Friday 27 March 2015

How Do We Know If The Bones Belong To A Male or Female?

One day, as you are walking in a park, you notice something on the ground, under a tree. It looks unfamiliar so you went nearer to see if you can see what object it is. So you went nearer and nearer. You saw a pile of dirt and when you looked closer, you startled upon what you had discovered. You had just found a pile of bones. And it looked like human bones. But how do you make sure that they are human bones? And what are you supposed to do when you stumble across some bones?

Well, if you come across bones, and if you see that the skull looks like a human skull, it is wise to give the police a call. The police will secure the area and call it a crime scene so that further evidence can be searched for. The police will call in an expert in bones which is the forensic anthropologist. The first step that the forensic anthropologist will do is to arrange the bones that are collected at the scene. This is mainly to identify if the bones belonged to a human or if it belongs to an animal.

So if the bones belong to a human, what else is needed to be done?

If the bones belong to a human, then other tests need to be done. There are many things that can be concluded when bones are being studied. From bones, we can know the gender of the person, how old is the person and also search for trauma or murder evidence of the victim. Sometimes, we can also obtain some DNA evidence from bones.

How do we know if the bones belong to a male or female?

There are several bones that can be observed in order to know the gender of the person. First, we can observe the pelvic bones, which is basically the hip bones. If you come across a pelvic bone, try and hold it and observe the weight. If it is thicker and heavier, most probably the pelvic bone belongs to a male. A female pelvic bone is thinner and lighter. 

Another thing to observe is the inlet, which is the front of the pelvic bone and the outlet, if you view the pelvic bone from behind. The female pelvic bone has a wider and round shape inlet. Why is that so? Well, it is mainly to deliver babies. If a female has a pelvic opening that is the size and the shape of a male’s pelvic bone, delivering a baby normally, would be almost impossible. The inlet of the male pelvic bone is narrow and normally has a heart shape. 

The forensic anthropologist will also examine the angles of the sciatic notch and also the subpubic angle of the pelvic bone. The sciatic notch is a large notch in the pelvis located above the ischial spine. In females, this sciatic notch is wider whereas in males, it is narrower. The subpubic angle is located at the inlet of the pelvic. It also observes the same pattern; in females the subpubic angle is wider and it is narrower in males. 

Can you guess which one is a male or a female pelvic bone?
The opening that can be seen in this pelvic bone is called the pelvic inlet. If you can observe, these two pelvic bones, have a different shape and size. The one on the left has a more heart shape and the pelvic inlet is smaller whereas the one on the right had a rounder shape and the pelvic inlet is bigger. The one on the left belongs to a male and the one on the right belongs to female. The reason why the female pelvic is rounder and bigger is to enable the process of childbirth.

The subpubic angle also provides clues on the gender of the person. A wider sub pubic angle usually indicates a female whereas a narrower subpubic angle indicates a male. In the pictures above, can you determine which pelvic bone belongs to a female and which one belongs to a male?

Another factor to consider while determining the sex of the person is by looking at the sciatic notch at the pelvic bone. This can be done by looking at the sides of a pelvic bone and observing the angle as shown in the diagram above. A wider sciatic notch usually means that the skeleton remains belong to a female and a narrower sciatic notch indicates that the skeleton remains belong to a male. By observing the pictures above, can you determine which pelvic bone belongs to a male and which one belongs to a female?

What else can be determined by looking at bones?

By observing bones, we can also know the age of the person. This can be confirmed by the process of ossification of the bones. What is ossification of the bones? Well, basically it's like this. We all know that bones are made up of calcium right? (Well, if you don’t know, now you know!) So as we grow older, more calcium will be deposited onto the bones. It's something like the sedimentation process. So in different stages of life, the deposition of calcium onto the bones differ as well. When determining the age of the bones, at the time of death, forensic anthropologists will observe the ossification process on the bones. 

Well, most of the observation of the bones are considered elimination or exclusion methods. Meaning that, by just observing the bones, it doesn’t mean that you can identify the person straight away. In some murder cases, even finding the identity of the victim is like looking for a needle in a haystack. Exclusion methods (like what gender is the victim and how old he or she is) are used to find the smallest details and evidence on the case. This evidence will accumulate and will lead the way to finding the culprit of the crime. 

So next time, if you stumble across some bones, don’t freak out. Just do your part by calling the police and let them and their forensic anthropologists do their part in identifying the bones. 

References :
1. Architecture of the Skeleton

2. Excavations of Skeletal Remains from an Anthropological Point of View by Danny Rinehart

3. Female Vs Male Pelvis by Dr Ren Allen Hartung, Glen Oaks Community College, Michigan

4.   Age determination by Dr Peter Maxwell

5.   Estimation of Biological Age by Epiphyseal Union by Jonathan Lewis. Western Oregon University

Shared by Nensirati Supahan
Guest Blogger

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