Last week I watched the 5th episode of BBC4’s ‘Secrets of Bones’ with Ben Garrod. This episode looked at how the skeletal system was adapted to help animals catch and eat their food. I wrote a summary of this episode in one of my previous posts but I purposely left out one particular feature of the episode as I wanted to go away, look up on it and give it justice. This was how the modern human lower jaw has become smaller over time.
Of course this particular part of the programme was going to be of great interest to me, as I have a particular fondness for the human skeleton and human evolution. As soon as this was mentioned my ears pricked up and I knew I had to go away and find out more. We were introduced to Carolyn Rando of UCL who is physical anthropologist and had been looking at changes in the mandible of humans since the medieval period in London. In Secrets of Bones we were shown four skulls of a Neanderthal, an early Homo sapien, one from the Medieval period and a post-medieval skull. Dr. Rando showed us that the position of our lower jaw has changed over time and from the medieval period where we had an edge-to-edge bite we now have an over bite and that this was all down to our diets.
Of course I had to go off in search of her research in this area and find the published work. This is when I came across her work, along with Simon Hillson and Daniel Antione, ‘Changes in mandibula dimensions during the medieval to post-medieval transition in Lond: A possible response to decreased masticatory load’. The aim of this study was to investigate whether a shift in diet during the Industrial Revolution altered the dimensions of the skull.
To do this a number of skeletons from the late medieval (1050-1550) and post medieval (1550 – 1850) were examined. The specimens were chosen based on age (18+) and whether they were from a site which was in use prior and/or during/after the Industrial Revolution. Using standard osteological methods a mandibular metric analysis was carried out, which included the measurement of the mandibula condyles. Other examples of these can be found on p. 29 of the BABAO Guidelines to the Standards from Recording Human remains.
It was found that changes existed in almost every mandibular dimension between the medieval and post-medieval period. These changes included a reduced mandibular width and ramus height and an increase of the gonial angle (the angle of the posterior corner of the lower jaw). These results fit alongside other osteological observations of the different periods. It has been seen that medieval skulls are generally larger, with more prominent faces and larger mandibles than modern ones. These changes, along with Rando et al.’s work have been attributed to a change to a softer diet in modern populations.
This change in diet was from rough, coarse foods such as wheat, cereals, oats and game to a diet which contained a higher percentage of sugar and fewer vegetables or fruit. These changes were a result of the Industrial Revolution and the consumption of processed food. These changes resulted in less tooth wear for post-medieval teeth and did not promote craniofacial growth development resulting in a smaller jaw.
On the Secrets of Bones Carolyn Rando concluded by saying that this is evidence that humans are still evolving and that we could only guess what would happen in the future. If our diets are going to become even softer, or liquid or pill based, it is difficult to say what will happen to our jaws.
I really enjoyed this episode and especially this feature about changes in humans. We are consistently looking at changes in our, and other animals, evolutionary history but it is fascinating to see something which is much recent. It is also a reminder that modern humans aren’t exempt from the process of change and that we too will adapt to them.
Full citation for the article:
Carolyn Rando, Simon Hillson, Daniel Antoine (2014) ‘Changes in mandibular dimensions during the mediaeval to post-mediaeval transition in London: A possible response to decreased masticatory load’ in Archives of Oral Biology – January 2014 (Vol. 59, Issue 1, Pages 73-81, DOI: 10.1016/j.archoralbio.2013.10.001).
Also avaliable through academia.edu