Origins of Life – What are the odds?

I hope to make this the first in a series of posts about current (relatively) origins of life research.  The reasoning behind this is two-fold.  The first is because I’m curious and the blog provides an opportunity to share what I learn.  The second is to counter the creationist plays against origins of life.

ResearchBlogging.org

I know of no scientist who will not admit that we will never know exactly what happened on this planet that resulted in life.  Of course, that’s not an admission that creationism is just as legitimate as science with this regard.  The thing is, if science can show that there are no physical or chemical reasons that life couldn’t form naturally, then there is no reason to invoke the super-natural.

I hope that everyone will agree that there are no restraints against the formation of organic compounds from non-organic reactants.  This has been demonstrated since 1952 when Stanley Miller and Harold Urey did their famous experiment.   Be sure look at the “recent related studies” in the Wikipedia article.  A recent examination of some of the original vials of material using modern methods resulted in a large increase in the number and kinds of organic compounds that were made in the original experiment.

In fact, organic compounds have been found in the oddest places; Titan,  nebula, and meteorites.  So I hope that there are no concerns with the fact of organic compounds forming.  In fact, the atmosphere and conditions on Titan have been shown to be able to form all five nucleotide bases as well as amino acids.

Now, the question, of course, is how did these disparate pieces come together and form the living system we see today?  Creationists will go on and on about how unlikely it is for complex RNA, DNA, and proteins to form.  They will say something like, “X process requires a DNA of Y length and the odds against that forming are 23895798148574925926594365094359043594632953295734587428574902875 to 1 or worse.

The problem is that creationists do not keep up on the research and the paper I will talk about today will show them just how wrong they are.

First, on the subject of odds, one must consider the length of time involved and the available area for such reactions to take place.  If we consider that one reaction takes place per second for a million years that reduces the odds of it occurring by 31.5 trillion.  (13 orders of magnitude) If we assume that one reaction takes place per every square kilometer on the Earth’s surface, then that reduces the odds by another 500 million.(8 orders of magnitude.  Of course, if you think in square meters rather than square kilometers, then you reduce it by a further 6 orders of magnitude.

So time and area can play a huge role in the reduction of the improbability that creationists push on an unsuspecting innocents .  [Of course, creationists only have 6000 years or so, not several billion to go from bare rock to modern life.]

But what about the other part, what about the nucleotide sequence itself?  Is that really necessary?

The answer is no.

Let’s take some process, like translation for example.  How large does an RNA need to be to catalyze this kind of process.  Well, the answer researchers at the University of Colorado and California have found is stunning.

Five.  That’s it.  An RNA strand that is a mere five nucleotides long can catalyze RNA 2’(3’) aminoacylation (that is, the process of adding an aminoacyl group to a compound. It produces tRNA molecules with their CCA 3′ ends covalently linked to an amino acid).  The active site is only three nucleotides.  It’s actually a complex with complimentary 4 nucleotide chain with it.  GUGGC/GCCU.

This image from the paper shows the kind of difference we’re talking about here.

These are all small trans-aminoacylating RNA complexes.  (A) C3 RNA.  (B) Intermediate trans complexes.  (C) Final GUGGC/GCCU complex.

So what does this mean for the odds of something like this occurring?

I’ll let the authors speak to this:

The ultimate importance of these observations may lie partly in the unknown number of other reactions that can be accelerated by comparably small RNAs. This is because for each such minuscule RNA reaction, there is a prima facie case that it would become accessible even after the most primitive ribonucleotide polymerization.

To see this, consider that, to pick every possible RNA pentamer sequence from arbitrary pentamers (with probability 0.9975), one needs only accumulate 4.1 × 10−18 gm of RNA. To possess every tetramer (with probability 0.9975) from a pool of  arbitrary tetramers, one would need 3.4 × 10−18 gm RNA. In a real polymerization, one would have a distribution of lengths; nonetheless, with only attograms of total RNA of distributed short lengths from some geochemical source, one would have not only our ribozyme, but every activity of comparable size.

So, the odds of getting this particular activity approach one with a bare 0.0000000000000000041 grams of material.  In fact, to get every possible RNA sequence of this length would require only 0.0000000000000000034 grams of material.

That means that the odds that creationists tout as nearly impossible are based on totally incorrect assumptions.  Reactions do not need 200 nucleotide RNAs or even 26 nucleotide RNAs to catalyze.  Five will do just fine and the odds of getting a five RNA sequence are very, very, very good.  I’d put money on it.

Addendum

I just had a brief e-mail conversation with the lead author of this paper (congratulations Dr. Turk) and she has mentioned that there is an additional paper (presently in review with JACS) regarding further reactions with the 5-nt ribozyme.  Keep an eye out.

_________________________________________________

Turk, R., Chumachenko, N., & Yarus, M. (2010). Multiple translational products from a five-nucleotide ribozyme Proceedings of the National Academy of Sciences, 107 (10), 4585-4589 DOI: 10.1073/pnas.0912895107

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10 Responses to Origins of Life – What are the odds?

  1. A very nice summary – and interesting dissection of what the assumptions really ought to be.

    I find that Creationists rarely think about assumptions, either because they fear they might start to question their own beliefs, or (more likely) they simply haven’t been trained for any sort of critical thinking.

    Also – Many thanks for the sidebar link! I have added you to my blogroll as well.

  2. Human Ape says:

    Your post is going to make Jeebus cry.

  3. Joe G says:

    Building blocks do not equal a living organism. Miller/ Urey also produced a host of toxins that if left to remian would have messed up their results. Also throwing time at something is not scientific.

  4. Pingback: Origins of Life – Darwin’s Little Warm Pond | Cassandra's Tears

  5. I wonder if the “G” stands for Gish?

  6. Pingback: Origin of Life – RNA Self Replicators | Cassandra's Tears

  7. Pingback: Origins of Life – Amino Acids and the Triplet Codon | Cassandra's Tears

  8. david salako says:

    Biogensis has discredited abiogenesis. Taxonomy-the science that classifies organisms on the basis of biological origin, desing and similarities also refutes abiogenesis. And the creationist account is consistent with this science.

  9. OgreMkV says:

    Biogensis has discredited abiogenesis.

    So where did the first living thing come from? Provide evidence that your explanation for this is possible. If you claim a designer, then you must provide evidence for a designer. Hint “It looks designed” is not evidence.

    Further, abiogenesis is a rich field of study with dozens of peer-reviewed papers published each year. Each and every paper has the potential to end abiogenesis research by showing that a critical step is impossible. Not a single paper has found this yet. Indeed, there are multiple pathways that are not mutually contradictory for life to develop from non-life.

    Taxonomy-the science that classifies organisms on the basis of biological origin, desing and similarities also refutes abiogenesis.

    Oh, do please explain this, in detail please. I would ask that you also include an explanation of the fact that taxonomy is a purely human developed and highly subjective approach (at the species level) and how this affects this claim.

    And the creationist account is consistent with this science.

    Which creationist account? In fact, there are so many (mutually contradictory) creation myths (because the universe we are in can only be created once) that they are divided into 5 categories of myth. Heck, even the Bible has two creation myths that are mutually contradictory.

    To my knowledge (and I have studied this) none of the creation accounts are compatible with any form of actual science. Even the Bible (which I assume is the creation myth that you subscribe too), if read literally cannot be squared with what is known fact about the universe, our Earth, and the organisms on it. If one the biblical creation account is not to be taken literally, then which one and how do you know. If both of the biblical creation accounts are not to be taken literally, then what’s the point in arguing about it?

    You see, you are stuck. If you say the Bible is literal, then it is quite obviously wrong. If you say that the Bible is not literal, then you have no argument anyway.

    But anyway, you have made claims, let’s see your evidence… There are links to 6 peer-reviewed papers in my article… match that number.

  10. Pingback: The Fallacies of Evolution | Cassandra's Tears

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