Updated: Aug 25
We are so excited to announce the American Journal of Human Biology has published an article by one of our very own Principal Investigator and Bioarchaeologist Extraordinaire, Dr. April K. Smith! That’s right, folks, they published some of her incredible dissertation, Exploring the Effects of Weaning Age on Adult Infectious Disease Mortality Among 18th–19th Century Italians. Dr. April Smith has not only worked in academic and private-sector archaeology for 10 years, but she is also a Bioarchaeologist with extensive experience with the analysis of human and faunal remains from archaeological contexts in Georgia, South Carolina, and, now, Italy!
While studying within the Anthropology division at the University of Georgia, Dr. April Smith and her peers Laurie Reitsema (University of Georgia – Anthropology), Antonio Fornaciari (University of Pisa – Paleopathology), and Luca Sineo (University of Palermo – Science and Technology, Biological, Chemical, and Pharmaceutical) received a grant from the National Science Foundation (NSF). And just like that, April was off to Italy!
April and her team worked in the towns of Italy and hunkered down in the labs of Georgia to investigate the health stories and weaning ages (the age at which an infant stops drinking breast milk and is introduced to alternative foods) of nineteenth century cholera victims through the simple examination of the victims teeth (yes, you read that right). “Teeth are great little reservoirs of information!” April says with a true researcher’s enthusiasm. “I’ve always been interested in disease and infection,” April continues, “so I knew I wanted to do something with diet and disease.”
But before they could examine these teeth the team had to go through the steps of the scientific method. (Remember that old thing from 5th grade science class?) Let’s go over the steps together, 1. Observe, 2. Question, 3. Hypothesize, 4. Predict, 5. Test, 6. Repeat!
Observe and Question
April’s team first observed “how early childhood stress (from weaning) affects morbidity and mortality later in life,” claiming, “stressors in early childhood that weaken the immune system may result in increased susceptibility to infectious disease in adulthood” (title page). In addition, April says, “weaning is one of the earliest potential periods of significant stress in early childhood.” April went on to explain that it is because “there is not a whole lot of research on ‘the role of early childhood stress in mortality from infectious disease’” that there is still a lot of uncertainty around the subject which “has caused a lot of conflicting results, especially in bioarcheology.”
It all boils down to one question: Does the stress of weaning affect your immune system and make you more susceptible to disease later in life? April and her team set out to find the answer.
Hypothesize and Predict
The team tested their hypothesis for the Developmental Origins of Health and Disease (DOHaD), which states that the stress induced by weaning can cause the infant to become more susceptible to external diseases (such as cholera) or even nutritional effects (such as chronic issues with metabolism) as an adult. So, to Keep-it-Simple-Xplorers (KISX), April and her team predicted that the nineteenth century Italian victims of cholera likely experienced higher amounts of stress during certain ages of weaning, supporting their theory that there is a correlation between weaning and the immune system.
But what about the teeth? Ah, yes, let’s test the theory and find out!
But first! A quick collection of data.
The team collected their in-field data from the Italian towns of Benabbio, Tuscany and Alia, Sicily, where nineteenth century populations had been severely affected by cholera. These two towns even contained massive cholera gravesites, such as at Camposanto Vecchio. Some were located in cavern tombs and others in medieval churches outside of town, “some with over 300 burials!”
Within these towns, the team then collected the teeth of both the general public and the cholera victims to compare their nutritional and weaning stories. April says, “the lyme would preserve the bones beautifully.” (Which, of course, is great for research, but not for the faint of heart).
It took the team a couple months to collect the in-field data, and they spent the remaining year of research at the Biological Anthropology Lab Complex and Center for Applied Isotope Studies at the University of Georgia.
To test our theory, the team had to think like forensic scientists and collect (yep, you guessed it.) teeth!
The reason for this collection of teeth was simple — it was based on the understanding that, as stated by our researchers, “weaning can be reconstructed in archaeological populations using stable carbon and nitrogen isotope analysis” (page 5). Now this may not be common knowledge to the rest of us muggles, but to our team of witches and wizards, it was known that a stable isotope analysis could be performed through the examination of bone or teeth to reconstruct even ancient nutritional habits.
That’s all very interesting but, for all of us muggles at home, what the heck are isotopes, and what is stable isotope analysis? Don’t worry, we had to rewrite, consult, and rewrite this article multiple times to even understand it ourselves!
Carbon and nitrogen are isotopes (chemical elements with the same number of protons and electrons but different numbers of neutrons) that are transferred from various foods we eat (yes, including breast milk). Stable isotopic analysis is a process used to identify these isotopes by something called isotopic markers.
Basically, April and her team studied the nitrogen and carbon isotope levels to provide insight into the nutritional and even weaning habits of the cholera victims via these isotopic markers (AKA carbon and nitrogen signatures).
Neato! But we are still a little confused about what isotopes tell us about our nutritional habits? That’s okay, we asked April to break it down further.
As April explains it, “the carbon signature tells us what kinds of plants people commonly ate” such as corn or wheat (AKA carbohydrates) and “the nitrogen signature tells us about the kinds of meat people commonly ate” (AKA proteins). It is during breastfeeding, April explains, that the child consumes the nitrogen from the milk. As the weaning process occurs and the child begins to eat different types of foods, the nitrogen declines over time. Therefore, “where nitrogen levels are no longer elevated, this is when the weaning ends. When the baby's nitrogen levels look like the mother's levels, then we know weaning is complete.”
Okay, we think we are getting it. So how did you go about this stable isotopic analysis? And please, show your work. Yes, sir!
“It took months of overlapping teeth samples,” April says, “four batches (five teeth each) at the same time” and involved the act of chopping up teeth and putting them in vials of acid. (Real mad scientist stuff!) “We took the tooth samples … like the whole tooth, cutting from crown to root” April explains, and “removed the enamel so that no mineral components were left except dentin,” (the main supporting structure of the tooth that is made up of living tissue and contains collagen).
Don’t grit your teeth, everyone, we have provided a diagram for visuals.
“Finally, we extracted only the collagen (a protein that strengthens teeth and gums and contains isotopes) from the dentin layer and ran an analysis to look at the isotopes (carbon and nitrogen found within the collagen) to estimate the age-at-weaning completion.”
I think we speak for everyone when we say, our collective brain hurts. So, go on, what were the results of all this teeth analysis, we are chomping at the bit!
Findings and Results
Well, to everyone’s surprise, there were no big mortality differences between the general population and the cholera victims in consideration of their age-at-weaning completion. The team did find, however, that the tested regions across Italy had a tendency to complete the weaning process all around the same age, between 2 and 3 years. Apparently, “the average age-at-weaning for all individuals with weaning curves is 2.8 years” (page 15). Additionally, their research found regional and dietary variations between the four different towns across Italy “with a wider range of varied nutrition along pilgrimage routes with trading.”
Conclude and Hypothesize Again!
“Overall,” April concludes, “our research highlights the importance of cultural context in dietary and weaning studies” and, more specifically, “demonstrates the ubiquity of weaning practices across Italy during the nineteenth century.” The team could also not completely rule out their hypothesis. It could still be true that, “individuals with below average age-at-weaning exhibit a statistically significant lower survival probability compared to individuals with above average age-at-weaning or no weaning curve.” (page 15). However, as the results conclude, “weaning practices were not a predisposing factor for cholera mortality in this study.”
Well, even though the research team didn't get the results they had originally hypothesized, they were able to confirm some unique information across citizens of nineteenth century Italy! Can you believe all this information was collected by the simple, yet highly complex, study of their teeth?! Science, are we right? At TerraX, we are just glad there are scientists like April doing the underrated work for us! It’s research like April’s — ahem, Dr. Smith’s — that keeps us learning and allows us to better understand our own bodies, history, and culture.
If you’d like to get into the details of April’s research you can read a summary here or purchase her work here. As always, be sure to check out future endeavors by our impressive and expansive team on Facebook, Instagram, and LinkedIn. We will be sure to keep everyone in the know on all of TerraX’s accomplishments and side hustles.
Catch you later, Xplorers!
— The TerraX Team