Yes; the current best indication is that DNA arose by by chance and natural selection.
As a scientific model that is a bit inadequate. For a real scientific model, you should have some idea of the intermediate stages, and of the features being selected; and you should have some line of empirical evidence to help test your ideas. This is very difficult for evolution of DNA; but we do have some usable indications which form a basis for scientific hypothesizing in this area.
For example, see
The Genetic Code and the Origin of Life
Editor: Ribas de Pouplana, Lluis, (Landes Biosciences, 2004)
Chapter 7: Origin and Evolution of DNA and DNA Replication Machineries
by Patrick Forterre, Jonathan File and Hannu Myllykallio
From an
on-line extract:
The transition from the RNA to the DNA world was a major event in the history of life. The invention of DNA required the appearance of enzymatic activities for both synthesis of DNA precursors, retro-transcription of RNA templates and replication of single- and double-stranded DNA molecules. Recent data from comparative genomics, structural biology and traditional biochemistry have revealed that several of these enzymatic activities have been invented independently more than once, indicating that the transition from RNA to DNA genomes was more complex than previously thought. The distribution of the different protein families corresponding to these activities in the three domains of life (Archaea, Eukarya, and Bacteria) is puzzling. In many cases, Archaea and Eukarya contain the same version of these proteins, whereas Bacteria contain another version. However, in other cases, such as thymidylate synthases or type II DNA topoisomerases, the phylogenetic distributions of these proteins do not follow this simple pattern. Several hypotheses have been proposed to explain these observations, including independent invention of DNA and DNA replication proteins, ancient gene transfer and gene loss, and/or nonorthologous replacement. We review all of them here, with more emphasis on recent proposals suggesting that viruses have played a major role in the origin and evolution of the DNA replication proteins and possibly of DNA itself.
It is all a bit technincal; but this should give a flavour of the kind of evidence and models being considered.
Cheers -- Sylas
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