Journal article chosen by Jason Scott:

Blount et al. (2012). Genomic analysis of a key innovation in an experimental Escherichia coli population. Nature. 489: 513-518.

Also, check out the News and Views for this article:

Hendrickson, H., & Rainey, P.B. (2012). How the unicorn got its horn. Nature. 489: 504-505.