This talk about gradual typing in Clojure makes a case for combining dynamic languages with slowly-more-specific typing. (These days, I like TypeScript for this.)
First delivery, Philly ETE ,April 2015:
Also, PolyConf in Poznan, July 2015: PolyConf 15: Contracts as Types / Jessica Kerr – YouTube
I wish I could find the version from Craft Conf; that was my favorite.