Setanta wrote:Dodge? That comes from the King of Dodge City.
What evidence do you, "real life," have that DNA was "designed" by a mind.
That is the burden of this thread. The member "real life" has been dodging this question since the beginning.
You don't want to even to begin discussing dna, Set.
DNA cannot have developed or 'evolved' in the open environment, even as a successor to an earlier replicator.
Why? DNA and some of the compounds leading to it would be easily degraded and destroyed in the open environment.
So where does that leave it?
Shapiro postulates that early replicators leading eventually to rna developed in a living organism, in what he calls a 'metabolism first' scenario.
Well, first of all , a living organism that cannot reproduce without reliance on things like 'physical forces splitting it' will likely have a very brief family tree to boast of.
But aside from that, it doesn't really avoid one of the problems cited by Shapiro:
Quote:To rescue the RNA-first concept from this otherwise lethal defect, its advocates have created a discipline called prebiotic synthesis. They have attempted to show that RNA and its components can be prepared in their laboratories in a sequence of carefully controlled reactions, normally carried out in water at temperatures observed on Earth....
I will cite one example of prebiotic synthesis, published in 1995 by Nature and featured in the New York Times. The RNA base cytosine was prepared in high yield by heating two purified chemicals in a sealed glass tube at 100 degrees Celsius for about a day. One of the reagents, cyanoacetaldehyde, is a reactive substance capable of combining with a number of common chemicals that may have been present on the early Earth. These competitors were excluded. An extremely high concentration was needed to coax the other participant, urea, to react at a sufficient rate for the reaction to succeed. The product, cytosine, can self-destruct by simple reaction with water. When the urea concentration was lowered, or the reaction allowed to continue too long, any cytosine that was produced was subsequently destroyed. This destructive reaction had been discovered in my laboratory, as part of my continuing research on environmental damage to DNA. Our own cells deal with it by maintaining a suite of enzymes that specialize in DNA repair.
The exceptionally high urea concentration was rationalized in the Nature paper by invoking a vision of drying lagoons on the early Earth. In a published rebuttal, I calculated that a large lagoon would have to be evaporated to the size of a puddle, without loss of its contents, to achieve that concentration. No such feature exists on Earth today.
And no such feature would fit inside the microsopic 'metabolism first' organism either.
Shapiro rather glosses over this defect , because he has burnt the bridge leading back to the 'replicator first' hypothesis.
He assumes the path while avoiding specific discussion on how to get around the gaping hole ahead:
Quote:An understanding of the initial steps leading to life would not reveal the specific events that led to the familiar DNA-RNA-protein-based organisms of today.
He assumes that some natural chemical path 'led to life', and wraps up the article with further assumptions:
Quote:However, because we know that evolution does not anticipate future events, we can presume that nucleotides first appeared in metabolism to serve some other purpose, perhaps as catalysts or as containers for the storage of chemical energy (the nucleotide ATP still serves this function today).
Some chance event or circumstance may have led to the connection of nucleotides to form RNA. The most obvious function of RNA today is to serve as a structural element that assists in the formation of bonds between amino acids in the synthesis of proteins.
The first RNAs may have served the same purpose, but without any preference for specific amino acids.
Many further steps in evolution would be needed to "invent" the elaborate mechanisms for replication and specific protein synthesis that we observe in life today.
