Have they ? Some place in West Africa looked more developed to me than many places in Southern Africa when I visited.
And if you're referring to (white) South Africa, it is the same story as the Americas, where technology got introduced by settlers. Without European settlers America would look much different.
South Africa got the cream
of Dutch, French, German and
later on British settlers, coupled
with rich mineral and other resources
it was a recipe for success.
BTW, when the Dutch first
arrived here in 1652, there
were already what they called
"coloured" people. They were
called strandlopers (beach walkers)
The apartheid government recognised
them as a seperate race, black, white
and coloureds.
These coloured people can also be divided
into further groups based on location,
like the Boesman or San from the Kalahari
and the Griekwa's in the Northern Cape.