Basically blues must be an expression that originates in a particular vocabulary of human emotion. Then you may research who became known for this way to express this, what posthumously is named "blues", and when the first records of that type of expression can be dated back to, and that's certainly interesting enough.

As I see your project, it's a research in mythology more than anything else. I doubt there excists certain dna proof of the original emotions that may have lead to form "the blues" as a form of artistic expression. But of course you can aim to tell as accurate a story as you can document, within the scope of your specific interest.

Recently I heard about a natural scientist in Denmark who is currently gathering hard proof that the indians was not the indigenous people in America. A highly controversial research that has the potential to rip the indians of some of the priveledges they have gotten on the account of being indigenous (I wonder who's funding it..). Sounds sad to me, but truths ain't what they used to be.