Evolution

The great scientist Charles Darwin is credited with introducing the idea of evolution although really others were having similar ideas around the same time. However it was Darwin who collected the evidence and wrote the book on evolution by natural selection. The mechanism of evolution is essentially simple. Living things collect changes by mutation ie random changes caused by things like natural radiation on the recipe or the DNA of the species. Most of these changes are either inconsequential or for the worse. Some enable the organism to better suit its environment. This change then enables the organism to reproduce better than its confreres and it will gradually become more common in the population. We can say it has evolved to become better fitted to its environment

It is important to realise that fitness in this context means better adjusted to its environment. Almost all advanced organisms reproduce sexually so fitness may mean nothing more than being slightly more likely to attract a mate. For example if women were preferentially attracted to red haired men then one would expect the population of red haired men to proportionally increase. This points to an important factor- the trait must heritable such that red haired men were more likely to have red haired children.

I’ve often thought that one problem with the general view of evolution is that it is called the “theory of evolution”. In some eyes this implies it is just an idea which may also be accompanied by other different ideas. This is not so. Evolution has a mass of evidence in its support while alternatives such as those advanced by creationists have no supporting evidence at all. There is a common misunderstanding about the status of scientific theories. There are those who say that because any theory is liable to change in the light of new evidence then why believe any theory at all. Any new scientific  theory has to incorporate within itself all the evidence accumulated for the old. Thus relativity incorporates Newtons Laws of Motion but also extends them to new circumstances such as velocities approaching light speed.

I have said above that to take part in evolution changes must be inherited by succeeding generations . For example if by reason of type of work someone develops a hunched back through carrying sacks on their backs their children will not show the same characteristic.

This facet of evolution has historically led to some interesting views. For a long time Russian communists insisted that children could inherit characteristics acquired by their parents during their parents life. This was known as Lamarckist inheritance as opposed the Mendelian as in the common view. This suited the communist political view that evolution could be directed by training or will. Serious scientists always maintained this was a fallacy.

However there is some tantalising evidence that Lamarckist inheritance is just possible in limited and particular circumstance. One reason for listening closely to this suggestion is that a possible mechanism can be dimly perceived. Inheritance is governed by the bodies code , its DNA, present in every cell. Essentially this code, derived from the parents, determines a lot about the organism ( say a human ) . While the nature vs. nurture debate continues it seems as though some 50% of the characteristics derive from the DNA. However there is some evidence that the DNA code can be expressed in different ways according to simple chemical changes. This evolving science is called epigenetics.

One feature of Darwinian evolution is that its rate depends on the rate of change in the environment. If the environment changes quickly then if variants exist which can offer better fitness then they will quickly come to dominate the population. Bacteria can evolve antibiotic resistance in as few as one hundred generations. If the environment is unchanging then evolution will be slow or zero.

This leads on to the  important feature which is that evolution can only work where there is sufficient diversity in the original population. If no variant exists which meet the environmental change then evolution can only operate very slowly until chance throws up a mutation which can fit and which will soon come to dominate. In contrast if the diversity exists such that say some variants can survive and thrive better at higher temperatures then if temperature rises that organism will evolve such that higher temperature variant comes to dominate the original population.

That brings me to another lesson of evolution which is that it is not directed. There is no ladder of evolution with humans at the top, We are where we are because we fitted our environment better. If the environment changes then if our genetic diversity permits we will evolve with it. There is some evidence that possibly evolution may result in apparent steps backwards. For example Neanderthals actually had a larger brain than humans. On the other hand it may not have been so well connected.

What did the harassed lawyer say? Get off my case