Crabs in a bucket
(twitter.com)
Perhaps, slowly over time, but I think it would end up like taming the silver foxes (https://evolution-outreach.biomedcentral.com/articles/10.1186/s12052-018-0090-x). They only selected the most "tame" foxes, and in the end, the resulting fox generations just looked like dogs. Makes me wonder if by selecting black for intelligence, if you'd end up selecting lighter and lighter skinned blacks!