QUESTION: Why are ancient towns buried under many layers of dirt, even though dirt is supposed to erode over time?

ANSWER: Until we researched this item, the Why staff's knowledge of archaeology was limited to the fact that the fabled Lost Ark of the Covenant is lost somewhere in a big government warehouse in Washington, which is just as well, since if you look inside that dusty old thing your head will either melt or explode or shrivel like a raisin.So naturally we were confused about ancient towns. It makes no sense that they're buried. Half the topsoil in Iowa has washed down the Mississippi into the Gulf of Mexico, and yet archaeologists are always digging up entire towns buried deep beneath the surface. At Jericho, the world's oldest known settlement, there are 12 distinct layers of construction going back almost 10,000 years. You have to wonder: Did the dirt just blow in and pile up, like snow-drifts?

Here's your answer:

1. Adobe. Many ancient settlements were made out of sun-dried mud brick. This stuff tends to slowly erode over time. So it's the houses themselves that erode, not the surrounding landscape.

"Mud-constructed towns accumulate debris faster than do stone towns," says Gus Van Beek, a Smithsonian Institution archaeolo-gist who has excavated ancient sites in Israel. He notes that mud bricks can't be salvaged, unlike stone blocks or heavy timbers. So homes just crumble in place, the mud is tamped down, and the once glorious home returns to the earth from whence it came. A new home is built on top, and over many thousands of years you get that chocolate-layer-cake Jericho effect.

2. Street trash. They didn't have sewer systems or semiweekly trash pickups by large groaning trucks. Towns were like giant mulch piles, and the street level slowly rose.

3. Alluviation. This is a word meaning "Pa! Lookit the dirt that got washed down into our yard!" It comes from highlands and fills up valleys. Bruce Smith, another Smithsonian archaeologist, says ancient American Indian communities can be found in the Little Tennessee River Valley under 6 or 8 feet of alluvial sediment. The opposite also happens at higher sites: "You'll find a lot of stuff just sitting on the surface of the ground because the soil has been eroded away."

Now, that's our kind of archaeol-ogy. You know: Absent-mindedly stub your toe on the remains of a brontosaurus.

QUESTION: Why does our reflection in the mirror sometimes seem unfamiliar, or even totally alien, as though we've suddenly been thrown into a "Twilight Zone" episode?

ANSWER: Maybe this hasn't happened to you - yet. But this is what it's like: You're happily doodling along one moment, comfortable with the knowledge that you are a specific person in full possession of a thing called an "identity," and then a moment later you glimpse your reflection in the mirror and SKREEK SKREEK SKREEK horror-movie violins interrupt the soundtrack of your life.

You think: Who is that? Is that YOU? That person right there?

This moment is quickly followed by the briefest flirtation with the possibility that your mind has been transplanted into the body of a total stranger.

This experience, or some variation of it, is universal, says Seymour Fisher, a professor of psychology at the State University of New York at Syracuse. In general, he says, people have poor awareness of what they really look like. Research shows that many people struggle to recognize themselves in photographs. (You say, "That looks nothing like me." Sorry, dear one. It simply doesn't look like the image you have of yourself.)

"People are uncomfortable with their own image, they're uncomfortable with their own voice, too; they react as though it were somewhat alien," he says.

It's easy to understand why we are repulsed by the sound of our voice: We're used to hearing it, in part, through the vibrations in the bones and cavities of our head, and when we hear it just through the eardrum it sounds appallingly goofy. But alienation from one's reflection or from photographs of one's self points to a larger problem: "Self-consciousness" is basically a negative experience. The more we are aware of our bodies, our faces, our little tics and warts and mutant hairs, the more negative we are likely to feel about ourselves.

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"The more you become aware of yourself, the more uncomfortable you are," says Fisher.

Which brings up the second reason we are jolted by our reflection: Fear of The Double. You know what we're talking about. Fear of . . . the other you. The evil one. SKREEK SKREEK SKREEK.

"All of a sudden," says Fisher, "you're you, and you're also this thing in the mirror. That's scary to people, the concept of The Double. We all have problems about splits in our identity; there are multiple aspects to ourselves, and it's a real job to make yourself seem like a single, unified, real person."

Washington Post Writers Group

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