 Okay, hello and welcome back to Ask an Archaeologist. I'm Sarah Kanza, the host of this afternoon's show. And Ask an Archaeologist is a series of live stream interviews co-hosted by the Archaeological Research Facility and the Phoebe A. Hearst Museum of Anthropology that we're putting together for Cal Week 2020, which is this week. Each day, this week at 11 at two, we're interviewing a UC Berkeley archaeologist and answering audience questions. So before we start the interview today, I wanted to let you know how you can ask questions. If you open a new browser window and go to sly.do, which is S-L-I-dot-D-O, and you can type in AskARF, A-S-K-A-R-F, and click on the Join button. And there you can type your questions and we will see them and ask them later on in the interview. And I'll remind you of this part way through the interview as well. So this afternoon, we're happy to have A.J. White with us who is going to talk with us about what we can learn from studying ancient poop. A.J. is a third year graduate student at UC Berkeley and he uses a fecal molecules to reconstruct ancient population changes. He's also interested in how climate change has impacted people in the past. He has worked in Egypt, Vietnam, the United States, Jordan, and he is currently working in his living room. So welcome, A.J. And we're delighted to have you. Thanks for joining us. So I'm sure the burning question on everyone's mind is how did you get into this particular area of research? Yeah, it wasn't something that from day one, I was like dead set on it. I think in archeology kind of have to keep an open mind for what opportunities are out there. And when I started grad school at Long Beach State before coming to Berkeley for my master's in geology, my advisor there had said, hey, check out this cool paper that uses fecal molecules to reconstruct ancient population change. What do you think about it? Do you think this is something that maybe we could do? And I thought about it and I was like, you know what, there's like a huge kind of emptiness in terms of like what we can do with poop and archeology. And I mean, for a long time, people have looked at copper lights, which is essentially fossilized poop or incredibly hardened poop. But there hasn't been a whole lot done on the molecular level and looking at what remains when everything breaks down except for a small amount of these incredibly persistent molecules. And I just thought, hey, that's like a huge kind of place that we could go and check it out. And we tried it out at a place called Gehokia in Illinois and it worked really well. I've since then tried it out in Jordan. It's been a little not as well, but we can get into exactly why that is. And I think it's good to talk about, you know, why some things work and don't. But yeah, it's something that kind of fell into my lap and I'm glad it did because I think there's a lot of things that we can do with poop. I think that's fascinating because, you know, when we think about archeology, we think of all the more, you know, the finds that are more harder, like bones and pots and that kind of thing. And we don't think of the molecular things that you could study. And that's much more recent research that's being done. Can you talk about how do you find these traces? Where do you find them? Do you have to find an ancient toilet? Do you have to go to a place where you know people were going to the bathroom or are these things everywhere? How does it work? Well, yeah. So don't think it's super gross. I mean, the first thing that people think is that I'm actually going out there and just like scooping up some poop. Just, you know, just getting it. It's not like that. So we're talking about poop that has almost completely gone away. And the way to imagine this is that there was a time before toilets, right? And there's a time where people were mostly practicing what we call open defecation, which means just going out and doing their business like you're camping. And so when that happens, you know, there's poop on the landscape, out in nature. And after it rains or something like that, it'll break it up into little tiny pieces. And a lot of those tiny pieces will get eaten by microbes. But there are certain little tiny pieces of poop that microbes find incredibly unattractive. Just like we find all of poop unattractive, microbes find a little bit of it. These very complex molecules that are very rigid, in particular, they're the breakdown product of cholesterol. And as you all know, cholesterol is something that's hard for us to break down. It gets, you know, caught in our arteries and causes big problems. So the same idea. It's very difficult to break down. And so they just leave it. And so it's a molecule that in the specific molecules called the prosanol. And it's something that, because the microbes don't want it, it just lasts in nature for a very long time. Now it's very hard to kind of, if you were to just go out to an archaeological site, it would be in this is an area where, you know, before toilets, which until, you know, that was actually much of human history until like the past couple hundred years, really. It would be hard to just guess where people went to the bathroom, right? You know, you'd be very lucky if you just put your shovel in and that's where you found these molecules. So to get around that, we target areas where these might have collected after being washed away by rain. And so if you're in somewhere where there's like a lake nearby, that's a catchment. That's an area where stuff naturally just gets deposited. And so we target lakes, wetlands, low places where the idea is maybe only a small fraction of what was originally in, you know, one stool will make it in, but it's still something. And, you know, we go and we, you know, collect big sediment cores, which are, you know, columns of mud. And then you can look at how much of these molecules are present at any depth. And the idea is, hey, you know, if we have more at position X and it's more than position Y, that probably means there are more people here. And if you're lucky, you can tie that into, maybe there's a migration story in the area. And they're like, oh, that's, you know, that's when it happened. That's when people came here. Or maybe it's the opposite. Maybe you can see where people leave. So yeah, that's the idea. It's not actual poop. It's very specific molecules that might accumulate in specific environments. Great. And so I know you had a recent paper that came out in an antiquity, American antiquity. That's correct, yeah. Yes, that about your work at Cochia on this. Could you explain a little bit about how, what that looks like? Sure thing. Yeah, so we first went out and, you know, went to Cochia. And by the way, Cochia for those who aren't familiar with it is like one of the biggest archaeological sites in this country. It's home to dozens of these monumental mountains. And to make dozens of monumental mountains, you need a lot of people. So it's thought that this area was a city that, you know, maybe was home to several tens of thousands of people. And what we did is we went and right at Cochia, there's a lake and we collected sediment from that lake and did the process that I just explained, you know, identifying where these fecal molecules are in the mud and then trying to link that back to the population at Cochia. And I did what I think 99% of most archaeology in the area does, which is I immediately went to what's called the Mississippian time period in terms of where my brain went. And that's the time period where most of those mountains were constructed when much of the people were there. There's a whole lot to say about it. And there's really great research. If you're interested on the Mississippians, you're gonna have a lot of fun learning about this stuff. It's totally fascinating. But the thing is that there was stuff that happened after the Mississippian time period that very few people have written about. We know for sure that there was an indigenous presence in the area at the time of European contact because the French missionaries established a mission at Cochia, like actually on the site. And there's almost no archaeological presence of this, very limited. And there's no archaeological evidence that's been put forward of to where the people that were living who were to be associated with this mission. And it must have been enough people to justify going all the way down there and building a mission. So we know there's a substantial amount of indigenous people around this area, but there's very little research about it. So what we did is we said, hey, we don't have archeology, but we do have this fecal, stand-up population reconstruction. And it doesn't just disappear at 1400 AD. There's 300 years of additional demographic changes. It looks like we do have a low period after the Mississippian occupation, which is what everyone talks about. But around starting around 1500 AD, the population numbers from our data seem to go up modestly, not a whole lot, but they go. And the idea is maybe that's when we start to see the movement of this population that was present at the time of European contact, which we think is probably a group of the Illinois Confederation who were called the Cahokia, and that's how Cahokia got its name. And so we're able to kind of tie that into this whole very under-discussed aspect of the local history. I mean, it's generated, it's one of those things where like, how much can you say without archeology? And I'd like to say that you can. There is a story to be had, even if we don't have stuff that our eyes can see in the ground. There's stuff in the ground that we can't see that still leaves a record. So that was kind of the fun thing about, you know. And can you explain why there isn't archeology during this time when there were actually people there? Yeah, I've tried to. It depends on how much you believe me. What my interpretation of this is, is that the two different indigenous groups that were present in this area at different times, the Mississippians under the traditional period of Cahokia. And then those came after, which are likely the Cokia, which is a member of the Illinois Confederation. It's very confusing, I'm sorry for that. But they had very different lifestyles. And so during the Mississippian period, this was people who were extremely sedentary, so sedentary that they were building, giant mounds that were as big as the Great Pyramid of Giza. In terms of their base, it's not their height, but the point is it's big. And you compare that to the Illinois peoples and they were mobile, they were semi sedentary. So they'd go on these long bison hunts in the summertime, where the groups would get together and it'd be this big outing. And the point is they're not where they are for the rest of the year. And so maybe there are big camps that are being built in the fall and the spring and the winter, resources are more scarce. People would go off to live in small family groups. When you're in the winter in a small family group, it's just maybe eight people, I'm gonna guess, a small number of individuals, they're not producing as much archeology. The less people that are in any sort of spot, you're not gonna be leaving as much stuff behind, it's gonna be a lot harder to see. And so Mississippian stuff is obvious. It's a giant mound, you're gonna find it. Stuff from the later time period might be a little more subtle. And I think it either is stuff that hasn't been found, it's stuff that's been destroyed by a fair amount of post 1900 just expanse. This is right outside of the city of St. Louis. So there's been a lot of just highway building, housing development, stuff like that. And finally, I wonder if some stuff that might be from this time period has been dated Mississippian just because if you don't have diagnostic artifacts and you find a small scatter of a chipped stone, you might think, oh, well, everything else is Mississippian, I'm gonna check the box from Mississippian and go on with your survey. I mean, that's super, I can't, that's just speculative, but I wonder if there might be a little bit of this kind of little recording bias going on. So yeah, I mean, I could go on with my theories, but that gets the idea across. Yeah, yeah, well, let's pause for a sec to remind listeners on YouTube that you can ask questions by going to slido.sli.do and typing in ask arf and you can pose your questions there and we will see if AJ can answer them. But in the meantime, can you talk a little bit about how animals, do they produce this too? And can their poop get in the mix and mess things up? Absolutely, so what I just told you about, this whole method is relatively new in terms of using these molecules for population estimates. And there's always a point where the method's looking great and then everyone kind of realizes, okay, here are the imperfections, here are the places where it kind of has a fair amount of limitations. As one of them is what you just mentioned is that humans aren't the only ones that make these molecules. Now, for everything that I've seen in the literature, humans make a way more comprosonal than anything else on the average of 10 times as much. But there are certain animals, they tend to be large domesticated animals that we've tested, things like sheep and pigs, cows make a little bit too, will produce a little bit. And so the point is, how can you tell whether you're dealing with a city of cows in the past or a city of people? And there are certain kind of ways around this and in Cahokia, we were able to kind of make the argument that, okay, this is before European contact, there's no large draft animals in the area. The only domesticated animal is probably gonna be a dog and dogs we know make almost, they don't make any actually. So carnivores don't really seem to be making this molecule. So we can say humans are the big animal on this landscape. And whatever is being produced, there might be a bear that goes by occasionally that makes a little bit of it, but we're gonna be pretty sure that this, whatever controls the changes is people. Now, if you're an area where there's a lot more animals that are present, that are particularly domesticated in animals like those I just mentioned, then it becomes a lot harder to pull apart the human and the animal signature. There are ways of doing this in terms of looking at more molecules, particularly bile acids and looking at various ratios of these different molecules to each other to say, if you have this number here and this number there, it's probably a pig. And so there's ways to get more specific, but you can't completely be 100% certain that everything you're seeing is human. And we're raining this problem a little bit on more recent work that I'm doing with my advisor, Lisa Maher here, Berkeley. And we tried this out at her site, which is in Jordan and it's very old. It's about 20,000 years old. It's amazing archeological site. It seems like there's a lot of people there. However, since there's been a lot of people there 20,000 years ago, there's also been a lot of camels there that have just been going across the desert. And so we were wondering, does camel poop contain some of these molecules too? And could that contribute to what we're saying in the sediment? So we tested camel poop and it turns out, like cows, they make a little bit too. So what we think is happening is that over time, their poop is broken up and kind of percolated downward into archeological sediment. And it makes it really hard to distinguish what's going on with people and animals. It's a real mess. And so what I hope to do now is kind of go out and say, okay, here are some of the limitations. Here are some of the places where I think it works really well. I think if you're like on an island, somewhere where you know exactly what's coming in and out, I think if you're in the Americas in a pre-contact setting, it might be a pretty good way to do, but in the old world, it's a little more complicated. So yeah, that's what we're getting at, that there's a lot of limitations to be discovered and we're kind of getting into that. And so how old is this approach? I mean, what does your research community look like? What's the size of, do you go to conferences for people who just do this or is this a really emergent? It's just the men's restroom. Not in any conference, no. Anyway, so what we do is, where this all started was in the 1960s or so, people started using a proxyl for sewage contamination studies. And they still do this today. If a pipe breaks near a port or something or somewhere where people go swimming, they'll go out and test the water. And if they find Caprosna, it's like, okay, no one goes swimming in this water, there's been a sewage leak. And so that's where it started. And then archeologists beginning around the 90s realized that this molecule doesn't just indicate modern sewage and modern human waste, but also is a molecule that can persist for a long time. And so they started first using it as like an indicator of a human presence. And so particularly for pooping, so people used, okay, let's say you've got an ancient fortress and you wanna know where people went to the bathroom. If you find an area where you just find a ton of these molecules, then you've found your bathroom. And so it was stuff like that. So there's studies from Roman forts that were finding where the privies were. It was used to try to find out where fields were maneuvered and other fields were not. But in terms of using it as a population indicator, that didn't really start until 2012. As far as I know, that's the first paper that went out and said, hey, we can use these as a way of telling how many people were here in a kind of relative sense. So in terms of population, it's less than a decade. But the whole thing has been around and there's a kind of cool history to it. And yeah, and the fact that it's still used for finding sewage pollution, it still goes on just as it has been for 50 years. So when you talk about like finding it in different parts of the site, say, I know this isn't necessarily the research you do, but if we were out of Roman fort or something, what kinds of tools would you use to sample areas? I mean, what kind of controls need to happen during the excavation to allow you to do your work? Yeah, I always joke that's good to wash your hands. Just because, yeah, you never know what sort of contaminates you might be bringing. We're dirty people as this whole outbreak has shown us. You can never be too sure about what you're carrying with you. But yeah, the first thing is, yeah, you don't want to contain anything. You don't want to be eating anything that has cholesterol and be touching anything with that. So if you just had like a pepperoni pizza, not a good idea to go out and do your sample. But let's say that you got, I wear gloves on and I'm in the field. And if you're not doing it, the approach we talked about before, which is you go to a lake, right? So if you're in an archeological site, the way we've done it is much like any sort of excavation where you have your profile, your sidewall or what have you, and you can pick depths that you want to sample. And this isn't anything you can see, right? So you just need sediment. Typically we fill up, at least for what I do is fill up one of these is about maybe 15 milliliters or a volume of sediment. And from that, we don't need a whole lot because we're gonna take what the sediment is and we're gonna go take it back to the lab. And we do what's called a solid and liquid extraction. And so you take the dirt that was in here and you want to get it into a solvent that will strip out the molecules you're interested in. And now it's out of the mud and it's into something liquid that machines can deal with. And then you do several controlled chemical reactions to further isolate the molecules you want. And then you put that in mass spectrometer, which is an extremely sensitive instrument that can tell you how much of these molecules are present to the nanogram. So you don't need a whole lot. And in terms of the sampling procedure, it's pretty simple. The analytical procedure is a little more involved. That's the part that takes the time. I see. And so it sounds like carnivores don't produce any trace of this, but herb ores and omnivores do. And so can you, is it refined enough to be able to tell like if there's a human population that is eating more of one type of food or more meat or more plant material, can you actually distinguish that from them? So I'm gonna break your question into two parts. The first one is that I don't think we have enough data yet to make, and I kind of, this is my fault because earlier I said all carnivores don't do this. The problem is we've only sampled, as far as I can tell, perhaps under 50 animals, specifically for this that I'm aware of. A lot of them are ones that we can easily get our hand on. So Steph, if you go to a farm, just sample everything there. So there needs to be, I think, just a lot more survey of just what the different of the animal came to, to find out, okay, well, is it true that we can say carnivores in general or am I just basing that off of the dog, which in that case I'm, so I think we need to expand the amount of animals that we're studying, but then let's say that it does pan out where there are differences based on these kinds of diets, right? Yeah, it might be possible to look into that. And I think it would be difficult because it would be a trade-off between, let's say you had someone who is ingesting very little cholesterol, so conceivably they would produce less coprostinol, right? The byproduct of the cholesterol breakdown in our guts. However, that might look that if you had a hundred of that group of people, would that just look like 50 people who were eating more cholesterol, right? Because it's not like there are multiple variables here. And so it would be difficult to pull apart whether it means more people or a different diet. At the moment, the assumption I make when I do these studies is that people have a similar diet through time. Of course there's gonna be differences in there, but you have to kind of choose some sort of assumption in order to make interpretations, otherwise you're just gonna say, ah, there's too many variables and leave it there. But one thing I've joked about doing and I actually might want to seriously do this is actually try that out myself and have these different diets and then just test what comes out to see if there are noticeable differences because one thing that's good to keep in mind is that we produce cholesterol as well. So no matter how vegan you are, there's still cholesterol in your body. Otherwise you'd be just a bunch of jello because you need cholesterol in yourselves to have structure. So we make cholesterol anyway. So it's complicated. I'm not sure if that completely answers it. Now it's fascinating to hear about this new area of research and I'd love the idea of being able to see beyond what's actually in the ground, what's being excavated and to be able to do these types of analyses. A listener has asked what's your favorite project so far working in this field? Gotcha. Well, I've been very fortunate to do these fecal stand-all analyses in multiple places. In Vietnam, we did a really cool project on an island and looked at sort of the timing of when the greatest populations were there. In Jordan, we've learned a lot in terms of the method but I'd say that in terms of what has, I'd say produced to me the most interesting findings is from Cahokia, what I was talking about earlier. And one thing we haven't talked about is that from the Cahokia study, we were able to say, okay, in our sediment core, here's what's happening with the fecal monkeys. But we're also gonna say, okay, well, what's happening within the environment based on what we have in this lake mud because we can see things that were going on environment just by looking at the mud with our eyes. There's like a very obvious mud and it looks like this real gray pulse of silk that just shows up and right after that our fecal molecules start to be in decline. Now, in addition to that, we sampled the mud for oxygen isotope analysis which is a way of getting what rainfall was like in the past. And we also find that around the timing of that flood it seems like rain started to change and it became drier during the growing season in the summer, which would be a big problem if you're making, if crops are much feeding your people. And so it seems that climate change was happening and it was having some effect on people living in this area, in addition to what was happening in their society and completely cultural realms as well. So what I really love about that is that I think we've been able to make a really clear sort of argument for how the environment and people go together through this method. And I think it can be quite powerful and I hope to encourage people to try this method out for, among other reasons, just that, that you can really connect the climate and people in a way that it's hard to do other ones. So I've really enjoyed making those interpretations and being able to pretty confident about them. Well, that leads nicely to another question about what people on archeological projects want to, should they all be doing this? Should they all be collecting these samples, even if they don't have someone like you on their team? And how would they go about that? Is that something they could do? Yeah, so what I feel like I'm learning now is that this isn't necessarily a method to just be applied universally to every single archeological site, due to the way that this molecule preserves and due to how other animals can affect its interpretation. So I think that if you're an archeological site and you've got a nice like wetland nearby, that's an area that, go get a core of it. And sometimes that requires specialized equipment and training to do. But if you have like a nice sedimentary archive right by your site, that's going to be an area where you can be pretty confident that the stratigraphy is real and tap, there hasn't been a lot of disturbance, things are gonna be in there. The problem with archeological site is that it's core of sediment a lot of the time, right? If you're dealing with sands or silceve and stuff where stuff can mix around. What I think was happening at our site in Jordan is that modern or near modern molecules are percolating into archeological sediments, which makes a real problem. So if you have somewhere where it's nice and tight in like a water blogged area, I'd recommend it. And you also have to consider the archeological context as well. Are there a lot of animals that might produce this in the area? Are you in Africa, Europe, or Asia? Or are you in somewhere where there might not have been as many large animals in that area? That would perhaps be a better option. So I'd say, yeah, think about the context. And if it checks those boxes, then yeah. And you can, there's plenty of people who are starting to do this when you can collect the samples and give someone an email who's published on this and say, would you be interested in analyzing this? And it is an expensive method, I might say. So per sample, it can be pretty pricey. It's not something that you can just say, oh, well, we'll just throw it over there. It does take some money, so it's something. And does the sample have to be sent to a lab and processed by someone like you, or do you send it out somewhere to be analyzed? Yeah, it depends on how comfortable your chemistry. I'm not a chemist, I'll go ahead and just say that. So to me, what I'm doing in the lab feels sophisticated. To a real chemist, they're like, oh, that's undergrad chemistry. That's not a big deal. Yeah, if you know your way around a lab, you can perhaps do the extraction procedure. And I imagine that any sort of university campus will have some sort of way to have this solid to liquid lipid extract, which is what you're doing. That's what you're making. Now, once you get to that part, you need to run it on a gas chromatography mass spectrometer. That's something that, I don't do that part because that requires a fair amount of training and understanding of a very delicate and expensive piece of equipment. So I'd say that at that point, you almost certainly need to send it out to a lab, but you might be able to do the extraction point and then send them the sort of the final project before it goes in. As I'm saying this though, I think it is best to perhaps send it out to somebody who specializes in this, even though theoretically you could take care of it. Good. So along those same lines then in doing this work, do you look at actual poop? Is another question that came in. I guess. What's that? I've seen it before. Yeah, so I do not look at actual poop, and that's something that I get asked a lot. And there's a whole tradition of looking at copper lights in archeology that is much older than what we're talking about here. And there's a lot of great things that can come from looking at actual poop, looking at the stools in terms of looking at diets and looking at macro remains inside of it, as well as looking at parasites and looking at how people's health was like in the past. But what we're talking about here is all at the micro level. This is all stuff where it just looks like dirt. And that's what's kind of fun about it too is it's like in any sort of volume of dirt, there's all sorts of stuff and it is crazy dirty. That's another problem running this on the mass spec because there's just so much stuff and dirt and it has so many sources and it's totally its own little world in there and it blows my mind. Yeah. Well, it's so great to hear about this from you and it's fun to learn about something totally new. And I'd like to thank you so much for joining us today for this session of Ask an Archeologist. So thank you for coming AJ, it was fascinating. And thank you to the listeners, the people who joined us online. I'd like to invite you all to our next Ask an Archeologist which will be tomorrow, Tuesday at 11 a.m. And it's gonna be with Scott Byram who will be talking about how archeologists use ground penetrating radar to map buried artifacts and ruins before they begin an excavation. So another chat about archeology without actually looking at artifacts. So I hope you're able to join us tomorrow. And again, thanks so much AJ for joining us. It was fascinating. Thank you. Okay, bye. All right, goodbye. Bye, thanks AJ. I don't know, I guess she turned it off. Boop.