The Pro-Natal Effects of Siege Mentality

I should say siege mentality is pretty pro-natal. I have kind of a side project. It's not published anywhere yet, but I've been working on these high fertility populations in modern societies. And what I find is that if you take an ethno-religious group, they don't have to be religious. The Roma have religious diversity there in ethnic group. But if you take a group and you geographically concentrate them, and then you like hit them with some really adverse group experiences, like a genocide, or some other kind of serious group threat,. the survivors tend to have really, really pro-natal cultural norms.