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The Sci-Files is hosted by Mari Dowling and Dimitri Joseph. Together they highlight the importance of science, especially student research at Michigan State University.
Welcome to the SciPhiles, an impact 80 nine FM series that explores student research here at Michigan State University. We're your cohost, Marty Dowling
Dimitri Joseph:And Dimitri Joseph.
Mari Dowling:Hi, Aubrey. Thank you for joining us today. Could you tell us a little bit about yourself and your research?
Aubree Marshall:Yeah. Thank you for having me. My name is Aubrey Marshall. I am a fifth year PhD candidate in the Department of Anthropology. Specifically, I study bioarchaeology.
Aubree Marshall:My research focuses on understanding ancient diet and health in Belize.
Dimitri Joseph:What populations are you studying?
Aubree Marshall:Great question. So I study a population specifically from cave and rock shelter sites from Central Belize, the Maya, specifically. Maya is in Mesoamerica, so Mexico, Honduras, Guatemala, and Belize. Belize being where I work.
Dimitri Joseph:What makes the Mayans and the Aztecs or specifically the Mayans for you so important?
Aubree Marshall:That is a fantastic question. The Maya are really interesting because there's a lot to learn first off, but there is some, I wanna say almost like misrepresentation of the Maya in general. So thinking about the Maya, a lot of people just assume that they are are an ancient population. So I do study ancient populations, but the Maya are a people that are still alive today. So there's a long history and the Maya from the time of the pre classic to the terminal classic, which is about 300 BC to 08/, were growing.
Aubree Marshall:And then there's a collapse. And so during this collapse, there is a period of depopulation of different sites. And I say depopulation, it's more like population movement and decentralization of power. And this all happens before the Spanish get here. When the Spanish arrive, they are walking around and of course, in their words, they're seeing like all these abandoned temples, which is not incorrect.
Aubree Marshall:There are a lot of temples in like Central Belize that are actually abandoned, but it's not necessarily that they just disappeared. Like, several people could think of if they don't know the region or don't know the history, they actually just moved. And again, there was that decentralization of power as well. A lot of the population seem to have moved on the coast. Like, you still have access to trade through waterways and stuff like that.
Aubree Marshall:So
Dimitri Joseph:You you're the first archaeologist that we've ever had on this show. Thank you for giving me just a a foundation of what archaeology research is like. And so from what I'm understanding, one, we have this ancient civilization, and they went through this specific time where there was a a drastic change in their population, and then there was a drastic migration that's associated with it. And there are these specific time periods that are very interesting.
Mari Dowling:Mhmm. And
Dimitri Joseph:for the last part, we have what you introduced for your research, which is diet and health. How do you put all of this together, and what are you trying to answer?
Aubree Marshall:It's a great question. So I'm really interested in the specificity of diet and how different aspects of social identity actually affect access to diet. With skeletal remains, it's always a little bit of a guess. But we do have standards of how to figure out an individual's age, their osteological sex, so male versus female, what they're born as, and socioeconomic status based off of grave goods. And so what I'm doing is I'm looking at the specific proteins from animals and plants that are found in the dental calculus.
Aubree Marshall:I'm also looking at age, so specifically older adults versus young adults and male versus female.
Dimitri Joseph:This is a very basic question, but what's a dental calculus?
Aubree Marshall:Yeah. That's Dental calculus is the mineralized plaque or tartar that's located on the surface of our tooth. If you think about your dental hygienist and when they're scraping your teeth, they scrape mine always. So that actually is what I'm studying.
Mari Dowling:In terms of plant matter and proteins, what specific proteins are you measuring in this research?
Aubree Marshall:The short answer is is that basically what I'm doing is I'm taking the extracted proteins from the calculus and I'm sending it to a person to put through a mass spec. And then all of the data that comes back from that, I'm putting into a genetic database. And then it'll give me information on the most likely protein sources. So sometimes you can have proteins, of course, that could be coming from different places because of the preservation of the proteins itself.
Mari Dowling:So if I'm understanding correctly, you basically get the proteins from the calculi. You analyze them using a mass spectrometer, which tells you what the makeup is of the protein, which you can match to a database Yes. And see what it is. So then I guess my next question would be what foods have you found that the ancient Mayans were eating?
Aubree Marshall:So we're still waiting for the protein analysis specifically, but some things we always expect is corn. This is a very big thing that people talk about in the Maya region. So corn being a c four plant, we can see chain yes. What is the c four plant? Good question.
Aubree Marshall:So when you're talking about plants and their photosynthetic pathways, we have three main types. We have c three, CAM, and c four. And so what we see in the Maya region is that earlier populations were eating a lot of C three plants. And then with the introduction of maize and agriculture, we're seeing a lot more C four in there. Maize being the main one, but there are other c four plants like amaranth, which was a very big plant for the Maya people, and we actually do have a very distinct microbotanical that can come from that.
Aubree Marshall:One of the things I really wanted to get out with my research is that c four plants are not just maize. There's like a super long list that actually was published, and it includes several plants from the region that are CAM plants and c four plants, which are also drought resistant, which is very important because there were a lot more drought periods during the terminal classic, which is when we're starting to see that decentralization of power and population movement. And was at one point considered, like, the one thing that caused the Maya to collapse. However, now we know it wasn't one thing. It probably was several.
Aubree Marshall:But droughts could have actually played a role, which means that you're looking at plants, not just corn. Corn is not gonna be the only thing contributing to the c four signatures. But when we're looking at isotopes of bone and teeth, we only get the generalized data of c three versus c four plants in the bone, if that makes sense, which is where my research comes in with the food specificity and food access.
Dimitri Joseph:From what I'm understanding, you're you're allowing us to more accurately resolve the protein sources
Mari Dowling:Mhmm.
Dimitri Joseph:That may be associated with Mayan history.
Aubree Marshall:Yeah. So proteins and the plants.
Mari Dowling:Before we go a little bit further, could you elaborate a little bit on what a microbotanical is?
Aubree Marshall:So they are tiny plants is the basic version, but there are three specifically that I'm looking for in my research and that includes something called phytoliths, which are like little silica based microbotanicals out of different parts of the plant. Then we have pollen, and we also have starches. Starches is a big one especially when you're looking at maize. You can find well, when you find maize, you're gonna find starches in the calculus. Then I can imagine that
Mari Dowling:you're studying these specific microbotanicals and proteins because they're able to be preserved in the calculi. So have you guys thought about, you know, are they eating things that maybe aren't able to be preserved and how do you account for that? They are for sure.
Aubree Marshall:And and it's not just that. There are plants that won't have identifiable micro botanicals with them. So these are things I have to think about in the research.
Dimitri Joseph:Do you have any early results that shows any disproportionate distributions of who's eating the meat Mhmm. Versus who's not allowed?
Aubree Marshall:Or So I found potentially pumpkin in calculus, and I found, like, maize. And there's also other things that we found, which is really cool, including, I think, fiber and charcoal and stuff like that or carbonized material, which is really cool because some of these things, you know, we can interpret as like occupation in terms of the fiber and stuff like that. But there has been previous research done on my sample with isotopes specifically, and there does seem to be some differences in between groups.
Dimitri Joseph:You also mentioned that one of the variables that you're interested in is their socioeconomic status. Mhmm. How do you go about defining the class of the individuals that you excavate?
Aubree Marshall:So there are a few ways. So in the caves and the rock shelters, there does seem to be signs of differing socioeconomic status. A lot of it based off of grave goods. For example, there is an individual that we found last summer that we believe was a scribe. What made us think that he was a scribe?
Aubree Marshall:So I say he because his osteological features suggest that he was most likely a male. And he was buried with what we think were ink pots, which I did actually collect samples from inside of that little shell to see if ink will come back, a stylus, and some jewelry. I the one that really got us to think he was a scribe was the stylus in the potential ink pot. And we did actually, that summer, find the first ceramic with writing on it, and it was in my unit. And I just have to put it out there because I was so excited.
Aubree Marshall:And it does say on there, this is the drinking vessel of, and it has the beginning of a name. So it was really it was a cool find.
Dimitri Joseph:Yeah. This seems like a very collaborative and team oriented research because, one, there's the excavation. Two, you need someone that can translate these ancient forms of communication. Could you give us a little bit of insight on how your research team works?
Aubree Marshall:So in the field, we have a lot of different archaeologists who do specialize in different things. So I'm a bioarchaeologist. Right? So me and my advisor focus on ancient human skeletal remains. There are also people who specialize in architecture.
Aubree Marshall:They'll look at buildings and they can begin to interpret when that building was built. If the structure is falling down, they can kind of almost rebuild it. We have architectural people. We have ceramicists. So we have people who actually look at the ceramics all day, and we have lithicists who look at the, like, stone tools and stone deb it's called debitage, but it's the leftovers of when you're making a stone tool.
Aubree Marshall:So we have all of these different people who specialize in particular things that come together, and each of us can do our part to analyze what we have available and then come together and be like, okay, what does this mean overall? Right? So what can we learn using each of these different little lines of evidence about this particular community?
Mari Dowling:I can see that this is a very interdisciplinary project, and you're all working together. But I can imagine that you have different projects and goals in mind. So is there a common goal that you're all working towards?
Aubree Marshall:We all come together, and the permits have, like, a particular research plan in place. So there is a single research plan that we all do work on. For example, this last season was working on Structure 14 to understand mortuary practices. But we also dug into a different structure to get an understanding of what that building was used for. In the field, I
Mari Dowling:am
Aubree Marshall:a bioarchaeologist, but I do archaeology. So I am helping lead excavation units and stuff like that. So I am doing my part and then afterwards in the lab is whenever I'm looking at skeletal remains. So we all work together in the field, partially because it's just hard. Working in Belize is hard.
Aubree Marshall:It's it's hot. There's a lot of mosquitoes. We work in a mangrove. I've almost fallen in from the boardwalk once. So like being there together because you are in a foreign country and while I do love Belize, the work is hard.
Aubree Marshall:So we work together and we really are just trying to help each other out.
Mari Dowling:Could you tell us a little bit about what the difference is between an archaeologist and a bioarchaeologist?
Aubree Marshall:Oh, yeah. This is a little bit of a historical thing. Actually, archaeologists, they go out in the field, they're digging. Right? Bioarchaeologists, up until, like, I wanna say relatively recently, they really just worked in the lab.
Aubree Marshall:And this is not always true. Right? There were bio works that went out into the field, but eventually, they started going to the field more and more because you're really thinking about how the person was buried. That's really important. But if you're an archaeologist and you don't think about the importance of that, if you're not recording it, then you lose that information.
Aubree Marshall:It's not like you can go back and, you know, re excavate. This is a one time thing. Also, preservation can be really bad. So if you have soil acidity that is not gonna be good for bone preservation, sometimes what happens is you excavate and you can get the individual uncovered, but as soon as you go to lift a bone, it turns into dust. Then having them in the field is so much more helpful and then also for identification of bone.
Aubree Marshall:I can do archaeological methods and I do, but my specialty does lie in in human bone identification.
Dimitri Joseph:Thank you for sharing your your fascinating research, Aubrey, and just giving us some insight about how one goes about studying ancient civilizations and studying the biology within ancient civilizations.
Aubree Marshall:Thanks. I love my research. I I really enjoy talking about it.
Mari Dowling:Thank you.
Aubree Marshall:Yeah. Thank you.