(1) People don't move.
(2) If they do move, then they stay put.
(3) They go with people they know.
(4) AND THEIR KIDS MARRY EACH OTHER WHEN THEY GET THERE.
I'm going to post a few more:
(1) If there is a road, people are more likely to travel along the road than across fields or through forests. (The road could be a foot path.)
(2) They are more likely to travel along a road to a destination on that road than they are to follow that road to a branch, then go along that road to a destination. The more turns involved, the less likely they are to go there. (<-- That is not a joke.)
(3) They are more likely to travel along a road to a destination that they have been to before. They're only likely to go somewhere new based on a description (or with a guide) if they've seen someone come _back_ from that description (or from that guide) and it all turned out okay. (<-- Seriously, I'm not making any of this up.)
If you are an ordinary person living in a world of a few houses, you'll go absolutely everywhere in sight of and a close walk of those houses (this is actually the principle behind another set of rules which can be summed up as: Before the mid nineteenth century, there was no such thing as privacy for ordinary people), unless someone stops you (physically or by believable threat of violence). _And_ you probably won't go anywhere else. There will be a person or people in your world who _do_ go somewhere else (possibly quite a long ways away, even by our standards), but you don't have a lot to do with that person and neither do most people you know.
If you are a not-ordinary person living in a world of a few houses, you will not marry someone from nearby but you will marry someone very closely related to you -- they'll just happen to also be a not-ordinary person living in a world of a few houses and so forth and so on.
From the perspective of ordinary people living in a world of way more than a few houses, not to mention high schools and automobiles, if we know anything at all about the world described above, we know about it because the not-ordinary person is a friend of ours who went there with the Peace Corps and/or an NGO, or because we read a centuries old letter or journal or whatever written by someone not-ordinary. It is, therefore, quite difficult to make sense of this. We can, however, make an effort.
(1) can be thought of as "People will take a much longer route that involves familiar roads by preference to a shorter, unfamiliar route."
(2) can be thought of as, "We go back to our old doctor/dentist/hair stylist/etc., even after we move 20 miles away (or, in extreme cases, a thousand miles away)"
(3) can be thought of as going on vacation to the same place(s) year after year, until our friends convince us that Aruba (or wherever) is totally amazing and we have to go there yes we do.
There's a really, brutally obvious exception to all these rules, and it's That Guy Who Always Knows the Shortcut and Refuses to Ask for Directions. I'm willing to allow for the possibility of a few crazy people out there, altho I would note that if they are really breaking all these rules all the time, they're acting more like the guy from _Into the Wild_ than they are like, say, Marco Polo.
And how reproductively successful are those guys, anyway?
When I read people writing descriptions from anthropology or history or whatever of how people lived their lives and found other people to reproduce with, I see nothing, and I do mean _nothing_ but support for these rules. I didn't come up with these rules from some Idealized Platonic Fantasy World in My Head about How People Should Act. I came up with them as a way to summarize what I encountered. But when I read people trying to write up little computer probability models of how people move around and find other people to reproduce with, they systematically break every single rule.
All that? All that is _normal_. That's just people. Okay. It's bothering me some that so many of the programmers claim they are being conservative when they are being the opposite of conservative, but I was a young programmer once; I've done that, too.
What I can't quite get a handle on are the innumerate anthropologists who accept the results of the inhuman programming. The assumptions going into the models are all _dead flat completely wrong_ and where they could sort of be right, the input parameters are lunatic. And I mean that by the belief set of the innumerate anthropologists. Yet they are accepting the results. And the programmers seem to really believe their models are somehow related to what the anthropologists are doing, _even when they say they decided to ignore all the anthropology and history_. These people are _scoffing_ at each other, and then backslapping because they agree on the results.
IMO, of course.