Last week my wife and I took our eighth-grade daughter to an open house at the local high school where students can specialize in visual and performing arts.

I was surprised to see, in the commercial art classroom, a member of our high priests group.

I had known -- once -- that he was a teacher at one of the high schools, but not this one. More to the point, I didn't actually care what he did for a living. I did not know him by his job. I knew him by what he said in quorum meetings, who he was in the ward.

It's one of the great blessings of Church life. The world labels people -- men especially, but women, too, these days -- by their career. And that includes assumptions about how much money they make, how educated they are, and so on.

But in Mormon wards, we can forget all that. People "are" their callings, but since those change rather often, our real knowledge about them consists of how well and faithfully they do their callings, what they say and do in meetings, how often you run into them setting up or cleaning up after meetings.

The Mormon ward gives us a way to know each other.

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A few years ago I read R.I.M. Dunbar's speculation on the reason why human brains are so much bigger than those of the apes.

Part of his idea is that human speech developed as a way of grooming each other, as other primates do, only without using our hands, so we could do our work and interact socially at the same time.

But I had to chuckle when I got to his observation that brain size in primates correlates with the size of the ordinary social group. Comparing the brain size of intensely social primates like chimps and baboons with the size of the average troop, Dunbar determined that the optimum group size for humans should be about 150.

I laughed because he had just tagged the size of a normal Mormon ward. Outside of Utah, if you get much more sacrament meeting attendance than 150, they start thinking about dividing your ward.

More than that, and you start to feel lost. It's just too many people to grasp all at once. It starts feeling like a bunch of strangers instead of a community you know.

When my wife and I lived in Utah, we saw first-hand how large wards -- like large schools and large companies -- can leave some members feeling like an extra. Unneeded. Anonymous. Lost.

Naturally, there's still a wide range of fluctuation. We remember the identities of a lot more people than just 150. But it's hard to be closely involved with more than that.

Have you ever sat down to list every name of every person whose name you remember? Start with every relative you can think of, living or dead, and then name all your friends from grade school. Then name the teachers. And all your bosses and co-workers. Then name all the famous people -- for instance, Lincoln, Columbus, Moses, Joseph Smith.

And then name everybody you can think of in your ward.

My guess is that most people hold a thousand people or more in their memories. And listing them all is an excellent way to start writing your personal and family history. Your memoirs. Your life and times.

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Dunbar is talking about the people we groom. The people we are intensely involved with. The people whose approval is important to us. The people we miss if we don't see them often.

That's where the Mormon ward really shines.

Never mind how well Dunbar's science holds up. After all, even the coolest scientific hypotheses run up against reality and often get dented or broken.

This fact will remain: Every active Latter-day Saint lives in a small town. A village.

Some people teasingly call this the "McDonald's Church." No matter what ward you go to, the menu is the same.

But the truth is the opposite. The roles are the same, but each ward, each village, has a character all its own.

And what is more disruptive than when somebody comes in and splits off or recombines villages? It can feel almost as painful as being conquered by some barbarian empire and getting dragged off to a new country. Nothing's the same.

There are regional differences, too. In the Mormon Corridor (Utah and some bits of Idaho, Wyoming, and Arizona), wards tend to be neighborhoods. Everybody lives in each other's laps.

This is what Dunbar considers to be an essential part of forming those intense 150-member communities. You have to see each other constantly.

Yet where I live, in North Carolina, our wards are spread out over many square miles. You can't just walk out into your front yard and see your village. You have to make a special trip.

The result, though, is not fragmentation, as Dunbar predicted. Often we are more involved in each other's lives, because we don't take our community for granted. It isn't just there.

We have to work harder to maintain that village, to recreate it week after week. But we do maintain it.

And the strangest thing of all: Our Mormon way of organizing ourselves just ... happened. There's no mention of "wards" in the Doctrine and Covenants.

They grew to exactly the right size to be the replacement for any and all competing worldly communities. It's part of the glue that holds us together.

We're all members of a worldwide Church.

But we experience the Church 150 people at a time.