Books are not supposed to contribute at all. They are supposed to be an overarching view of the knowledge and ideas that exist in the area of interest. His books were meant to educate the public about evolution through natural selection.
Yes, I specifically said books, because the three writers I mentioned are all smart guys who did important work early on in their careers, but then went on to write a lot of junk on other subjects.
The problem is that it's not Dawkins' or Chomsky's academic articles that have showed up on HN, it's the other stuff.
For contributions to the field please refer to his journal publications. A partial list is given in: http://en.wikipedia.org/wiki/List_of_publications_by_Richard...