Evolution (Introduction)

by dhw, Wednesday, April 22, 2009, 10:20 (5490 days ago) @ George Jelliss

We are once more discussing abiogenesis ... the theory that life can arise spontaneously from non-living materials. My difficulty with this theory is the need to believe that sheer chance can create something as complex as replicating molecules. The degree of disbelief will be proportionate to the degree of complexity, and this is where George and I disagree. - George: But we have unravelled the DNA code. What we don't know are the full consequences of its working. - Unravelling a code does not make it any the less complex. Crick and Watson were awarded the Nobel Prize for their work in this field, which suggests something a bit more intricate than your average Sudoku. I'm sure there'll be another Nobel Prize for anyone who can create a replicating molecule out of non-living materials, but it'll take some brilliant scientific minds to do it, as opposed to a billion Chinese chucking chemicals into pots and hoping for the best. - I wrote that evolution could only have happened because the original forms of life contained the potential capability or "code" for variation. - George: You have the totally wrong end of the stick here! The code tries to ensure continuity without variation. It serves to make an exact copy of the replicant. The variations come in by accident, chance mutation, permutation, whatever you want to call it. - I had myself pointed out that variations were caused by random combinations, the impact of the environment, accidental mutations. There is no disagreement here, except for the end of the stick and the potential of the first replicating molecules, so let me offer three simple variations on the very first set of originals, which I shall call blobs.
 
1) Blob 1 has a head-on collision with another blob; they combine and form a bloblob. From now on the new form replicates bloblobs.
2) Blob 2 is hit by a bolt of lightning, which gives it a large mole on its cule. From now on it replicates blobimoles. 
3) Blob 3 makes a mess of things while trying to replicate itself, and its (non-)replica is a blobimess. From now on this replicates blobimesses.
 
My point is one of simple logic: in all cases, the transformation would have been impossible if the blob's "code" had not been capable of being transformed. In other words, when chance assembled the first replicating molecule, it also built in the possibility of variations. Otherwise after the collision, the lightning and the mess, there would either have been more replicated blobs, or no replications at all. (Natural selection will then decide whether bloblobism, moles and messes are worth preserving.) - You say variation is "just a different atom or molecule being in a different place and producing different results." Why "just"? If the code tries to ensure continuity without variation, the fact that nevertheless it can be changed but can still function suggests to me an additional complication, not something to be brushed aside with a "just". - So put it all together, and what have you got? Chance creates the first replicating molecule (an amazing feat of engineering), it has the potential for infinite variations (an additional touch of genius), and it relies on yet more chance (accidents etc.) to trigger the operations that will produce the variations. Evolution goes from blobs to us, through billions of lucky breaks underpinned by the logic of natural selection, which ensures that the good lucky breaks survive and improve. I can believe that chance has played an enormous role in evolution, just as it does in our human lives. However, Chance the Nobel-prize-winning scientist goes beyond the bounds of my credence.