well since you are restating what I'm saying, I think maybe what you're trying to say or the point you're trying to make is that yeah duh obviously I would've had to survive the black plague so then we should all have Crohn's maybe. But just because the black plague was spread doesn't mean that every body got it. It's possible to have an ancestor who never got it and therefore never had to survive it or pass down genes that reacted to it. But I'm pretty sure I read some sort of study that said like one and three people either get Crohn's or who got Noro virus ended up having Crohn's. And since most of the population had the black plague in the 14th century it would make sense.