that would depend on the definition of sub human and i cant find a good definition. i'd guess an impairment of any type by birth would make you less then human, aka subhuman. However if you cure this impairment, would that mean a subhuman can become a normal human?
Or is a subhuman, someone who is born completely normal, but rejects his humanity and decides to follow his animal instincts? In this case it should be noted that i consider the humanity in people their ability to get over their instincts and "evolve" their mind. Or in other words, learn things, just out of curiosity, while not indulging into hedonistic lifestyle by satisfying the most basic needs(from time to time you should satisfy them thought :P ).