ive heard the saying, sprinters aren’t made they are born. and i notice all the best sprinters for 100m are black, is this just a coincidence? is there any scientific reason, and could a normal person get to that level?
No a normal person could never be a world class sprinter 
Higher fast twitch muscle fiber percentage, a proper CNS for speed, more mesomorphic physiques, high testosterone levels, natural strength, quick reactions, high muscle elasticity, long achillies tendons.
These are ^^ different things which sprinters wouldnt require and world class sprinters would have every single one of them.
wow… thats pretty disheartening… would this be the same for say 200 and 400m runners
200m runners require the same things, as for 400m i would think anything affecting more muscle mass be less of a neccesity and and the ability to develop a better anaerobic system and lactic acid tolerance be more of a importance.