We’re excited for the upcoming release of Rob Dunn‘s new book, The Man Who Touched His Own Heart, on February 3! After taking on the parasites, microbes, mutualists and predators that shape our human selves in his last book, The Wild Life of Our Bodies, Rob has moved on to explore the history and science of our most vital organ, the heart. Get a sneak preview of the book in this Q & A:
Interviewer: I’d like to ask you more about the story behind the story of your heart book.
Dunn: OK, sounds great.
What is the heart?
Oh, an interesting question to start. The heart is the muscle, an enormous muscle, just under the rib cage. In humans it has four chambers. On the right side of the heart, blood enters a first small chamber from the body, devoid of oxygen, and is squeezed into a larger chamber (the right ventricle) which contracts and sends the blood to the lungs where it picks up oxygen before returning to the left side of the heart which pumps even more forcefully to squeeze the blood down the miles of arteries, arterioles and capillaries. We think of the heart primarily in terms of moving oxygen (and carbon dioxide), but really it moves everything. It moves immune cells. It moves sugars. It connects the many cells of the body. To me it is like a frame the hangs up the pieces of a mobile.
I’m not sure I follow the analogy with a mobile…
I mean, without the heart, nothing else in the body makes sense. The heart is what gives us circulation. Every other element of our bodies really just functions relative to circulation. The intestines digest food to provide nutrients to the circulatory system so they can be distributed. The kidneys and liver, they help control what is and is not in the blood. Even the brain, it steers us away from things that put our circulatory system at risk and toward things that provide it food. And we didn’t really understand any of what I’ve just said until the 1600s.
Were you hyper aware of your own heart when you were writing the book?
I guess so, but maybe more so hearts in general.
Yes, you mean in people?
In people, in other mammals. In birds flying through the sky. Once you start thinking about it, hearts are everywhere. I sometimes wonder what it would be like if we could hear, in one place, all the different calls of animals. Mice singing. Crickets. Bats. Ants chirping. I wonder it too if you could hear all the hearts, it would be deafening, so many beats.
Like a drum circle.
Like a really loud drum circle, with some slow drums, like human hearts, and lots of fast ones. Shrews beating super fast. Mice too. Squirrels. It is silly I guess, but anyway I think about it.
What got you interested in the heart? I know you’ve done a lot of research on humans and the species that live on and in them, but how did you get from there to hearts?
The more I study humans, the more fascinated I become by how much we still don’t know about the biology of our own bodies. It was just a few years ago, for instance, that my friend Bill Parker finally figured out what the appendix does. Similarly, we are working a lot on the axillary organ and no one really has a clue what it does. But even as I realized that many features of our bodies are poorly understood, overlooked geographies of flesh and blood, the heart seemed like one thing that we must, by now understand. And yet as I started to look into it, it became very clear that we are just beginning to understand the heart. We have been trying to figure out the heart for several thousand years, but nearly all of the work we would think of as modern has happened in the last fifty. And then, on top of that, what seems to be most missing from our understanding of our own hearts is how it compares to those of other animals. The very first comparison of heart disease in humans and chimpanzees wasn’t done until 2011. 2011! And so for me, the combination of the extreme technological innovations in dealing with the heart, the ancient history of interest in it and the exciting modern work considering our hearts and bodies in light of the rest of biodiversity, all of that made the heart fascinating, inescapable really.
Wait, back up a little bit, are you saying that chimpanzees and humans have different kinds of heart disease even though we share 98% of our genes.
Yes. We get heart disease due to atherosclerosis, clogging of the coronary arteries. They get a totally different sort of heart disease. That is two mysteries then, two mysteries no one noticed until just recently.
So what is going on there, why is there that difference.
No one really knows yet. If anyone tells you they do, they are lying. Basically, only two people in the world are studying this difference, Nissa and Ajit Varki, and it is just one of the things they are studying. They have some interesting ideas about what might be going on, but the truth is no one knows yet and if they, for whatever reason, stopped studying this question, no one else would be. This is amazing to me. It is especially amazing when compared to the other realm of what is going on with hearts, the more medical side of the story. I think the clear lesson from what we know about the basic biology of the heart and its diseases is one of humility. On the other hand, the lesson from the side of cardiology and heart surgery is one of progress, but perhaps just as conspicuously, repeated waves of incredible hubris.
Has there been more done when it comes to the heart in terms of medicine? More than in the context of basic biology? It seems like there must have been?
Yes. Yes. Definitely. But maybe not quite the way you would imagine. The study of the heart in the context of medicine starts no fewer than two thousand years ago. The great Greek scholar Galen spent a great deal of time trying to understand the heart. He failed to see the big picture, but captured many details accurately. I’d love to travel back in time to meet him. He was quite a character. But it wasn’t until the late 1890s that the first heart surgery was performed. The 1890s. And then it really wasn’t until the middle of the last century that heart surgery took off. What this means is that nearly everything we know about fixing the heart, transplanting hearts, making artificial hearts, replacing valves, squishing open arteries and all the rest, we have figured it out in the last half dozen decades. It is a VERY new field, but it is now an enormous field. Big meetings of cardiologists, for instance, can have tens of thousands of participants. Contrast that with the two people comparing the hearts of chimpanzees and humans!
Do you do anything different in your own life to keep your heart healthy?
That is a good question. I think that we all hope that an ideal diet can be found that will allow us to live forever. It seems silly when I put it that way, but that is what diet books all imply they will give us. Eat grapefruits and live forever. Or only meat. Or only squirrels. Well, maybe nobody has said that about squirrels, but you get the idea (I am writing from the South). For all the reasons I discuss in the book, finding just the right diet is very, very challenging scientifically. What is easier is noting the really bad diets and lifestyles. Too much sugar, for instance. It seems very clear that is not good. Nor is smoking. Nor is living in the pollution of many U.S. or world cities. Yet, even once we agree on something like that, it is hard for an individual consumer to do much about it. We’d get a lot further by thinking about designing policies, cities and landscapes that help to remedy known problems. That sounds like I’m pushing off decisions onto politicians alone, but I’m not. Some of these changes are ones anyone can make. Plant trees. Figure out things that make it easier for you to stay mobile and bike to work. If neither of those things is possible, well, move someplace with more trees and where biking is easier.
I guess the other thing though is less what I do then how I see the world. The fact that we still don’t understand key features of the heart strikes me as an indication that humanity is only beginning in its journey to understand this world in which we evolved and, recently, gained consciousness. We look back at other societies, “the ancients” in some broad sense, and we think them dopey. But they didn’t think themselves dopey. In the same way, I suspect that the future will regard our ignorance as astonishing, particularly with regard to how our own bodies work.
Were there any facts about the heart that surprised you when you were writing?
The heart pumps something like 8000 liters of blood a day. If you stretched your blood vessels all out, they would go around the Earth several times. The littlest vessels, the capillaries are a cell wide, one 50th the width of a hair! The blood the heart is pumping, it accounts for 8% or so of body weight. A lot of you is sloshing around at any moment. A blue whale heart beats just 4 or 5 times a minute, a shrew 1000 times. But their hearts are very similar in structure. In whatever animal one finds it, the heart is a pretty amazing hunk of meat.
Is there anything that you didn’t put in the book that you think should be in there?
That is kind of a mean question. Yes, a lot. Though maybe not quite in the way that you are asking. I take you to mean, do I have regrets? I don’t have regrets yet about what I excluded, but there are stories that I think are absolutely fascinating, touch on the key ideas of the book, and yet just didn’t quite fit in the narrative.
Can you think of one right now?
Yes. A lot of great science happened before 86 AD in the Roman Empire. Then the dark ages came and that science basically disappeared, only to be rediscovered in the early Renaissance, some 1300 years later. This much I talk about. For the heart, that rediscovery happened in waves. Da Vinci was the first, and he built on the old Romans to discover things no one before him knew and that no one would know again, in some cases, for five hundred years. Then, separately, the anatomists in the Venetian Empire also rediscovered the ancient learning and, in their case, VERY, VERY SLOWLY started to build upon it. All of that I talk about in the book. But what I don’t talk about is the thin thread that connects the knowledge of the ancients, antiquity, to Da Vinci and the Anatomists. Who was it that kept around the documents that Da Vinci and the Anatomists build on when they started their work? That thread is an absolutely fascinating one, tended largely by Muslim scholars who hand-copied the ancient work and preserved it. Their story is a big one that has been told in part by others, but I would love to write about it more. Islam saved knowledge. As it was, the science of the early Renaissance was hard, challenging in every imaginable way, but if it wasn’t for the Islamic scholars, I’m not sure it would even have been possible. I think that one an reconstruct a world in which, from a scientific standpoint, the Renaissance simply doesn’t happen.
To go on a little bit, because of the number of years we are talking about—from the fall of Rome to the beginning of the Renaissance, the ancient knowledge didn’t have to just be preserved, it had to be saved again and again. One of my favorite moments in this thread is in Toledo, Spain, where, for a moment in history, less than a hundred years, the Muslim caliphate, Christian scholars and Jewish scholars coexisted and, in that coexistence, worked frantically to translate all of the documents they could get their hands on. It is thanks to this group that we know Ptolemy, for example. It floors me just talking about this now how contingent our knowledge of the entirety of the western past is. Most of what we know could have been lost. And much was lost. Many beautiful insights, stories, poems, songs. I could have written, as I guess you see from that fact that I am going on, a lot more about that.
Do you have a favorite character from the book?
That is a good question. You know, the people I write about, they come to inhabit my life. They come to my dinner table with my wife and kids. They go to beers with my friends and me. As I am writing about them, I can’t help but talk about them and try to relate to their experiences. In the story of the heart, many of the key individuals are not one hundred percent likeable, not, I am saying, great to have to dinner. Even some of the folks who I think of as heroic, Helen Taussig for instance, are not necessarily so obvious likeable. But I do like Helen Taussig. She inspired a fair amount of animosity in her life. She struggled through challenges, but she did so with a sometimes abrasive personality. Yet, I get the chills when I think about the story of her second career. I mean, after retiring and moving into a retirement home she went to work every day at a museum dissecting, tiny birds. Who does that? And her friends, her scholarly friends, many of them doctors she trained, they clearly thought that this was the work of a wandering old mind, greatest gone a little punk with rot. They thought that when she died. But it seems clear to me that this work in her retirement, it was some of the most innovative in her life. I marvel at that. I suppose I also aspire to that, to the possibility of creative ideas throughout my life.
But she is just one. I find the pathos of Christian Barnaard fascinating and also tragic. I’m intrigued by the bullheaded persistence of Werner Forssmann. Favaloro was a hero in the simplest possible terms, a tragic Latin American hero of the sort that Marquez might write about, except real. Or Ajit and Nissa Varki, a couple off on their own studying what everyone else is ignoring and, in doing so, challenging really fundamental aspects of what we know about our hearts.
OK, so it sounds like maybe they are all your favorites.
You’ve mentioned several times new discoveries in the heart. What do you think awaits.
Well, I can tell you about one thing we are working on that has been fun. It is has been noted for a while that most mammals–rats, mice, humans, whales and the like–get about a billion heart beats in their life times. This is, somehow, the natural longevity of a body. The heart’s beat is a measure of how much work individual cells do and, as the beats go on, the cells wear down and become more susceptible to the maladies that do us in, including heart disease and cancer, but also just about everything else. But some mammals, well, they get a few more heartbeats. We are one of those mammal species. If you are lucky and live out the average life expectancy in a developed country, you will get about 2.5 billion beats. That is more than a lifetime of extra beats! The amazing consequence of public health and modern medicine, including the medicine of the heart. But there is a catch. While there are more than 5000 species on Earth, only about 20 of them have been studied in the context of the relationship between heart rate and life expectancy and so we are starting to study more. Our hope is to be able to find more mammals that, without health care, eke out a few extra heart beats. We can learn from those mammals, we think, about longevity, about living on despite the wearying beating of our hearts.
But that is just us. I think other revelations will come from looking at the species that live in hearts. Or by comparing the maladies of apes to those of humans. The work on stem cells is exciting. It is an incredible time. We are still so naive about our hearts that it is easy to imagine many discoveries on the horizon that seem impossible now.
The Man Who Touched His Own Heart by Rob Dunn (published by Little, Brown and Company, 2015) is available on February 3.