Why is there racism? not one test Genetic or any other type can tell if u r black or white it can not define any race? so there is only the humanrace?

So why is there racism? The word racism or race implies a certain type of person but in reality there isn't a type.

Why is there racism? not one test Genetic or any other type can tell if u r black or white it can not define any race? so there is only the humanrace?
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