How do we even know that Africans had surnames centuries ago? Did they have a written language where these tribal people lived? If anything, they probably used a patrynomic system: Bob, son of John = Bob Johnsen Also did their tribal life include the nuclear family, or did the 'village' raise the child?
They probably had some form of family name, or tribal name, and certainly some names for the places where their tribes lived.
There are still indigenous languages in Mexico that aren’t written. When I was doing ESL there were a few kids I was working with that didn’t speak Spanish. They had no background in written literature of any kind. No schooling and no background in Sentence composition etc.
Obviously, if there weren’t written records, or a family bible of some sort, the history is Oral. What I found fascinating in Obama’s pedigree, after two or so generations in Africa from his dad, the only information was the continuing last name of Obama. Nothing else.