Theoretical origin of life; hydrothermal vents (Introduction)

by David Turell , Thursday, June 30, 2016, 18:42 (3068 days ago) @ David Turell

Back to the possibility of hydrothermal vents: - http://nautil.us/issue/37/currents/the-fly-in-the-primordial-soup - "The idea that life began at hydrothermal vents challenges the older, familiar scientific creation story of the “primordial soup.” In a letter to Joseph Hooker in 1871, Charles Darwin fancied that life originated “in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity etc., present,” in which a “protein compound was chemically formed ready to undergo still more complex changes.” In the 1920s, the Russian scientist Aleksandr Oparin and the British polymath J.B.S. Haldane independently fleshed out models of how life might have arisen this way, out of an ancient ocean with the consistency, Haldane said, of a “hot, dilute soup.” The name stuck. - *** - "The soup has an intuitive appeal: From it you can derive the building blocks of life. But it also has a fatal flaw: No matter what it produces, it's dead. Lightning bolts may spark biochemical reactions, but the energy quickly dissipates and the system returns to equilibrium. Primordial soup requires evolution to go uphill, thermodynamically, toward increasing order. It's like one of those “gravity hills” much documented on the Internet, where cars seem to roll uphill. Starting from heat, rocks, and seawater, amino acids and nucleotides self-assembled. They organized themselves into even more ordered molecules such as enzymes and proteins. From them evolution built the first cells, and eventually redwoods and roses, honeybees and apple trees, hyenas and humans. - "But the gravity hills are a trick of perspective. A carpenter's level would reveal the truth, but you don't often see one in the “like-magic” gravity hill videos. The laws of physics, in fact, remain intact. So too, say the vent theorists, with the emergence of life.2-5 Evolution only seems to move toward greater order; in the larger scheme, it's downhill all the way. Vent models posit that given the initial conditions, the emergence of life was not a near-miracle. It was inevitable. - *** - "Russell and his colleague Allan Hall, now an archaeologist at the University of Glasgow, chimed in. You're right, they told the Millerites: Black smokers are too hot, and acidic, for life to have formed there. Near them, though, they wrote, one ought to find mineral tubes that emit lukewarm, alkaline fluid. They would be ideal sites for the emergence of life. - *** - "Modern hydrothermal vent models suggest an explanation of how that chain was built. The giant battery of an early Lost City drives an engine that makes complex molecules, mainly out of carbon, hydrogen, and oxygen. Iron sulfide, as well as other small molecules found at the vents, act as “coenzymes”—catalytic nanoengines that drive the reactions lying at the heart of all metabolism. The chimneys, in short, have a kind of metabolism, which takes energy from hydrogen, CO2, and other molecules, and uses it to build more complex molecules, mainly out of carbon, hydrogen, and oxygen. The most ancient metabolic pathways in biology recapitulate the chemistry of that early Lost City. - *** - "If Barge and I watched our laboratory model long enough, would it too evolve a metabolic pathway? Enzymes? Genes? Barge is taking the first steps in that direction, though the steps are small. Instead of building a chimney, she deposits iron sulfide and other minerals onto a porous, inert disk. That disk can serve as a membrane between, say, a positively charged fluid and a negatively charged one. Barge measures the voltage and pH differences across the membrane—the flow of electrons and protons. Those currents drive chemical reactions that are fundamental to life. The next step will be to get the chemical reactions to evolve more complex molecules. “You could also set up experiments,” she says, “to test the emerging feedback of organics with minerals.” Simple catalysts could favor reactions whose products were more complex catalysts, which could produce yet more complex catalysts, in a feedback loop leading ultimately—way down the road—to protein and DNA. - "In one of my two worlds, the chimney developed a slender stalk, and then a heavy bulb swelled at the tip. “That one will probably break,” Barge says. It did: a dead end of evolution. But the chimney in the other flask grew a fat, flat base and tapered mountainously into a series of peaks that, if you were a water flea, would seem majestic." - Comment: In this article, which should be read completely, the author visits a lab which recreates sea vents. No success so far but life stared in the oceans and the vents are a likely spot. At least there are chemicals and heat to begin with. Still the issue of chance or design.