Ghosts of the past II: muscles and fasciae in the primate forelimb domain

Many forelimb muscles (e.g. coracobrachialis, rhomboids, serratus sheet) are much less complex and much smaller in humans than in other primates. Yet human muscular variations and persistent fascial sheets indicate that increased size and complexity were once the norm. These muscular reductions are associated with equivalent skeletal gracilisation. Is it possible that molecular phenomena, not unlike those producing reduction of the jaw muscles and associated with gracilisation of the skull in species with reduced need for powerful mastication, may also have reduced forelimb muscles with gracilisation of its skeleton in species no longer using a forelimb for powerful locomotion? Could such molecular and skeletal changes be dated (as for the masticatory muscles) thus giving the time of origination of prehuman forelimb reduction and true bipedalism?