Bone Stories: Forensic Anthropology for Mystery Writers
The table is littered with bones. A yellowed femur rests near a skullcap, sawed off with surgical precision. A jawbone, ripped from the rest of its skull, hangs open in an eternal scream. Toward the end of the table, a set of sharp instruments reaches out with long, metal fingers.
This may sound like a horror movie, but I’m actually describing the hands-on display at the RMFW & RMMWA September event. Last Saturday, I joined many other writers at the Sam Gary branch library for a crash course in forensic anthropology, led by Dr. George Gill.
We mystery writers know that bones have stories to tell. The question is: how can we find the clues to excavate these stories? As Gill explained, there are four “core pillars” of anthropology that he attempts to glean from skeletal remains: age, sex, ancestry, and stature. For decades, these were the primary pieces of the puzzle forensic anthropologists provided to law enforcement. But, as DNA testing has gotten better and cheaper, a fifth puzzle piece has jumped to the top of the list: trauma.
Through a fascinating and hands-on presentation, Gill showed us how to gather these clues for our own stories.
How do forensic anthropologists determine age at the time of death? One method is to measure the bone using a digitizer or caliper, and then cross-reference the length in a table of age ranges. You can also look at bone fusion to determine age in older children and young adults, and bone erosion in older adults.
To illustrate this last point, Gill used a skull with teeth that had eroded down nearly to the gum line. This was a Native American woman, he explained, and a combination of diet and the hide work she had done while alive had worn down her teeth. By looking at diet and dental erosion from others in that region, he could make a fairly accurate estimate on her age of death.
Determining biological sex, Dr. Gill explained, is “more exciting.” On a skull, you can look for specific features. The brow ridge is typically large and pronounced in males and smooth and less developed in females. Similarly, mastoids (rough surfaces behind the ears) and the nuchal ridge (where neck muscles attach at the base of the head) are larger in males. “I guess we’re supposed to be doing something more with our heads than we have the past million years or so,” Gill joked.
Other bones that are useful for determining sex include the femur, clavicle, and breastbone. While size varies across populations, you can generally determine sex from the length of these bones.
Because of the ways different ancestral groups have evolved over time, anthropologists can look at specific features in the skull to determine ancestry. Members of an ancestral group typically share a similar head shape, nose opening size, and palate shape.
In some cases, Gill was able to use these distinct features to identify a person’s ancestry even more accurately than that person’s own records.
Perhaps the most straightforward of the “core pillars” is stature. Forensic anthropologists use an ostimetric board to measure the length of a long bone (like a femur) and then plug that number into a formula based on sex to get the person’s height. Gill joked that this number is often more accurate than the person’s own records, since vanity and footwear tend to inflate our numbers on drivers licenses and doctor visits.
Now that DNA testing often answers the questions of age, sex, ancestry, and stature, the big area forensic anthropologists are increasingly helping law enforcement is that of trauma.
With gunshot wounds, you can look at the diameter of the entry wound to determine the maximum size of the bullet. You can also look at fracture patterns to determine entry and exit wounds. Entry wounds will have an internal bevel with a distinctive fan shape, while exit wounds will be larger and more jagged with an external bevel.
Some wounds can be harder to determine. It can be hard to tell, for example, if someone has fallen off a high place or been hit with a blunt instrument. This is where forensic anthropologists have to know how to assess antemortem, perimortem, and post-mortem fracturing. A fracture from long before the person’s death would show clear signs of healing. Similarly, cuts and marks in bones will look different depending on how soon after the person’s death they were made and how much moisture was in the bone.
Gill wrapped up our session with some fascinating example cases he’d worked on. My favorite part of the day, though, was getting up close to the bones. Let’s just say my styrofoam Halloween decorations no longer seem up to snuff.