Of course they have. Because there's a very obvious thing that has been scientifically confirmed for longer than most of us have been alive, and it is too hot of a potato for western poltical systems to deal with, so it has had to be suppressed, deplatformed, defunded, and made so taboo that merely saying it is will get you instantly fired from almost any job:

Sub-Saharan Africans have an average intelligence that is only moderately above that of a european adult with downs syndrome.