Carved in Bone

then the female. “Okay, I’ve noticed some of you carefully studying the pelvises of your classmates. So I’m sure you’ll have no trouble identifying the differences between the male and female.”
    A laugh rippled across the room—a good beginning. “Which is the female, number one or number two?”
    “Number two,” chorused a handful of voices.
    “Very good. How can you tell?”
    “It’s wider,” chirped one girl.
    “Cuter, too,” added a boy.
    “The bones in front come out farther,” said someone.
    “That’s right, the pubic bones project more,” I said. “Why is that?”
    “Pregnancy?”
    “Right, to make room for the baby,” I said, “not just during pregnancy, but also—especially—during childbirth.” I rotated the pelvis backward by 90 degrees, giving them an obstetrician’s-eye view of the bones that frame the birth canal. “You see the size of that opening? That’s what a baby’s head has to fit through during childbirth. Now compare it to the male’s.” I held up the narrower pelvis in the same position. “Any of you fellows think you could pop a baby out through there? You better hope you never have to try!” I heard a few murmurs along the lines of “Ouch, man.”
    Next I showed them the female’s sciatic notch—the notch just behind the hip joint where the sciatic nerve emerges from the spinal column and runs down the leg. “See any difference here?”
    “Wider.” “Bigger.”
    “Correct. That’s another result of the geometry of childbearing: as the female’s innominates flare out at puberty, this notch gets wider. Notice that I can easily fit two fingers into the base of this notch, but only one in the sciatic notch of the male? So ten years from now, when you’re working a forensic case, and a hunter or a police officer brings you nothing but a single innominate bone, you can tell immediately whether it came from a man or a woman.”
    One of the girls near the front—Sarah Carmichael, according to the seating chart; she wore sensible clothes and asked sensible questions—said, “But if those changes don’t happen until puberty, how can you tell the sex of a child’s skeleton?”
    “Good question, Miss Carmichael. The answer is, you can’t. Before puberty, there’s no reliable way to distinguish between the bones of males and those of females. All you can do is tell whether the bones you have are the right size for a boy or a girl of a given age.”
    Most of them looked puzzled, so I trotted out an example. “When I looked at the child’s bones that were recovered in the Lindbergh kidnapping case”—a few heads nodded, but there were blank looks on a lot of faces—“I couldn’t say for certain whether they were the bones of a boy or a girl. All I could say was that they were consistent with the bones of a twenty-month-old male—which is how old Charles Lindbergh Junior was at the time he was kidnapped and killed. But the bones would also have been consistent with a twenty-four-month-old female.”
    Sarah raised her hand again. “In that case, couldn’t you do a DNA test on the bones and compare it to the parents?” Sarah’s quickness and interest actually made her far more appealing than any temptress in a slithering skirt.
    “You couldn’t back then, of course—the crime occurred about sixty years before DNA testing became common—but you could now,” I said. “The bones have been kept in glass vials; there’s even a little bit of soft tissue on some of them still, so there’s probably plenty of DNA for a test. But the authorities and the Lindbergh family seem confident of the identification: the clothing matched what the boy was wearing, and one of the feet had crossed toes, a genetic anomaly that was pretty distinctive. So there’s really no good reason to put the family through more anxiety this long after the case has been closed.” Sarah nodded thoughtfully.
    “Let’s get back to the pelvis,” I said. “I’m going to pass these around. Be careful. I know most of you fellows have never handled a female pelvis before, so this is a good time to practice a gentle touch.” That was an old joke; it used to get laughs throughout the room, but something had shifted over the past few years, I’d noticed. The boys would still laugh, but the girls tended to frown now instead. I made a mental note to drop that line from the lecture next year.
    As the pelvises made the rounds of the class, I explained how the face of the