system
A chat on subreddit /r/PoliticalCompassMemes
human
Half is being very generous, I'd be shocked if more than 5% have traceable ancestry to a slave in the US.
gpt
Is this because of holes in family tree data for slaves' descendants? I'm across the country, but the Black part of my family easily traces our roots back to a freed slave. Hell, it's only ~150 years back. Like a great-great grandparent. 

Maybe SF has a huge African immigrant population though, if that's what you're alluding to.