Darwin says Apartheid was good for blacks?

The data:

In 1904, there were 3 491 056 blacks in South Africa (67.5% of the total population), and 1 116 805 whites (21.6%). In 1996, there were 31 127 631 blacks (76.7%), and 4 434 697 whites (10.9%). Blacks grew 9 fold, whites 4 fold.

The analysis:

In Darwinian terms, "[n]atural selection is the differential survival and reproduction of individuals due to differences in phenotype." Since the different development paths of blacks and whites during Apartheid was based on race, it is obvious that Apartheid was a form of natural selection.

If blacks bred more than twice as much as whites, then in Darwinian terms they were more successful under Apartheid than were whites. QED.

Or did I miss something blindingly obvious? Was there a lot of white flight during the period of white supremacy? A lot of immigration of free blacks to terrible oppression in SA? Did the NGK hand out condoms and tell Jannie and Sannie not to have kids?

I must be missing something! The narrative must survive! Help me survive this cognitive dissonance!