"I offer this authenticated 2nd century scroll as  evidence that musical  instrumentation evolved in parallel to human skeletal evolution.  It is obvious from this illustration, that as Homo erectus evolved into Homo sapiens, he evolved more ribs.  The theory is that,  after dinner*, he had more bones to play with and his tonal experience grew.  The more primitive man had only 6 bones in his rib cage - thus the famous 6 tone scale of the well documented "cave jams" petroglyphs.  Presently mankind has 12 bones in his rib cage,and thus we have the current 12 tone scale and mankind's musical epiphany.

 

*dinner consisted of the less musically inclined neighboring villagers."

 

excerpt from - "Modern theory on musical expression and evolution" Dr. Brak Enbones et al, BONES AND THINGS vol 12, 1997 192-3.