7 Dec
2006
7 Dec
'06
3:43 p.m.
I've read a number of articles that speculate that there was an "RNA world" even before DNA. In these articles, the first self-replicating lifeforms (or pre-lifeforms) were based purely on the messenger characteristics of RNA. This short-lived world was soon superseded by DNA. The only remaining RNA organisms are generally pathogens. I don't have a clue whether this supports single or multiple origins for DNA, but it's kind of interesting.
From what I have read, it seems clear that certain "features" or traits have evolved in DNA multiple times/instances in the history of life here, which may indicate that the evolutionary paths may not be infinite.