Really?
I thought Darwin first made the theory of natural selection on the voyage of the Beagle but was too chicken to publish it. Much later in his life Wallace sent him a transcipt for Darwin to read about his theory of Natural selection (Wallace was in Indonesia and noticed the adaptive radiation of species on the different islands). Darwin was shocked that they both came up the idea independantly, so Darwin (who was filthy rich) sent Wallace (who was filthy poor) over to London and presented the idea to the academic community. Shortly after that Darwin published a book on natural selection which is why he got the credit. (if wallace wrote a book first, we might call darwinism wallacism)
/shrug, mabye i'm totally off