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.