Forensic evidence – by the foot
Crime scene investigators dust for prints to identify criminals, but it turns out that patterns inside the foot bones of human remains also could contain clues about a person’s identity, thanks to a tool from another dusty profession: archaeology.
Combining high-resolution imaging with geographic information system (GIS) software, commonly used to map objects at archaeological digs, reveals individual variations in human bone microstructure, a study shows.
When unidentified human remains are discovered, the foot bones are sometimes intact because they were protected by the deceased person’s shoes, said David Rose, a captain in The Ohio State University Police Division and a doctoral student in anthropology at the school. Any information about the person, such as age, sex or body size, could be useful as law enforcement officials attempt to identify the body.
A study shows that imaging and analysis of a human foot bone could provide information to help law enforcement identify human remains. This polarized microscope image captures the cross section of a metatarsal, or long foot bone. The red/black dots indicate sites where geographic information system (GIS) software tracked the presence of osteons – microstructures influenced by the load placed on bones over time. Courtesy of David Rose.
“Our bones adapt to the load that’s placed on them. Patterns of tension and compression show up in our internal bone structure, and this software lets us look at those patterns in a new way,” Rose said.
It’s not altogether different from finding patterns at ancient burial sites. “We try to identify important clusters of objects such as household tools or agricultural tools that would indicate patterns of human activity,” said co-author Julie Field, assistant professor of anthropology. “Based on certain scientific criteria that you give it, the software gives you a statistical measure of whether the objects you’re looking at actually constitute a cluster.”
In their inquiry, the researchers studied the cross section of a metatarsal – long foot bone – from a deceased woman. Rose used microscopy to capture an extremely high resolution image of the bone cross section and then used ArcGiS software to map the location of microscopic structures – osteons – within the bone.
Osteons are created over time to fix small cracks or maintain mineral levels within the blood. The loads placed on bones over a lifetime affect the size and shape of the osteons as well as the direction of collagen fibers from which they are made.
The deceased woman’s metatarsal bone reflected the predicted pattern of normal bone alteration over time.
During her lifetime, the force of walking would have formed concentrations of certain types of osteons along the top and bottom of her foot – where signs of foot flexure and compression would be expected.
“Dave’s work allows us to visualize, analyze and compare the distribution of microscopic features that reflect the development and maintenance of bones, which we can relate to skeletal health and disease – for example, bone fragility in osteoporosis,” said co-author and anthropology professor Sam Stout.
Many more bones would have to be studied before GIS software could provide meaningful insight into bone biology, Rose said. “The real advantage to this method is that it offers a new scale for the study of human variation, offering to shed light on how we adapt to our surroundings.”
The research was published in the American Journal of Physical Anthropology (doi: 10.1002/ajpa.22099).
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