According to the paper I linked earlier in the thread, the suggestion is made that viruses may have "invented" DNA!
This would have been by an early "reverse" transcription mechanism, from RNA viruses, in the hypothesised RNA world. So what we call the reverse process may actually have been the "forward"process, initially.
There certainly seem to be reasons for thinking that viruses played a key role in the evolution of early life.
(I'm ploughing my way through the paper. If I come across any more dramatic claims for the role of viruses I will post them.)