All Things AAFS! Quick Tips

This Quick Tips post is the sixth in the series on age estimation on skeletal remains, if you haven’t read the previous post click here, or to start at the beginning click here. The previous post provides an overview of the pubic symphyseal surface method of ageing, whereas the first post covers the basics.

The method was primarily developed by Iscan and Loth (1986) who studied the metamorphosis of the sternal end of the fourth rib. They found that the metamorphosis corresponds to the age but does vary by sex.

In their study they examined the “form, shape, texture and overall quality” of the sternal end which is found at the anterior (ventral) end of the shaft. This end is a roughened, porous, cupped oval surface which attaches to the cartilage attached to the sternum. From this they were able to define a series of phases that depict the metamorphism of the sternal rib end over time.

Anatomy of the rib cage. This method was primarily developed by Iscan and Loth (1986) who studied the metamorphosis of the sternal end of the fourth rib. They found that the metamorphosis corresponds to the age but does vary by sex.

At the start the sternal end is flat or billowy with regular and rounded edges, and over time its rim thins and become irregular, with the surface porosity increasing, and the end becomes irregular. This method can be applied cautiously to the 3^rd or 5^th ribs as well, but not the others.

References:

Iscan, M.Y., and Loth, S.R. 1986. Estimation of age and determination of sex from the sternal rib. In: K. J. Reichs (ed.) Forensic Osteology: Advances in the Identification of Human Remains. Springfield, Illinois. Pg 68-89.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

If you’re new to the realm of archaeological, anthropological and forensic sciences (AAFS), or are a student needing sturdy and reliable references, or wondering “what archaeology or anthropology textbooks to buy?” Check out our new ‘Useful Literature’ page!

There is a relatively easy way to see whether a fracture to a skeleton is ante, peri or even post mortem. It is essential to detail and deduce which category a fracture falls into, as this is very important to see whether the fracture had played a part in the person’s death.

To first classify a fracture, we need to understand what the different categories mean. Some of you will already know these terminology, but here’s a quick reminder;

If a fracture is ante-mortem, it means that the fracture was made before death of the persons.
With peri-mortem fractures, it means that the fracture was received at or near the time of death of the persons – so could have been the fatal strike.
Post-mortem fractures are fractures that have been received after death, so during the time from death to the time of recovery. These fractures are usually from excavation processes, dismemberment, or even natural processes (soil, animal and plant activity).

You will be able to determine if a bone fracture was ante-mortem due to there being signs of healing which is shown by cell regrowth and repair.

With peri-mortem fractures, the person died before the healing started to take place, but the fractures will still contain the biomechanics that are present in ante-mortem fractures.

Post-mortem breaks tend to shatter compared to peri-mortem breaks which splinter, this is because bones which are in the post-mortem stage tend to be dry and rather brittle. Another big indicator of a fracture being post-mortem is the difference in colour.

The ‘Quick Tip’ that my applied anthropology lecturer taught me on how to easily distinguish between peri-mortem and post-mortem is to look at the fracture and decide; is it a clean break, as if you were breaking in half a bar of chocolate? If it is, then the fracture is most likely to be a peri-mortem fracture. If the break looks crumbly, like breaking a biscuit in half, it’s post-mortem fracture. Obviously this tip is not the most scientific, but it’s an easy way to begin your distinguishing process.

Skull with signs of post-mortem fractures. This photo is from a practical lab session.

If you look at the photo above it illustrates a post-mortem fracture. You can determine this easily due to the colour difference on the edge of the fracture, where it is a much lighter colour compared to the rest of the skull and the crumbly nature of the cut.

References:

Most of this is my own knowledge that I learnt during my degree in my anthropology lectures/lab practical sessions. But if you’re looking for a published journal check the one below. It is very informative and easy to understand if you’re a beginner in the world of anthropology/archaeology! It also highlights some problems that can arise when distinguishing trauma, it’s really interesting!

Smith, A.C. 2010. Distinguishing Between Antemortem, Perimortem, and Postmortem Trauma. Academia.edu. Available from here in .pdf form!