Both man and animal have the instinct to guide them to whatever they need to keep them healthy.
But man, with the progress of 'civilization', gradually lost that instinct. Somebody, however, in the community did retain enough ability to consult his animal instincts and usually was accepted as the 'healer'. Apart from nature healing: diet, medicinal herbs, bone setting, minor surgery etc., he also used faith healing, in which he made the patient to relax and gave suggestion. In all cultures for centuries, faith healing followed a pattern, but later on faith healing tended to be left to sorcerers and quacks.
With further progress of civilization, belief in the effectiveness of faith healing began to dwindle and vanish except among the very credulous and very poor.
Franz Mesmer provides the link between the ancient healing techniques with faith healing in its various manifestations today.