ForDisc was not, on the other hand, programmed to estimate age. Estimates of age required looking at multiple features of the skeleton and making judgments, sometimes complicated or subjective ones, about the degree of development or maturity in the bones. Those weren’t the kinds of automatic calculations a computer program could perform.
It was my custom, when doing a forensic examination of a skeleton, to keep quiet until my students had examined the bones and offered their opinions. Miranda was used to this, and she required no prompting, beyond a tilt of my head and an inquiring lift of my eyebrows. She began by setting the skull upside down in a doughnut-shaped cushion, exposing the upper teeth and the roof of the mouth. Then she picked up the lower jaw in her left hand, pointing with the little finger of her right hand at the teeth. “So. Both third molars in the mandible are fully erupted,” she said, “which would indicate an adult.” Still holding the mandible in her left hand, she touched her pinkie to the wisdom teeth in the upper jaw, which were small and well below the level of the second molars. “The third molars haven’t erupted in the maxilla,” she said, “but these appear to be impacted, unlikely ever to erupt through the gums. So, his teeth say that he was probably at least eighteen years of age.”
She laid the mandible down and lifted the skull from the cushion that cradled it. Cupping it in her left hand, she used the tip of a probe to trace the pattern of the four sutures, or seams, in the roof of the mouth. One of these, the palatomaxillary suture, ran from one side of the palate to the other, like a line drawn between the second molars. Another, the incisive suture, also ran sideways, just behind the four incisors at the front of the jaw. Two of the sutures ran along the midline of the roof of the mouth: the intermaxillary suture extended from the front of the mouth to its intersection with the palatomaxillary suture, and the interpalatine suture ran from that intersection to the back of the palate. In most subadults—people under eighteen—these four sutures were not fully closed; the joints were still in the process of being filled with new, growing bone. By eighteen, though, they tended to be fused, and during the decades of adulthood, the suture lines gradually smoothed and faded, or obliterated, sometimes disappearing altogether. In 09-02, the maxillary sutures were fully fused, but their lines remained vividly drawn. “The maxillary sutures are fully fused, so we know he was an adult,” Miranda said, “but probably a young adult. Not a geezer, for sure.” I smiled at the way Miranda bounced back and forth between scientific formality and slang.
“I’m gonna save us both some time here,” I said. “I know you know the basics. You’ve probably got the whole osteology handbook memorized by now, right?”
“I’m a little fuzzy on some of the specifics on page two,” she said.
“What’s on page two?”
“All that Library of Congress copyright stuff,” she said.
“I’d be worried if you were wasting brain cells on that. Okay, let’s skip ahead. Instead of talking me through the whole skeleton, show me what you think can pin down his age more precisely.”
“Three things,” she said. “First, the anterior iliac crest.” She pointed to the large, curving edge of the hipbone and used her finger to trace a line near the edge. A faint seam there marked a joint in the broad bone, as if the Creator had decided the hips were a touch too narrow and had gone back and tacked another sliver of bone along the outer edge. It wasn’t actually an afterthought, of course, but an epiphysis, a joint that had remained open while the bones were still growing, then closed when the final growth of adolescence was done. “The epiphysis is completely united, so that suggests he was in his early twenties, at least, and maybe mid-twenties or later. The prime of life, in other words.” She wiggled her eyebrows, and I smiled; Miranda was poised between her mid-and late twenties.
“I’m following you so far,” I said, “even though my brain is well past its prime. Second?”
“Second, the pubic symphysis.” She picked up the two halves of the pubic bone and showed me the face where they met at the midline of the body. “The symphyseal face shows a lot of beveling in the ventral area,” she said, pointing to the rear portion of the joint. “That suggests late twenties or beyond.”
“Are you basing that on the work of Todd, or McKern and Stewart, or Suchey?”
“All of the above,” she said.
I smiled. “Good answer. Third?”
“Third is always most important,” she said. “Third, the clavicle.” She picked up the left collarbone, which was nearer the edge of the table, and indicated a faint, smooth seam near the end that joined the shoulder. “The lateral epiphysis is fully fused, which you’d expect, since the dude’s a grown-up. But the medial epiphysis”—she pointed at a ragged, incomplete seam near the bone’s other end—“isn’t completely united yet; it’s still undergoing terminal union.”
“Leading you,” I said, “to conclude what?”
“To conclude that G.I. Doe was thirty. Plus or minus a year or two.”