I can't believe nobody has hit on the idea that music = intelligence. I admit that I did skim a little, so if I missed it, I apologize.
It is known that women and men are attracted to intelligence just as they are attracted to a good physique. It is also very apparent that to be skilled in music requires not only good coordination but also an intelligence in music that correlates with general intelligence. In Africa, life probably became a little mundane and very easy at times for humans. There wasn't much in the way of expressing one's intelligence when everyone already knew the best way to kill an elephant, trap a zebra or find some fruit. It is easy to speculate that the guy who could hit the drum the best, thus demonstrating his intelligence, was getting all the ladies. Its also very easy to see, with the curiosity of man that was needed to generate innovation, that the sound a drum makes would be interesting in the first place. This could be true for art as well.