Here are three lists of real-life extraordinary human anomalies from the "Cracked" website:DNA Mutations That Make Ordinary People X-Men
Personally, I wouldn't classify genes for adventurousness and happiness as superpowers, simply normal variations. The Argentinians who have a supernormal tolerance for arsenic and the Inuit who process dietary fats differently from the rest of us, though, strike me as bona-fide extraordinary.
A sample of abilities everybody has in infancy but loses as he or she grows up:5 Superpowers We All Had as Babies
A recurring theme of these infant "powers" is that growth requires pruning and focusing so that some abilities get lost as a necessary part of adjustment to the needs of adult life. For instance, pre-verbal babies can hear and produce all the sounds possible to the human vocal apparatus; when they learn to talk, however, they "forget" how to process the sounds their native language doesn't use. Reminds me of the scene in MARY POPPINS where we're told all babies understand the language of birds, yet as they learn human speech, they lose that gift.
How about a man who can touch live wires with impunity because he has seven to eight times greater resistance to electricity than the average person? Or the autistic savant with perfect visual memory, who can draw a whole city in accurate detail after seeing it once? The man who can control his autonomic body functions so well he can sit almost naked on ice without freezing and the man with reflexes faster than the human eye can follow also fit credibly into the "superpower" category:6 Real People with Superpowers
If the environment changed radically enough in some distant future era, could one of these traits become so important to survival that it spread widely through the population, making individuals who carried that gene an elite group? In the back story of Tanith Lee's SABELLA, a human-like species evolved a form of gender dimorphism in which women fed on the blood of their mates, so that the population could survive dire, long-term food scarcity. How great a change in the environment would be required to generate alterations in human biology this extreme? Or the tendril-bearing, telepathic mutants of A. E. Van Vogt's SLAN or the Simes and Gens of Jacqueline's far-future Earth?
Margaret L. CarterCarter's Crypt