We present to you: "The Grand Unifying Theory of Superman's Powers."

Since Time immemorial, man has sought to explain the powers of Kal-El, a.k.a. Superman. Siegel et al. Supposed that His mighty strength stems from His origin on another planet whose density and as a result, gravity, was much higher than our own. Natural selection on the planet of krypton would therefore endow Kal El with more effcient muscles and  higher bone density; explaining, to first order, Superman's extraordinary powers. Though concise, this theory has proved inaccurate. It is now clear that Superman is actually flying rather than just jumping really high; and  His freeze-breath, x-ray vision, and heat vision also have no account in Seigel 's theory.