Bone Specialist On Call

A Smithsonian anthropologist applies his expertise to cases of missing children and disaster victims

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"Anthropologists avoid the term 'race,' but law enforcement agencies still refer to four main population groups: white, black, Asian and Hispanic."

Some differences among the groups show up in bone lengths, but most appear in the cranial structure. "A long-headed Nordic skull, for instance, would look quite different from a Hispanic one," Hunt said. "But now there is a lot more genetic interaction, an effect of our transient and mobile society, so you get a blending of these features."

In addition to overall size and shape, there are other variances in skulls. From the nasal aperture you can tell about how wide the nose was, and if the nasal bridge (the spot between the eyes where the nose begins) is preserved, it can suggest a large or small nose. The nasal spine, a bony projection at the base of the aperture, might indicate whether a nose hooked down or turned up.

"Many of these features are literally just skin deep," Hunt said. "The next stage is one of my specialties, craniometric analysis, which is the study of skull measurements. You put about 80 measurements into a computer to get an analytical model that best fits one of the main population groups."

Subtle deformations of bone can even hint at an adult's occupation, as constant use of a certain muscle will literally pull the bone it is attached to, misshaping it slightly and creating, for example, a heel spur.

But how do you go about identifying a child, say one who was abducted as an infant and is found at age 7?

"First of all, you need to understand what happens when the baby fat goes away," Hunt said. "Children grow at different rates, with spurts at various times. At 4 to 6 years they have big heads because the brain case is larger than the face. Then around the third grade, the face starts growing and pretty soon a kid has a bigger face."

Teeth are also a major clue to age, he said. "In the first grade kids lose their front baby teeth, and their permanent ones begin coming in. The teeth of Hispanics tend to grow in four to six months sooner than those of whites.

"Then the mandible (lower jaw) grows and the maxillary (upper jaw) grows," Hunt continued. "By the fifth or sixth grade, the molars are coming in. When you look at photographs of kids that age, many seem to have pointy chins. It's because their lower faces are growing."

Other very noticeable changes occur again between 12 and 14, when the brain case expands and the body length increases, while the facial growth slows down. These changes are heavily influenced by sex hormones. "Before the sex hormones kick in," Hunt said, "it's very difficult to identify a child's sex from the skeleton."


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