The design of the human jaw actually makes it 40-50 percent more efficient than for all great apes, Australian researchers have found. "Pound for pound we're actually biting harder than a gorilla or a chimpanzee," they say. They also found no big difference between the bite force of a human and that of the "nutcracker man", a fossil hominid, once body size was allowed for. While we have not strongly compromised our ability to crack a hard item or bite off flesh, for better or worse we are less well adapted for hours of chewing tough leaves and bamboo tubers!