Ok .. so, to throw a little more fuel on the fire, try this one out …
This is a Youtube slideshow presentation called:
The origin of Life – Abiogenesis – Dr Jack Szostak.
Szostak was awarded the 2009 Nobel Laureate in medicine for his work on telomerase. He is thus a highly credible scientist in the field.
Summarising, these are what he says are the crucial major steps described in his theory on how abiogenesis can lead to 'life' (my summary ... of his slides):
Abiogenesis steps (~7:30 minute mark)
- monomers diffuse into a fatty acid vesicle;
- monomers spontaneously polymerise and copy any template;
- heat separates strands, increases membrane permeability to monomers;
- polymer backbones attract ions increasing osmotic pressure;
- pressure on the membrane drives its growth at the expense of nearby vesicles containing less polymer;
- vesicles grow into tubular structures;
- mechanical forces cause vesicles to divide;
- daughter vesicles inherit polymers from the parent vesicle;
- polymer sequences that replicate faster will dominate the population.
Thus the beginning of evolution.
Early genomes were completely random and therefore contained no information. (Ie: way, way simpler information content than modern DNA/RNA).
It was their ability to spontaneously replicate, irrespective of the sequence that drove growth and division of the fatty acid vesicles.
Any mutation that increases the rate of polymer replication would be selected for.
Mutation + Natural Selection = Increased Information
Early beneficial mutations would include:
- change sequence to contain only the most common nucleotides;
- don’t form secondary structures that block replication;
- form sequences that are stable, yet separate easily;
- form secondary structures that show some enzymatic activity ;
- Just like RNA, early nucleotides could both store information and function as enzymes.
Early polymer enzymes would:
- enhance replication;
- use high energy molecules in the environment (near thermal vents) to recharge monomers;
- synthesize lipids from other molecules in the environment;
- modify lipids so they don’t leave the membrane.
AND THAT’S IT … a simple two component system that spontaneously forms in the pre-biotic environment, that can eat, grow, contain information, replicate and evolve.
Simply through thermodynamic and electrical forces.
The long chain organic molecules he starts with, are the fatty acids: 'Stearic Acid' (an 18 Carbon saturated fatty acid) or 'Oleic Acid' (18 Carbon unsaturated fatty acid). These are rather ordinary long chain organic molecules comprising C, H and Oxygen.
So, according to his theory, all one needs is a warm, wet planet and some long chain organic molecules in order to declare: 'LIFE' (as we know it).
The question is: can we find some long chain organic exo-molecules ?
Interestingly, this is
exactly what the MARS MSL/Curiosity rover is equipped to look for !
Cheers