Presenting “Microbial Archaeology”

Popularizing a Complex Field in a Media Presentation

[Soundtrack: Dire Straits, “Brothers in Arms“. A perfect melding of lyrics and video presentation. The music reminds me and binds me to memories of soldiers that I served with in the past. Visceral impact. A perfect example of a successful presentation]

When examining the role of microbes (single-celled organisms) in archaeology, it is important to note that this is a relatively new discipline. Because of its multi-disciplinary nature, especially one that overlaps with the rapidly growing fields of biology and molecular genetics, publicly available presentations on this subject have generally failed to keep pace with reports in the academic literature. Nevertheless, some relevant presentations have been made available to the public, including a TEDx talk on DNA as “The Splendid Tapestry“, a brief overview of “Archaeology of the Invisible: Adventures in Genomics“, and the selected presentation, “Microbial Archaeology“, which was delivered to the Max Planck Institute for the Science of Human History in August, 2021.

The presentation was designed for an online delivery, and the benefits and limitations of this approach are evident throughout the presentation. The advantages of a prepared online presentation:

• There is significant time available for preparation and rehearsals; as a result, hand-offs between the two speakers (Drs. Irina Velsko and Zandra Fagernas) are quick and seamless, and there are no interruptions in the presentation
• For the presenters, there are opportunities to review and repeat content to ensure that it is accurately delivered. This can be improved because the speakers have access to scripts and supplementary material
• The viewer has the ability to pause, or “rewind” to ensure that they have understood all of the relevant material
• The presenters have the ability to include literature references to support their argument
• Finally, the presentation is available to a wider audience – it’s an exciting story, and now people can log on and take advantage of it when it is convenient for them

These advantages are balanced by some disadvantages:

• The presenters are clearly not interacting with an audience during their presentation. I feel that having an audience for a presentation provides a more realistic sense of “feel” – the presenters will change expression, intonation, and interaction to engage with the audience, making the presentation more engaging to the viewer. An interactive audience demands honest, humour, a sense of a shared discovery and knowledge – all of these are lacking, leaving the viewer with the feeling that they are being talked at, rather than talked with.
• The presenters have focused on their particular research interests, which is to be expected. However, it is obvious when they stray beyond their knowledge – their delivery becomes high-level, and their comments are glib (“it’s ongoing research, and it’s really cool”) compared to the rest of the presentation

To begin, the presenters have a clear interest in one particular type of microbe – bacteria. They avoid speaking about the archaea kingdom, viruses, plant organelles, diatoms, etc. Thus, the title is misleading, and they fail to really identify the extensive role of microorganisms in the human realm. A minor point, perhaps – but it misdirects the viewers who may be expecting a more balanced presentation.

The first half of the presentation, delivered by Zandra, is focused on bacteria as a causative agent for diseases. The usual suspects are discussed, such as the role of Yersina pestis as the causative agent for the plague. I would argue, however, that what is presented falls under the purview of biological anthropology, and that it does not represent archaeology. The methodologies described focus on extracting and analyzing microbial DNA, but there are no human-made artifact involved. The microbes and their DNA exist solely in the context of an illness, and they do not have any archaeological role outside of that.

Irina, for her part, speaks of bacterial “collectives”, or microbiomes. Micobiomes are isolated from dental plaque (oral biome), bones and teeth, coprolites or paleofeces, latrines, and pottery. Instead of demonstrating novel roles of these microbiomes in archaeology (they can be used to locate or date a site, thy may serve as bioindicators of human activity), Irina emphasize that changes to these bacterial populations reflect host changes, and help us to understand “long-term changes to human condition” that reflect changes to health and disease. Again, microbial archaeology is almost synonymous with biological anthropology; the authors are failing to position their findings as representing a sub-discipline of archaeology.

There are some minor errors during the presentation; for example, Zandra confused the substrate lactose with the enzyme lactase (48 min); however, her discussion on the dairy mystery, and why lactase production by humans has continued when it is biologically not required is interesting . Zandra provides a soup-to-nuts overview of the issue and the methodologies involved, progresses from extraction of the ancient DNA from dental calculus through to sequence analysis of the DNA as well as how this is reflected in changes to the proteins that are expressed.

If I had to pick one issue for improvement, it would be the visuals (slides). Perhaps the presenters were confined by an expected visual layout or expectations for a summer course; however, the slides are almost monochromatic, and boring. White background, green titles and highlights, and black text. Many slides have no images, just a few (or a lot) of words with no interpretations to draw the material out, and make it relevant to the viewer. For example, the cladogram of Y. pestis DNA (min 16:17) is presented, and a couple of the branches are discussed, but Zandra makes only a limited effort to draw out the information, or give it context. Why should we care?, I ask. Fortunately, the image is referenced at the bottom of the slide so that a viewer can look up relevant information; however, it would have improved the presentation if the presenter cited other research in a more meaningful way.

As an introduction to a general summer school audience, this is a solid presentation on limited aspect of the subject matter. The presenter’s interests are clearly focused on microbes and their resultant pathologies. As a result,they undersell the potential impacts of the field of microbial archaeology. They fail to discuss microbes and their role in prospecting potential sites, dating these sites, or understanding human activity. They do not highlight how bacteria may destroy samples, or aid in their preservation.

Though much was said, more remains unsaid.

If I was presenting the same subject material, I would avoid the well-trod ground. There are multiple presentations on tracing plagues by analysis of ancient DNA, so I might acknowledge and just reference this material. Instead, I would focus on microorganisms (if I was keeping the subject broad to demonstrate the breadth of their impact on the field of archaeology) or bacteria. Visuals would be more eye-catching, and would be focused on maintaining a consistent context and being meaningful to the viewer. Most importantly, I would deliver the presentation to a live audience to both improve my delivery, and to catch and respond to the questions and concerns of the audience.