I don't know about percentages or fibre but if you look at Cordain's book he breaks all this stuff down. This is our best guess of how our ancestors ate and I figure if people thrived for millennia, it's OK for us too. If this really interests you then I suggest you start with the Weston A. Price research on diets of indigenous populations. They obviously vary from place to place but there are some interesting patterns of what they don't eat as well as what they do.