Prehistoric people could not write and so therefore they couldn't not pass down any knowledge about medicine.
Prehistoric people believed in spirits. We know this because of the cave painting they left.
We know that they must have known something about the bone structure. This is because of how they buried the bodies.
Prehistoric belief about illnesses
They believed in spirits and that when a person became ill, there was an evil spirit inside of them.
Prehistoric surgery was very simple. We know that they performed trepanning on those who were ill, to get rid of the evil inside of them.