Natural Selection opens with a birth, of sorts, and ends with another. Kind of. A landscaper is working the grounds outside a prison, but when he takes a break and walks away from his riding lawnmower the clippings bag begins to move. A seam rips open and out pours a scrawny, filthy, mulleted man clearly thrilled to have escaped from jail. A few states away Linda (Rachael Harris) and her husband Abe (John Diehl) are waking in bed. She makes moves of a seductive nature, but he shuts her down with a reminder that God would not approve. She’s barren and unable to conceive, and God only approves of fornication in the service of procreation. It’s a struggle that she accepts without complaint, but when Abe suffers an ironic stroke that puts him in a coma while “donating” at a sperm bank she discovers he’s been doing so since they were married over twenty years ago. Double standard? Maybe, but when she’s informed he has a son named Raymond she sets off to find the young man and unite them before Abe passes.