Is Sarcasm Genetic??

Let me preface this with saying that Jason and I have a relationship and banter that includes alot of sarcasm. We tease, we joke, we mildly insult but we always know that it is just in good fun and how we interact sometimes. Though I don't think we ever thought that Jakob would, at such a young age, grasp the form of sarcasm. Maybe it was a fluke, maybe we are reading too much into it, but we almost fell off our chairs the other night. We were finishing up dinner and Jakob had already excused himself from the table. Aiden was swinging in his swing with a full belly and a grin....oh and the hiccups. Jakob walks over to the swing, looks down at Aiden and says..... "Nice Hiccups" - with just a slight ooze of sarcasm. It was hilarious. He then proceeded to sit down on the floor and play with his many many hotwheels. So the question is - nature vs nurture?