Thursday, March 10, 2016

Break It Down!: Taphonomic Factors Affecting Parasite Preservation

Greetings Fellow Parasitophiles!

Today, is an exciting day for's the day that I sent my dissertation manuscript off to my supervisory committee for approval before I defend my dissertation here in a few weeks! (Things are getting very, very real!) In celebration of this occasion, I decided to allow myself more writing! (I really am a bit of a nerd sometimes...well, most of the time...and more than a bit...) In trying to decide what to share with all of you, I realized that I had not yet posted about my most recent paper. So, here it is! My first paper of 2016 and the story behind it!

I remember sitting at coffee one Friday, as I do with my advisor for our weekly lab meetings, and discussing some of the various factors that affect the preservation of parasite eggs in archaeological materials. We talked about both the abiotic (non-living) factors, like soil pH and climate, and some of the biotic (living) factors, like the actions of decomposer species. My advisor turned to me and said something along the lines of, "you should write a paper on that sometime".

I found the idea intriguing and thought about it a lot over the next few months. I started working on a manuscript without a clear idea of where I would go with the paper. I thought about how to categorize the major contributing factors that affect the preservation of parasite eggs in both positive and negative ways. I eventually came up with five broad categories of taphonomic (taphonomy is the study of decomposition and preservation) factors that affect parasite eggs existing in archaeological contexts. Those five broad categories were as follows:

[From Morrow et al., 2016]

1) Abiotic Factors--Those non-living things that influence preservation, such as temperature, soil conditions, and the chemical environment in which archaeological materials are found.

2) Contextual Factors--Those reflecting the archaeological context from which we collect parasite data. (i.e. parasite eggs in mummies preserve differently than those in coprolites or latrines)

3) Anthropogenic Factors--Those arising from the interactions humans have with the deposition, manipulations, excavation, transportation, and analyses of archaeological materials.

4) Organismal Factors--Those inherent in the biology of the organisms you are studying, such as the features of an egg that make them more susceptible to degradation or the natural history of a parasite that makes it more likely to be recovered from human feces.

5) Ecological Factors--Those involving the interactions of parasite evidence with other organisms, like decomposers, predators that my ingest parasite eggs, or vectors than can transport the eggs from one fecal deposit to another.

Each of these broad categories could be further subdivided into other categories and can affect the preservation of parasites in both positive and in negative ways. To provide examples of how these factors affect parasite egg preservation, we presented three case studies and discussed these five categories of taphonomic agents for each case.

I won't go into case-by-case detail (you are more than welcome to read the paper if you are interested in that bit), but I will tell you a bit about the three cases. These sites were each near and dear to my heart as they were the first three things that I published about. (One in a special historical journal that hasn't come out yet and two peer-reviewed articles that I talked about in previous posts here and here.)

Case 1: The recovery of intestinal parasites from historic mummies in Vilnius, Lithuania. In the first paper about these parasites, we highlighted a taphonomic issue that only arises with the analysis of mummies.

Case 2: The recovery of intestinal parasites from coprolites recovered from medieval skeletonized burials in Nivelles, Belgium. In the original publication of this material, we discussed an instance of extreme parasitism revealed by the analysis of coprolites from one one of the burials.

Case 3: The lack of parasites recovered during the analysis of embalming jar contents from crypts containing members of the famed Medici family of Florence, Italy. The potential reasoning for the lack of parasite evidence was discussed at great length in the original paper (which is still "in press" after several years). These reasons ranged from taphonomic to cultural in nature and included a discussion of how Medici affluence likely played a role in reducing the risk of parasite infections and in providing the most effective treatments of the time to control for infections had they occurred.

Each of these studies demonstrated a range of taphonomic considerations for the interpretation of archaeoparasitological data. This paper concludes with a discussion of how important it is for researchers to consider taphonomic factors when they discuss their findings. It urges future studies to discuss the five broad categories of taphonomic factors that may have positively or negatively affected the preservation of their parasite eggs.

I have to say that this is probably my favorite paper to have ever published. I love how it turned out. I was happy to have run with a simple suggestion (which my advisor may or may not have expected me to actually follow through with so quickly) and to have created an article that is actually really important for the advancement of the field. I got to work with an undergraduate as a mentor and I got to publish with an international colleague. I feel that this experience has helped me to grow in many ways professionally and I am proud to have such an elegant paper to show for it.

The Moral of the Story
When your advisor gives one of those small comments like, "you should do...." don't brush it off and put it on your list of things to do after you graduate. Take a little time to assess whether or not you could actually gain a lot from working on something might end up with something that is much bigger than you had originally thought it would be! Also, don't let your dissertation be the only thing that you leave with when you graduate. You are much more marketable if you can show that you have the ability to do other things!

Title Shot!