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Forensic Anthropology

The American Board of Forensic Anthropology defines forensic anthropology as the application of the science of physical anthropology to the legal process. The identification of skeletal, badly decomposed, or otherwise unidentified human remains are important for both legal and humanitarian reasons. Forensic anthropologists apply standard scientific techniques developed for the purpose of physical anthropology to identify human remains, and to assist in the detection of crime. Forensic anthropologists frequently work in conjunction with forensic pathologists, odontologists, and homicide investigators to identify a decedent, discover evidence of foul play, and/or the postmortem interval. In addition to assisting in locating and recovering suspicious remains, forensic anthropologists work to suggest the age, sex, ancestry, stature, and unique features of a decedent from the skeleton.

     All forensic anthropologists must follow a set of legal guidelines and procedures, with the first step being the determination of the origin of the remains, or more simply put - is it human? Following these procedures, they must determine 
1. Are the bones human?
2. How many individuals are represented?
3. How long ago did death occur?
4. What was the person's age at death?
5. What was the person's sex?
6. What was the person's race?
7. What was the person's height?
8. Are there any identifying characteristics such as old injuries, disease, or unusual features?
9. What was the cause of death?
10. What was the manner of death (homicide, suicide, accidental, natural, or unknown)?

    For a forensic anthropologist, when all that remains of a person are small bits of bone, these are the questions he or she must ask. Human bones that are whole and still attached to each other are simple to identify, but when bones are broken, burned, chewed, or spread over a large area, identifying them becomes rather difficult.

     "Is it human" is a perfectly sensible and legal question since, the Smithsonian Institute in Washington D.C. estimates that 10 to 15 percent of all bones that are presumed human are really animal. The process of weeding out that 10 or 15 percent saves law enforcement agencies from going through those useless investigations. When a bone or set of bones comes in from the police department, the forensic anthropologist has to study and identify it, meaning he or she has to know both human and animal bones. Expertise in both human and animal anatomy is one of the most important strengths of the forensic anthropologist.

     The forensic anthropologist must first compare the unknown bone to a reference collection, a set of skeletons of animals common to the area. If the unknown bone is not matched to one in the collection, the forensic anthropologist must then consult other specialists such as an ornithologist (one who studies birds). If the bone is a fragment, such as from a skull, the scientist may try to fit the bone to a human reference skull, trying to match the contours of the bone fragment with those of a complete skull. In the case that there are multiple fragments, he or she must first piece them together like a puzzle.

     An examination of the epiphyses of the long bones can provide a good indication as to the species origin of the bone because of the angle of the joint. Human leg bones are attached to the pelvis at an angle that allows us to walk upright on two legs unlike animals that walk on all fours. If the epiphyses have been broken off and only the shaft of the bone, called the diaphysis, is left, then an examination of the inside of the bone will aid investigators in discovering what kind of animal if came from. 
Bone is not solid but has a dense and hard outer layer with a spongy interior. The thickness of the outer layer, called the cortex, compared to the thickness of the total bone can indicate whether a bone is human or animal. In an adult human, the cortex is about a quarter of the total thickness of the bone. Large mammals such as bears have a thicker cortex, roughly a third total diameter, while birds have thin bones, their cortex is only about one eighth total diameter. 

     Inside living bone there is a spongy material called cancellous tissue. Within this tissue are osteons, which are round tunnels that hold blood vessels and nerve fibers and carry nourishment to the surrounding bone. In humans, osteons are scattered randomly throughout the tissue. But in most animals the osteons are lined up in rows, so that a cross section under the microscope looks like a stack of bricks.

     Well, just why is quick positive identification of an unknown bone important? One example comes from Colorado Springs, where a dog gnawed on a bone until the owner became curious as to where the dog had gotten the bone, went to take it away. As the owner got closer, he saw that the dog was chewing on what looked like a human foot. When the police where called to investigate, they found that it was indeed a foot, but there was no soft tissue left, and the last row of phalanges were missing, making it look very much like a human foot. The police began to launch a full-scale search for the rest of the body throughout the neighborhood. When a forensic anthropologist was called in the next morning, he saw that the foot was short, with no arch, and was missing not one row of phalanges but two rows. The forensic anthropologist concluded that the foot was from a black bear, and the search for the body was called off.

     There are a number of animal bones that are routinely mistaken for human remains, such as the foot bones of a polydactylous pig (pig with five toes), or the rib cage of a sheep. Once a case comes to the attention of the police, it has to be thoroughly checked out no matter how bizarre, and it is not enough to say the bone is not human; the forensic anthropologist must then name the species it belongs to. Eighty five to ninety percent of the time the species does turn out to be human, and then the search begins. Who was this person and how did he or she die?

Postmortem Interval: The amount of time elapsed between the examination of the body, and the time of death.

Epiphysis: A part of the bone that ossifies separately and later becomes ankylosed to the main part of the bone.