After a period of reading journal articles I put together some disparate thoughts on positive selection, which is a central issue for my PhD. I started writing with the intention of making something short, maybe three paragraphs at most, that encapsulated a key debate in evolutionary biology, namely 'how does natural selection effect the genome?' Then I discovered how hard it is to explain complex ideas succinctly... The link below will take you to the article, where you can learn about one of the great debates in population genetics. Anyway, enjoy, if that's the right word:

http://public.iwork.com/document/?a=p1059453001&d=Natural_Selection.pages
Cagan