Of my own family, about 3 out of... 20(?) couples met locally. That was a big source of diversity. Match.com is a big source of indiversity. If you both line up

Of my own family, about 3 out of... 20(?) couples met locally. That was a big source of diversity. Match.com is a big source of indiversity. If you both line up on an ideological scale, live next to people who have that ideology, pretty soon you forget how to think. Now you have to deal with these people at work. That's one example from a list of examples. People live in bubbles to the point to where I see people in real anguish over who gets elected. And WRT marriage- oh hell yes. I have access to a behavioral ecologist, and she can tell you how pernicious all this is. The easy story is haemophilia in the royal lines in European history. This will be hard on our genetic ( and mental ) diversity. She calls it "electing the President based on a multiple-choice test" for one thing. But it's really more about people living in cognitive bubbles, which makes their thinking hidebound, it makes risks seem larger than they are and it stifles the culture. Throw in a rising Mandarinism - that which is not required is forbidden, and that which is not forbidden is required - and we'll see.