A superman is not a man, not a creature of the species Homo sapiens; this is the fallacy of Nietzsche, the fallacy of H. G. Wells. These, like others who deal with the matter, have believed that a man, a human being, raised to the nth degree, represents the superman. Nietzsche picked one set of qualities — those of fitness, potency, power — Wells chose another set, the contemplative, the serene, the intellectual. So probably, a Neanderthaler in his filthy cave, using his embryonic imagination, might have pictured his superman as a giant in strength and size, a mighty hunter, one whose meat-pot and belly is never empty. Certainly he never considered a race whose very thoughts were partly beyond his conception, and he saw nothing ironical in freezing to death upon a ledge of coal. As we are to the caveman, superman must be to us. His coming is surely a possibility; perhaps it is inevitable.
Stanley G Weinbaum, The New Adam, 1935
A neat analogy, but probably the human race will never evolve again. So the superman will be an alien; an alien we will find impossible to comprehend or even recognise.
He is unlikely to come from the planet Krypton in his underpants.