From WordNet (r) 1.6 [wn]:

  evolution
       n 1: a process in which something passes by degrees to a more
            advanced or mature stage; "the development of his ideas
            took many years"; "the evolution of Greek civilization";
            "the slow development of her skill as a writer" [syn: {development}]
       2: the sequence of events involved in the evolutionary
          development of a species or taxonomic group of organisms
          [syn: {phylogeny}, {phylogenesis}]

Drexler mentions that in knowledge evolution, the ideas that are evaluated and evolved are memes. This is from Richard Dawkins and his book The Selfish Gene. Memes have gained a special status in the geek/hacker world.

See Also: meme