Chris Kresser spoke at a recent MindBodyGreen conference;this is his 20 minute introduction to Paleo. He explains well the evolution of the genetic mutation for lactase tolerance, and why he believes after doing a "Paleo diet reset", people should try to re-introduce the "gray area" foods..dairy, legumes, etc.
http://www.mindbodygreen.com/0-1457...is-kresser.html

http://chriskresser.com/why-paleo-i...-world-by-storm
His book, Personal Paleo Code, has the best explanation of not only how to do an elimination diet, and importantly, how to slooowwwly reintroduce each food in sequence, to test your tolerance.