Did Life Begin as “Failed Mineralogy” on the Seafloor?

first_imgExclusive  Another origin-of-life expert made a presentation to a filled auditorium at the Jet Propulsion Laboratory on Dec. 2 (cf. 11/05/2004 headline).  His scenario differed radically from last month’s.  Instead of trying to get ribose (for RNA) to form in a desert, he put his speculative natural laboratory 4 to 10 km underwater at the bottom of the sea.  Why?  Because the surface of the Earth would have been a deadly place: under attack by UV radiation (“disastrous” on the early earth, he said; for contrasting opinion, see 05/28/2003 headline), volcanoes, and meteorite impacts of world-wipeout class.  For his model, he needed a safe haven “out of harm’s way,” and found one, he believes, near deep sea vents.1    Dr. Michael Russell (geologist, U. of Glasgow) believes life began in an alkaline hydrothermal reactor.  Russell has a simple view of life: “Life emerges because of a chemical disequilibrium,” he said, as a kind of natural feedback mechanism “to solve the problem” of the need for a catalyst between carbon dioxide (oxidizing) and hydrogen (reducing).  “Don’t be vivocentric,” he cautioned the audience; a mineral-based catalytic cycle does the same thing as life, acting as a natural regulator between extreme conditions.  He also emphasized that living systems rely on convection, and generate byproducts.  “What does life do?  It makes waste,” he began.  (The waste in his model that might provide astrobiologists with clues on other planets is acetate or acetic acid, i.e., vinegar.)  At another point, he dismissed life as simply “failed mineralogy.”    Building on his belief that life emerges in environments far from equilibrium, his scenario proposes an environment with strong gradients.  His illustrations portrayed a battle between high temperature water, laden with alkaline substances and metals, rising up through cracks in the crust to face the cold, acidic ocean water, loaded with dissolved carbon dioxide.  He explained that this sets up a temperature gradient, a redox (oxidation-reduction) gradient, and a kinetic barrier that produces a 500 millivolt energy source at just the right temperature, about 40° C (hot, but not too hot, “like California”), where life could start cooking.  At the junction of all this turmoil, a “membranous froth” forms, providing a nest where organic chemicals like amino acids could form and evolve.  He thought that 35,000 years or so (the presumed lifetime of the Lost City thermal vents—see 07/25/2003 Quick Takes), was plenty of time to get life started.  Amino acids would link up, with help from mineral platforms, into chains up to six units long.  These, in turn, through hydrogen bonding with nucleotides, could spontaneously induce a prototypical “coding” that would not have depended on one-handed (homochiral) peptide chains.  Heterochiral polymers would have actually been preferable at first, he said, and might have been selected for homochirality later, the left-handed ones winning the luck of the draw over the right-handed.    Another thing life requires is compartmentalization – a membrane.  With apologies to the biochemists, who assume today’s lipid membranes would have been a requirement for life, he proposed that iron sulfide (FeS) might have been just the thing at that early stage.  It might have formed sandwich layers where the polymers of life grew, spalled off, with more forming in their place, producing a steady supply of prebiotic ingredients on which natural selection could act.  He did not discuss harmful cross-reactions or interfering products, but made the setup appear like a “self organizing proto-enzymatic system,” a forerunner of the complex acetyl-coenzyme A pathway employed by today’s living cells, which is assisted by proteins called ferrodoxins that act as electron-transfer agents.  The “extremely steep gradients” at the seafloor, he felt, could allow FeS to handle the electron transfer work.    In short, he proposed a “peptide world” first instead of an RNA world, the popular choice among those in the origin-of-life research community (see 08/26/2003 for other options).  In fact, he felt it a big mistake for most researchers to promote the RNA World hypothesis (see 07/11/2002 headline), because to him it is highly unrealistic, given the assumed geological conditions on the early earth.  “You’re not going to get RNA in the early earth; it is too unstable in water,” he emphasized (yet failed to mention how it appeared in the primitive “coding” with peptides he described earlier.)  Moreover, he flatly admitted the Urey-Miller experiment was completely unrealistic (see 05/02/2003 and 10/31/2002 headlines), because everyone since Darwin knows that carbon dioxide (not hydrogen or methane) must have been the predominant atmospheric gas.    By contrast, he sold his model as meeting all the realistic early-earth geological requirements, and getting free fringe benefits as a bonus.  For instance, he touted his model as providing a mechanism for proton motive force (pmf), in addition to electron transfer.  Pmf is observed in all organisms to build ATP.  Understanding how pmf arose in prebiotic conditions is, for most researchers, a difficult problem, but he claimed his model produced it as a “free lunch.”  This represented the tone of his talk: getting life is quick and simple.  In a somewhat overconfident manner, he described life as a natural consequence of disequilibrium conditions readily available deep under the sea, here on Earth or on any world undergoing convection and chemical disequilibrium.  The audience gave him a hearty round of applause.    Noting that the audience may have missed the fact that his scenario falsified the previous speaker’s (and vice versa), this reporter asked during the Q&A period about it.  “Benner said that ribose was essential to life, yet is unstable in water, so he theorized it had to form in a desert with borate to stabilize it,” I said.  “You are proposing that it formed in a deep sea environment.  How do you reconcile your view with his?”  “I don’t,” he responded without hesitation.  “I’m a geologist – he’s a biochemist.  To me, you must start with a realistic geological scenario for the early earth.  There were no deserts!  There was no borate, a rare mineral in cosmic terms.  I consider that a highly unlikely scenario.”2  He had stated emphatically earlier in the lecture that organic molecules did not come from space, as some astrobiologists suppose.  Regardless of what the cosmologists say, “There were no organic molecules on the early earth,” he said forcefully, “even from space.”  He didn’t need special delivery anyway; all the ingredients cook up just fine in his frothy alkaline reactors.  No primordial soup here; in fact, his first life has to invade the oceanic crust to survive, because the open ocean is the last place to put fragile early life forms.  Like a desert, it would have provided nothing to eat.    When a listener asked him his opinion about when life originated, he speculated confidently it was about 4.4 billion years ago – in geological terms, almost immediately after the earth cooled enough for the oceans to form.  He made it seem an almost automatic result of the circumstances.  To someone not vivocentric, it appeared to be no big deal.1Russell agreed with Stanley Miller and Jeffrey Bada (see 06/14/2002 headline) that black smokers are not suitable locales; too acidic and too hot (400° C).  He suggested pH of 10-11 (strongly alkaline) was more appropriate.  Contrast this with the highly acidic conditions found on Mars (see next headline).2Quotes are paraphrased but quite close to the actual statements.This reporter could not suffer bluffing to go uncontested, so he went up afterwards to talk to the speaker in person.  A series of questions nailed the bluffing to the wall:Chirality:  Like Benner, Russell admitted that 100% pure one-handedness is vital (see online book).  He admitted during the talk that amino acids racemize immediately (i.e., they revert to mixed-handedness).  His lecture had bluffed about heterochirality being acceptable at first, but he provided no means other than chance to achieve 100% homochirality later.  He seemed to assume getting a six-unit peptide of one hand was plausible, and that was sufficient (see next point).Information:  He confused chemical specificity with information when I charged him with pulling information out of a magic hat.  “The small peptides you propose are no more informative than a child’s alphabet blocks bouncing around at random,” I said.  When he tried to declare that a six-link peptide chain “has a lot of information, because it will only join with certain side chains and reject others,” I reminded him that such an arrangement provides no functional information (it doesn’t “do” anything useful—see 06/12/2003 headline).  Information is not the same as natural law.  I reminded him that sodium chloride (table salt) links up naturally, too, but provides no real information.  How much information is necessary to provide function?  As a real world example, he admitted that the simplest ferrodoxins are more than 53 amino acid units in length.  But that is an exceedingly high degree of information for just one protein molecule, especially when each unit has to be one-handed.  Getting something that size by chance is astronomically improbable.Genetic Takeovers:  I reminded him that Benner had warned against proposing too many genetic takeovers, because each one requires a radical overhaul of the conditions.  Compounding ad hoc conditions raises charges of telling a just-so story.  Yet his model invoked three takeovers: minerals, then peptides, then RNA.  He responded that the first two were “co-evolving.”  Reader, please ponder: does that really solve the problem?  Is it not a personification fallacy?Gaps:  He admitted that there is a huge gap between his proposal and the operation of the simplest living thing, especially considering the highly complex translation process between DNA and proteins involving transfer-RNA (see online book).  Yet he did not mention this gap during the talk when the audience was present.If a layman can nail a PhD chemist, it doesn’t mean the layman is bright; it means the chemist’s story is weak and shatters easily.  After I hammered away with these pointed questions, he asked me in mild exasperation, “Well, you’ve got to start somewhere.  What is your model?”  “You wouldn’t like it…. ” I replied, then thanked him for his time and bid him adieu.  There wasn’t an opportunity to elaborate, and my model was not the issue.  Before you can get a horse to drink, you have to salt the oats; you have to create thirst, and get him to admit a need.  The horse will come to the water when licking the salt lick over and over doesn’t satisfy.    Think about his last point.  To an evolutionist, proposing a just-so story is better than admitting ignorance.  It doesn’t matter whether it is highly implausible, or whether it contradicts (and essentially falsifies) other popular models, or whether it contains gaping canyons between the model and the real world (see 05/22/2002 commentary).  “What is your model?” – the question illustrates the assumption that something is better than nothing.  Is that always true?  Some people feel uncomfortable with silence and fill the air with verbiage.  But talk is cheap and sometimes less than worthless.  Telling a hungry hobo in a boxcar, “If we had ham, we could have ham and eggs, if we had eggs,” is less helpful than shutting up.  Saying it with feeling is worse.  Jeffrey Kargel (see next headline) suggested that the decreasing evidence for life beyond earth should generate “an increased respect for life on our own planet.”  Calling life “failed mineralogy” and quipping “What does life do?  It makes waste” is profoundly disrespectful.  Evolutionists need more respect for life.  They need to silently ponder the complexity of DNA, RNA, proteins and molecular machines.  Only then we can reason intelligently about alternatives like intelligent design.    So the first two lectures in a JPL series called “Life Detection Seminar,” have already falsified each other.*  In effect, they canceled each other out, leaving the audience behind square one, heading backwards.  Both models required highly implausible conditions.  Improbabilities do not add up to probabilities.  They multiply into impossibilities.*Here is the abstract of Russell’s presentation from the advertisement, with comments inserted and emphasis added to highlight the speculative elements and logical fallacies.  Compare this model with Benner’s scenario last month (see 11/05/2004 headline).  Notice the personification fallacy as he assumes these chemicals were striving upward to bigger and better organization:It is suggested [by whom? – identify yourself] that life got started when hydrothermal hydrogen reacted with carbon dioxide dissolved in ocean waters in a hydrothermal mound (pH ~10, T =100° C) partly composed of metal sulfide [life is more than chemistry; it requires specified complexity arranged for function].  This mound was the hatchery of life [misleading analogy] and the vent fluids bore life’s waste products back to the ocean.  Bacterial life is characterized by its wastes [reductionism], e.g., acetate, methane, oxygen and hydrogen sulfide.  The first waste product of life was probably [let’s see the calculation] acetate.  So we may think [who’s we?] of the hydrothermal mound as a natural hydrothermal flow reactor in which iron and nickel sulfides catalyzed the formation of minor concentrations of amino acids [you’re gonna need a lot of ’em, baby] and their polymerization to short peptides [Whoa! peptides do not form in water easily] – peptides that got caught in pore spaces while most of the acetate was eluted to the ocean [ad hoc; how convenient the good stuff lingers, while the bad stuff escapes].  These peptides wrapped themselves around inorganic metal sulfide and phosphate molecules [ad hoc], and also coated the inside of the pores [story’s over; now it’s a death trap].  The efficiency of the acetate generator was optimized by the emergence of the first organic living cells [Whoa! He just jumped the canyon in a single bound!] through the intervention of nucleic acids [Whoa!  Another canyon!  Where did they “emerge” from? – the same conditions are hostile to nucleotides] in the metabolizing system [systems are built by intelligent design].    The hydrothermal mound continued to support a community of cells through to the community’s evolution and differentiation to bacteria and archaea [evolution always assumed; does he have any idea how complex these critters are?].  The archaea added waste methane to the effluent.  From the mound the only safe escape route was down [only intelligent agents care about safety], down into the ocean floor where nutrients and energy were still available.  Any cells discharged to the ocean would have starved [only intelligent entities suffer hunger].  Thus the ocean floor sediments and crust were colonized and the deep biosphere was born. [Presto!  Now clap for the magic show.](Visited 28 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img

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