even notice and continue their work undisturbed, with evolutionary theory alive and well and flourishing.

      Yes, the topic was if DNA could have been spontaneously generated. But you deviated the conversation to those fallacious metaphors about Mt Rushmore and typing monkeys.

      Be well Edward. I shall let you have your fun undisturbed by me.
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      Jun 13 2013: Mount rushmore is a carving done by humans.
      Seems to be completely different to organic life and DNA
      Suggest this is a categorisation fallacy.

      Is a god organising all the cells in our body?
      Or is it happening now without agency?

      Is your argument basically that low probability events don't happen in nature.

      That it is impossible for self replicating molecules, precursors to DNA to form naturally.

      Yet you think it possible that some other dimensional being could make all this. What is the probability of that?
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        Jun 13 2013: Hi Obey. My intent for the comparison was to illustrate how one probability compared to another can lead to discovery of the gullibility of humans. No one would allow for the possibility of Mt. Rushmore being spontaneously formed by natural (non-human) activity, but those same people readily accept the exact same mechanism as the sole cause of the entire Universe! I am unfamiliar with the elements of a "categorisation fallacy", so I stand by my comparison. God is organizing all our cells. No, I do not insist that low probability events (albinism, giantism, conjoined triplets, Cubs fans, etc.) cannot happen in nature. A zero probability is also known as "impossible" and a negative cannot be proven so I cannot state it is impossible for self-replicating molecules to form naturally. It is accepted though that a certain number of repeating zeroes constitutes a virtual impossibility. I do not advocate that "some other dimensional being" created the Universe and everything in it. Thank you!
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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.

  • Jun 11 2013: I've always heard the theory. But unlikely things happen as one would expect Now very often.
    • Jun 11 2013: Yes. After all the universe is huge. Therefore unlikely things must be happening all the time.