In short... You can't use natural selection to explain the origin of DNA, without assuming the existence of the very thing you are trying to explain. Because, you need DNA to have natural selection.
An in depth discussion of this quote would be off topic as has been mentioned, but you might want to create a seperate topic about this quote in the Origins of Life forum.
Can science that is limited to natural causes counter this observation, or must we invoke interference by intelligence?
Well this begs the question "Is intelligence natural?" Does intelligence have to be supernatural? I consider myself to be perfectly natural, and I also consider myself to have at least some intelligence.
However "intelligence" doesn't lend itself well to being used as an explanation of observed phenomena. It isn't predictable in any way shape or form. For something to be good science (or even science at all) it has to make predictions. It isn't enough to just be a sufficient explanation of current observations.
What predictions can be made about intelligence (natural or supernatural in origin)? Can you say "Intelligence would produce this result, but not that result"?
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