Ecce Homo – I Sopravvissuti (1969) aka Behold Man – The Survivors
In a post-apocalyptic world, a wife chooses a strong, young man to screw her (and maybe re-populate the world) over her old, sick husband and an intellectual. She chose with her libido, not realizing the fact that the intellectuals have long inherited the earth, and hence, her choice will end in tragedy for her.