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Tue 6 Oct, 2009 02:39 am
There is obviously an enormous amount of evidence for the evolution of species by natural selection. However, evolution seems to require the existence of DNA. This leaves open the question of how DNA itself developed, or evolved.
What is the evidence for the evolution of DNA? Are there any data which indicate how, or if, DNA evolved from more primitive molecules?
Secondly, could 'natural selection' have had a role in the development of DNA? It is hard to see how natural selection could act at this level, given that natural selection seems to require the presence of DNA in the first place.
@jeeprs,
You know, I found a lot of plausible answers in
The Selfish Gene by Richard Dawkins. An enjoyable read. He explains, in relative detail, his beliefs of the primary formation of the DNA molecules. Brilliant, brilliant book. Worth the time, if not just for the sake of the read.
@jeeprs,
Yes but the existence of genes presumes the existence of DNA. There is nothing in the book about how DNA came to be in the first place. I am not a creationist, I don't believe that 'God made DNA'. But I neither evolutionary theory, nor genetics, explains how it came to exist. (I admit though I haven't read The Selfish Gene, although have read excerpts and synopses of it).
@jeeprs,
jeeprs;95381 wrote:There is obviously an enormous amount of evidence for the evolution of species by natural selection. However, evolution seems to require the existence of DNA.
What is the evidence for the evolution of DNA? Are there any data which indicate how, or if, DNA evolved from more primitive molecules?
Secondly, could 'natural selection' have had a role in the development of DNA? It is hard to see how natural selection could act at this level, given that natural selection seems to require the presence of DNA in the first place.
DNA has some chemical and structural differences between prokaryotes and eukaryotes, and many many viruses (including flu and HIV) use RNA as their nucleic acid. Some use single stranded DNA, some use double stranded RNA (which with trivial exceptions, like small double stranded segments in rRNA and tRNA molecules, does not exist in eukaryotes).
RNA and other nucleic acids are much less chemically stable than DNA. It is very likely that the earliest nucleic acids were not DNA, but DNA by virtue of its stability was very advantageous.
@jeeprs,
jeeprs;95381 wrote:There is obviously an enormous amount of evidence for the evolution of species by natural selection. However, evolution seems to require the existence of DNA. This leaves open the question of how DNA itself developed, or evolved.
What is the evidence for the evolution of DNA? Are there any data which indicate how, or if, DNA evolved from more primitive molecules?
Secondly, could 'natural selection' have had a role in the development of DNA? It is hard to see how natural selection could act at this level, given that natural selection seems to require the presence of DNA in the first place.
How life appeared in the first time is still largely an open question but I think there are at least sufficient reasons to accept (at this time) as a first choice research program the hypothesis that the first, rudimentary, replicators (sufficiently small to have appeared by chance and in the same time sufficiently complex to carry information) evolved via a process of darwinian evolution into the DNA world. Chance may be a solution for the appearance of the first replicating molecules (of which I am personally rather skeptical). Another solution is that life is 'inscribed' in the laws of physics (strong anthropic principle); there is little evidential support for this hypothesis [which I prefer at this time, as a first choice, purely personal, working hypothesis - no strong ontological commitment] but the future may be full of surprises, even a form of teleology is not out of question...
Paul Davies [first class thinker in spite of his detractors] on the origins of life:
http://cosmos.asu.edu/publications/papers/OriginsOfLife_I.pdf
http://cosmos.asu.edu/publications/papers/OriginsOfLife_II.pdf
@metacristi,
Paul Davies is my choice of current science writers - I am still working through his Goldilocks Enigma (published elsewhere as the Cosmic Blueprint).
I still don't think that it will ever be possible to apply the principle of Darwinian evolution to the pre-cursors of living organisms. Apart from anything else, problems of getting evidence - unless we found an early planet somewhere. I am favouring the idea that 'life has a tendency to appear'. It doesn't sound that controversial, does it, but it seems anathema to some of the physicalist thinkers. In fact where I am going with all this is that there are laws governing the evolution of life other than simply Darwinian ones, which provide the 'pull' but not the 'push'. I see life as evidence that the universe is self-actualising, but I realise that too is probably not scientifically kosher. But it is a long way from flat-earth creationism as well.
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