Webinar: Climate Change Threatens Great Ape Biology
Aired June 17, 2021
Briana Pobiner:
All right. Hi, everyone. Welcome to our monthly Human Origins HOT Topic discussion. Today's program is Climate Change Threatens Great Ape Biology, and this is part of our ongoing HOT Topic Human Origins Today series. My name is Briana Pobiner, and I'm a paleoanthropologist and educator at the Smithsonian's National Museum of Natural History. Whether this is your first time joining us or whether you've attended a HOT Topic before, we're really glad that you're here. And before we get started, there's just a few housekeeping notes. So this discussion offers closed captioning. You can turn them on or off via the CC button, which should be located at the bottom or maybe the top of your Zoom interface. As you have questions during the program, please go ahead and submit them to the Q&A, which is probably at the bottom or the top of your screen. It looks like two little speech bubbles and we'll sort through as many as we can. The Q&A part of the program, which is towards the end, really flies by.The Q&A box is also where we'll share any relevant links during the program, so please keep an eye out there.
So the way this program works is we'll start with an opening presentation by our speaker, who I will introduce in a moment, and then I'll join her here to take your questions. So some of the questions that are posted in the Q&A I will read out and Alexandra will answer. So now I'd like to ask Alexandra to turn on her camera and I will introduce her. We're really excited today to have Alexandra Kralick with us. She is a Ph.D. candidate in biological anthropology and an NSF GRFP fellow in the Department of Anthropology at the University of Pennsylvania.
She studies the growth and development of sex differences in the great ape and human skeleton, and in particular the lack of a clear sex binary. Her dissertation examines the skeletons and dentitions of two male types of orangutans, flanged, and unflanged. Her previous work is on gorilla dental development and wrist bone shape, and she earned her BS in biological anthropology from George Washington University. She's also involved in public science communication, including writing an article for Sapiens, an online anthropology journal, which was picked up by The Atlantic. You can follow her on Twitter @BioAnthFunFacts. So now I'm excited to ask Alexandra to share her screen and turn on her microphone. I'm going to turn off my microphone and my camera, and I will be behind the scenes during Alexandra's presentation, and when she's done, I will come back on and we will get to the Q&A. So thanks so much for being here.
Alexandra Kralick:
Hi, everyone, and I just really want to thank Briana for having me. Speaking at the Smithsonian Human Origins HOT Topic series has been a dream of mine for over a decade since I went to one of these my senior year of high school. So thank you all for coming and helping making this dream come true. A quick warning before I begin. One slide does contain an image of human remains, teeth, so for anyone who does not wish to see that. So in 1981, life for mountain gorillas was incredibly stressful. There was only 250 mountain gorillas left on the slopes of the Virunga volcanoes. They'd lost most of their habitat and they were on the verge of extinction. Back then, it was projected that the mountain gorillas would go extinct by the year 2000. But thanks to sustained and well-funded international conservation efforts, they didn't.
In 2012, when I went to go see them on the lower slopes of Mount Karisimbi in Rwanda, they were thriving. When a German tourist stopped to take a photo of the dominant silverback gorilla, his camera lens looked like an eye and it was too close for comfort for the big silverback. So he stood and pounded his chest to assert his dominance while I was standing directly behind him, paralyzed with fear. I saw the muscles ripple down his back and I looked to the guide for direction, adrenaline running through my body, as he directed me to stay still. He was not the only silverback. There were two in the group and it was a large group of 33 gorillas who were descendant from the very gorillas that Dian Fossey studied.
You may have seen the film adaptation "Gorillas in the Mist" with Sigourney Weaver. Back in 1981, only 250 mountain grills were left in the wild. The gorillas lived in groups that weren't very large, and they were usually defended by a single silverback male, but this one had two. When I went to see the mountain gorillas in 2012 in Volcanoes National Park in Rwanda, there were barely more than 500 gorillas. Combined with the Bwindi National Park, there were a grand total of 880 mountain gorillas left in the wild. Today, there are more than 1,000. This dramatic quadrupling in such a short period of time is a rare inspiring story of hope in the world of conservation. This was done by the hard work of lots of organizations protecting the gorillas from poaching and gorilla doctors treating their diseases and so much more. But even though their home is protected and their numbers keep growing, the room they have to live in has not gotten any bigger.
This has had a number of consequences. Group sizes had to increase, so big silverback males had to tolerate additional silverbacks to protect groups of such large sizes. The gorilla groups encounter one another more often, so the silverback gorillas get into fights more often than they did in Dian Fossey's time. A lot of what I saw was different from the way the gorillas were in 1981. Social dynamics are changing. This is one of the clearest effects of climate change on gorillas. Group sizes are increasing, and there are often multiple silverback males in a group. Similar changes are happening to other endangered great apes. Just like gorillas, orangutans are encountering one another more often too, but in orangutans' case, it's not the adult males that are getting in fights, but the females. Adult female orangutans today have 10 times more instances of aggression. Some of them die from these fights, but they aren't pushed too close together because their habitats are protected and their populations are increasing.
In fact, it's the opposite. In the same 40 years since the '80s when mountain gorillas were quadrupling in number, Bornean orangutans lost half their population. Orangutan populations declined by as much as 97 percent in the 20th century due to hunting and forest loss. The situation is so bad that orangutans are set to go extinct in the next 50 years. Bornean orangutans are endangered. Sumatran orangutans are critically endangered, and the new species of Tapanuli orangutan is the most endangered of all the great apes. Something that makes life harder for orangutans in particular is that they primarily eat fruit, as opposed to mountain gorillas, who eat lots of leaves. Fruit naturally goes in and out of season and can be scarce at times, and those times are getting worse, with wildfires. In the late '90s, there were a bunch of wildfires in Southeast Asia that decimated a third of the wild orangutan population.
Then just in the last two decades since 2000, orangutans have lost over 80 percent of their habitat. 2,000 to 3,000 orangutans are killed every year. You might remember the massive wildfires in Indonesia in 2019. During a wildfire, there is a fruit shortage. So the orangutans go into starvation mode and resort to eating bark. At some points, they starve so much, they lose muscle mass. Females conceive fewer babies during these times, being hunted, losing their homes to logging, running from wildfires, all of this is incredibly stressful. So I sought to test how stress is recorded in their bodies and what it can tell us about how they're responding to climate change. Now, the stress I'm talking about is not the kind of stress they have because they have too much homework. No offense to anyone who has too much homework. I know how stressful deadlines can be, and they can mess with our eating habits. But the kind of stress I'm talking about here is starvation mode.
And orangutans, their major documented stressor is nutritional stress because the regular fluctuations in fruit availability. And orangutan habitats, trees go through fruiting episodes, where they make a lot of fruit over a very short period of time every few years. So these are known as masting events and they're irregular and unpredictable. The nature of the orangutan diet was making life stressful for orangutans well before all the recent climate change problems, which now make finding enough fruit even harder than every year, causing orangutans to spend more and more time in starvation mode. Orangutans are affected by severe stress, and I sought out to test how stress is affecting their biology in one really unique way, the growth and development of adult male secondary sex characteristics. Researchers have wondered for a while if stress affects certain types of orangutan males more than others.
The kind of orangutan male you already know about is the flanged male, who has his secondary sex characteristics. So secondary sex characteristics in humans are things like a beard, armpit hair, an Adam's apple, and orangutans, when they go through puberty, they get stinky like human males, but they also get these big cheek pads and throat pouches for calling to females. So when you go to the zoo, you may have noticed the face pads on the adult males. They're called flanges, and they're attractive to the females. We call these males flanged males. But what you probably don't know is that there's another type of adult male that you've probably never heard of because it only is found in the wild. This mysterious other type of adult male orangutan that you've probably never heard of before is the adult unflanged male. You can see them on the left here. He kind of looks like a fully grown kid or an adult female, like an adult man who has never grown a beard.
These males don't go through normal puberty and have delayed the development of their secondary sex characteristics like the cheek pads called the flanges. They can delay the development of these from anywhere for a few to 20 years, but they all eventually become a big flanged male someday. This phenomenon, where there are two different kinds of adult males, is called sexual bimaturism, and it's incredibly rare in the animal kingdom and we don't understand why it happens. Some researchers have long suspected stress may play a role in determining which male a kid orangutan grows up to become. So that's what I sought to test. There are two possible predictions as to how stress affects the two different types of males. The first one proposes that adult unflanged males have higher stress, similar to how subordinate male baboons — so like the lower-ranking baboons — have higher stress hormone cortisol levels than the dominant ones.
This was the main hypothesis for a long time until people started doing hormone testing on orangutan unflanged males themselves and found that the unflanged males have the same or lower stress hormone cortisol levels as the flanged males. So the second hypothesis came along that the adult unflanged males are an adaptation to avoid the negative effects of stress in the body or that they have experienced lower stress levels. But all of these studies are just hormone studies of a snapshot in time in adulthood when they can't really tell us what makes an orangutan turn into a flanged male or what makes others turn into adult unflanged males. To answer that, we need to look back at childhood, at that time around puberty, to see what their lives were like then. And then, later, what kind of male they became.
So to my knowledge, no study has linked childhood stress to adult outcomes in orangutans, of if they become flanged or unflanged, until this one, until mine. My collaborator and I did this by tracking the effects of stress during childhood on their skeletons. So at the Smithsonian, when you come to visit, you may have noticed a whole floor inaccessible to the public up above the exhibits. There are rooms full of drawers upon drawers of collections that were typically brought to the museum around 100 years ago. And luckily, just before the pandemic hit, I came to study the orangutans of those drawers. Here, you can see me holding up the humerus of an orangutan male who fell and broke his arm and it rehealed incorrectly. He didn't have a doctor in the wild to reset his bone, so it healed with this big lump. So you can see skeletons hold a lot of stories, and the body part I looked at to learn about orangutan stress was their teeth.
So you might be thinking, "Why teeth? How can stress be recorded in teeth?" Well, it's possible because teeth grow like rings on a tree. Trees grow bigger by forming a new layer on the outer perimeter of the trunk every year. And because trees grow more with better rainfall, rings from a rainy season are really thick, and rings from years of drought are really thin. So here, a red bracket is showing you a ring from a year of drought, and the white bracket is showing you a year of heavy rainfall where the tree grew a lot. So teeth reflect a similar pattern, although it's not about rainfall, but about stress.
So new layers of tooth growth come in waves. You can see these waves look like rings on a tree from this black and white microscopic image. The period of tooth growth during something really stressful will look thin, like a tree ring from a year of drought because the stress causes the tooth to slow its growth. So this period of slowed growth shows up on the tooth surface as a dent, because the tooth didn't grow out as much as usual. So quick warning, the next slide will contain an image of human remains to illustrate this. Since severe stress leaves dents on the surface of teeth, we can learn from dental remains about life experiences. So look at these teeth on this image here and see if you can spot any dents on the surface of the teeth of this image. Look for the deepest dent you can find. I'll give you a second.
So I find a bunch of dents when I look at this image. Here's a number of them. I think this one looks particularly deep. You can kind of see it. When our moms give birth to us, our bodies stop growing for that period of time because it's incredibly stressful to be born. So we all have one of these lines on our teeth from being born, but it's unlikely you have any more than that, unless you went through a period of starvation or severe illness with a sustained fever as a kid. That's probably the only one you've got. So really only very stressful things cause these. These dents are called linear enamel hypoplasias or LEH for short. So linear refers to the line. Enamel is what makes up the outer surface of your tooth, and hypoplasia means an underdevelopment. So it's a line of enamel underdevelopment.
So while not that common in humans today, orangutan teeth are full of them. Like we talked about even before climate change, the fruits orangutans eat come in and out of season in these masting events. So even 100 years ago, orangutans had periods of starvation where they ate bark. So here are two images of molds of orangutan teeth with the dents highlighted with arrows on the left and a white star on the right, so you can see the dents on the outside surface of these teeth, and they're really deep. The image on the right is from my research paper. They are a permanent record of the systemic stress during childhood development, and the trauma has to be severe enough to disrupt this process of enamel development. So my collaborator, Kate McGrath and I took dental molds from the teeth at the Smithsonian and at the Academy of Natural Sciences in Philadelphia.
And then Kate used this really high, fancy, high-powered microscope to image the dents and then take point clouds that she read into an image analysis software, which would create this elevation model so we could get the depth of that dent. So you can see in this image the whole process. The top image is the tooth itself, with the dent pointed out with an arrow and all the way at the bottom, you can see that's depth being measured. Then I added the data from who was flanged and unflanged by pulling out the skins of the orangutans in the collection and looking at the skins of their faces to tell if they had those face flanges, those cheek pads or not. I also measured their cheeks and categorized the ones with bigger cheeks as flanged and smaller cheeks as unflanged. Our results showed substantially deeper defects in flanged males than unflanged males.
So flanged males experienced more severe stress events during dental development than adult unflanged males. In fact, flanged males not only had deeper defects than unflanged males, but notably and uniquely deep defects among apes. This means that flanged males experienced way more severe stress events during dental development than adult unflanged males. So our results supported hypothesis two. Males experienced significantly more severe stress events during dental development than adult unflanged males. So this means that it's possible that orangutan males who flange early do so because they had greater childhood stress, or that the ones who go on to become these adult unflanged males were less stressed out when they were kids.
So orangutan habitats, though, are getting more and more stressful like we talked about. Since males flange early when they've had stressful childhoods, more and more orangutans are becoming flanged at puberty. Since orangutan childhoods in the wild are getting more and more stressful, there's less opportunities for these less-stressful childhoods, which my results suggest means fewer and fewer orangutans going on to become adult unflanged males.
So this means adult unflanged males are disappearing in the wild. Adult unflanged males are rare, and they're a unique phenomenon among animals. Since adult unflanged males are only ever found in the wild, and since the wild is getting more stressful and they're disappearing, we have precious few years left to study them. If orangutans in general only have 50 years left in the wild, at this rate, adult unflanged males will go extinct long before the hat. And the sad thing is there's still so little we know about them and why this happens and why they exist. Plus studying them can provide clues for a number of other things. It's possible that past fossil hominid ancestors might have had a pattern somewhat like this, and we can't understand that pattern and that phenomenon now, for if we can't understand that pattern and phenomenon now from species alive today, how are we going to understand it in the past, in the fossil record?
Further, understanding it can help us understand human stress and growth and development. There's some evidence that humans who have more stressful childhoods might go through puberty earlier, like the orangutans who are the same, just way more dramatic. So with climate change, the world is predicted to be a lot more of a stressful place for children, especially in parts of the world that are going to get hit really strongly by climate change. So an understanding of the way that different physiological responses in the body distress can affect and alter development is crucial. Orangutans, as one of our closest living relatives and cousins, can help provide these clues, but we only get to understand these clues and these phenomenon if we keep orangutans around and alive, and we reduce this stress that they experience.
The main threat to survival of orangutan populations in the wild today is the massive expansion of palm oil plantations. Greenpeace finds that palm oil suppliers in the world's largest brands have cleared more than 1,300 square kilometers, or 500 square miles, of rainforest, an area the size of Los Angeles, just since 2015. It's like six years. Palm oil companies prefer to clear primary forests rather than degraded ones or grasslands for economic reasons. And after palm oil plantations are established, displaced and starving orangutans try to find food in those plantation areas, and they're considered agricultural pests and they're often killed in really brutal ways. So palm oil may sound like something kind of foreign to my viewers here from America, but palm oil's actually the most widely used vegetable in the world. It's a small ingredient in the U.S. diet, but more than half of all packaged products that Americans consume have palm oil in them. It's found in lipsticks, smokes, soaps, detergent, and even ice cream.
You could help by limiting palm oil consumption, donating to research and conservation organizations, choosing sustainable palm oil and encouraging companies to purchase sustainable palm oil. So sustainable palm oil is an option that can really help to save orangutans, palm oil that's produced without contributing to deforestation. But if you reach out to companies, you'll hear them say that they've made commitments to switch to this sustainable palm oil that's not causing deforestation. Yet deforestation by palm oil is still a really big problem. So why is that? Well, many companies make commitments to stop buying from deforesters at a future date that they just push back later and later and later whenever that date approaches. So despite promising not to buy palm oil from rainforest destroyers, the world's biggest brands still have in their supply chains, companies that destroy rainforest. So the products you see on the right have palm oil in their ingredients, and their companies promise not to use palm oil from rainforest destroyers.
But Greenpeace discovered that they source the palm oil from at least 20 palm oil groups that actively cleared rainforest. So the problem goes way beyond individual purchasing choices. We need to actually hold companies accountable on an institutional level. Corporations have the power to help save orangutans, and it's time to hold them accountable, especially to their promises. Saving orangutans is not impossible. It's very possible. It once looked impossible to save the mountain gorillas back when there were only 240 left in the wild, and now their population has over 1,000. We've saved them from the brink of extinction. It took a lot of hard work from a number of organizations to protect gorillas, to stop poaching, to stop the killing and capture of gorillas and much more. But success stories in conservation are possible. In fact, two years after I visited the gorilla group in Rwanda, they were doing so well that they had become the largest mountain gorilla group ever, at 42 individuals.
As you can imagine, that was a lot for the main silverback Carrera to manage. A subordinate male named Agisha challenged Carrera and won. Agisha broke away with 23 other group members and created his own group, which today is really big at 31 gorillas, and it includes three other silverback males. Groups getting huge and needing to split used to be less common, but it's happening more and more often because mountain gorillas are living with populations bigger than we ever imagined. If we work hard enough through sustained and well-funded international conservation efforts, orangutans too could be thriving, saved from the brink of extinction just like mountain gorillas. So I want to give a big thank you to my research collaborators and funders. I couldn't have done this without your guidance and support. A special thanks to my collaborator and longtime friend that I met in that trip I mentioned to you to Rwanda, who conducted this tooth project with me, Kate McGrath. You see our picture from those years ago here, and you can feel free to follow me on Twitter to stay updated on my future discoveries and also on my website.
Briana Pobiner:
Wonderful. Thank you, Alexandra. We've got a bunch of questions that have come in already, so I think we'll just jump right in. So there are two questions that are kind of similar, so I will ask them together. One question is from Ronan who asked, "Are there any zoos in the world that contain an adult unflanged orangutan male?" And Molly asked, "You mentioned that there are only unflanged males in the wild. Is that because there is no scarcity of resources or food for captive orangutans?"
Alexandra Kralick:
These are fantastic questions. So what happens in zoos is there's a period of time that you can go through puberty. So everybody you know goes through puberty at a different time. There's a range of times. So in zoos, sometimes you get males that we call it delayed adolescence. They're flanging little bit later than other ones, but it's still within the range of puberty. And you probably know humans like this who went through puberty a little bit later than their peers, but they still went through puberty at normal time. It's just later in that range. So that happens in zoos.
We're not entirely sure why we never get these adult unflanged males. You'll never get one that stays unflanged for 20 years in a zoo, only in the wild. Now my hunch is that my research shows they're only happening when they're not stressed out. So my hunch is that zoos are still stressful to some extent and that's suppressing it. We thought for a long time that being around a flanged male was affecting it and stuff. Maybe sometimes you only have one male who can be adult, so they always flange. So it could also depend on the composition, but I think probably it's a little bit stressful. There are some rehabilitation facilities in Indonesia, but just not any in zoos.
Briana Pobiner:
Thank you. Sorry for that. I had to plug in. My headphones gave me that battery low warning. So we have a couple of questions that are more about your research methods. So Sophie asked, "Can an individual get tooth dents due to stressful experiences in the womb prior to birth?"
Alexandra Kralick:
What a fun question. Yes, totally, completely. So yeah, your teeth are developing in the crypts, so your teeth don't come out until you're done breastfeeding and you're starting to eat real foods, but they're still developing inside of the crypts inside the bone. And so if something really happened, like a period of starvation as a fetus, that could affect dental development for sure. I don't think we see a ton of those. I haven't really noticed that. And then also the period of time I'm looking at is beyond that, but it's entirely possible, I think.
Briana Pobiner:
Nice, thank you. Here's a question that I think is asking about the skeletal collections from Matthew. "How do you tell the difference between unflanged males and female orangutans?"
Alexandra Kralick:
Oh, I love that. So their faces look the same. In fact, they look identical. So you wouldn't be able to tell from the skins. But luckily, at the museum, they have numbered everybody and so I can use the number and I can look at the skeleton. Now the skeleton also doesn't look that different from adult female. The thing that is different is they have the really big canines, the big sharp canines. Ultimately though, I mean that's a good indicator, but I didn't know if I could trust that or not. What I'm ultimately using is the person who collected the orangutans wrote down the biological sex based on the external appearance when they recorded them and put them into the collection. So I feel like that's the most reliable one. That's a very reliable indicator of biological sex. So that's what I've been using. But ultimately, if I didn't have canines and I didn't have that, I probably wouldn't be able to tell because they look really similar.
Briana Pobiner:
Yeah, nice. That's a good question. We have another question kind of along these lines from Neanne who asked, "Could the adult unflanged males as revealed by their skins preserved in museums, could they used to be flanged individuals that at some point lost their cheek pads? Does that ever happen, do you know?"
Alexandra Kralick:
So what happens at Cheryl Knott's site in Borneo is they have these kind of past-prime males where they've been flanged for a while and it's getting to be a lot. And so their flanges kind of shrivel a bit, but the skin would still be big. And so I would still know and none of them were like that. It's a thing that doesn't really happen everywhere. What could happen though is the flanged males that I studied could have at one point been unflanged. So all of my unflanged males were never flanged before. But my flanged ones could have at one point been unflanged. So that's something I have to be careful about so I don't over-interpret the results for the flanged ones because they could have at one point been unflanged, but I can be really sure about the results for the unflanged ones because there's no way they were ever flanged.
Briana Pobiner:
Okay, thank you. So here is a question from Mr. Palma's grade seven class. "Our class is wondering if orangutans go through puberty in a similar way to us, to humans?"
Alexandra Kralick:
Mostly, yeah. So I think they get a little hormonal. They get really stinky. They move away from home. They probably move away from home earlier than we do. So that's really different that when they're going through puberty, they're leaving their mom versus, we don't do that until later. But they're definitely hormonal and stinky. That's similar and they get hairier. That's similar too. So yeah, all of those are really similar. But the face pads are obviously really different. They get a throat pouch, which is really different. I guess you could kind of think of that as analogous to the Adam's apple. But I don't really know if there's anything analogous for the face pads. But the female puberty I think is a little bit more similar to ours. And the males are doing it around age 14 too. So it's a similar age to us. So there's a lot of similarities and that's why when we study it, there's a lot we can learn about humans because ultimately, it's the same process. They have really, really, they have the same bones. They have mostly the same physiology that we do. Their body operates in such a similar way. It's just a different plasticity to it. So there's a lot we can learn from them.
Briana Pobiner:
Nice. And actually, since you mentioned females, we have a couple of questions about females. So Rowan and Saoirse asked, "Do you also see stress in teeth in female orangutans?" So I'll do that. And then there's a similar question after that.
Alexandra Kralick:
Yes, we do. I have one tooth that I analyzed with Kate of a female, and she's got a lot of data from females. So ultimately, teeth grow differently between males and females. So the male teeth grow at a different pace than the female teeth, and that affects the dents. So we actually expect the dents to be less deep for the males. I think I'm getting this right, that they are growing faster, their teeth faster, because they have to get really big. They have to get those big canines. So because the tooth is growing faster, the dents won't dent down as much. And in fact, the unflanged males have really similar dents to the females, but the flanged males have these really, really remarkably deep dents. I might be getting that opposite, but I have to look back and double check which the rate was. But ultimately, they do have dents but the dents' depth is similar to the unflanged males, and the flanged males have these remarkably deep dents, but the females are going through periods of starvation too, for sure.
Briana Pobiner:
Excellent. So along a similar line, Molly asked, "Are there measurable differences in females that have experienced stressors other than these dental LEH, similar to the flanged or unflanged males?"
Alexandra Kralick:
Yeah, there's other ways you can look for stress in a skeleton other than LEH. So a really good one is asymmetry. So when a body looks asymmetrical, so one part, one half of the body looks a little different than the other half, theoretically when you're not stressed out, everything develops symmetrically. So if you look at asymmetry in the face, asymmetry in the skeleton, that can be an indicator that something was stressful and it disrupted development to not happen consistently and uniformly.
So there is some asymmetry in some females. The females at the Smithsonian are mostly from the wild. There's a lot of stress in the few that come from zoos, especially from earlier times before zoos really ... Not really as much from zoos today as badly unless they had a disease and they got to live for a long time with it, so that could have been painful and stressful, but not really the zoo's fault. If they just had an illness, they're keeping them alive. But there are some formerly, some zoo ones from a long time ago that do have that asymmetry and have some dents from that kind of thing, maybe not eating the right food, stuff like that.
Briana Pobiner:
Sure. Okay, so here's a question since we've been talking about males and females of orangutans. So Samantha asked, "I don't know if you can answer this if there's a definitive answer, but who do you see more stress in? Females or males?"
Alexandra Kralick:
Well, the flanged males. They have dramatically more stress, just dramatically, yeah. I would probably guess we're getting pretty comparable dents between the unflanged males and the females and they look really similar, like we talked about. They're really hard to tell the difference between in a lot of ways. But those flanged males had really stressful childhoods. It's remarkable. It's interesting. So it's not really that stress is affecting males disproportionately compared to females. It's just that some males had this remarkable stress and then they went on to become flanged.
Briana Pobiner:
Got it. So here's another question from a class. So Ms. Hicks's grade two-three class, Dominic wants to know, "How old do orangutans live to?"
Alexandra Kralick:
Oh, well it depends if they're in a zoo or not, because they live a lot longer when they have medical care and stuff like that. So they can live at zoos maybe until their 40s. It doesn't usually get a lot later than that. I don't think you get a lot in their 50s. That would be really special. I think the oldest living chimp might have been up until the 60s or something. That's chimps and not orangutans, but in the wild they're usually living until their 30s. So yeah, late 30s I would say is usually how long they're living in the wild, something like that. It's very variable though. Some live a lot longer and some live short, especially if they're getting diseases or they're getting ... they have such stressful lives out in the wild. So a lot of things can happen. So that can affect this average lifespan. If they're getting killed at a young age, that's going to affect that distribution.
Briana Pobiner:
Absolutely. So here's a question about maybe next steps in your study. So Say asked, "Would your study involve fossil teeth of orangutans also?"
Alexandra Kralick:
I really want to do that and I've been talking to Kate about this. I don't think we have canines, but we have molars. So orangutans are one of the few apes that we actually understand their fossil history a little bit better. So gorillas and chimpanzees don't really have fossil ancestors for them. It just didn't preserve very well. But orangutans used to live all over Asia, so they even lived up into China. And so places like that where they used to live preserved a little bit better than the rainforest they live in today. And so we've had, I think even as far as India and Pakistan, but definitely in China, it's like this wide distribution across Asia, we found some fossil ancestors of the orangutan. They're not orangutans, but they're their ancestors.
So it would be really cool to look at all of this and what we can piece together. So I'm hopeful that my work is piecing together enough clues that if we got a few different pieces from an individual, mostly we just have one thing or one other thing. We have a skull or we have a tooth or something. But if we can get a couple pieces from one individual, then it's possible we can start piecing together patterns of stress and flanging in the past. That would be really amazing. So I'm trying to get enough clues that if we get a few pieces, we might be able to start thinking about that.
Briana Pobiner:
Nice. I think that might have just answered this question, but in case you want to elaborate, Kasoon asked, "Can we use this hypothesis to look at other animals in prehistoric eras?"
Alexandra Kralick:
Yeah, I think people are really wondering whether or not this happened in fossil ancestors for orangutans. And I don't know if you guys have ever seen "The Jungle Book," the new one with the giant orangutan. It's actually based on the orangutan ancestor called Gigantopithecus. And it was so much bigger than today's orangutan. It was like 10 feet tall. It was huge. So Gigantopithecus is a really fun and interesting ancestor to the orangutans. People wonder whether or not it's the source of Yeti myths in Asia. It was huge. So it would be really fun to understand if those massive ones, especially the males were flanging, but also this ability for males to be so plastic in their development is a very hominin thing. And so looking at the human fossil records, seeing if there's more plasticity in male development, it's totally possible that our ancestors had some flexibility and plasticity.
So figuring out those clues from the orangutans will help us be able to piece that together. But also just generally biologically understanding how this really weird thing happens can help us understand other animals. So this kind of happens in fish, lizards. It's not really that common in mammals, but there's a whole debate in biology about how having two different types of males can happen biologically. And so if I can piece together enough clues about the physiology of how this is happening, even just the study about stress can help the people studying this kind of thing in lizards and fish because they're looking at stress too, and they're wondering if stress is affecting the two different types of males when it happens in bower fish and stuff like that. So it's going to contribute more generally to understanding when this weird thing happens in the animal kingdom.
Briana Pobiner:
Nice. So quick question, you mentioned Gigantopithecus. Can you tell us what that is?
Alexandra Kralick:
Yes. Gigantopithecus is a fossil ancestor of orangutans. So we have a few pieces that we found. I think Gigantopithecus might have been found in China, somewhere like that. It was found in Asia, not in today's orangutan habitats, but when their ancestors had a wider range. Back in the Miocene when it was the Planet of the Apes, there were lots of different ape species back then. And so the precursor to orangutans, one of their possible ancestors was a 10-foot tall, massive, probably orangutan-looking creature in Asia. And it probably lived alongside some of the precursors to humans, but not really in the hominin lineage. So when I talk about the myths of the Yeti, it would be more like maybe people stumbling upon these bones and being like, it looks so humanlike and it's massive. And that could have maybe been how the Yeti myth could have come about. Just one fun idea people have, I don't know. It's a possibility.
Briana Pobiner:
And so these are millions of years old, is that right?
Alexandra Kralick:
Yes. This is over 8 million years ago, I would say.
Briana Pobiner:
Okay, great. So here's a question not about orangutans, from Ronan, who asked, and it's not about teeth either, but, "Why did gorillas have black fur? Black absorbs sunlight? Is it cold in the rainforest because the tree canopy blocks out so much sunlight that they need to stay warm? Or is it for another reason, if you happen to know?"
Alexandra Kralick:
Well, I don't think we studied this. I don't think we have anybody trying to answer this question, not because it's not a good one. It is chilly. I don't know if you saw the pictures of me in the rainforest, but I was in black and I was in layers. So it is chilly up there. So you don't expect that when you hear Africa, but I was not prepared clothing wise when I got to Rwanda. It's definitely chilly. And women walk around with these shawls. It's not cold, but it is chilly. I would describe it as. It probably gets down to the 50s at night. So that's enough that having a nice furry coat would help. But I would add that it probably also contributes to allowing for the silverback to show up. We don't know that, but you have that beautiful silverback for the silverback gorillas.
And so having that kind of contrast between black and silver, that might have contributed to the black evolving compared to that chimpanzee color, which is less of a deep black. And also mountain gorillas have much more of a deep black color than even western gorillas kind of have an orangier, redder color to their hair. So mountain gorillas, as you saw in my pictures are really black. Yeah, so I don't know, it could be about it's colder definitely in mountain gorilla habitats or something about the silverbacks or something just else about their habitat. I don't think anybody's really trying to answer that and they should.
Briana Pobiner:
That's a good question then. Great. So Samantha asks, "Ms. Gomez's grade seven class wonders, How close is our DNA, the DNA of humans, to orangutan?"
Alexandra Kralick:
Yeah, it's about 98 percent. So it's really close and ultimately, it's just tiny little changes of what's turned on and off really because they have such a similar physiology and body to us. It's more turning on the genes that create hairiness. It's most of those are where the differences are coming from because they're just so remarkably similar.
Briana Pobiner:
Nice. We have a couple of questions that are similar, so I'll ask them together. Rachel asks, "I know there's been recent research into intergenerational stress in humans. Do you think that intergenerational stress could have an effect in proportions of flanged and unflanged orangutans?" Also, Maggie asked, "What about epigenetic stress?" And Nancy asked, "Can stress of an adult female effect deformities in their babies?" So kind of similar questions, I don't know if you want to take one or more of those.
Alexandra Kralick:
Yeah, I don't think we have answers to a lot of those. I don't think people are studying intergenerational stress in orangutans. It's so hard to track them. I'm so impressed with the sites and what they have done. But often when a mom has a baby, the baby will go off on its own when it's ready. And it's often leave the study site. So it's hard to then track generations if a baby's going off and leaving that study site. It happens way more in orangutans than in gorillas and chimpanzees. So it would be challenging. I think it would be a little bit easier to do it in zoos, but the stress is not the same. It's not nutritional stress or disease stress. It would just be like life is maybe not fun under a glass. So we definitely don't have the answer.
But just like I was saying, their physiology is so similar that yes, it probably would. Knowing what we know about humans, there's no reason to believe that wouldn't translate to orangutans, that if moms were stressed out, that there's no reason to believe that wouldn't affect the baby. In terms of whether or not it would affect flanging and unflanging, I wasn't looking that far back into whether or not they were getting stressed out when they were a fetus. But I do think that's entirely possible, given that I'm finding such stress events really early too, all the way up to the period around puberty. We don't know what period of time the stress is affecting what they become. But regardless, if they're getting programming that the mother's stressed out, running from fires, going through starvation mode, yeah, that's going to affect kids. And I bet that that's affecting the distribution too.
Briana Pobiner:
Speaking of flanged and unflanged, and here's a question from Sydney. "If you know this, do unflanged males and flanged males have similar success with mating? Would it be advantageous either way to be flanged or unflanged?"
Alexandra Kralick:
We do know the answer to this. So for a long time, we thought unflanged males weren't having babies, but we started doing genetic testing. Orangutan researchers started finally doing genetic testing and we're finding a few babies that had dads that were the unflanged males. It varied significantly from site to site. Some sites, it wasn't that many, only maybe one baby and others it could be as much as half or more of the babies. So the unflanged males are usually mating with females that have never had a baby before. And the flanged males are definitely the preferred choice for females that have had babies before.
So it's more like you can sneak around. You're not really having the pressures of being this big flanged male when you're an unflanged male, but you can still have mating opportunities. You're just not really the preferred choice. So it's a trade off here. You're not as stressed out and producing all this testosterone and going up the trees and calling out for these females and doing all that stuff that a flanged male has to do, but you're not really the preferred mating choice. So it depends place to place how beneficial each strategy is and how well they do. But it's entirely possible that they do well sometimes, yeah.
Briana Pobiner:
Here's an interesting question, another one from Rowan and Sarsha. "Are there ever flanged females, like non-binary humans?"
Alexandra Kralick:
I love this question because a big reason why I do this work is I'm interested in busting the sex binary. And so ultimately, I keep telling you how the biology of the unflanged males looks just like the females. They're just as strong as the females. They have the bone composition and often size and shape and the face of the females, yet they're making babies like a male. So I think they're a really great example of how biological sex is on a spectrum. From really big flanged males to females, you have this in between that happens naturally in the world. And so the world doesn't naturally have just only big males and small females. It has the spectrum. And even within unflanged males, you have the spectrum of sizes and within flanged males and females. But it's a really good showcase of how biological sex is variable and isn't just dichotomous big, small.
In terms of having intersex individuals and stuff like that, there's not any that I've encountered. But again, given how similar they are to humans, you'd expect it. But 1.7 percent of people have some intersex traits. So I would expect somewhere around 1 or 2 percent of orangutans are doing something between being male and female in some way, whether it be genetic or hormone or something. You might encounter females with really high testosterone levels that start to have really big muscles and maybe a little bit of a ... I don't know. I haven't ever found a flanged female, but I do think that that kind of variability and overlap exists in nature.
Briana Pobiner:
Nice, thank you. Here's an interesting question from Amy. "Could the cause of the deeper defect in flanged males also be that the orangutan is placing more energy into puberty than into dental development? So in other words, the pubescent male is already diverting energy to developing flanges and then when they experience stress, they form hypoplasia defects more readily than the unflanged males."
Alexandra Kralick:
Yeah, that's possible. I think that some of the places we have hypoplasia could be around puberty. And so the hormonal studies, some of them look at the individuals that are going through puberty that are flanging. And when we look at the males who are flanging, in the process of getting those flanges, sometimes they're the most stressed out males of all. Sometimes they have the highest cortisol levels of all. It depends whether or not you're looking at the wild or captivity and where you're looking. But sometimes they're the most stressed out. So theoretically, they could be going through the process of flanging and that's so stressful that's producing a hypoplasia. It's going to be really hard to piece that out. But I do think that it's not only that given that we're having these hypoplasias also earlier in the dental development as well. So it's more like it's probably not either-or, but it could be an and. It could be a both.
Briana Pobiner:
Okay, thanks. So Ms. Romaco asks, "My class would like you to explain what sustainable means please. Thank you."
Alexandra Kralick:
Yes. So it's entirely possible to produce palm oil without deforesting. So we're talking about sustainable, we're saying, "Can we produce this in a way that doesn't continue to get rid of forests? Can we produce this in a way that doesn't destroy the forest anymore?" And it's entirely possible. We can do it in a way that continues to produce palm oil without hurting orangutans or the environment. That's possible. And we have the ways to do it. And on that side, I had some of the ways the Roundtable for Sustainable Palm Oil has come up with, for companies to do this in a way that doesn't end up hurting the animals or the environment. They just have to not clear fresh rainforest, use existing places and do in a way that doesn't overtax the environment.
There are ways to do it. It's just not economically advantageous for companies. Companies will make less money if they care about the environment. So they don't want to do it. So that's why we have to put pressure on them because they can. It's possible to save the orangutans. It's possible for them to make palm oil without hurting them. And we don't have to stop making palm oil. We don't have to hurt the economy by saying no palm oil at all. We can do this in a way where we don't hurt orangutans if we just put in the time and the money and the effort.
Briana Pobiner:
Thanks. All right, back to flanges. So Sue asks, "Birute Galdikas told us that the flanged males were the dominant males. Isn't it possible that greater stress during development comes from more aggression in those males that ultimately become flanged?"
Alexandra Kralick:
Yeah, I think a lot of people have been thinking that. So there's actually instances of aggression as early as age four, so really young. And so theoretically, if these big flanged males are being aggressive towards little ones at that young age, that could be contributing to it too. So it might not just be nutritional stress or diseases. I mean those are the things we mostly study in hypoplasias, but people want to study more social stress because social stress, we know humans and apes are so much like us. Social stress can be really, really stressful if you've been isolated from your group or if you've been attacked and you're in pain and you're healing an injury. So I do think that these instances of aggression could be contributing to it, and it's not totally clear whether or not flanged males are aggressive towards adult unflanged males, but we do have instances of aggression among kids or between adults and kids. And so that could be contributing to what I'm seeing.
Briana Pobiner:
Great, thanks. Here's an interesting question from Yen. "Is there any evidence from the teeth that orangutan populations living in marginal habitat experience more stress than those in prime forests?"
Alexandra Kralick:
So from the teeth, these are from 100 years ago. So this is something that I want to look into. It's like what the people who collected them wrote down as types of places where they are from. But we're not really talking about the marginal forest that we have today. So ultimately, an amazing way to do this is something Kate and I keep talking about is there are orangutans who have been rescued. They were in really marginal places. They were wandering in and out of these agricultural areas or wandering in and out of plantations. The plantations want to kill them. They get rescued and they get brought to this rescue place. And theoretically, if we can put some molding stuff on their teeth, we could actually see whether or not living in that marginal place costs a lot of stress. So Kate and I really want to do this someday. It's definitely a future direction for my work, is looking at the orangutans today, especially where they come from, especially the rescues and seeing how that's on their teeth. It's just not really a question that I can easily answer from the ones from 100 years ago.
Briana Pobiner:
Yeah, that makes sense. Here's a question about flanges in general. So Jamo asks, "Are the flanges just skin or cartilage or is there any bone in there?"
Alexandra Kralick:
No bone, but it is fat. It's fatty. Yeah, so it's skin. I don't think there's really any cartilage in it. It will move the muscles and stuff a little bit around. But mostly what you're looking at is a fatty pad. It's kind of funny, which is why it's like people never thought they could study it on bones until I figure it out that you can figure it out from these skins. They're mostly just these big fatty pads.
Briana Pobiner:
Nice. So the collections are very valuable in that way.
Alexandra Kralick:
Yeah.
Briana Pobiner:
Here's a very relevant question from David. "Have the orangutans and other apes been affected by COVID-19 infections?"
Alexandra Kralick:
So far, the wild ones have not, and that's only because of incredibly really, really hard work that people have been doing who live near them and study them. So gorillas, the number one cause of death for gorillas has been human respiratory diseases. There's been huge outbreaks of tuberculosis in both gorillas and chimpanzees. So people who work in gorillas have been making sure no one gets near them and everybody who has to be near them wears a face mask and stays really far away. So a recent publication actually just came out about how they've been successful in preventing even finding out how bad COVID would be. But a lot of times, if apes get human respiratory diseases, it's worse for them than it is for us. This happens a lot. So people have been desperately working really hard not to find out how bad it will be for orangutans and gorillas and chimpanzees. And in fact, I believe some apes and zoos have actually gotten the vaccine, which is really cool. But it's something we've been working really hard on because they're so closely related to us. It could be really bad if they get it.
Briana Pobiner:
Yeah, absolutely. Here's a just general population question. So Ronan asks, "Are there less than 240 orangutans in the wild today?"
Alexandra Kralick:
Oh no, there's tons of thousands. There's plenty in the world to save. We have way more left than we do with mountain gorillas, so that's why I know it's sad and I know they're disappearing at a really fast rate, but it is entirely possible to save them. There's a lot still left.
Briana Pobiner:
Excellent. And so this is a good question. I think we have a few minutes left, but this might be our ending question or I might be able to take one more after this. So Ronan asks, "Is climate change only threatening great ape biology or is it also threatening other primate species?"
Alexandra Kralick:
Oh, it's threatening every animal for sure. It's threatening apes in particular because they live in these rainforests. So it's easier, like for example, baboons. Baboons can live in the grasslands. They can live near humans pretty okay. I mean they're almost considered rats in some places. They're just doing pretty well around humans. So it's still affecting them and they still are changing their diets, but it's way worse for apes because they rely on rainforests that are so much more temperamental to climate change than, for example, like a savanna or animals that can live near humans well. They just don't live near humans well and they don't want to. So that's why it's just so much worse for them than other primates. But all primates are affected by climate change, negatively. It's just these are among the most affected.
Briana Pobiner:
This is a sort of career-related question from Brethan. "What apes have you worked with?"
Alexandra Kralick:
Oh, gorillas and orangutans. I haven't really worked with chimps. I have measured some of them in collections, just kind of as a comparison for the work I've been doing with gorillas and orangutans, but I've worked a lot with gorillas and orangutans.
Briana Pobiner:
Nice. And then, let's see, there's actually since you mentioned gorillas, maybe we'll just end up with a couple questions about gorillas. So Mr. Palma's grade seven class is wondering why only the dominant male has a silverback. And Daniel asked, "How long is the lifetime of gorillas compared to humans?"
Alexandra Kralick:
Yeah, so the lifetime for gorillas is like half what it is for humans who are doing great. Again, it's really similar to orangutans. So really getting up to the 30s, maybe 40s if they're really lucky. Poppy recently passed away. It's a gorilla that Dian Fossey studied, and I think Poppy lived into the 40s and it was really impressive. So it happens in the wild and it can be even better in zoos, but it's just not as long as us. To be honest with you, think about gray hair probably in terms of stress. So I like to talk about Barack Obama and how the presidency seemed like it affected his hair in graying ways and how stressful the presidency probably was. And so I bet that being this big dominant male who's defending his group, I mean the silverbacks have to defend, they fight, they can get really injured. It's really hard work to be a dominant male in a gorilla group.
So I imagine that it's incredibly stressful. So I imagine that similarly to how humans can gray a little bit more when they're stressed out. And we have a lot of instances of that, of people even who went off into the military, had a stressful time in the military, come home with streaks of gray in their hair. So why would it not be similar for gorillas who are doing this really stressful job and they get gray? Instead of streaks in their hair, it's on their back. So I think it's probably really similar to that.
Briana Pobiner:
Excellent. Thank you. All right, so we are at 12:30. We're going to wrap up. I just want to thank Alexandra so much for her presentation and answering all your great questions. So we're going to conclude today's virtual program. So please join me in thanking Alexandra for sharing her work with us. And I'd also like to give special thanks to those who made this program possible. This includes the behind the scenes team who helped sort through your questions, our donors, volunteers, and viewers like you. And finally, to all our partners who help us reach, educate and empower millions of people around the world today and every day. And we thank you.
I hope you'll join us for our other programs over the summer. Our next HOT Topic program is currently planned for August 19th, so we are not having a HOT Topic program in July. We'll put a link in the Q&A where you can find information about our upcoming programs and how to sign up for the museum's weekly eNewsletter, which is really the best way to stay informed on upcoming programs and learn more about the museum's research and exhibitions. After this webinar ends in a moment, you'll see a survey pop up asking for some feedback about the program. Please take a moment to respond. We're very curious to know what topics you might be interested in seeing for future programs and we appreciate your input. Again, thank you to our participants, thank you to Alexandra and thank you to the audience and we'll see you in August. Thanks.
