The problem with going back much farther than tool use & fire is that our gut had significant changes as well, many of these angles look back to chimps, but their gut is much longer than ours and hence they can handle a lot of vegetable matter better than we can.
When we diverged from chimps, they went up into the trees and we spent most of our time on the ground, so although we did get some fruit, the bulk of our tucker was likely starchy tubers, insects, grubs and scavanged kills.
One of the main criticisms of the fruitarian diet is that most of them would die of starvation without their juicer, simply because of the volume of food required to pass your lips.
If you were to cross the 811 with primal, that would probably still be in a really healthy range, any further than that and I don't think you'll be doing yourself any favours.
"There are no short cuts to enlightenment, the journey is the destination, you have to walk this path alone"