Evolution

12.               Evolution

In an essay sent to Darwin, A.R.Wallace wrote comparing evolution with the action of a steam engine governor, and how any imbalance in the animal kingdom would be reduced ‘by rendering existence difficult and extinction almost sure to follow’.

Feedback operates at different levels (as it often does) in the process of evolution.

Right down at the gene level, feedback loops were identified by Francois Jacob and Jacques Monod in 1962. Some genes are controlled by activator and repressor proteins, which are themselves the product of other genes.

At the other end of the process, the rise and fall of populations is another case of a balance between positive and negative feedback. A rise in population leads to an increase in births, which leads to a further increase in population. This can lead to a population explosion, as in the famous case of Australia and the rabbits. Normally the growth will be limited by a shortage of food supply, and/or an increase in the number of predators, parasites or diseases. In Australia, none of these were present to limit the growth until a disease (myxamatosis) was ‘imported’ especially for the purpose. The reduction in food supply is a negative feedback opposing the positive feedback of population growth. As the population grows, the food supply is reduced, and this reduces the birth rate.

Likewise when a tasty animal increases in numbers, so its predators will have an increased food supply, and their numbers will grow, and hence reduce the numbers of tasty critters. These population swings will often run in cycles of increase and decrease. Sometimes however, they will stabilise at an ‘evolutionary stable state’.  Other times, as famously discovered relatively recently in the 1980’s, they can fluctuate seemingly at random between high and low levels. This is now called ‘chaotic’ behaviour, and has led to a whole new subject area in the study of chaos and chaotic systems (see James Gleick’s book Chaos).

Arms Races

The term ‘Arms Race’ was originally coined to explain the propensity of human societies to engage in a continual battle between developing methods of attack and defence. As soon as a new weapon is developed, others try and invent defences against it. So the sword produced the shield and helmet, shrapnel produced the flak jacket, radar produced ‘smooth’ profiles, and so on. The development of defence is a kind of negative feedback as human kind tries to reduce the effect of weapons of attack. And the new methods of defence provoke further developments of new weapons. So there is a kind of see-saw effect which is reminiscent of the Flip Flops described in the electronics section.

The term Arms Race has been hijacked by evolutionary theorists to describe the process of two species evolving in competition with each other. So one perhaps develops a poisonous toxin to kill or paralyse its prey, then the other develops an antidote to defend against it.

There are similar but mores subtle examples of this kind of thing, which have been collectively called the ‘Red Queen’ effect, and Matt Ridley has written an excellent book with this title. The idea is that some genetically determined characteristic is selected, not because it has any actual benefit, but because it is ‘fashionable’. A typical example, quoted because it exemplifies a ‘useless’ feature, is the Peacock’s tail. The length and strength of a large tail is selected because it gives males the benefit of pleasing the females, who are themselves selected for a preference for large tails. These two selection processes drive each other in a positive feedback loop. Just like in our first example of positive feedback, the whistling sound system, there does not have to be any significant starting point (why tails for instance?). The feedback loop causes some such feature to be driven more and more once it is started. This is reminiscent of human fashion, as described previously.

There is still considerable debate on some of these issues in evolution – some people give more emphasis on the fact that a large tail could act as a signal of strong health for example. And the whole issue of why sex evolved at all is still an open question, though there are many good ideas. The whole ‘Red Queen’ method depends on having different sexes, so the feedback loop can involve both of them. The Red Queen name comes from Alice in Wonderland, where the Queen tells Alice that you have to run faster and faster to stay in the same place. This sounds tiring, and it has been argued that the whole arms race idea is pretty wasteful. It causes species (or countries) to expend a lot of effort to try and stay ahead of the competition, rather like ‘keeping up with the Joneses’. I suppose that is one of the snags with the free market competitive model, but then it does have advantages. Cooperation rather than competition can lead to stagnation, and who wants that? It can all too easily lead, in the wonderful words of Tom Lehrer, to ‘A sense of futility’.

You could argue that the whole mechanism of evolution is a feedback process. Each species (or its genome) evolves changes that are successful in being reproduced in its environment. So there is a constant feedback between the species and its environment. And the whole thing is driven by energy, ultimately from the sun. So evolution is quite simple really, it is a kind of heat pump, which extracts energy from the sun, and builds an ever more complex system of life. (Some people would argue about the ‘ever more complex’ bit, but I am pretty confident in it).

Actually, there is an alternative theory that life on earth was driven by energy from the earth, not from the sun. Energy is present in chemical energy in rocks, and in thermal energy below the earth’s surface (think of hot springs and volcanoes). There are some good reasons to suppose that life may have started from these energy sources rather than sunlight, though this is by no means established. Personally, I prefer sunlight, but then I was born in the Mediterranean.

Of course, it is not true that evolution is simple. The more we learn about it, the more complex it gets. For one thing ‘the environment’ against which a species evolves includes all other species, as well as the geographical local one. Some species will affect it more than others, but they are all woven together in such a global tangled web that it is impossible to extract out a part of it. And it is not only the local geography that is involved, as we are only too aware these days with the advent of man made global warming, which is already having an impact on the distribution of other species.

And as I have already indicated, evolution takes place at a number of levels. Evolutionary methods themselves evolve. They have to when you think about it – the earth wasn’t born with DNA lying around. It evolved, and so did all the enzyme mechanisms for copying, cutting, extracting, joining and correcting that form part of the incredibly complex DNA toolkit. Chromosomes also evolved, as did cells and mitochondria (the cells power plants). Cells evolved into organs and organisms, and organisms evolved groups, tribes, nation states.

And now we are evolving ever more complex systems of economics, government and (especially) technology. The growth of all this complexity shows a characteristic exponential nature that is the hallmark of positive feedback. This is best illustrated by looking at figures on a log scale, where an exponential curves show up as straight lines. Anyone can see if a line is roughly straight, but it is harder to tell if a curve is a true exponential. For example, the growth in GDP per head in the USA over the last 100 years looks pretty much a straight line on a log scale, and even large events such as the great depression and WW II show up as blips on the line.

There has been a lot written in the past few decades about a ‘singularity’ in the evolution of human life, which is predicated around the year 2020 (this is not a precise figure). The growth curve of many long term demographic trends, such as global population, energy consumption, materials extraction, GDP, all look like hitting some kind of wall around 2020.

There are other trends, too that are predicted to reach some kind of threshold around this time. Ray Kurzweil, in his book ‘The Singularity is Near’ lists some of these, such as the possibility of having computers that are as intelligent as humans. In case you think this is pie in the sky, IBM recently announce that by 2012 they expect to have a computer with the raw processing power roughly equivalent to the human brain. Of course that does not mean that it can lean to read, cook, and sew. But still, it is food for thought, and an indication of the rapidity of change now taking place.

There are other examples, too. I believe it is no coincidence that the current global economic mess is happening now. It is simply an example of things that are more likely to happen when the rate of overall complexity is changing so rapidly. Attack always evolves before defence, and the economic banking and trading systems have evolved too far too fast for them to be in control.