Ah, another issue of vanishingly little consequence. I mean, really and truly, I doubt that even a majority of those who said they believed in 'non-theistic' evolution could say more about it other than 'we came from the apes' or 'survival of the fittest innit'. In the end, an understanding of the principles of evolution is pretty f-ing worthless unless you are or want to be a biology teacher, a biologist or possibly a medical practicioner (and no, those involved in animal husbandry do not count, as humans found that process easy enough long before evolutionary science even came to the fore).
It seems that this poll is just another excuse for the clever chappies to gush about the ignorance of the 'dumbs' (or whatever it is in Atlas parlance) despite the fact that most of the 'dumbs' a probably perfectly content.
This. If we really want to worry about what Americans don't know or understand, our priorities should be on:
1) Literacy
2) Personal finance