If people believe that half black half white ancestry results in higher IQ than 100% black ancestry
Then If white males impregnated black women and prevented black men from impregnating white women and white males also impregnated white women with each white male impregnating multiple women
Then this would raise the IQ of the world more than white males only impregnating white males and black males only impregnating black women
Polygyny for white males
Nobody for black males