Dr. Rebecca J. Gilmour

biological anthropologist & archaeologist

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    Cranial Articulation Spiders and MNI

    In today's osteology/bioarchaeology class we worked started to learn about the cranium, with one of the objectives being to think about the cranium in its 3D space, and learn what articulates where. It's definitely a complex set of structures, so I thought I'd break it down into smaller chunks and represent the cranium as a schematic. Once I got going, I saw that there was the potential to also teach about how bioarchaeologists estimate minimum number of individuals (MNI)!

    In preparation for this exercise, I made a number of decks of 12 cards each (sphenoid, frontal, occiput, ethmoid, R maxilla, L maxilla, R zygomatic, L zygomatic, R parietal, L parietal, R temporal, L temporal). I punched holes in the edges of the cards to represent the number of bones that each element articulated with, and stamped each set of cards with a different colour skull. I then shuffled ALL the decks together, and created randomized new decks of 12 cards each. 

    MNI Activity

    Each group of students was assigned a deck of random cards and their first activity was to determine the minimum number of individuals in two ways: 

    1) Using duplicates of the bones listed

    2) By integrating greater specificity but using the colours to suggest different identifying attributes (e.g., maybe the green individuals were infants, the blue individuals were very robust males). 

     

    Cranial Articulation Activity

    Once students had estimated MNI, we sorted our decks out so we each had a single-coloured skull deck.

    Students then worked together to arrange the cards approximately as they might be in life, and then start to find the articulations between the various cranial bones. Students used pipecleaners of varying lengths to join the cranial elements together and identify the major sutures between articulating elements. 

    Image

    McMaster University students in ANTH 2FF3 working to articulate their 'crania'. Images used with permission. 

    The activity worked well overall! The biggest challenge was sorting out the mixed-colour decks to get a full deck of a single colour. I think that using these simplified cards as tools to learn MNI estimation worked really well. It got students thinking about how to tally MNI, without the added complexity of also having to identify the skeletal element. In future iterations of this, it would be useful to then have a 'mixed bag' of bone for students to further apply this knowledge. 

    In terms of articulating our cranial elements in a schematic fashion, the biggest challenge was leaving enough pipe-cleaner space so that the bone-cards could be easily linked. I think this exercise hammered home the interconnectedness and complexities of our crania, but it could easily be simplified by removing splanchnocranial bones to concentrate only on the neurocranium. 

    No photo description available.

    My test schematic demonstrating the connections between each cranial bone using pipecleaners of various sizes. 

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