This is a 27minute long interview and well worth the time invested. Matt LaLonde approaches the 'ancestral diet' in a very logical and scientific way. The arguments of "do this because our ancestors did" is NOT a valid argument. Introductions of new foods into a species' diet can happen and be greatly beneficial. Sadly, things like wheat, especially the dwarf wheat we eat today that's been on planet Earth since the 1970s is not one of those things. Grains have one defense mechanism, to irritate the digestive tract of something that eats them.
Matt also explains how testimonial evidence is not valid science either - just because you 'heard' about somebody that ate a certain way and lost weight has NO bearing on how it will affect you. We are all an experiment of one and we have different genetics and (more importantly) epigenetics.
Look to your body as an extremely complex system. Treat this system with a know quantity of fuel for a while. Then introduce a new fuel and measure its affects.
This interview also is the only source I have where a scientist cover how to be a smart vegetarian! eating foods we are designed to eat while avoiding meat if you choose to for ethical reasons.