Imagine, if you will, that Rock Music was a person (I almost wrote "Imagine Rock was a person," but realized that without the word "Music" in that sentence it could sound like some sort of slam against Dwayne Johnson).  Every person is a product, in many ways, of the DNA they have been handed by their ancestors.  We even talk about things like "lizard brain," referring to our most basic, primordial impulses still lingering within us even after millennia of evolution.  This same thing can be said of music.  Music is a product of its influences and no matter how removed from whatever wellsprings lie at the birth of any genre, there are still those basic elements that were there at its inception--elements that either remain within the musical structure itself (like the near-ubiquitous clave rhythm in Latin music) or at least inform the way the music will evolve (for example, sampling was once a necessity for inner city music artists who couldn't afford musical instruments but has now become a staple of rap and rap-influenced music).  

In the case of rock music, you can use the example of Call & Response:

Call & Response is a musical element found within many musical traditions throughout sub-Saharan Africa.  There may be several centuries' worth of time between when the first African slaves were brought to the Americas and the birth of rock music in the 1950s, but you can nevertheless find Call & Response cropping up all over the place within every genre of rock music, even to this day.  So, when musicologists are studying the history of music, they are in many ways genealogists studying that music's family tree.

If we were to look up Rock Music's family tree, what types of music and traditions would we find as its ancestors?  What would Rock-n-Roll's ancestry look like?  

I decided to create this fancy little graphic that can help visualize this very thing:

Cool stuff happens with musical miscegenation...