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Beginning of life on earth.
(excerpt from a post at Church Of Virus BBS)
posted on 7th February, 2005
Evolution might be the answer to this as most think, but in fact evolution isn't relevant to how life started; it can only occur after "life" - that is, self-replication - has started, since evolution really just means a process in which something passes by degrees to a different stage over time and not the start of life itself.
The answer to this must lie in the field of chemistry, as life in it's most basic form of self-replication is a chemical process. A collection of appropriate atoms, under the right circumstances will form molecules. This follows from the nature of physics and atoms, and should not be surprising. So for example, few gasses are found in monoatomic form. Intead we expect to find eg. Hydrogen in the form of H2 molecules.
In the same way, natural forces govern the fact that molecules will combine to minimize the energy state between them, forming clusters or crystals. Again, no surprises here. For example, a hypercooled, supersaturated salt solution, will, given one crystal of salt added to it, rapidly "condense" to form a much larger crystal (and release heat), minimising the energy in the solution.
Given a suitable mix of molecules and a source of energy, the results can be unexpectedly complex. In the famous "Miller experiment", an electric discharge (as we would see from lightening) was applied to a simple mixture of methane, ammonia, water vapor, and hydrogen (molecules that would have been present in abundance in the atmosphere of prebiotic Earth). Within two weeks, a vast number of molecules had formed in this experiment, including "biochemically significant" compounds such as amino acids, hydroxy acids, and urea.
Now consider that this was a pair of flasks with a capacity of a few hundred ml, not a planetary volume. And consider that it the period involved was a few weeks, not a geological era. Given a significant number of molecules, energy and time, rather than unlikely (even if the chance for any one to form is minute), the formation of a large number of "self-replicating" molecules is inevitable. Even if the odds were say, 1 in a billion (109) against it happening in a year (and we know that in a small flask, two weeks is enough time to form amino acids, the building blocks of DNA), so the odds are much better), with trillions (1012) of molecules and millions (106) of years involved, the odds would be good that billions (109) of such molecules would form. And of course, once the first self replicating molecule forms, it would replicate itself until it ran out of material or energy, or some disaster occurred which would wipe it and it's descendents out. But with this happening in millions of locations, sooner or later, replicators would meet, compete, swap molecules, and evolve. What we would call evolution.
But the replication started under the chaotic* conditions before evolution began. Of course, life on earth may not have happened this way, viable replicators from elsewhere may have arrived on a comet or meoteorite (not impossible). But if that happened, then those replicators could have formed this way.
But this is just another theory, which indeed sounds really interesting & logical.
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