A Bone to Pick: Basics of Palaeopathology

Palaeopathology is the study of ancient diseases, trauma, disability etc. by examining human remains. Like forensic anthropologists, palaeopathologists also work with a degree of uncertainty. When most of our data comes from the examination of human bones, there are specific limitations we must contend with.

Bone can only react in one of two ways when something is wrong; the bone tissue can either grow or it can resorb. Both bone growth and resorption are normal and happen throughout your life–this process is caused by cells called osteoblasts and osteoclasts–but disease, trauma, and malnutrition can create abnormal formations of bone called lesions. The lesions formed by excess bone growth are called proliferative, and lesions formed from resorption are called lytic.

Each disease will affect bone in slightly different ways, that is if they affect the bone at all. But because of these limited types of bone reaction, certain diseases can look very similar. For example, scurvy and cribra orbitalia are both characterised by lesions in the orbitals (eye sockets) which can be hard to distinguish without training and practice.

Scurvy is a metabolic disease caused by a lack of vitamin C. As our bodies need vitamin C to form collagen, and our blood vessels require collagen for structural stability, the capillaries in the eye sockets of those with scurvy begin to bleed. The presence of blood in the orbit stimulates new bone growth and creates proliferative lesions.

Cribra orbitalia, which is often attributed to iron difficiency anaemia (rightly or wrongly is still up for debate), is charaterised by lytic lesions in the same area.

Below are pictures of both conditions, can you tell which one is which?

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These are excellent examples of each type of lesion, so this is pretty much as easy as it gets. Most presentations of these lesions will be less pronounced, more fragmented, or both. Which makes our job a bit harder.

You can check your answers and access the original images here and here.

Too easy? Let’s try this one:

Do these skulls all feature the same pathology? Or are there two pathologies? Or even three?

What differences in these lesions, if any, can you observe?

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Hint: there are two diseases and one trauma featured above. Can you tell which ones are which?

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The first skull is an example of caries sicca, a major sign of venereal syphilis.

The second skull has a penetrating gunshot wound to the forehead.

And the third skull is an example of lesions associated with calvarial tuberculosis.

We can differentiate all of these conditions by looking at the remodeling (healing) process, or the origin of the lesion–for example, did it start inside the skull and move outwards or start on the surface and move inwards?

Another practical issue palaeopathologists face is something called the osteological paradox.  And while this term seems big and scary it’s actually pretty simple.  In order for a disease to show up in the bone, it has to be around long enough in a living body. We call this kind of disease chronic.  If a disease is too deadly and kills a person quickly, it won’t have time to affect the bone.  We call this kind of disease acute.  Therefore, when we see an individual from an archaeological site with a pathology, we know that actually this individual was probably one of the healthier ones. So ironically, when palaeopathologists study pathology, we’re usually studying the healthier individuals of a community.  This can be problematic when trying to ascertain general health trends and quality of life.

 

If you’re interested in the diagnostic criteria for any specific diseases or want more info about bone biology, keep your eye out for upcoming posts or comment below!

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