My question is how primitive was early man?
One strange thing popped into my mind: Trepanning was apparently quite widely used surgical procedure already in the stone age. It appears that many of the patients even lived quite long after the operation, since their skull structure had healed.
The stereotypical cave man has mainly been described with a club, rather smashing skulls than repairing them. Of course there aren't any medical reports available from 6500 BC, so we can't tell the reasons for the operation. Later generations have documentedly used the method for various purposes, starting from letting evil spirits out.