I agree with you on #10, because it is obvious to me that there was no genetic physical barrier, but only a mental barrier stopping white sprinters from breaking 10 and competing in the sprints in general. Look at other sports and you see that decades of inferiority complex (and social conditions) beginning in the 1970s or 1980s in many sports led to black dominance. Hard training and belief in your self among a large population working at it means that you will have athletes of all races at the upper levels, whether cornerbacks, running backs, sprinters, and distance runners.