You've got to wonder, since we have a more primitive hominid in our immediate , why couldn't all the DNA to make that hominid still be coded in our DNA, just waiting for the proper RNA to make little junior a real knuckle dragger. Chickens to Dinosaurs should even be simpler. Not T Rex, but one of those little green ankle biters from Jurassic Park II. It would make a great little jungle pest, as if the tropics don't have enough problems already.
Alas, most biologists are far too busy doing, you know, actual research to look into the politics of cellular differentiation. I feel no such restriction. I've got lots of half baked physics postulates too, if anyone's interested.