As Richard Dawkins says, the first replicators were probably not DNA or RNA. Nucleic acids are highly specialized and probably out-competed earlier, simpler replicators. Although it typically uses a cell, DNA can be made to replicate in the lab with polymerase chain reaction protocols, and this is probably what the first replicators did. They were probably organic molecules that bumped into other molecules and used them to replicate themselves. The copying procedure wasn't perfect, so they turned out copies with differences... very rarely, the differences caused the new replicators to replicate faster or more efficiently than their parents, or be less vulnerable to damage; and now we've got the basics of evolution. There is some evidence now that viruses predate other forms of life; Discover magazine even had a recent cover story about it. But the first replicators were definitely much, much cruder.
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