As a result, Dr. Bass insisted that we be able to instantly identify small fragments of bone, as well as the whole bones that are standard fare in most anatomy and anthropology classes. This seemed like a daunting challenge at first, but we soon learned that all bones have identifying features that make them unique, distinguishing each bone from every other and even separating right from left. For example, the metacarpals-the bones extending from the palm of the hand-all look alike at first glance, but if you look at the end that joins the wrist bones, you can see that each has a slightly different shape.

Once we'd learned the secrets of each individual bone, we had to be able to look at a fragment and pick out the one feature that would help us identify it. The mandibular condyle, for instance, is a tiny part of the jawbone that fits into the corresponding groove of the skull-no bigger than a plump raisin. It has a shape that is unlike any other piece of the human skeleton, and once its image is firmly anchored in your mind, you can not only recognize it, you can tell which side of the jaw it comes from, even if the rest of the jaw is missing.

As soon as we started to feel the first glimmer of confidence in our ability to identify adult skeletal material, we had to step back in time and learn how these bones looked while they were still growing. The bones of newborns and infants were a wonder to behold, but the differences in shape and size from adult bones added yet another element of confusion. Soon I learned, though, that even the tiniest bones had a distinctive shape that resembled at least a portion of their adult counterparts.

The skull is incredibly difficult to understand in its infant form, and even adult skulls are tough to deal with when they're fragmented. Almost everyone can recognize the familiar shape of a complete human skull, but together the cranium and the face contain over two dozen separate components. Big, relatively flat bones form the back, top, and sides of the skull, with smaller, more complex bones surrounding the eyes and face. In decomposed or skeletonized infants, these bones are thin, incompletely formed, and not connected at all, looking more like big, irregular restaurant-style corn chips than human bones. Again, Dr. Bass insisted that we know skull fragments backward and forward. He knew, and we were soon to learn, that the skull is a favorite target of murderers.

I must admit, it took me a while to hit my stride in osteology class-the way an anthropologist looks at bones is simply so different from the way an orthopedic surgeon views them. I was used to seeing bones live and whole, within a huge organic structure of which they were only a small though vital part-not as isolated elements that might be found scattered in a field or piled in the corner of a basement.

But once we moved from whole-bone identification to the analysis of fragments, my competitive spirit came through. My friend and fellow student, Tyler O'Brien, would sneak into the osteology lab with me each night, and we spent hours quizzing each other on every fragment in the collection. First we learned by sight-“Half of a right patella.” “Portion of a lumbar vertebra.” Then we shut our eyes and set ourselves to learning by touch alone the unique characteristics of each bone.

That process had taken months-but it had served us well. Both of us, as well as most of the class, could now take the merest glance at a whole bone and tell you what it was and which side of the body it came from. We could pick up the smallest fragment and find the key to its identity. Solving these intricate three-dimensional puzzles became a new and thrilling game.

Soon we were ready for an even more fascinating task-applying this knowledge to forensic anthropology analyses. Now, though, it was no longer a game. We were being taught to practice on real cases-albeit cases that had been solved years before. But our subjects were real people who had died violent deaths. It was up to us to figure out who they were and what had happened to them.

The routine was always the same. Dr. Bass would bring a collection of bones into the classroom on Tuesday morning, along with any pertinent case information, and leave everything there for a week. A skull, mandible, two thigh bones, and a section of pelvis might be piled on top of a tray along with the preliminary notes taken on the day the bones were found-for example, “Human skeletal remains found in a ditch along Alcoa Highway on July 7, 1987. No clothing was recovered.” Then we had to analyze the remains, explaining what they told us about the victim's age, race, sex, stature, and any other clues we could come up with.

There were only about fifteen students in our class, so we split into teams of three or four and took turns examining the bones during the week and in our Thursday class. By the following Tuesday, we were each expected to produce a report-just like the ones we might turn in to a police investigation-telling the investigators everything we'd gleaned from our anthropologic examination. In fact, the class was as much about preparing the report as it was about analyzing the remains-no forensic anthropologist will last very long if he or she can't document evidence and share information with investigators-and it was made crystal clear from the beginning that we were to choose our words carefully and back up our opinions with good, hard science.

I was used to writing reports, of course, but only in the style of the medical records I had worked with at the clinic, in which a typical entry might state confidently, “This is a forty-five-year-old White female, 5'6'' tall weighing 145 pounds.” Of course, you could describe a whole body-living or dead-in that kind of detail. When all you've got is a skeleton, you can never be that specific, though you can usually come up with a more basic biological profile. For example:

BIOLOGICAL PROFILE: Case # 02-17

Every biological profile, Dr. Bass told us, would ideally include the anthropologist's “Big Four”: sex, age, race, and stature. If you're lucky, and you've got the evidence to go further, you can put in ancillary information such as weight and maybe hair color. Often, human remains do survive with enough intact hair to determine color, because hair is made up of dead cells, which don't decompose as soft tissues do. Even a single long, blond hair found stuck to the underside of a skull can help tremendously when you are trying to identify skeletal remains.

Sometimes the associated evidence-evidence found with a body or remains-can give you a clue. Clothing, for example, can help you determine a person's weight and size, though, of course, it too tends to decompose. In the end, though, the bones last longest-and they hold many secrets if you know what to look for.

One of the most basic ways we identify each other is by sex, so when I'm looking at newly discovered bones, I often start by asking myself whether they belonged to a man or a woman. Under these circumstances, I hope I've got at least part of the skull or the pelvis, because these bones possess the best morphological features to reveal the differences between male and female. (“Morphology” means the logic of shapes, the characteristics of a structure that can be seen but are difficult to measure.) Males, for instance, usually have a line of bone that juts out to form the “brow ridge,” a horizontal ridge between their forehead and the tops of their eye sockets. This ridge is smaller, or absent entirely, in females. Males also have distinctive areas-much bigger than women's-for their large muscles to attach behind each ear and in the back of the head, near the hairline.