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Bare Your Teeth: How Watching Monkeys Eat Can Teach Us About Our Evolutionary Origins & Teach Us About Ourselves



Episode I: Transcript

Waking up to the rain around the world is always going to be special for me. I was born and raised in the Pacific Northwest in the United States, and the rain feels like home. When I learned part of my Ph.D. research would include fieldwork in a rainforest, I was thrilled. When I hear the rain, I get to take myself around the world with just a sound. All I have to do is close my eyes. My name is Risa Luther, I am a Ph.D. candidate at the University of Minnesota, and I study monkey teeth.

It’s 5:30am in Kibale National Park in Uganda. The forest is wide awake. The researchers, however, are not. The researchers in this area of the park are split into two types: the chimp people and the monkey people. The chimp people are long up and gone. They head out to meet the chimpanzees before they wake in the morning, and the team will follow them through the park until they find a spot in the trees to go to bed for the night. The chimp people do what we call, “nest to nest.” They literally follow individual chimps from their nest in the morning until they make their new nest to go to bed in at night. The rest of us, the various monkey people, don’t usually do, “nest to nest,” but we do rise early and work most of the day. So, with that alarm and that rain, hopefully, the sun is rising shortly. I’ll need to rise with it, and gear up for a day in this forest. 

A rainy day from our porch, Kibale National Park, Uganda
A rainy day from our porch, Kibale National Park, Uganda 

Our field site here is a set of small, simple cement cabins, with wood and tin layered roofs. They’re little duplexes, with research students on both sides. My roommates, Kandra and Marissa, and I, live on one side of our house, and Jack on the other. Our side has three rooms, just two bedrooms, and a common space with a table and chairs. A small, but comfortable, living arrangement.

Kandra, my roommate and another student researcher, is up already. I can hear her brushing her teeth outside our window, before I open my eyes. Despite it being her first field season, she is adapting well, seemingly unphased by the early mornings. Just don’t ask her about the bathroom situation, or the army ants, and you would never know anything is amiss.

Some people ask me how I got into what I do and it’s kind of a funny story. Flash back to the first day of my undergraduate spring semester at Macalester College, I was walking around desperately trying to find classes to fill my course load. I was stuck with the last slot for the last day of registration. Due to this “great timing,” I naturally didn’t get any of the classes I wanted, or thought I needed, to become that lawyer I am clearly not becoming now. 

Well luckily in a last ditch effort, two faculty I emailed, emailed me back, saying I was welcome to come and see. One was an introduction to public health. Side note, one of my moms works for the state of Oregon Public Health Authority, so of course I was like, “This is it. I can finally see what this is all about, right?” The other class was an introduction to biological anthropology with Dr. Scott Legge. The public health professor emailed back, happily offering me a spot, ready to give me the code to register, before I’d even arrived. Scott emailed back saying the class was full, but I was welcome to come by class and, “give it a shot.” 

The challenge was, despite those emails, I couldn’t actually try both. The classes were scheduled for the same day, the same time slot, the same building, the same floor. Classrooms 03A and 03B, directly across the hall from one another. Of course, what do you do when you’re 18 years old and panicking over a decision right in front of you, but call your mom. With 5 minutes before the classes were set to start and upon giving her a rapid-fire synopsis of both, I was left asking my mom a simple, but difficult question: “Left or right? 03A or 03B? Public health or biological anthropology?”

My mom said left, and I turned right and walked into Scott’s class. Why did I just do that? She clearly said left, but I went right. I truly didn’t mean to turn right. My brain fully said left, but my body insisted on going right. Right into 03B. Right into a bioanth lab being taught by Scott. Scott’s first words to my class were, “Truth be told, I would be way more comfortable if half of you were dead.” And no, he wasn’t kidding. 

It’s 5:45 am and it’s time to get ready for the day. Luckily, even when I’m half alive before 6:00 am, my series of daily rituals I follow each morning kicks-in and adequately preps me for a day in the forest. I untuck my mosquito net and find my sandals and I am out the door to brush my teeth, looking for our water which we boil twice before filtering, so we can safely use it for drinking, cooking, and right now for brushing my teeth. One of the easiest tasks to forget is prepping water, but I live and die by my reminders both on my phone and sticky notes in the field. 

Kandra (left) and Marissa (right) walk toward our house, Kibale National Park, Uganda
Kandra (left) and Marissa (right) walk toward our house, Kibale National Park, Uganda

I catch my other sticky note reminder on my bedside table. “BAG REPACKED?” it says in my tired, messy, all caps scrawl. I double check to be sure I have enough of everything I need: binoculars, pencils, pens, add in my newly filled water bottle, lunch, camera, and phone. Yes y’all, this is 2023. Most of us bring our phones with us, though, in the rainforest, mine comes with me in a drybag with my camera. I’m not planning to spend money on a new phone with my grad student salary due to getting stuck in the rain…in the rainforest. 

Bag ready, getting dressed for the day can be a bit of an unexpected task in the rainforest. The name of the game is layers. Or, perhaps more aptly, waterproof layers. You have your undergarments, of course, but then you will likely want breathable pants and a shirt. Those pants should have pockets on pockets. No such thing as too many pockets, I say. 

Monica (left, UMN anthropology undergraduate) and Risa (right) at a field site on Rusinga Island, Kenya
Monica (left, UMN anthropology undergraduate) and Risa (right) at a field site on Rusinga Island, Kenya

Over your t-shirt usually goes a long-sleeved, button down. You want something loose and lightweight enough to breathe, but thick enough to keep the bugs away. On your feet you want a good pair of crew socks that won’t rub. And be sure to tuck your pants on into those socks, unless you want the bugs to crawl up on you.

Over the socks go your gumboots. These are big, thick, and clunky. But when you find yourself trekking through the rainforest swamps, you’ll be grateful for big, thick, and clunky. Also, it turns out, lots of bugs struggle to climb up the side of those slick outsides of the boots. Are you picking up on the theme, yet? Bugs are a thing here.

On your head you’re going to want a hat. Most of us go for a brimmed, bucket-hat, keeping the occasional sun that reaches the forest floor out of our eyes and off our necks, especially for those of us who are tipping our heads back to look up to the canopy at the monkeys all day. Sometimes I opt for a baseball cap, but that can leave the back of your neck unprotected. So, you know, choose at your own risk because again there could be bugs falling from above. Always consider bugs. Sure there are ants and caterpillars in this rainforest, but they are not our friends. They’re very cool, honestly, but not our friends. Neither are a longer list of little crawlies I’ll spare you all from hearing about.

It’s almost time to head out, but first a quick run down to the “choo,” the bathroom, before walking to the lab to officially start the day. The “choo,” Kandra’s enemy out here, second only to the ants, is a two-stalled outside structure about 30 yards from our house, right next to the forest. The wood structure sits atop a hefty cement block with a small rectangular opening in it, just big enough for you to squat over the top of. For those of you who have never used a squatty potty, it can be a bit of a steep learning curve, but you get the hang of it eventually. And when you do, you’ll be proud.

I’m a biological anthropologist by training. The Cambridge dictionary will tell you that an anthropologist is someone who “scientifically studies humans and their customs, beliefs, and relationships.” For me, this definition doesn’t quite do it. Through my training, I learned that, at its core, anthropologists are all attempting to answer the same basic question: what does it mean to be human? Cultural and linguistic anthropologists strive to answer this through studying human culture and customs and their languages, dialects, and behaviors. Archaeologists on the other hand study the past, how we lived in the past, and our material culture, what we’ve left behind.

Assessing tooth wear with the Gorilla skeletal collection, Field Museum of Natural History, Chicago, IL, USA
Assessing tooth wear with the Gorilla skeletal collection, Field Museum of Natural History, Chicago, IL, USA

I am, however, a biological anthropologist, so how do I ask what it means to be human? Simply put, people in my subdiscipline look at humans as a biological species, over evolutionary time. In my case, I study our closest living relatives, non-human apes, like chimpanzees and gorillas, and some monkeys, to learn more about humans. So, as you can put together, there are many different angles, perspectives, methods, techniques, but only together do we address humanness and what it really means to be human.

At the field site’s lab, my field assistant Godfrey and I get our gear packed. If every researcher could only be so lucky to have a Godfrey with them in the forest every day. We head into the forest to find the first troop of monkeys for the day. The rain has lightened up allowing us, as we get closer to where we left, to scan high up in the trees for movement. As we listen to the sounds of the forest, we try to catch a few noises in particular.

Today, we’re looking for black-and-white colobus monkeys. They are what their name describes: monkeys that only have black and white coloring. A bushy bunch of white hair surrounds their all-black faces and the tops of their heads have a poof of black hair that fluffs up, there is a part down, making a goofy little hairdo. The rest of their body is black except for a large U-shaped bunch of bright white hair around their back that starts at their shoulders and descends around its back. This white U has usually longer hair than the rest, so it hangs slightly down around their body. Their tails are very long with short black hair until you reach the end where you’ll find a giant white puff of hair. These are medium-sized monkeys, as far as monkeys go. The adult males can get up to around 30 pounds and the females a little smaller, closer to 20 pounds. They end up around two feet long from head to butt, though their long tails nearly double their body length.

Black and white colobus monkeys (Colobus guereza), mom and baby, Kibale National Park, Uganda
Black-and-white colobus monkeys (Colobus guereza), mom and baby, Kibale National Park, Uganda

Now, for why I am watching them. I study primate dietary ecology – or more generally – I study what primates eat. These black and white colobus monkeys are strictly folivorous – meaning they are plant eaters. They consume a variety of different plant parts: young leaves, mature leaves, flowers, flower buds, stems, petioles, and even tree bark. They are part of the primate family Colobinae that have special adaptations in their gut to allow them to process this excess cellulose (or plant parts) and extract all the nutrients they need. 

While you shouldn’t pick a favorite child, they’re my favorite monkeys. So much so, I ended up getting their skull tattooed on my calf, as any mother would. In their living form, I love the colobus’s giant white poof at the end of their very long black tail. Partially due to its usefulness, given these are often the first things we see up in the trees upon hearing their calls. Partially because they all have their own unique tail, a way we identify each individual within each troop. 

This time (as many a time) Godfrey’s expertly trained eyes beat me to it in spotting our first troop. I have to admit defeat to the daily competition we’ve created, but, I’m of course grateful for his skills.

It’s now time for data collection, and we’re going to be with these monkeys for the long haul. The long haul, in our case, being the better part of the next eight or more hours.

Lots of people find out I study monkeys and apes and they get really excited and ask if I ever get to hold and play with them and that usually winds us down this long, sometimes arduous road of explaining ethics of human-wild animal interaction. Long story short – definitely no monkey holding involved in my work. That is – not while they’re alive. While part of my research includes a detailed understanding of what these monkeys and apes eat while they’re alive, the vast majority of my research actually occurs once they’re dead. I do a lot of work with their skeletons, but more specifically with their teeth. 

The goal of my dissertation is to improve our understanding of the evolution of the earliest apes – our earliest ancestors – who lived in the early Miocene, approximately 23 to 15 million years ago. To do this, I look at the apes and monkeys that live today. I look at where they live, how they live, and most importantly, I look at what they eat and how that changes the surface of their teeth over their lifetime. 

I travel to museums both in the United States like the Field Museum of Natural History in Chicago, the Smithsonian Museum of Natural History in Washington D.C., the American Museum of Natural History in New York City and museums abroad like the National Museums of Kenya and the Uganda National Museums to look at the teeth of skeletons of extant primates – that is, those species who still exist today – to mold the surfaces of their teeth. 

So, just like when you would go to the orthodontist and have a tooth mold done for braces, or if you’re like me, an anxious or stressed grad student or adult and need a night guard, I go and use that thick putty-like material to take a mold the teeth of these primates’ teeth. I spend hours carefully going through collections in the back rooms of museums, looking at one specimen at a time to assess the state of its teeth. Is it in the right condition to be molded? Does it have all the right teeth present? Are there any major cracks or defects that would lead to damage? These collections usually smell like naphthalene and let me tell you, if you know what moth balls smell like, multiply that by a thousand and you still won’t know how overwhelming naphthalene smells when you’re surrounded by it for eight hours a day. But to get to make use of and respect these primates for scientific research is why I’m here, so some more vick’s under my nose, and back to the cabinets I go to find some more specimens to pull, more photographs to take, more molds to make. Choose the right shoes for these days, it’ll make all the difference.

Once all the molds are done, I can return to the University of Minnesota for scanning. Each mold is microCT scanned and reconstructed to a three-dimensional surface I can view on my computer. I use those scans and surfaces, with the help of some math wizards, to construct models and machine learning algorithms of how these species’ teeth change over time by arranging them from totally unworn, shiny new, to totally worn down, flat and often concave surfaces.

I’m using models created based on the living species, whose diets we know and are familiar with, thanks to decades of field work, to better understand the fossil species from the Early Miocene. Gaining a better understanding of the diets and environments of our earliest ancestors. This will give us a better understanding of the context for when and how our earliest ancestors evolved, bringing us back around to the question of what it means to be human.

EPISODE II: Transcript

By 10:30 am we are in our groove now, data collection well underway for the day. The rain has stopped for now, but it’s the rainforest. It will undoubtedly rain again today. Today, we are collecting a series of focal follows. What this means is that we typically start by identifying the troop, scanning and making sure we know the individuals in the group by age and sex, recording where we found them and when, and then selecting an individual to focus on – one who is eating.

As a team, we time how long an individual is eating, what they are eating, and record, with the help of lots of practice and a good pair of binoculars, how much they eat. We follow the same individual monkey for ten minutes at a time, recording each feed, before moving on to another and rotate through each member of the troop. We do this on repeat until the troop moves to a new tree and we follow them when they move until we’re ready for a short break for our own food. This is timed differently every day, but typically if the monkeys nap, we take this as our cue to eat.

Risa and a chimpanzee, Kibale National Park, Uganda
Risa and a chimpanzee, Kibale National Park, Uganda

Learning how to do fieldwork at a dig site, then a savanna in a national park, and then a rainforest in another national park, all of these places felt off at first for me. But thankfully, feeling out of place is not really new for me. Growing up, I wasn’t quite White enough to be White, but wasn’t really ever Mexican enough to be Mexican. And growing up the low-income, queer, Mexican-American triplet daughter of lesbian moms was definitely not the way to stay under the radar. So being a Latina woman in STEMM and a queer woman in STEMM, I’m not exactly new to being the odd one out, definitely not a stranger to feeling different than the people around me. But that doesn’t mean it’s not exhausting sometimes.

Arriving at Kibale National Park, at this field site, it was like taking both a literal breath of fresh air in the forest, but also socially and emotionally fresh. This was the first time, in my years of research experience, that I was working at a site that was not only predominantly women, but also there were other Latina women. Natalia and Kandra are the first Latina women I have ever worked with in biological anthropology. The few and mighty. 

Remember earlier when I mentioned that you would be so grateful for those clunky, large gumboots? Well, that’s the sound of pulling through one of the many swamps in Kibale National Park. While we were sitting for lunch, we watched our troop head downhill away from us. This is good news and bad news. The good news is we are pretty certain we don’t have to stop our lunch, get up, and follow them right away or risk losing them for the afternoon. The bad news is they are headed straight for my least favorite place to walk through in the whole forest: the swamp. In the swamps, the monkeys come down low enough so that I’m not straining my head all the way back. I don’t even have to use binoculars, usually.

I know what you’re thinking – “Risa this is a swamp” – but I’m telling you right now, this place has so many flowers, pretty leaves, and fascinating looking plants, and I lack the words to describe its beauty. So, you’ll have to just trust me. But, also trust me when I say, I am not cut out for walking through it. I’m just not. My short little legs and I are really not a fan. I am all of 5 feet 4 inches, and with one wrong step, I am sinking in thick suctioning mud up to my thighs, with all thought of monkeys and data collection gone from my mind for the immediate future.

Okay, so quick pause before I finish telling you my swamp nightmare. Does anyone else’s family have a signal to find one another in the grocery store or was that just mine? Growing up, my mom taught us this whistle that if we were out of sight, she would do it and we would do it back. A call and response, basically, until we got close enough to find one another, without, like, screaming throughout the store. When we were really little, it was the clue that, like, if you hear this noise, you freeze where you are, and you whistle back. The general rule was, “If you can’t see me, you’re not safe.” We still do this, me and my siblings. We’re all in our twenties now, and we will still hear our mom whistle when we’re home visiting and out grocery shopping or something. And just without a second thought, whistle back and turn to see where her whistle is coming from.

Okay, so when you first go into the forest you learn some important rules. When your field assistant tells you to run, you run. That’s not common, but yeah, if say, there’s an elephant minding his own business that you didn’t see when you were walking. The other is, like, you also don’t want to be screaming your head off when something goes wrong. We have signals to each other to find one another when we’re out of sight. Which, with my short little 5 foot 4 inch height, happens more than my pride wants me to admit. Especially in the swamps. Especially, if I take a misstep. 

To quickly locate each other we would send of a quick hoot, sort of like an owl, not really like a chimpanzee, and wait for your partner to respond. You do that back and forth to find one another. You’re not usually too far, this process doesn’t usually take long. Unless you’re me. Stuck in the mud. Up to your thighs.

But then again, don’t, like, go adventuring in the muddy swamps in a Ugandan rainforest and you won’t find yourself rapidly sinking into the mud, wondering how you found yourself becoming the real-life Velma with your glasses missing, bag dropped, and hooting like a mad owl hoping Godfrey is not too far ahead of you to forget that he got stuck with the clumsiest American in the lab this summer! 

My various identities are integral parts of who I am. Until my sophomore year of college, I never had a Latina woman educator. Not once in K-12 except for a Spanish teacher, but even most of my Spanish teachers were White men. Some of them were cool guys, but White men, nonetheless. My sophomore year of college taking a general anthropology course, Dr. Olga Gonzales was the first person to encourage me to embrace my Latina identity in scholarly work – even if that wasn’t going to be cultural anthropology. Lo siento Profe! 

According to the National Science Foundation awarded doctorate data, in 2021, only 3.84% of all doctoral degrees were awarded to Hispanic or Latina women1. That is, approximately 2,008 of a total 52,250 doctoral degrees went to Latina women. Abysmal honestly, in a country whose second largest ethnic group is Hispanics according to the 2020 Census. Though we’d be here for hours, if you got me goin’ on the problems with the Census. But the point stands, BIPOC people, Latina women, we are sorely underrepresented and underrecognized in academia. And that’s part of the reason that I’m here.

As promised, the rain is back, but thankfully the day is winding down. I pop under a tree to dig my rain slicker out of my bag. Our last round of observations are done, and with Godfrey’s help, I scribble down where we are in the park to try to start looking for our troop in this area of the forest tomorrow and get ready to hike back toward the lab. It’s about 4:30pm. Not a bad day, honestly. A longer day than usual, but we got a lot of data, worth it really. And so far, no serious bug bites or big animal encounters or anything. And I didn’t even fall, aside from being stuck in the swamp, and we’re not gonna count that. Despite the rain, the sun is going to be up a few more hours, this means maybe some warmth after my shower. 

Around 6:00 pm, I can hear Kandra getting plates, so it’s time for dinner. I can hear water splashing, so Marissa is back from the field. Jack, our neighbor we share our house with, is a chimp guy, he is out for nest to nest. He won’t be back until later so just the three of us will eat tonight. We have a small cement porch with a table, we nearly always eat outside unless there are baboons around. There’s a common phrase you probs know, “blank around and find out” that fits well here – you just don’t eat when the baboons are around or you will surely find out.

Godfrey (left) and Risa (right) in the forest, Kibale National Park, Uganda
Godfrey (left) and Risa (right) in the forest, Kibale National Park, Ugand

Baboons are like the annoying small dog your friend never bothered to train. Cute, but aggressive and boy will they do just about anything to get your food. We lost one too many avocados and containers of popcorn to them and there’s nothing so sad as watching your avocado walk away in the cheek pouch of the biggest, baddest baboon knowing there’s nothing you can do about it. But like I said, find out. Dinner tonight is one of our favorites: beans, peas and rice with a side of avocado and tomatoes and a separate container with fresh pineapple and passionfruit.

After dinner, just like when I’m doing work in museums, my fieldwork days end with data entry. I try to stay on top of entering data every day, or nearly every day, because we all know I’m not quite that consistent. I don’t want to wind up with thousands of data points to enter later in the summer and a mountain of regret. But data entry as a group is a lot more fun. Kandra grabs her computer and her data from the day and sits to get going. Marissa grabs the mandazi – or doughnuts – and I find the Nutella we somehow managed to score on our last trip to town and we sit down for data entry and dessert while we wind down.

Graduate school, and research, can be lonely work, you make friends when and where you can. 

At museum visits, you find the postdoc or graduate student in residence, introduce yourself, ask them about their research, what they like to do in the city, go with them to happy hour or for coffee on a break. While you bond over your shared nerdom, finding the one other person in the museum who is excited about fossil teeth or who wants to discuss different metrics for assessing changes in dental topography or how exciting it is that the International Commission on Stratigraphy has officially deemed the Early Miocene it’s own age in the Miocene epoch, so we can capitalize the “E” in Early now, it’s been rare for me to find friends who belong to the same or similar identities as me. 

Risa above the forest, Murchison Falls, Uganda
Risa above the forest, Murchison Falls, Uganda

To find other women in the field is always a relief, especially in STEMM. This is, in part, why Kibale was so special. But to find others from low-income backgrounds and other out, queer scientists, other Latina women, is far less common hopping in and out of museums. Especially when traveling through countries in which some of those identities are illegal today. This is why meeting Kandra and Natalia was such a privilege. To be surrounded by smart, strong women and other Latina scientists from similar backgrounds. It’s a level of understanding and familiarity that I think many of us are looking for, especially those of us who aren’t a part of the majority. You can stop fighting so hard to just be seen and heard and just exist for a while. 

While we worry and advocate loudly for changes to be made abroad in countries we visit for research when we see laws enacted we see as cruel, we have also ground ourselves in the reality that there are serious fights still happening for us in the US, that when we return home from research, we are still the non-White, non-majority graduate students begging our universities to listen to us. It shouldn’t be our job day in and day out to address this, but by the simple fact that our skin is a different color, that we love different people, that we were born into families that make less money, it is. 

Most nights end the same way – together – tired, but happy nerds gathered around someone’s porch. Lots of laughing, usually at someone’s expense. Today my getting stuck to my thighs in the swamp is the story of the day. We’re all here to collect data, to do research, to work for some academic, personal, larger goals, something. But, we’re also here together and there’s nothing like the friendships you make when you are in an isolated forest for months on end with little to no internet access, cell signal, or outside contact except for occasional trips to the nearest town. 

Ending the day at a museum is different, but comes with a similar feeling of exhaustion and satisfaction of a full day of work and a shower to look forward to. I have found recently that I am often the first in and last out of the collection. The sound of my shoes echoing through the giant rooms where the specimen cabinets are housed is eerie. For me, starkest contrast to ending a day at the museum instead of the field is a hot shower. Though there is something refreshing in the hot evening in the rainforest about getting in an icy shower, I’m not gonna lie to ya, getting in a nice hot shower, rinsing away the smell of naphthalene, soothing your sore muscles from standing with poor posture all day with hot water is a relief. 

While I think we all get caught up in the moment in our research, we’re nerdy, and I am reminding myself here, on the record, for you all to hear, and to help me hold myself accountable to – this degree, this research, it’s just the beginning for me. Something I’m proud of is being the first in my family to earn an advanced degree. I am a triplet and my triplet sister is a Ph.D. candidate as well. She is a therapist getting her Ph.D. in counseling psychology focused on supporting people who experience discrimination in her research and clinical work at the University of Oregon. Our triplet brother likes to joke that soon he’ll be able to introduce us: “This is my sister Dr. Luther, and this is my other sister Dr. Luther, you can call me Luther.” We were the first in our family to earn master’s degrees and we will be the first in our family to earn doctoral degrees as well. We’re the educated, queer, loud, Latinas they warned you about. And proud of it.

  1. National Center for Science and Engineering Statistics (NCSES). 2022. Doctorate Recipients from U.S. Universities: 2021. NSF 23-300. Alexandria, VA: National Science Foundation. 

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