Hmm. I believe that the human digestive system developed that acid to digest meat over a period of time, after meat was introduced into the diet. However, I could be wrong. Also, there are some physiological aspects of the human body which you are ignoring, that could be used to argue against meat eating being natural. These would include molars, a longer digestive tract, a relatively weak jaw, saliva which is more suited to disolving fruits and nuts than meat, no mauling tools or sharp claws on the body, lack of great speed, and no real natural physical advantage over other animals. And finally, no other animal (a minority of humans) breeds its prey to kill and distribute among its society. Just pointing out some things you could have missed.