Life: a replicating chemical reaction Sorry to crash the party, but I've read a couple books recently outlining some facts pertinent to this discussion that you guys will probably find very interesting. Somewhat long-winded and I'm no pro, but I think a few minutes of perusing will be rewarded with snazzy biochemistry knowledge.
Despite the centrality of photosynthesis to the modern biosphere, it has been found that prokaryotic organisms can survive in many climes, wherever energy can be harnessed by chemistry. Competing theories were formulated that considered the possibility of extremophile prokaryotes as the first lifeforms, a likely option considering the possibly turbulent conditions of an earth that, 3.8 billion years ago, was still in volcanic apoplexy. It became common currency that early Earth was profuse in nitrogen and carbon dioxide gas as well as water, with paltry amounts of ammonia and methane, conditions prevailing in the interface between the atmosphere and Earth’s surface, but due to the chaos induced by land birthing tectonic shifts and magma emissions it seemed likely that life would have burgeoned in more stable deep ocean environments, though a viable energy source of course had to be available.
This led scientists to deep sea hydrothermal vents surrounded by teeming populations of single-celled life. Near boiling ocean water heated by the molten mantle beneath earth’s crust froths above fissures that inject hot gas and simple sub-units of macromolecules such as amino acids and other carbon compounds into rock enclosures, eroding microscopic pores into their bulk. Chemicals circulate in and around these tiny chambers that act like nodes between wormlike tunnels connecting this collective chemistry to the outer ocean. It is postulated that dissolved gases such as carbon dioxide, hydrogen and nitrogen, organic molecules, and proton gradients from hydrogen atoms stripped of electrons all subsist in this supercharged environment, a conjunction which provides conditions for a lifelike metabolic cycle without the presence of membranes; networks of linked pores within the rock are the totality of requisite structure, functioning like a congregate of cell walls. Metal ore surfaces exposed within the chambers may catalyze energy transfer, acting the role of primitive enzyme. It is an intriguing model, one that seems to explain what would be bacterial descendants living in droves nearby, and scientists have recently committed to testing it.
An experiment was designed that placed a solid clay brick with microscopic pores and channels in a sealed cylinder of aqueous solution. A tube pumped a heated flow of water through the clay in such a way that circulation was achieved, and further tubes introduced the gases and organic molecules of hydrothermal vents to solution in a concoction that mimicked actual conditions with high fidelity. Scientists planned to set the apparatus in motion and determine whether larger molecules can be formed this way. The effort is ongoing and should disclose much about how life’s metabolism may spontaneously irrupt into existence.
It is not hard to imagine a sort of membranous biofilm adhering to the interior of the rock, becoming gradationally studded with as well as inhabited by amassing macromolecular clusters conjuncted to the nutrient rich external cycle, expanding and budding off living vesicles as the first cellular organisms. Each evolutionary step is improbable on its own, but metabolic self-sufficiency together with mutational self-replication only had to materialize once or rarely, and billions of years of naturalistic trial and error in prokaryotic time is like a macrocosm of the universe.
Quantum mechanics, in particular superposition, has been implicated theoretically in one of its stranger applications, namely to the theory of evolution. It has long been a quandary as to how the extremely improbable leap from inorganic to organic chemistry transpired, especially how the first self-replicating molecules emerged when they cannot even perform any functions at all without the enzymes that simple intuition tells us they must have preceded in time. Looking at the relationship of DNA with the crucial enzymes DNA polymerase and reverse transcriptase, it is hard to see how the vastly complex symbiotic evolution through hundreds if not thousands of more primitive forms could have occurred. We have not recreated it in a lab, as the basic ingredients simply do not yet come close to the refined machinery of actual life in our experiments. The means of evolution have been quite alien to the evidentiary legacy of molecular genetics.
What seemed even hypothetically impossible a few decades ago has become more tenable in the 21st century. Researchers discovered that RNA, single-stranded replicators, are much more prone to mutation than DNA, as RNA polymerase does not proofread its genetic copying, so unprecedented enzymes are constantly being produced by new code in even modern eukaryotic cells, some of which can perform novel functions and change the intracellular metabolism, at least temporarily. RNA’s replicational flexibility shortens the theoretical timeframe necessary for substantial evolutionary transition. Ribozymes have also been observed in the cytoplasm, hybrids of RNA strands and protein chains that catalyze some of their own functions. This could be a descendant molecular species of the missing link: self-directing replicators. It is becoming increasingly convincing to think of the living cell not as a factory or manufacturing plant with a fixed and inextricably interdependent set of mechanical structures, but rather as a dynamic ecosystem in which its elements are semi-autonomous, competing with each other, coalescing into flexible symbiosis, adapting to the general nanoscale environment at a rapid rate.
Even with the viability of a microscopic RNA and ribozyme ecosystem as the breeding ground of what became modern life, the chances of a collection of thousands of different types of symbiotic macromolecules each containing thousands of atoms arising in perfect evolutionary sequence is astronomically small by the standards of Newtonian-influenced conventions in solution chemistry. A degree of functional order on that scale emerging out of a completely inorganic environment would require a much longer duration than the entire 14 billion year history of the universe in the context of thermodynamically-driven diffusion along with energy transfer between particles of a roughly spherical nature and their particle chains and loops, let alone the less than 3 billion year incubation of prokaryotic life. This led scientists to wrack their brains about what could accelerate the rate of evolutionary formation.
The tentative solution, still in its purely theoretical and experimental stages, is the idea that certain protons and electrons in macromolecules can be in superposition with themselves as they undergo some kind of vibrational fluxing within and between atoms, existing as multiple overlapping wave phases modeled according to the Schrodinger equation of quantum physics, meaning that each macromolecule is in hundreds of different configurations at once, greatly reducing the time necessary to achieve a functional, adaptationally effective form. The beginning of the replicator-generating evolutionary process would lack competition, with relatively primitive molecules free to adopt all possible forms instantaneously, until in this blindingly fast metabolic tailoring of the organic to the inorganic surroundings a real replicator or replicator/enzyme hybrid was born.
Expansion and diversification of replicator populations would exert additional forces of natural selection as self-propagation inclined towards greater relative efficiency, causing the replicators' sites of quantum behavior, modellable as superposed wave functions, to collapse into forms providing greater reproductive fidelity, more stable, thermodynamically-driven structures adapted for the inheritance of enduring traits, though the pragmatisms of faster reaction rate, magnified biochemical triggering and more complete energy transfer must have kept quantum effects from becoming entirely vestigialized, a total decoherence. Though heredity has not yet been created from non-life in the lab, it may be the fastest and most inevitable step in evolutionary history, capable of happening in myriad ways. Quantum mechanics makes it almost assured that we will someday evolve nascent life out of inorganic chemistry by artificial means, perhaps very soon.
Snazzy factoids, wouldn't you agree?