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Gerry:
Your heart. You never think about that endless rhythm unless it skips a beat. The human heart is said to be the hardest working muscle in the body, but how did that extraordinary muscle evolve? The average adult heart beats seventy two times a minute, a hundred thousand times a day, three million six hundred thousand times a year. That’s over two and a half billion times cradle to grave during a seventy year lifespan. Your thumping cardiac muscle is an elegant example of dynamic strength combined with endurance. My guest this time on Talking apes is Dr. Rob Shave, a professor of sports and exercise physiology, and a co-founder of the ‘International Primate Heart Project’. For many of his hundred thousand beats each day, Rob’s heart is pulsing him towards a clearer understanding of itself, and the evolution of our hearts. He approaches the challenge by exploring the hearts of our closest cousins, chimps and gorillas. Those apes like us have hearts that murmur with the mystery of our earliest ancestral heart. And by comparing those hearts to hunter gatherers, rainforest people, traditional agriculturalists and endurance athletes, Rob is working to examine the acute and chronic effects of exercise and environmental stress upon the heart. Hi, I’m Gerry Ellis and this is Talking Apes, where we explore the world of apes and primates with experts, conservationists, and passionate primate lovers from around the world. Talking Apes is a podcast that well, especially today, gets to the very heart of what’s happening with and to apes like us. The Talking Apes podcast is made possible by generous support from listeners like you to non-Profit GLOBIO at GLOBIO.org. Hi Rob, and welcome to Talking Apes. It’s been a few years and way too long.
Rob:
It’s great to see you, Gerry. I wish we were over in Africa somewhere, maybe Zambia, maybe having a short little glass of whiskey whilst we have this chat, that’s what I’d really like to be doing.
Gerry:
I can’t tell you how I long for that. Well, we actually met a couple of years ago, I think three or four years ago now, and you were looking at chimp hearts and I had heard about you and I was trying to catch up with you somewhere in the world. And lo and behold, I walk into Chimfunshi Sanctuary in Zambia and guess who’s showing up as well in that sanctuary? So just to get everybody on board, what the heck were you doing there?
Rob:
Well, we’ve been going to Africa for, I don’t know, it’s probably about eight years now, working with colleagues over there looking at chimp hearts, gorilla hearts a few bonobos here and there, we’re just trying to-
Gerry:
We being?
Rob:
So myself and a colleague, I was gonna say colleagues, friends, that I’ve been working with for a number of years. So Dr. Amy Drain, who was a PhD student of mine at the time, she and I’ve been going there quite frequently Dr. Glynn Howardson, who’s been a research colleague of mine for a number of years. And then various students along the way have come to help out or run specific studies. So the idea behind the project really is to better understand heart disease in our closest evolutionary cousins and also to get some insight into the human heart. How has the human heart evolved? So yeah, that’s what we were trying to do. But I remember vividly meeting you for the first time because I just jumped off the back of a crazy land rover journey and you ran up, grabbed hold of a bag and thrust a beer into my hand. So you obviously wanted something.
Gerry:
<laugh> No, that’s how I meet everyone is just grab their bags and thrust a beer in their hands. <laugh> So the project that all your colleagues you working on, that you were just outlining is called the International Primate Heart Project, and that’s the topic for today, primate hearts. And so maybe you could start us off by just giving us a little anatomical description of what our heart is because I mean obviously everyone knows they have a heart and most creatures have a heart, but I’m not sure that we all really understand what that thing is thumping in our chest.
Rob:
Sure. So, hearts have fascinated me for years. I mean, I used to work with athletes and so understanding their cardiovascular fitness in relation to their athletic prowess was something that I was fascinated by. And that then led me down the road of my PhD where we used cardiac ultrasound to look at the hearts, and I vividly remember looking at a heart for the first time. So you put the ultrasound probe on a chest and there you see this beautiful organ that just works. I mean it works without us thinking. It’s pumping continuously. Four chambers, two atria at the top of the heart, two ventricles at the bottom, sending blood to the lungs where the blood picks up the oxygen, comes back to the heart, and then the left side of the heart pumps that blood around the body to get the oxygen to the working tissues. It also helps with thermoregulation, but it’s just an amazing organ that never stops. And it’s a phenomenal piece of machinery if you like, and, it’s constantly working at rest, but it’s got this capacity to rapidly respond should it need to. So in the olden days where we were being chased by a saber tooth tiger, it could respond really quickly, it could increase cardiac output. The amount of blood pumped outta the heart each beat. So the stroke volume or the cardiac output, how much blood pumped over a whole minute goes up dramatically to meet the demands of exercise. So yeah, it’s a phenomenal thing.
Gerry:
So is that demand, is that the same demand that a chimpanzee or gorilla or I guess any other creature on the planet, but since we’re talking about great apes in particular, is that the same demand, does their heart look like our heart? I mean, if I pull a chimpanzee or orangutan heart out of their chest and pull my heart out of my chest, would they all look the same?
Rob:
So, I mean that’s the fundamental question we’re trying to answer. And when you first look at a chimpanzee heart or a gorilla heart, it’s broadly the same. So yes, it’s got two atria, it’s got two ventricles it pumps at approximately sixty to seventy beats per minute. But when you start looking at it very, very closely, there are some quite marked differences. And that’s part of the work we’ve been doing, is really trying to characterize exactly what the heart looks like. So as I mentioned earlier, we use cardiac ultrasound. So it’s a system very similar to what’s been used to scan pregnant women. So by using that machine, we can look at the heart, we can look at how big the chambers are, how much blood is in the ventricle as it relaxes. And then as it contracts, we can look at how thick the walls are. So depending on the demands that the heart has to meet, the heart will remodel to respond to that. So if you need a lot of cardiac output because you’re an endurance athlete, you’ve gotta have big chambers. But if say you have hypertension, so if you’ve got high blood pressure and the heart is working against that high blood pressure, the walls will respond and so you’ll get thicker walls. So it’s an incredible organ that is really, really responsive to either physiological demands or pathological demands. So if you have disease or something like high blood pressure, the heart responds to maintain its ability to meet the demands, in the face of the challenges associated with disease.
Gerry:
I guess I’ve known it’s a muscle but I never thought of, I haven’t had that conversion in my brain, thinking about if you increase exercise and stress and things, you can increase the size of the muscles in your legs or your arms or wherever. But I guess I hadn’t put those two together and think, well, you could do the same thing with your heart. Because most endurance, I’m sure there’s some genetic things going on there, but most endurance athletes at least, let’s say you’re a sprinter like Usain bolt, I would assume your heart, you’re born with a heart that’s similar.
Rob:
Well, it’s broadly similar, of course with athletes there’s a large genetic component there, and if you are, let’s say, just say genetically talented, you have the ability to adapt and respond probably better than some other individuals. And you’re absolutely right, the heart is a muscle and it responds and it adapts. And so if you think of an endurance athlete, an endurance athlete will have an extremely high VO2 max, I dunno whether you’ve heard that term, but VO2 is your overall aerobic capacity. And that is largely determined by your heart’s ability to generate a large cardiac output. So those endurance athletes, those cyclists, those marathon runners, they have the ability to generate a large cardiac output. So the volume of blood that’s in their heart and then ejected from their heart each beat is much larger than someone else’s, and that’s related to adaptations in the heart itself. So the chamber gets bigger but also our circulating blood volume. So the amount of blood going around the body in endurance athletes that might be fifteen to twenty percent larger. So they just have this expanded capacity to increase cardiac output to meet those demands. Now some of that is genetic, but we’re all trainable and we can all improve. So it’s definitely worth doing the physical activity that everyone is recommended to.
Gerry:
Well, is there the reverse of that then? If an endurance athlete increases that, does somebody who, I guess the opposite way, the ultimate opposite way would be just sitting there all day long and not moving. But Usain Bolt’s heart, he’s a sprinter, it’s a hundred meters and it’s over with two hundred meters, it’s over with. Is his heart smaller?
Rob:
Okay, so now you get into the point of a really big question in exercise physiology. Do hearts respond in different ways to different types of exercise training? And the way in which this is historically been looked at is very much in a sort of dichotomous approach, where you have your marathon runners on one end and then you have your resistance exercise, so your weight lifters and your powerlifters on the other. So very different, what we call a phenotype, very different body shapes that have been adapted to the specific types of physical activity that they do. And in terms of their hearts, there’s huge amounts of data showing that the endurance athletes have a well adapted left ventricle, so their left ventricles get much larger to manage that cardiac output I mentioned earlier on. Whereas the resistance type athletes, they don’t need to generate that high cardiac output. What they have to do is deal with a sort of pressure overload. So as they lift large weights the heart is sometimes exposed to a large pressure overload. And so the heart’s gotta work harder to accommodate that, the walls get thicker. So you get a much, much more muscular heart. And so the way in which it’s thought about is you get a pressure overloaded heart, which is remodeled with thick walls and that’s in your resistance athletes, and you get a volume overloaded or a volume adapted heart in your endurance athletes. And that’s much more of a cavity increase in size, so that there’s quite a differential response to the training. There’s bags of data to support the endurance side, less so on the resistance side. And that’s certainly an area of work that we are still interested in, and others are as well.
Gerry:
So now that brings up a question in my brain thinking about this in terms of apes. And we’re gonna talk about the work that you’re doing on non-human apes, bonobos, gorillas, chimpanzees, orangutans. But my first thought is, well wait a second, these are animals that are in the wild, I mean they have their sort of quiet times, but they’re also very active sometimes, very much so in the case of chimps, they’re explosive <laugh>. But then on the other side of that coin, you have great apes in captivity. Which, like us, are not doing what they should be doing, they’re not moving. I assume you’re going to tell me that we are sitting around all day long doing what you and I are doing right now, just talking to one another and not getting out and doing as much moving around, which is probably not traditional for our heart.
Rob:
Completely. And that’s only made worse at the moment. Covid forced us into this place even more, so the last eighteen months we’ve been sat looking at screens talking through zoom. But you’re absolutely right, and the concept you you’re touching on there is something that’s termed evolutionary mismatch, whereby we have not evolved to sit down all day long, we’ve evolved to be highly physically active and that’s related to hunter gathering past and then moving from a hunter gathering past to subsistence farming. Those components of our evolutionary history mandated lots and lots of physical activity, and we just simply aren’t doing that anymore in the postindustrial societies. I mean there are still some preindustrial societies that are doing that type of physical activity. And I’m sure we’ll come onto that a little bit later. But yeah, at this moment in time, people living in North America, Europe, we are not doing what we’re meant to do. And even those taking part in the forty five minutes of physical activity that we’re supposed to be doing, that’s again not really covering, or it’s not replacing what we should be doing. So the mismatch is that our whole bodies, and in this case specifically our cardiovascular system, have been selected to support a very, very specific type of way of life. And we don’t do that anymore. So as hunter gatherers, we were going out and we were walking for several hours a day trying to hunt down animals, as subsistence farmers we were out in the fields planting crops and harvesting and preparing food. So many, many hours of low level physical activity and we’re just not doing that. And so that has some significant repercussions. So I’m interested in cardiovascular health and cardiovascular disease, but at the same time, they’re the diseases that are increasing in prevalence across society at the moment.
Gerry:
Are there examples, if I can back up a minute to something you said earlier, I mean you’re sort of looking at the evolution of this muscle, the heart. Are there any examples out there of people who you can look at, you could look at their hearts and say, okay, that’s probably pretty close to what our heart would’ve looked should have looked like, so that you can create some kind of baseline vision of our hearts so that look at our hearts now and go, okay, there, there are seventy five percent far off base <laugh> we’ve got a long way to get back to home.
Rob:
So that’s exactly what we’ve been doing. There’s a number of populations around the world who still live a more traditional lifestyle. And the one that we’ve worked with, with colleagues out of Boston, so Dan Lieberman and Aaron Baggage, one’s a cardiologist and one’s an evolutionary biologist, the three of us went down to Mexico to work with the Tarahumara. And a good portion of Tarahumara are still living a very subsistence farming type lifestyle. So we spent some time down there and we looked at their hearts and we looked at their physical activity and they’re sort four, five times more physically active than even the people meeting the guidelines that we currently have. And so the demands that the heart has to meet are markedly different. And the other piece haven’t mentioned that that’s relevant here as well. It’s not just the physical activity, it’s the thermoregulation. So as we exercise, we get hot and we have to dissipate that heat. And part of that is it sending blood to the skin to lose heat through sweating. And if you think again about our evolutionary history, we will have spent a significant amount of time physically active in hot environments. So not only are we now not moving, many of us now live in thermoneutral environments. So even though I’m living up in Canada and through the winter it’s very cold and in the summer it’s very hot, I’m inside and I’ve got air conditioning. And so we’ve got just this neutral balance, but the whole system isn’t getting the stimulation that was required or maybe not required, but the stimulation that our evolutionary history meant that we were adapted for. And that’s gone. And so coming back to your question though, there are still some populations who are living that traditional lifestyle, and so we are able to get almost a blueprint of what a heart in the human has been selected for and therefore what it should look like.
Gerry:
I had never thought about the thermal side of it. So when people are saying we need to get our heart rate up for half an hour three times a week, they should be saying, and you also need to be sweating three times a week as well.
Rob:
Absolutely. But if you do the former, the latter will probably come.
Gerry:
<laugh> Yeah, that’s really interesting. So how does this relate to your work with great apes hearts, non-human great ape hearts? How does this connect?
Rob:
Okay, so I mentioned Dan Lieman. So Dan wrote a really interesting paper, I think it was back in 2011, where he’s talking about the human as being born to run and he outlines the hypothesis that we’ve been selected to be an endurance type animal to help hunt, gather. Now I was rereading a book that referenced that paper while I was sat on holiday and all of a sudden I was like, okay, well if that’s the case then our cardiovascular system must have been selected as well to support that. And I got into, didn’t know Dan at the time, but I got in touch with him and I kind of floated this idea and he’s like, yeah, absolutely, that makes complete sense. But of course the cardiovascular system doesn’t sit in the fossil record. So, most of Dan’s work is looking at the fossil record. And so, we go backwards and forwards and we settle on the idea that we need to scan our evolutionary cousins, we need to look at the apes, to get some idea of where our evolutionary journey as an endurance type animal may have come from. And so off the back of that, I sent an email to a zoological collection in the UK, and I sent it off not really expecting to get much of a response cause I was asking quite a big question. I was asking whether we could come and assess their animals. And bizarrely a couple of things just coincided. And two days later I get an invitation to go and scan a gorilla. So from an initial idea and an email, we were working with one of the zoological collections in the uk and it’s all spanned from there. So by looking at the apes, we then have an understanding of our evolutionary past. It doesn’t start at that point, but that’s our kind of a a model of our last common ancestor. I mean that’s not perfect by any means, the human lineage split off back six million years ago and then somewhere between that split and where we are now, we move from spending a lot of time in the trees to walking upright, to doing far more physical activity than the apes do. So yeah, I’ve rambled a bit there, so we’ve gone off track.
Gerry:
No, no. Actually it’s spawned a couple of other questions, which is exactly what your work when we first met in Zambia did, the questions started swimming in my head and it’s why I was so excited to have you on for Talking apes. So a couple of questions that you touched on there. One is, how different are our hearts? Just again, if I pull my heart out, I pull a gorilla’s heart and orangutan heart, lay ’em out on a table. All of the ape hearts, would you know which one belonged to which, so let’s start with that.
Rob:
So, brief anecdote. Right at the start, we took some images and I sent them to a cardiologist, a human cardiologist. And I was a little bit naughty in that I didn’t tell him it was a chimp heart. So I just sent him an echo and he came back, he said, oh, what’s going on there? He just assumed that it was a human heart. So there is nothing when you first look at it, that makes you think it’s different. However, what we’ve now done, we’ve assessed nearly four hundred and fifty chimps now. So we’ve got a really pretty good handle on what a chimpanzee heart looks like. And when we do all of those measures, the fundamental differences are in two or three places. One of them is that chimps, the walls, the heart muscle itself, are a little bit thicker. So in the human world that would suggest that the heart is adapted for pressure. So, they’ve got relatively thick walls, the cavity inside the ventricle is a little bit smaller, and so it doesn’t actually eject as much blood. The overall cardiac output is a little bit lower. Now that suggests that perhaps the overall metabolic demand that the heart is feeding is probably a little bit less in the chimps. And that that’s probably related to our large brains and also the physical activity that we typically do. So two big structural differences, thick walls in the chimp heart, less thick walls in the human heart and a bigger ventricle in the human heart. But the other piece that’s really interesting to me, and I’ve spent a number of years looking at an area of cardiac physiology, which is called cardiac mechanics, which is how the underlying function of the heart supports both filling and emptying. And probably the most remarkable difference is the way in which the heart actually relaxes. So during the relaxation phase, which is called the diastolic period, the human heart, the ventricle actually un-twists. So the underlying structure of the human heart allows the heart to twist during the ejection phase. And then un twist very rapidly during the relaxation phase.
Gerry:
So like screwing a light bulb in?
Rob:
Almost, or very much twisting out a towel. So if you had a towel that’s wet, so you twist out a towel, you squeeze out the water. So as you twist it, you squeeze it out, but then it springs back and that spring back actually creates some suction. And in the human heart we’ve got this underlying structure that allows that. So we get very, very rapid filling early in the diastolic period. Now remarkably the chimps, we don’t have that at all. There is no rotation at what’s called the apex of the heart. So they don’t twist at all. And our thinking here is that the twisting action is an adaptation in the human heart that enables the heart to generate those large cardiac outputs during periods where the heart rate is high. So when the heart rate is high, you have less time for the heart to fill. And so to compensate that, we’re suggesting that you’ve got this very rapid untwisting mechanism that helps the heart fill during those high heart rates and then therefore generate the higher cardiac outputs. So it’s quite a remarkable difference in the function. And one of the things that that’s related to in the chimp hearts, we have what’s called trabeculations. So it, it’s a long word, which basically means there’s these large folds in the muscle. And because of those folds we think that the ventricle isn’t able to do this rotation, isn’t able to rotate and untwist. Whereas in the human heart, the derived human heart, there’s very few of these trabeculations. So that was one of the key findings of the research study we published a couple years ago.
Gerry:
Is it only the chimp heart? Do we see that in the gorilla heart? The orangutan?
Rob:
Great question. Really, really good question. Whilst we’ve got a lot of data on the chimps, we do have some data on orangutans and bonobos and gorillas. And from what we’ve seen so far, they also have these trabeculations, they also have these folds. And so if you think about the great apes, and we are one of those great apes, a fundamental difference in the human heart is this lack of trabeculation, folding of the ventricle, and our ability to untwist and create these large and diastolic volumes which help generate the large cardiac output. So it’s peculiar, if you like, to the human heart, whereas it appears that those folds are the kind of initial substrate in all of the other apes.
Gerry:
I’ll kind of jump over here a second, but as you were describing that, I was wondering, what about, it’s not an ape, but a primate like baboons. Baboons tend to be, from my observations, they tend to be a bit more often active in large groups. Cause it seems to be this, if we look at a group of baboons, your general observation is, they seem to be even more like us in the sense that there’s constant interactions, there’s constant reactions. Have you looked at baboon hearts at all?
Rob:
We haven’t at all, I mean it’s something that I would like to do. And yeah, I think some of the things we’ve seen are probably related to physical activity, but also that thermoregulation, and from a primate perspective, we’re also peculiar in that we’ve lost all our fur. And so our ability to lose heat is really driven through peripheral vasodilation. So our ability to send blood to the skin and then sweat, whereas all of the other primates don’t have that mechanism. So coming back to what I said earlier on, I think it’s that combination of physical activity and thermoregulation that are both supported through the cardiovascular system and therefore wholly dependent on the activity of the heart, the major pump.
Gerry:
Have you had a chance to look at any kind of hearts on tropical people, and I’m gonna throw out a couple of words here, the Dayak in Borneo and the Ituri in the Congo basin, they’re both people where you can actually find some groups that are living not completely traditional, but very close to traditional kind of hunter gatherer existences in a equatorial, hot, tropical condition, just wondering about their hearts compared to, let’s say, a chimp.
Rob:
Absolutely. We haven’t been able to do that as of yet, I mean there’s a population called the Hadza which I’m sure you’ve probably come across. They would be fabulous to look at, they probably are the closest population to still taking part in hunter gathering lifestyle. But yeah, I mean, changing tack again slightly. One of the fascinating things about the hunter gatherer individuals and also the Tarahumara, one of the things we showed and has been shown in some other subsistence farming and hunter gathering populations is that those individuals do not see the same age related increase in blood pressure that we see in post-industrial societies.
Gerry:
Really, why is that? Do you know?
Rob:
Well I mean it’s probably a combination of things. It’s probably a combination of physical activity and diet, that probably come to bear on this. But it’s one of the questions we are very keen to answer, and we’ve got a project plan for the next year or two once Covid has calmed down. So we’ll go down and really try and look at those mechanisms.
Gerry:
So I’m clear, as you look at, let’s say you and me in this culture and society, and I assume our diets also play a big part in this, our heart disease levels, our heart pressure levels, all those things kind of go up as we get older. And what you’re saying is with the Tarahumara, they don’t, they just flatline till death.
Rob:
Exactly, flatline, so we’ve got data on about 120 Tarahumara men from age about age fourteen to ninety two. And there doesn’t appear to be any age related rise in blood pressure. It’s been shown in a few studies. But if you go to the large data sets from Western populations, the big famous NHANES data set, the blood pressure in western populations starts the rise above the age of thirty five to forty and it continues to rise. So if you were only to look at those data, it would suggest that the rise in blood pressure is a natural aging phenomena. But if you go back and you look at a population that is living the lifestyle that we’ve been selected for, that rise in blood pressure just simply doesn’t happen.
Gerry:
Is that the same for chimp’s, bonobos, orangutans? Do we know?
Rob:
We don’t know that yet. Now the question I often get asked is what is the resting blood pressure on a chimpanzee? And I’d love to be able to give a really solid answer on that. But all of our data is collected whilst the animals are anesthetized. Now we work with sanctuaries, so it’s something I wanna make sure people are aware of, is that we are working with sanctuaries who are caring for these animals. We work with them during regular health checks, so these animals aren’t anesthetized for the work. It’s important that I state that.
Gerry:
Okay, yeah, that was a question I was going to ask you because we’re talking about, I mean, it makes sense if you’re talking about a gorilla in a zoo, but we were talking about the apes, and I’m just wondering how do you measure the heart rate of a wild chimpanzee swinging through the forest of Uganda? <laugh> I assume you’re not doing that.
Rob:
We’re not doing that, I mean, it would be possible, but it’s completely unethical to do it. So all of our data from health checks, we have some relationships though with some zoological collections where they’re worried about the hearts of the animals in that care. And we’ve been able to collect some data from those animals, which gives us some sense of heart rate, but we can’t get blood pressure. So all of the blood pressure data we have from the chimps are from anesthetized animals. So, of course the aesthetic agents have an impact on the measures we take. And so all we can do is carefully monitor those data during our assessments.
Gerry:
Well, I’ll just jump in for a second with my observations and especially my filming of you at work, there were these health checks going on and you guys were always the last ones to get to jump in. Obviously there were key things that the vets in these sanctuaries were doing. And animals that they were working on, for those of you listening, these were rescued from the bushmeat trade, from the illegal pet trade. So they weren’t captured for the purpose of being in a sanctuary. They were actually all orphans who had were living there, or grown up there in a small number of cases, they were what we call oops babies. They were born in the sanctuary because the birth control failed in some way. But the vets were at work doing their general health checks, and then when they finished, you guys got to jump in with your equipment, which is pretty elaborate I have to say. You seemed to have cables and wires and stuff going in every direction possible. You guys were like a NASCAR team when you jumped in and getting the wheels off and filling it up with gas and all of that. I was blown away by how fast you could do what you were doing and collect all this data.
Rob:
We’ve got pretty slick at it. I mean at first it was a bit of a bizarre experience for myself and my colleagues because we work with humans generally. And so to take the equipment that we typically use in the human setting and to then all of a sudden be dropped in the wilds of Africa at a sanctuary working on the floor, yeah, it was a bit challenging. But we got to the point where we can collect most of our data in ten or fifteen minutes working around and with the veterinary teams. But something I think that’s worth pointing out, and this comes back to what I said earlier on about the invitation to go and scan a gorilla, that first ever opportunity, it was a little bit of serendipity really from a research perspective because I had this initial question that I was interested in. But at the time when I reached out to that zoo in the UK, there’s concerns over cardiac health in captive apes. And I was unaware of that at the time, but there was a number of animals who had died and the vet teams were trying to work out what was causing these deaths. And one of their theories, their working theories, was that they had some kind of heart disease. And so my question to them was initially was, well, what’s normal? What does the normal heart of a chimp or a gorilla look like? And they couldn’t really give me any data. And I’m used to huge human data sets, I’m pretty sure, Gerry, that if I put an ultrasound probe on your chest, I’ve got a good idea of what your heart’s gonna look like because of all the data that we have. Those data just weren’t available in these apes. And so a significant portion of the work that we’ve been doing, and especially that of Amy Drain, a PhD student, has been to characterize the normal structure and function of the chimpanzee heart. So she’s been able to make all of these measures and now has created papers where we’ve got the normal range. So now the vet teams looking after these animals can actually refer back to, okay, is this normal for a chimp or not? And they now can tell that. And so that’s been a really important piece of our work and something that we are really, really proud of is providing that information back to the vet teams who are working with these animals.
Gerry:
Yeah, I mean, I know that one of the biggest problems with captive and zoo type settings, especially with it seems more so with gorillas and orangutans than others, is heart disease, because they just aren’t active, or as active as they should be in the wild, and their diets are different.
Rob:
So Gerry can I ask you a question? What do you mean by heart disease?
Gerry:
Yeah, well that’s an interesting question, isn’t it?
Rob:
The reason I ask, and I’m not being flippant is that
Gerry:
No, no, no.
Rob:
When I first came into this area, that’s what the vets were telling me, like, oh, these animals are dying of heart disease. And I’d just say, What do you mean by heart disease? Because if you go to the human model, and I’ll call it that, or you go to the human ape, we suffer from many different types of heart disease. So we might have hypertensive heart disease where our cardiovascular system is dealing with high blood pressures, but we might have atherosclerotic heart disease, which is related to our poor diets, where you get vascular disease, and so the blood supply is being turned off a little bit. And then you’ve got a whole load of congenital cardiac diseases and disorders that are inherited. And so the vets were saying to me, chimps are dying of heart disease. And I’m like, okay, I don’t really know what that means because it could be so many different types of pathology. So when we typically talk about heart disease in humans, people normally think about atherosclerotic disease. But the fascinating thing, and probably the most interesting thing about the chimps is they do not get atherosclerosis. So even though the captive animals are sat around not doing very much physical activity, in some cases they’ve had poor diets. And unfortunately in some research situations they’ve had poor diets or they’ve even been fed very poor diets. So some populations have been fed diets to give them very, very high cholesterol. Even in that situation where they’re not doing any physical activity, they have high cholesterol, poor diets, they don’t get atherosclerosis. So our nearest evolutionary cousin does not get the primary cardiac disease that humans get, but they do get something else in the zoo populations, and certainly a lot of the work from Haley Murphy’s group has been looking at this, the captive apes seem to get this fibrosis. So the heart muscle itself is becoming stiff and it’s got fibrous tissue in it. And what’s causing that? We don’t know. I mean, there’s a number of working hypothesis on that, whether it’s stress related or maybe it’s related to high blood pressures.
Gerry:
And it’s not something get, we don’t get that kind of fibrosis?
Rob:
We can. So if we’ve had a heart attack, our heart, the tissue becomes fibrosis. If you’ve got some certain inherited diseases that lead to fibrosis, or high blood pressure can lead to fibrosis. But the primary cardiac pathology we have is atherosclerosis, fibrosis is secondary. Whereas in the apes it seems to be a primary disease, and we don’t know what’s causing it.
Gerry:
There’s something I know in that some of the sanctuaries, I’m thinking of Tchimpounga in the Republic of Congo, I read something by the vet there, it was something called sudden cardiac death that the chimps suffer from, is this related at all?
Rob:
So, absolutely. It could be. And yes, there’s been a number of incidents of sudden cardiac death in captive animals. Of course, trying to diagnose what caused that sudden death is problematic, especially in sanctuaries where we don’t often have the techniques to assess the animals as much as we really would like to. If let’s say you felt some palpitations in your chest, you’d go to the doctor, they’d probably run an ECG, they might do an echocardiogram if they didn’t get an answer before, you know, it might have twenty four hour ECG. So you walk around and it would be monitoring your heart completely. You then might end up going into an MRI and all of these techniques would be used to understand what is causing that palpitation. We obviously can’t do that with the chimps, but there’s certainly been some cases of inherited disorders in apes that are similar to humans. So we’ve worked with a collection where they think that their population has a disorder called, and this is a mouthful, so I apologize, but arrhythmogenic right ventricular cardiomyopathy or something called ARVC. So ARVC is a well known pathology that causes sudden cardiac death in humans, and this small population in a zoological collection in the UK believe that their chimps are, they’ve shown, that they are gene positive for the ARVC. So in certain cases that could be the precursor to southern cardiac death, but the fibrosis could be as well. So we know that in humans, if you have a fibrosed heart, it can cause arrhythmia, which might then precipitate southern cardiac death. So that’s possible. But the really interesting piece on the fibrosis, so another study that’s come out from looking at pathology records from sanctuaries, there doesn’t appear to be that much fibrosis in the sanctuary populations. The fibrosis seems to be much more prevalent in the zoo populations. Now that could be a bunch of things. It could be diet, it could be stress, it could also be that actually the zoo populations are just much older. The oldest chimps in the world are definitely those that are held in zoo. So maybe it’s a natural consequence of aging, but I think there’s probably a combination of the above.
Gerry:
Well that kind of brings me, I mean we could go on for hours, <laugh>, I literally could go on for hours. But that brings me to a couple of final questions. One is, if there was one heart type out there or one heart group that you would absolutely, we kind of touched on a couple of times, but if there was one out there that you could study, what is it and why? What heart out there would shed the most light on what you’re curious about?
Rob:
There’s a number. There really is, and I’ve been having conversations with zoo teams and vet teams all around the world. So giraffes are fascinating, diving mammals are fascinating but bizarrely at the moment, the one group that I really want to look at is really highly experienced and highly trained human sport climbers. So humans who are climbing all the time, because then what we would have is a model of the human heart that has been selected for physical activity associated with hunter gathering, but then has been trained in a way that is much more reminiscent of what the apes are doing.
Gerry:
So rock climbers?
Rob:
Climbers and sport climbers. So the guys and girls who are doing lots and lots of very rapid ascents up and down. And if you think about it. when they’re holding on huge amount of contraction of forearms and you get this massive blood pressure response. So the heart of those climbers is seeing that high blood pressure. So I’m really interested to see basically how the human heart would remodel to the lifestyle of a chimpanzee.
Gerry:
I mean filming chimps in the wild, well, orangutans as well, but especially chimps in the wild. As one researcher told me, they move through a 3D-3D world, because they’re not only moving through the three-dimensional world we think of on the three axis, but they’re also interpreting information in a three dimensional world. Whether the branch is slippery, the tensile strength of it, they’re encountering a poisonous snake or they’re trying to get to some fruit. So yeah, that blows me away. I hadn’t even thought about climbers, but yeah, you got the guys who climb rapid walls and men and women who do that.
Rob:
Yeah, and so the flip of that, I mean you are giving me the sort of new topic world that I can choose any heart. Now I know that this isn’t possible, but what would be really interesting is a chimpanzee who had trained, obviously we can’t do that, but a chimpanzee who’s trained to do endurance activity. So there you would have a situation where you’ve got the heart that’s adapted for the pressure environment. Can that heart remodel to accommodate what’s required for endurance type activity? I mean, I really don’t think it probably can, cause I think the structure is such, coming back to that twisting motion is such that it wouldn’t adapt. But that would be the kind of ultimate experiment to look at. But of course we’ll never be able to do that.
Gerry:
Well if we ever are, you’re coming back on and we’re talking about it. <laugh> That sounds really, really cool. Rob, this has been so fascinating. As I said, we could talk for hours. This whole idea just is so interesting to me and I’m hoping as we discussed in Zambia, I’m hoping that we can get out and actually film you doing some of the stuff in the field with the Tarahumara, and for further afield with other groups and things if we can. Cause it’s just really fascinating to watch you at work and watch your team at work, and the things you’ve been learning. I mean, getting to see that, I know you sent me some film at one point of those folds in the heart and all of that, and it was just, wow it was mind blowing.
Rob:
Well Gerry, it’s been a real pleasure to talk to you and to share some of the work we’re doing, I mean, it’s the start of a story I think. We’ve got so many more questions that we’re gonna go after. But I also just wanna thank all of the people who’ve been involved with the work. This is a huge team effort. The likes of Amy and Dan and Aaron and certainly the vets, Tolita and Yedra all of these people are just wonderful people and they’re the ones who’ve been able to facilitate this work, and we we’re just incredibly grateful
Gerry:
With every beat of my heart, I want to thank Rob Shave for sharing this incredibly insightful look into how our heart possibly has evolved for the last four thousand or so beats of your heart. You’ve been listening to Talking apes. For each episode, we explore the world of apes with experts from research to outreach with passionate primate people and conservationists from around the world. Our guests are at the very forefront of news about our wild primate cousins. You can find previous episodes of Talking apes on our website at www.GLOBIO.org/talking apes or wherever you get your podcasts. If you have any questions for us here at Talking apes or ideas about future podcasts, you can always email us@mediaGLOBIO.org.
