While there are limits, they're sometimes further than you think. I am a 5'10" white guy, and I really wanted to dunk basketballs, so I "just did it more". I dunked on shorter hoops, read books, experimented with every method of practicing and training, soaked up sports medicine journal articles, and pored over everything related on the internet. Eventually, I could dunk quite easily, and even developed my own system for helping others do the same.