If you listen to those whose theistic belief causes them to question Evolution through Natural Selection you might be expected to believe that the evidence is incomplete or weak. You might hear about how radiological dating can be inaccurate. Dawkins has spent a lifetime trying to address in detail how we know Evolution through Natural Selection is an accurate model of the development of life on earth.
However, perhaps this very literature makes the explanation sound weak; that the theory relies on complex and questionable scientific deductions. This of course couldn't be further from the truth. I'm writing this article to indicate exactly how strong our evidence is through comparison.
Imagine a man accused of murder. He is accused of shooting a woman in the middle of a crowded room with a gun registered in his name. The several witnesses in the room clearly identify the shooter. One of the witnesses had the presence of mind to video the shooting and the events leading up to it. The police recover the gun and find only the fingerprints of the accused on the gun. High velocity blood splatter is found on the clothing of the accused.
Any one of the above points alone might have indicated the accused is guilty of murder but all five independent and reliable lines of evidence make this an open and shut case. It would be difficult to see how a jury would be able to conclude anything other than guilt.
Evolution also has at least five independent lines of evidence that all converge not only to support Evolution as a theory but also provide a very precise tree of life. Even without any dinosaur bones or microscopes we would be able to examine the morphology of living animals. From comparing the similarities and differences between animals we can construct a reasonably accurate picture about how modern living animals are related. Morphology is our first line of evidence.
Of course we do have fossil remains and can date these fossils with a reasonable degree of accuracy. This evidence has been used to show animals changing form slowly over time. There are good fossils for the entire development of land dwelling mammals to whales and the development of man from a common ancestor with Chimps to modern humans. Fossil evidence is the second independent line of evidence.
Now we break out the microscope and examine embryos. It is an interesting fact that development of animals of all kinds has a common mechanism. In many ways we can see the evolution of life itself in the development of a embryo. Whether you are a fly or human our development is similar. Processes of differentiation and segmentation are similar in all animal life. In fact there is a common gene for eye development that if dis-activated will cause eyes not to develop. The same gene exists in flies and humans. Embryology is the third line of evidence for common ancestry.
Let us now delve into the genome. It is now possible to sequence the genome; that is read out the source code of life as if it were data on a hard drive. Well perhaps not that easy, but similar in principle. By reading the code for different animals we can compare how similar animals are to one another at the level of DNA. There are in fact at least two methods for using DNA to determine relationships between animals.
The first is simply comparing one genome to another and quantifying how similar they are, and how much they differ. The closer the DNA matches the closer the relationship. Direct similarity of genomes between different species is yet another independent line of evidence.
A more precise approach to genome comparison, especially among species which are closely related, is to consider sections of non- coding genome. There are sections of DNA which are not used to code proteins, and are therefore not affected by natural selection. They are mutated over time at a more or less constant rate. By doing statistical analysis on these segments we can work out how related each species is to others. This forms the fifth independent line of evidence.
Five independent lines of evidence. Any one of which would be sufficient to establish the interrelatedness of animals on earth. All telling the same story within the limitations of the evidence. If this were a Jury it would be an open and shut case. Guilty as charged.
The case for Evolution only gets stronger if you look at its dynamics. Any process that implements the required components of Evolution, ie inheritance, iteration, mutation and selection, will begin to evolve. Considering the fact that we know that life on Earth exhibits these features one would have to ask how life could fail to evolve?
Simple computer simulations that exhibit these features always evolve. They don't require a precise configuration because the process of natural selection is robust. A recent example of evolving clocks using computer simulation varied mutation rates and other critical parameters of the simulation. In every case Evolution was able to develop accurate clocks.
Evolution is more than a topic of academic interest. Genetic algorithms are algorithms developed by iteration and selection. They are able to solve problems that cannot be solved by humans. They are used to design planes and cars. Evolution is more than an explanation for life, it is a process applicable to many realms beyond biology. It will continue to inform and improve our lives in many ways.