Colonial Schoolbooks (Belgian Congo). Anthology.
"9. The children often ask me: "Why are we not as intelligent as you Whites?"

10. The Whites are looking insistently for knowledge of things that are not even discovered. This the reason for which their intelligence does only increases, and that people give them a lot of honour. On the other hand those people of your regions, that were more intelligent than the other, were treated with jealousy by some other people, and some were killed either after have been obliged to drink poison or otherwise. A lot of people died at home because of fetishes, because the soothsayers often deceived your forebear. They ruined the best people, and protected those that were happy with their bad practices. This is one reason why intelligence doesn't increase in your countries. Another reason is the indolence. Some consider the latter as the most important reason."