Tuesday, 30 September 2014

Two very different pictures of the origins of life

The question of the origins of life has become neglected in biology, low status; and is now the interest of a really tiny minority. This is probably simply an index of the catastrophic decline of the subject of biology, rather than active hostility - but there are some fundamental questions raised by the origins of life which are disturbing. 

What is life? For 'cutting edge' biology since Schroedinger it has implicitly become focused on reproduction of organisms, replication of genes - and the process of natural selection. That which is subject to natural selection is 'life' even when the entities are not 'alive'.

So, from a biological perspective, the first 'living' things were non-biological - were some kind of inorganic molecules replicating themselves, transmitting their structure or patterns of interaction to 'offspring' - growing in numbers and spreading by copying or extension of their structures or processes.


Insofar as the origins of life are treated from a biological perspective I think it would be fair to generalize that by the mainstream modern biologist, the problem is seen as one of creating a 'breakthrough organism' - either one or a few - which then expanded and evolved to fill the planet, branching-off into sub-types to make the many types of organisms visible today (plus those which have become extinct).

So the picture in the mind is of an inverted pyramid - a few instances of life at the origins at the base of the pyramid, the breakthrough organisms - supporting a vast variety of later later which came later in evolutionary history.

And the reason the pyramid has a small base is that the origin of life is seen as rare and difficult. THE big problem is getting-replication-going: of creating a breakthrough organism.

Therefore, the 'classic' picture is that it is difficult for entities to replicate - but once replication is established, then it becomes easy for replicators to fill the planet and be naturally-selected to make many types of organism.

In brief summary, the mainstream biological view is: hard to make life, easy to sustain life. And especially easy to sustain life in the primitive world of the earliest forms of life, where there was so much less competition.


I suggest we may have this the wrong way around. And that it is easy to make life, but hard to sustain it.

And it was especially hard to sustain in in the primitive world of the earliest forms of life, where there was so much less competition and constraint. Because (biologically) competition and constraint is good!

Competition helps build organisms that can sustain themselves over multiple generations, because competition maintains the integrity of the replicators (by eliminating corrupted replicators) and without competition rapid extinction is extremely likely.

Thus competition - of particular types - is usually necessary for the survival of a species (a replicating entity) beyond a few generations.


So instead of an inverted pyramid, the picture of the origins of life I would like to paint is more like...

a globe sparkling with many random dots of light, sparks of life - life flashing into brief existence here, there, and (almost) everywhere - but almost immediately extinguished.

Extinguished by mutational meltdown, because the populations are small and the lineages of life have not evolved a mechanism for purging mutations (random variations) from each generation. Life can form, but it cannot keep its integrity, cannot keep its structure, cannot maintain the networks of communication.

The information being replicated or propagated is corrupted by error (entropy), like making an analogue audio-tape recording from an analogue tape of an analogue tape... after a few cycles there is nothing left but noise. Life easily emerges, and as easily goes extinct.

Until after a while a population devises a way of dealing with this tendency to extinction and maintaining its information intact for enough generations, to make a big enough population, that it is protected from extinction, and can devise a wholly effective way of purging errors (e.g. deleterious mutations) from each generation of its system of replication: so errors do not accumulate and this intrinsic cause of extinction is abolished. 


So, when viable life originates, on the globe, a spark does not flash out of existence, but becomes a steady point of light which grows and changes and leads to more growth and change. This happens here and there until the whole globe is covered with light of many hues - flickering and competing (growing, pulsing in size, or receding to nothing). 


Of course, new and viable life is then confronted by all the other causes of extinction upon which biologists have traditionally focused - change in climate or environment, pressure from predators and prey, within-species competition and so on. But that can only happen after solving the primary tendency for life to self-extinguish, to be a mere spark .