This is a great audio documentary that examines the origin of the 5 note clave.  This is the basis for so many rhythms and popular music all over the world.  This is such a powerful ground to use in sessions.  As human beings we almost know this rhythm on a cellular level.

http://www.bbc.co.uk/iplayer/episode/p00dwqdw/The_Friday_Documentary_25_02_2011/