How does DNA fit into evolution theories? What does it have to say on DNA?
Fossils like archeological specimens are more or less direct relics of the past. DNA is another method termed "
renewed relics". For historians renewed relics could mean eyewitness accounts handed down by oral or written documents. We cannot ask any living witnesses what life was like to live in the 14th century, but we know about it thanks to written documents.
Written documents in turn are more reliable than oral tradition by a disconcerting margin. frustratingly, oral tradition peters out almost immediately unless preserved by the decaying of the facts and amazingly after just a few generations historical facts about real history rapidly degenerates (or blossoms, depending on your taste) into myths about demigods, devils and fire breathing dragons. Oral traditions and it's vulnerability is well explained by "chinese whispers", a game I use to play as a child and at school if anything to demonstrate the fallability of oral tradition compounded further by a great example from world war 1 within the british forces and I think it is well worth telling:
A message to be passed on orally back to headquarters from the front line was a simple one
"Bring reinforcements we are going to advance"
This message seems simple enough, however as the message was passed orally through a chain of people finally the commanders at the headquarters recieved the message:
Bring three and four pence we are going to a dance
What use is this information to the commanders. I need not go on about oral tradition but will return to it shortly besides the theory of evolution has no equivelant to oral traditions.
Writing is a huge improvement, paper papyrus or even stone tablets may wear out and decay but written records have the potential to be copied accurately for an indefinate numer of generations. This is good in theory but not in practice, if you was to write a letter to me 10 generations ago and asked each generation to write it down, if you write it down with painstaking accuracy being very careful of your writing style, it has a good chance of reaching me accurately. However, if through the generations the letter was go through language changes such as from English to French then you start to get something similar to "chinese whispers". For example, there exists a consonant sound between the English hard c and g (it is the French hard c in
comme) but nobody would attempt to represent this sound by writing a character which looks intermediate between c and g.
We have today an accurate account of the destruction of Pompeii in 79AD because a witness, Pliny wrote down what he saw. The accuracy is retained firstly because it is his writing and his words, secondly it was not subjected to oral tradition before being committed to text.
It is only a theoretical ideal that copying retains perfect accuracy. In practice scribes are fallable and not above massaging their copy to make it say things that they think (no doubt sincerely) the original document ought to have said. Made worse if such a documents source goes back to oral tradition. Afterall writing cannot take us beyond the point of it's invention which was only about 5,000 years ago. Identification symbols counting marks and pictures can take us back further perhaps some tens of thousands of years. But such time scales are mere chicken feed when looking into the history of evolution.
Fortunately, when we turn to evolution their is another kind of duplicated information which goes back an almost unimaginable large number of copying generations precisely because unlike modern to old or differing languages it has a "self normalisation", in other words the written text of DNA information in all living creatures has been handed down from remote ancestors hundreds of millions years ago with awesome accuracy.
DNA messages are written in a true alphabet like the Roman Greek or Cyrillic.
(If you found a civilisation that existed 1 million years ago who used Roman true alphabet in written documents would you not conclude they were Roman ancestors or conclude they have nothing to do with the romans and were a seperate civilisation). A powerful suggestion when you consider the alphabet of DNA has never been observed "different" from any species where DNA has been extracted.
The DNA alphabet is a strictly limited repetoire of symbols with no self evident meaning. Arbitrary symbols are chosen and combined to make meaningful messages of complexity and size. Where English has 26 letters to the alphabet and Greek 24 the DNA alphabet only has 4. Most useful DNA spells out three letter words from a dictionary limited to just 64 words, each word called a "codon". The dictionary maps 64 code words (codons) onto 21 meanings (the 20 biological amino acids plus one all purpose comma) Human languages are numerous and always changing and contain tens of thousands of distinct words, but the 64-word DNA dictionary is universal and unchanged. The 20 amino acids are strung into sequences of typically a few hundred , each sequence a particular protien molecule. Whereas the number of letters is limited to four and the codons to 64, there is no theoretical limit to the number of protiens that can be spelled out by different sequences of codons. A "sentence" of codons specifying one protien molecule is an identifiable unit often called a gene.
Understood this way, the DNA record is an almost unbelievably rich gift which every individula species carries and has had passed down since life first began almost like a "Genetic Book of the Dead". A descriptive record of ancestoral worlds including it's body form, it's inherited behaviour and the chemistry of it's cells. The food they sought, the predators they escaped, the climates they endured. The message is ultimately scripted in the DNA that fell through the succession of sieves that is "natural Selection"...........
Finally, to finish on a little point. DNA also brings with it some truths which identifies past mistakes within even taxonomy. It was believed that the Hippopotomas and Pig shared a common ancestor, DNA showed us that it;s closest living ancestor (like chimps are the closest common ancestor to man) is not a pig at all, it's the Whale........... Go figure hu
I have to stop my fingers ache.......
to the Muslims
