"Why does mana in the world react with our body to produce only a particular elemental essence? Why cannot one wield all the elements? Why does the percentage of elemental affinity one has matter?
"Why is thunder superior to fire if both are just a subsidiary of the world's mana? " Oogway asked Ronan , as he wanted to invoke curiosity in the young one's mind , as he paused to let Ronan process these questions for a bit before continuing as he said
" When a human child is born , that is considered the best time to measure his/ her talent and elemental affinity... why is that the case?
it is because the world's mana had not yet reacted with their bodies hence traces of other elements will not be present in the bodies.
Humans develop elemental affinity in their mother's womb itself during the third trimester as that is the time when they form their dantian.