Pharyngula

Hey, how about these article titles?

Comet Impacts Really Could Have Been the Catalyst For Life on Earth
Comet Impacts May Have Produced The Building Blocks For Life On Earth
We Now Know For Sure How Life Began on Earth

We’re getting this sudden flurry of articles touting the contribution of organic molecules from cometary sources to the origin of life on Earth. They’re all bullshit. The media hype machine is going crazy again over science the journalists haven’t thought it through.

There’s nothing wrong with the core of the original paper that sparked this frenzy of nonsense: the investigators showed that the energy of comet collisions can drive the assembly of amino acid monomers into short linear peptides. They made extremely cold pellets of glycine ice and fired them with a propellant gun into a block, and presto, they got tripeptides out of the collisions. I can believe that.

What I can’t believe is that early cellular biosynthesis was catalyzed by comet impacts. This explains nothing. It is not enough to postulate that there was, once upon a time, a cold soup of organic subunits in the ocean, that just sort of congealed into life — it doesn’t work. The authors made no calculations about the concentrations of their tripeptides in the prebiotic ocean (it would have been an exceedingly thin, dilute soup), don’t consider that these compounds were probably degrading as fast as comet-smashing was making them, and that their mechanism does not say anything at all about what reactions early precursors to life would have been using to synthesize peptides. I’m certain the answer didn’t involve waiting for a giant ball of ice to smack into the protocell.

For some reason, journalists and the public love these scenarios of cosmic forces colliding in big explosions to create life — it’s as if they desperately want Michael Bay to be in charge of biology. It’s not how it would have worked. If you want to look for answers to the origin of life, you need to look at conditions that generate a gentler flux of energy that is a better analog to metabolism. It’s about flow, not bang.

The best summary of how actually abiogenesis would have occurred is Nick Lane’s The Vital Question: Energy, Evolution, and the Origins of Complex Life. You know how crimes can be solved if you use the principle of Follow the Money? Life can be understood if you try to Follow the Electrons. It makes no sense to look for life’s beginnings in cataclysmic collisions, you need to search for gradients and reactions with energies that wouldn’t disintegrate cells.

Or you could try reading a paper by the always-entertaining William Martin, if you’re in more of a hurry.

The very familiar concept that life arose from some kind of organic soup is 80 years old and had best be abandoned altogether. The reason is that life is not about the spatial reorganization of preexisting components, it is a continuous chemical reaction, an energy-releasing reaction, and a far-from-equilibrium process. The proposal that life arose through the self-organisation of preformed constituents in a pond or an ice-pore containing some kind of preformed prebiotic broth can be rejected with a simple thought experiment: If we were to take a living organism and homogenize it so as to destroy the cellular structure but leave the molecules intact, then put that perfect organic soup into a container and wait for any amount of time, would any form of life ever arise from it de novo? The answer is no, and the reason is because the carbon, nitrogen, oxygen, and hydrogen in that soup is at equilibrium: it has virtually no redox potential to react further so as to provide electron transfers and chemical energy that are the currency and fabric of life.

If not soup, what? Life is about redox chemistry, so the site and environment of life’s origin should be replete with redox reactions. Alkaline hydrothermal vents provide a good model for understanding early chemical evolution because they have some similarity to living systems themselves. Perhaps similar to some types of hydrothermal vents observable today, such as Lost City, alkaline vents during the Hadean would have offered a necessary and sufficient redox potential (in the form of the H2-CO2 redox couple) and catalytic capabilities (in the form of transition metal ions) to permit organic synthesis at a specific location in space and stably over geological time to give rise to the chemical constituents of life and to foster the transition from geochemically contained chemical networks to bona fide free-living cells. Why, exactly, are alkaline hydrothermal vents conceptually attractive in the origin of life context? There are a number of reasons, many of which are old as the discovery of vents themselves but they remain current.

protongradient

These ideas have been around for years, but they never seem to get the kind of press extraterrestrial bullshit gets. It’s the lack of explosions, I suspect.

Comments

  1. #2 Tim H.
    Western Missouri
    August 23, 2015

    Some folks need drama, cometary impact provides that,. I don’t see it as much different from those who’d rather think about names in the Domesday book than the more likely event of “Random spawn of whoever was loose in their ancestral regions”.

  2. #3 Daniel Corcos
    France
    August 23, 2015

    I should have added some comet impact to my model. Sperm cannibalism is not sexy enough for evolution journalists.
    http://www.ncbi.nlm.nih.gov/pubmed/26286030

  3. #4 See Noevo
    August 23, 2015

    PZ,

    You’re on a roll.
    Your last three articles have generated a total of 8 comments, 4 by me.

    Back to this one, though:
    The definition of “redox” is what?

    If you know so much about how life began, and what was required, why hasn’t anyone been able to create life in the lab?

  4. #5 Michael Kelsey
    SLAC National Accelerator Laboratory
    August 24, 2015

    @See Noknowledge #4: Please try typing “redox” into Wikipedia, and you can read the definition for yourself. Anyone who has taken a high school chemistry course (assuming you went to a high school, and one which actually taught science) will know what it means.

    Since you don’t know basic chemistry, and you obviously (given your hundreds of ignorant posts) are not familiar with current research, you aren’t competent to express an informed opinion on the subject.

  5. #6 JSintheStates
    August 24, 2015

    I’ve read Nick Lane’s book. He emphatically states that life on planet Earth DID indeed start here! You must have read something else—on the internet!

  6. #7 See Noevo
    August 24, 2015

    To Michael Kelsey #5:

    Well, since you know so much about chemistry, perhaps you could answer for PZ, and for the benefit of others (besides me) reading this particular article and blog:
    Why hasn’t anyone been able to create life in the lab, Michael?

  7. #8 Morbeau
    August 24, 2015

    Are there huge steaming realms of ignorance from which spring, fully-formed, streams of unaware trolls? Or do the trolls exude the miasma of ignorance that obscures rationality in so many discussions? Spontaneous generation or special creation?

  8. #9 See Noevo
    August 24, 2015

    To Morbeau #8:

    “Spontaneous generation or special creation?”

    I think what PZ and Michael are proposing sounds a bit like “spontaneous generation”, don’t you?
    SG was a sound, or at least widely-held, theory for a long time, a couple millennia, I think.
    But it was abandoned when Louis Pasteur came along.
    Yet, maybe it HASN’T been abandoned after all!

  9. #11 Michael Kelsey
    SLAC National Accelerator Laboratory
    August 24, 2015

    @See Noknowledge #7: Because no one has bothered to run all of the pieces together at once, and there are still details to be resolved (electron transfer via solid catalysts vs aqueous solution, energy input to maintain a non-equilibrium state, etc.). But the basic chemistry for each stage is fairly well understood. Please feel free to look it up.

    If you actually read anything about the subject, rather than just parroting the ignorance you collect from your Internet echo chambers, you would already be able to answer the question yourself.

  10. #12 GregH
    August 24, 2015

    SN: “SG was a sound, or at least widely-held, theory… Yet, maybe it HASN’T been abandoned after all!”

    Seriously, the depths of your ignorance know no bounds.

  11. #13 G
    August 26, 2015

    Tim @ 2 pegs it: “Some folks need drama, cometary impact provides that.”

    Thankfully, dinosaurs are nothing if not “dramatic,” so the discovery of fossils provided enough drama-fodder to spark a popular interest in paleontology. Arguably that contributed to widespread acceptance of evolution and data about the age of the Earth. Microscopic blobs are hardly as dramatic, though I suppose a time-lapse of single-celled organisms eating each other, if projected on a large enough screen and accompanied by ominous music, might suffice;-)

    See @ 7: What will you say when we do manage to create life in a lab, and the findings are discussed in these pages? Do the thought-experiment and give it some speculation.

    Years ago while I was picking up some gravel, sand, and cement for a concrete project, a guy at the materials yard said something interesting that had a kind of deep wisdom, and I’ve never forgotten it: “God took billions of years to make rock, and we can do it in 28 days” (28 days = the time required for fresh concrete to harden to its full structural strength).

    If you believe that a divine creator brought the universe into existence from nothingness, including this rocky planet of ours, contemplate the fact that we can “make rock” at will, in any shape we choose, including homes for the multitudes and towers that reach for the clouds. Is that not a routine re-enactment of a divine act?

    Not only that, but we can take rock (iron ore) and convert it to steel, a most wondrous material that each of us uses every day at almost every meal. Contemplate that, while looking at a spoon, fork, and knife. We can also take pulverized rock (sand) and convert it from something opaque to something transparent (glass), with which we can overcome declining vision (eyeglasses), and peer deeply into the infinitesimals (microscopes) and the infinite (telescopes).

    All of these things are the results of chemistry in action. All of the processes of life, such as breathing and the digestion of food, involve chemistry in action. Chemistry is also the stuff of our very thoughts, as emotions themselves are the subjective sensations of the action of neurochemicals on neurons.

    Rather than complain that chemistry somehow lowers what is sacred to the level of the mundane, I would suggest the opposite course: contemplating the ways in which our knowledge of chemistry raises what is mundane to a level that we should respect as sacred.

  12. #14 See Noevo
    August 26, 2015

    To G #13:

    “See @ 7: What will you say when we do manage to create life in a lab, and the findings are discussed in these pages? Do the thought-experiment and give it some speculation.”

    Your suggested thought experiment for me has been concluded.
    Results:
    1) Whoever conducted the ground-breaking experiment would probably win a Nobel Prize.
    2) He/She/It/Them would probably be named person/persons/its of the year.
    3) I would know, as all scientists would, that a successful abiogenesis experimental result would NOT PROVE that life on earth began that way nor in ANY abiogenesis way.

  13. #15 dean
    August 26, 2015

    Shorter #14: I will never admit that any result in science that contradicts what I believe my bible says should be considered valid.

  14. #16 G
    August 27, 2015

    See @ 14:

    Clearly it’s true that demonstrating abiogenesis in the lab does not provide conclusive evidence that life on Earth began in exactly that manner. There’s no fossil evidence of the very first life, and we can’t get into a time machine and go back 3.8 billion years to observe first-hand.

    I don’t have a problem with the position “God used chemistry to make life” because it’s untestable and thus outside the domain of science.

    But I do have a problem with “chemistry has nothing to do with life” because that’s demonstrably false.

  15. #17 Michael Kelsey
    SLAC National Accelerator Laboratory
    August 28, 2015

    @G #16: The position you cite, “God used chemistry to make life,” is (as you say) untestable because of its premise. The second half, that life originated via chemistry (however triggered) _is_ testable, and several of the component stages have been successfully tested and demonstrated.

    However, that position is *NOT* what See Noknowledge advocates. Rather, he claims that “life cannot possibly have originated via chemistry” (however triggered) because of various IDiotic and content-free claims like “irreducible complexity” or “specified complex information.”

    Hence See Noknowledge’s response to your question.

  16. #18 See Noevo
    August 28, 2015

    To G #16:

    “But I do have a problem with “chemistry has nothing to do with life” because that’s demonstrably false.”

    Who has made any claim that “chemistry has nothing to do with life”?

  17. #19 See Noevo
    August 28, 2015

    To Michael Kelsey #17:

    “The second half, that life originated via chemistry (however triggered) _is_ testable…”

    No, it is not.
    What is testable is whether life NOW can be elicited from chemistry.
    However, you cannot test whether the FIRST life on earth eons ago in fact DID come from chemistry.

    “Rather, [See Noevo] claims that “life cannot possibly have originated via chemistry” (however triggered) …”

    Please cite specifically where I made such a claim.
    I’m betting you won’t, for two reasons:

    1) I can’t recall making such a claim, and
    2) You being you.

  18. […] We Now Know For Sure How Life Did Not Begin on Earth. […]

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