How do the allusions in Octavia Butler's novel Kindred relate to historical context?

In Kindred, Dana, a present day
descendant of a slave and her white owner, finds herself traveling back in time
involuntarily. She begins to understand that she does this when the life of one of her
ancestors is in danger; when she saves them, she ensures her own present-day existance.
Butler uses this plotline to show the horrors of slavery. One of Dana's ancestors is
owned by the other. When Dana is in the past, as a black woman she, too, is treated as a
slave. She has to save people she does not like and endure situations that are horrible,
in order to allow her own future self to be born. Butler shows various horror of
slavery--rape, physical brutality, separation of family members--while writing an
interesting time travel novel. She was one of my favorite SF authors, and died far too
young.