Wednesday, August 26, 2009

How Forensic Anthropologists Read Bones

I just thought that this would be of general interest. I know that I had a conversation with a person once who thought a bone was a bone was a bone. Enjoy!

When bones or skeletons are found, they are taken to a forensic laboratory for examination. The job of an anthropologist, a forensic scientist specializing in the area of bones, is to examine the bones, to possibly deduce the gender, age, height, race, as well as medical history and manner of death.

The first step an anthropologist takes during the examination of bones, is to find out whether the bones are human or animal, as sometimes certain animal bones will resemble that of human bones. Once this has been determined, the next step is finding the age of the bones by noting the growth and decay that has occurred in the bones.

Determining Growth Rate:

Teeth that have or have not grown can also reveal the age of the skeleton, as young children will have not lost their milk teeth and at the age of 18, wisdom teeth first appear. During the teenage years, bones become thicker and larger and fuse together in a process known as 'ossification'. Ossification occurs in 800 points of the body and is the best guide to revealing the age of a child's skeleton. An example of ossification occurs in the arms, where at the age of six, the two bone plates form at either end of the outer forearm (radius).

At the 17 in males and 20 in females, the lower bone plate and the radius fuse together and soon after, the upper bone plate and radius fuse together. The bone in the body that finishes growing last is the collarbone, which ceases growth at 28 years. In the bones of the elderly, degeneration begins to occur. Anthropologists will look for tiny spikes that start to appear on the edges of the vertebrae, the wearing of teeth due to age and joints that show signs of arthritis. All of the bones in the body will deteriorate with age.

Determining Gender:

When determining male and female in a skeleton, anthropologists look at the skull and hip bones, as there lie clues to the sex of the skeleton. The skull has three points in determining gender. These are the ridges located above the eyes, the bone situated just below the ear and the occiput, the bone located at the lower back of the skull. The latter two bones are muscle attachment sites, all of which are more prominent in men, indicating greater strength. The difference in hips is very obvious, as a man's hip are narrower and a women's hips are wider, being built for child bearing. However there are smaller differences in other bones, which anthropologists rely on when there is no hip or skull bone.

Determining Height:

Determining the height of a skeleton involves reassembling the skeleton and measuring the length of significant bones. By adding 10-11cm or four inches onto the bone length, it accounts for the missing tissue and muscle. If parts of the skeleton are missing, certain individual bones are used as a height guide. The longer the bone is, the better and more accurate the estimate will be, so the femur is measured first. The human height measures roughly two and two thirds the length of the femur, though it also depends on the race and sex of the skeleton.

Bone Defects:

Disease, injury and birth defects are also revealed in the bones. Birth defects such as spina bifida, some infectious diseases, poor diet and cancer can all be damaging to the bones. In the case of injuries, broken bones and mended bones are easily visible and because they are so easily visible, mended bones can reveal identity. Work and hard labour leave damage such as occupational arthritis, which visibly changes the appearance of affected joints. The skeletal remains of someone who has died a particularly violent death are evident in the bones. Bullet wounds leave round holes, sharp weapons cause chips to be taken out of the bone and fractures in the bones also suggest forms of violence. Distinguishing between fractures that occurred before and after death is difficult, but there are some clues that are helpful. For example, the bones of a deceased person break differently compared to the bones of a live person and healing at the edge of a fracture indicates injuries during life.


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