What is life? How do we define it? Gone are the days of MRS. GREN!
But this still leaves us with the pressing problem of what is life; some scientists define this as the ability to reproduce, to replicate. This however, brings us into a world of debate; are viruses alive, are self-replicating minerals alive?
To prevent this, most biologists at least state that it has to have a recognisable cell structure with organelles and at least some naked DNA!
In this case it would appear that replication must predate life, this is important for the origin of complex hydrocarbons, as they may have been a product of life or life may be a product of them.
It has been hypothesised that the tidal action of the early Earth may hold the key, as mentioned in LIFE THE UNIVERSE AND EVERYTHING, the earth did not originally have a moon and the tidal action has been dimishing as the moon has moved further away to its present day position. During the Achaean the tides would have been several meters even at the centre of the ocean, meaning that the coastal zones were large areas with periodic in washings and out washings.
The result of this periodicity would have been a random sorting of the hydrocarbon ooze which is thought to have accumulated on these ancient beaches, this may not seem important but all the experiments that have been carried out to emulate the early Earth have produced a large variety of molecules most of which do not appear in life chemistry! The reason for this is discussed in THE PRIMORDAL SOUP.
The resistance of these molecules to being washed away or move in respect to each other would have caused a differentiation to occur. But each section of molecules should still have been masses of randomly branching multimers instead of the nice straight sequences of the polymers we are used to seeing when we see hydrocarbons. Some of these would be adhering to mineral grains and catalysing further. Then due to the high numbers of molecules i.e. millions to one sand grain one some of these would have developed the property of self-replication, possible by cannibalising the surrounding molecules.
This like their production in the first place would be due probabilities and randomness; in fact exciting new research is being done using stochastic methods!
Once self-replication was mastered then a Darwinian type of natural selection would have been able to occur but these would not be such big complex molecules as DNA or even RNA. This is discussed further in PREBIOTIC VS THE BIOTIC WORLD.
Replication may in fact have started outside of the biochemical range all together on sheet silicates such as clays. It has been shown that sheet silicates can replicate due to the cation-anion interactions, which actually keep the sheets alined with each other. Due to atomic radii certain anions prefer to line up with preferred cations leading to complement pairs similar to those that occur in the nucleic bases of DNA and RNA.
Hydrocarbon components are capable of attaching themselves to these sheet silicates via these same ionic components and it is thought by some scientists that as a result when the clay replicated so did the organic molecule. However, if this was the case then we should still be able to see remnants of this beginning within the cells that make up life on the Earth and there is none. However this feature could have been lost later on by the ancestor molecule from whence sprung life!
It is important to realise that many chemical substances other than nucleic acids can form compliment pairs, even acids and bases will aline with a preferred partner. Whether the origin started in one of these areas and flipped to the life chemistry we now know is a frustrating question to the scientists who study this area.
|Introduction||Organic vs. Inorganic||Prebiotic vs. The Biotic World||Replication, Probabilities, and What is Life||The Primordial Soup||Soap Bubbles from Outer Space||Under the Ground, Under the Sea, and From Above||Life, the Universe, and Everything||Glossary||References||Contact Details|