Actually the roots of the blues originated and evolved during slavery in the old South through the spirtuals. I find much of Delta Blues, which I really love btw, reaches and speaks about pretty much all aspects of the human condition including lust, humor, despair, longing, joy, jeolousy, revenge, hate and hope. Did I leave anything out? I'm sure plenty and the blanks can be filled in with pretty much any adjective describing the human condition which these people endured. The point being it is folk storytelling to music by a people oppressed over a long period of time and a means to let it out without verbally complaining of the conditions which would have surely brought added pain and punishment.