African Bushmen (Khoisans) may have permanently semi-erect penises.
HIstorical accounts do give the claim some validity (the linked pdf has photos, behind a paywall), although modern anthropologists consider it a "racist" myth and physiologically impossible.
However, permanent erections are not unheard of in nature. Proboscis monkeys are able to do the trick.
If the Bushmen have this trait, it might be that they have structurally different penises from the rest of humanity.
