Life, the Universe and Everything
The Rise of Auto-Catalysis
This is probably not what opponents … want to hear, but it seems that a kind of molecular natural selection applies even to the world of geochemistry. Some types of molecular chains outcompeted other molecular chains for the planet’s resources, and gradually they led to the kind of molecules that life depends upon – all this before the first living thing oozed forth. …
[L]ife wasn’t a freak accident at all, but the likely outcome … "Life is an elaboration of something very simple," …
But of course! We have really known this since The Selfish Gene was written. We have really known it since the 50’s, when amino acids were created in simulated versions of the early Earth’s environment. Loren Eiseley had thoughts on it. Heck, we have really known it since 1859. Everything since then has been a matter of digesting the meme. I myself use the term "auto-catalysis". I notice that Susan Blackmore uses the same word. I suspect she got it from Dawkins who got it from Heidegger by way of the daughter of Heidegger’s student.
Autocatalytic reactions proceed slowly at the start because there is a little product present, the rate of reaction increases progressively as the reaction proceeds then it again slows down as the reactant concentration decreases.
Imagine a world of rocks and sand, pitted and pockmarked, and hammered with asteroids, volcanoes, earthquakes, floods, ice, storms and blistering sun. The chemical complexity has been increasing since the beginning, each puddle a composite of its history. Minerals leech into the water, acid rain and organic compounds rain down upon the rocks, interacting in strange ways. The environment amounts to a mass-produced chemical experiment. Each hole in the ground is a separate test-tube, subjected to different amounts of heat and radiation, different levels of exposure, evaporation cycles, drainage frequency, altitude, pressure, salinity, chemical constituency, molar concentration. The contents of one puddle flush unpredictably into other puddles and they all drain to the deep sea where hot smokers add more variations. As you cross the isopleths of the multiple control variables, you find that every possibility is tried – repeatedly over Deep Time. Strange things are bound to happen. We can only imagine.
Auto-catalysis, in my definition, is the property of a chemical, simple or complex, to foster its own production within a given environment. The consequence of that property is that there will be more of it. A byproduct of that property is that other, possibly similar, chemicals will also be promoted. I contend that this aspect serves one of Darwin’s requirements, the need for variation.
At some point, within the n-dimensional filtering mechanism represented by the early Earth, some mildly auto-catalytic chemical occurred by chance. Actually, given that the opportunities were so great, it’s hard to maintain that there was any chance involved. In my mind’s eye, the very color of the planet began to change as a new regime took over. Stagnant chemical bywaters were changed irreversibly by the infusion of small splashes of solution or contamination by peculiar motes of dust. Complexity increased. I suppose in some places complexity decreased, but the tendency of the auto-catalytic process to produce variants would eventually lead to competition among more and more alternatives. Scarce resources were used up and cannibalistic reactions were rewarded. Those chemicals resistant in any small way to being recycled would come to predominate.
I picture, in my fantasy, the calculating eyes of H.G. Wells’ Martians watching the planet Earth go through slow, but visible, changes. The rate of such changes, some subtle, some startling, increased in frequency and rapidity until some plateau of stability was attained. That was the beginning of Life, at least on Earth.
The article asks, "Did life begin in a small warm pond at the edge of a primordial sea …? Or deep beneath that sea …?" This is a false dichotomy. It probably began everywhere. Each environment contributed part of the process, subjecting auto-catalytic reactions to different chemical stresses. The puddle on the left contributed a twist and a proton; the puddle on the right contributed a curl and a radical. The significant action moved from sea to shore to desert and mountain slope. The different experiments merged and overlapped, influencing everything else. Chemicals were evolving and honing their "survival" skills. Darwin's theory requires inheritance, variation and natural selection. Auto-catalysis of chemicals in a complex environment exhibits these features. RNA came later.
- The Physics of Ice might give you some idea of how complex even the simplest seeming chemical process can be.
- Kurt Vonnegut suggests that chemical evolution may not be finished, but it might not be good for us.
- Mad Cow Disease represents a possible model for continued organic chemical evolution.
- Natural Selection is postulated to be involved in the Origin of Universes. The related concept of the Anthropic Principle warns us that any generalizations we make about the Cosmos and our exclusive position in it are biased by the fact and nature of our existence. We don't get to look at all the other possibilities.
2/27/2006 12:41 PM
In terms of auto-catalysis, it is not even necessary for a single chemical to have that property. If a system of chemicals working together have a net auto-catalytic result, then the necessary environment has been established in order for evolution to commence.