Jesse Bering explains some of the psychological barriers to understanding evolution at Scientific American.
In short, humans intuitively expect order to be the result of a conscious design.
I find this subject especially interesting because it parallels my favorite topic-- the widespread denial of basic economics.
Like evolution, markets create order without the guidance of a conscious designer. Despite the overwhelming consensus on this, many laymen still believe that the economic order is controlled by rapacious businessmen who set monopoly prices (in competitive markets), exploit third world workers (by "forcing" them to accept low wages), etc. And the solution, of course, is to change the designer, usually to the government.