This poem seems to be spoken by a kind of omniscient, or all-knowing, being. After all, the poem starts off in the Land Without Time (not to be confused with the dinosaur movie. C'mon folks!). And our speaker seems as comfortable delving into the mysteries of Africa's ancient past as she does talking about the continent's current state of affairs. Either our speaker has some serious memory power or she's something slightly more than human. While we have a hard time remembering what we had for lunch last Wednesday, our speaker has no problem sifting through the last million decades or so.
Other than some serious memory power, however, we don't get to know all that much about our speaker at all. Is it a man? A woman? Young? Old? We sure don't know. And maybe Angelou wants it that way. After all, with a fairly unobtrusive speaker, we don't get caught up in what our speaker thinks about the events or actions or actions she's describing. The actions get to speak for themselves.
Sure, we know that our speaker is fond of Africa (after all, you probably wouldn't describe something as "sugarcane sweet" if you didn't have a soft spot for it). But other than that, she's forcing us to be unbiased witnesses to the work of the poem. She's not planning to intercede with her opinions or feelings. That way, whatever we think of the things that have been done to Africa, we'll think them on our own terms.