Some almost random thoughts..

Monday, October 6, 2008

Life and the Evolution of Sex.


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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Laughter and storytelling:

All humans are equipped with the ability to experience the same social emotions like shame, pride, envy and respect. But the applicability of these emotions can vary strongly from group to group and over time. So the brain needs us to constantly calibrate our social morals with those of our group. The most efficient way to do this is through storytelling. We evolved a love of listening to stories, because in a stone age setting that would expose us to the reactions of our group to the story. We slowly but surely mirror the reactions we hear around us, like laughter and outrage, so that we end up in sync with the social morals of the group. This shows why watching comedy without the studio laughter is difficult. Not only can't you laugh with others, you actually get the message that what you hear shouldn't be deemed funny, because nobody else is laughing.

Laughter and storytelling combine to make us compatible in behaviour, because when it comes to social morals, it did not pay to be different. In the modern world, we have automated the storyteller in the middle of the group, into the TV-set we mostly watch on our own. But without the vocal reactions of our group, it might have become a waste of time.

Hunting and gathering.

As humans we solved our basic food problem. Getting the calories we need to survive is easy. But like animals in the zoo that get fed, we have kept much of the display behaviour related to our feeding methods throughout our evolution.

The gatherer into gossip and fashion.
The success in gathering partly depends on the quality of your information network. You need to hear in time where the latest fruiting tree is. There may be more than enough for the person that finds it, but not enough for everyone. A gatherer that finds food will share the information with someone that seems likely to be able to return the favour another time. So gatherers have evolved a need to signal having a quality social network and being 'up to date'.

Gossip and keeping up with fashion trends are modern display behaviours linked to the innate need to be up to date and to be seen to be up to date. With gossip, a gatherer has a special interest in being the first in relaying otherwise useful bits of information.

The hunter into sports and career.
Stone-age hunting is a team effort needing diverse skills. You are better off hunting with a few others. But you do not want to bring anyone along who can't pull his own weight. You do not want to share the meat and the glory with a slacker. So the hunter has evolved a constant need to show they will make a valuable team member to other hunters. That is what gets you on the best hunting party and that gets you the best food and possibly 'extra' mating opportunities.

Every opportunity you have to compete with others to show off your skills can help you get picked by the best. Modern sports and even career are behaviours linked to the need to show you are a valuable team member and you deserve your spot in the highest league. The displays needed to establish and keep your deserved rank would settle down in a small group. In our modern large group the hunter has become stuck in this display behaviour because there is always a higher league to get into. And people's social circle has become more homogeneous through the sorting that happens in school, housing and work arrangements. So there is always someone close ahead or behind. This may be an important driver behind the 'never enough' economy.

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