Life and the Evolution of Sex.

DRAFT

Life is a replicating molecule. This molecule can go on replicating until a copying error creates a mutation that either manages to crowd it out or split off.

This mutation is not necessarily an 'improvement' to the replicating molecule. The replicator often gets pushed into a corner where replication takes more energy, or where it is more vulnerable to external disturbances due to an increasing specialisation on specific sources of energy. So most replicators won't slide down the hill of replication errors very far before dying out.

The picture below shows life sliding downhill as it mutates. The least mutated life forms at the top, the most mutated life forms near the lower end. Every red dot is a life form that is still alive today. The ending black lines are life forms that have died out in the past.

Looking at the sliding slope of replication errors, nothing downhill can be used as an explanation for anything uphill. Replication with its errors is not a process that can 'look ahead' in any way.

At some point sexual reproduction transforms the single gene line into a gene pool as shown in the enlargement.





Sexual reproduction, cause and effect.
By a chance mutation the replicating molecule hits upon the mechanism of sexual reproduction. Reproducing sexually makes it possible for the code to achieve a higher growth rate out of existing resources, because it doesn't waste energy on building faulty organisms. It provides an error check, see earlier post. At every mutation further enhancing sexual reproduction, an extra error check got built in making the code more energy efficient in reproduction than its original.

Downhill, after further mutations have built up, the single gene line of the replicator becomes a wider gene pool. Mutations that are viable but that do not make it as the species standard create genetic diversity. From this genetic diversity, organisms can be built in slightly different varieties using genetic recombination.

Once the code replicates from a gene pool rather than a single gene line, two important changes in life happen:

First, life can adapt within the gene pool without further mutations, which gives it increased resistance against external disturbances. That is why sexually reproducing species manage to stay alive for longer. (The peppered moth can turn white or black depending on external circumstances, without needing any mutations. A recombination of existing genetic variation can be enough.)

Second, the gene pool makes it possible to recombine a mutated gene in many ways, increasing the chance of hitting upon a version that can crowd out the original, or split off. So sexually reproducing replicators are more instable, which explains the explosion of species reproducing sexually.

The protection against external disturbances and the increased speciation are the result of sexual reproduction. But not the cause. Simply because these effects only happen further downhill from the first appearance of sexual reproduction. Sexual reproduction could evolve because it offered a more energy efficient way of reproducing, that is why the code that uses it prevailed.


A better theory of life.
This model explains how sex could evolve (more energy efficient reproduction) and why there is so much of it around today. (Adaptation within the gene pool provides protection against external disturbances. Sexual reproduction increases vulnerability to mutations increasing speciation.)

Organisms can adapt within the gene pool. This is a reversible and not entirely random process. Adaptation is bound to find the 'white or black' version from existing genetic diversity if the benefit is large enough.

Life mutates downhill. This is an irreversible, pure chance and unpredictable process. Evolution downhill follows a path dependent direction making it hard to predict where it will go.

The model shows how earlier theories of evolution had to lead to confusion. They clumped together adaptation by genetic recombination within the gene pool and the separate evolution downhill by genetic mutation. To understand the cause and effect of sexual reproduction, these two mechanisms in life must be looked at separately.
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