Thanks for that explanation, Megan.

Because of my sociological background, I'm prone to credit history and cultural socialization for reasons why African American music is as it is -with "history" starting in Africa.

I admit to having a very negative visceral [excuse the pun] reaction to theories that body type have something to do with intellect. So to think that body types have something to do with how a group of people as diverse as African Americans sing...If I correctly understand what is being said, and admitting that I just don't know enough about the subject, my initial reaction is to give that theory two thumbs down.