Teenage Caveman (2002) on Netflix

In a post-apocalyptic society, a tribe with a few survivors lives in caves with an abusive religious leader. When he was raping the teenager Sarah, his son David kills him and is sentenced to death, tied to a pole. However, Sarah and David friends decide to release him and leave the caves. They find a destroyed city, and in the middle of a storm they are rescued by two locals, Elizabeth and Neil. The couple of survivors introduce the teenagers to sex, drug, beverages and clothing and sooner they find that Neil is a genetic experiment of a new breed of predators, and Elizabeth was modified by his semen.