312 | Thomas Levenson on The Mutual History of Humans and Germs

0:00:00.5 Sean Carroll: Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. One of the great things about the existence of podcasts as a medium, I guess it's not that different from just interview shows on radio or TV, but they're a little bit more ubiquitous now. So they provide a glimpse into things almost as they happen. Obviously, news events can happen very rapidly, but the increase in knowledge that we get through scholarship and research, happens on a relatively more leisurely timescale. And by talking to the kinds of people that we get as guests here on Mindscape, you can see science and research more broadly as it is being done. You get some interesting results, but you also get some insight into the messiness of, "We don't know the answer yet. We're still thinking about this. There's still some controversy. Let's see where we go." And it becomes pretty obvious that of course, we're all human beings. We have our favorite ideas, favorite ways of thinking and so forth. It's a human endeavor, science and scholarship more broadly. So it can be possible to forget that it has always been that way. Because the science that was done in the past, we receive as students and readers and listeners in kind of a finish, polished form. We are given Maxwell's equations or Newton's laws in notation that is much easier to understand than what they actually used.

0:01:33.0 SC: And we're given the final result after they had to go back and forth and think about lots of different things. So things we take for granted now, the Earth is round. Species evolved from previous species due to natural selection. The germ theory of disease, for example. Of course, diseases are carried by germs, that's very natural. Diseases can be contagious. One person talks to another one, they carry the disease now, it makes sense that some little agent was carrying the disease from person to person. But it took a long time, as it turns out, for the germ theory of disease to catch on. And it's worth revisiting that history, both because the science is fascinating, but also the twists and turns in the human side of the story are fascinating as well. So today's guest is Tom Levenson, a longtime friend of mine. He is a professor of science writing at MIT and an active science writer, author of a number of books that I can highly recommend. "The Hunt for Vulcan" About looking for that little planet that was hypothesized to exist between the sun and Mercury back in the day. "Einstein in Berlin" About some of Einstein's formative years.

0:02:41.8 SC: And my favorite, which is "Newton and the Counterfeiter" About Isaac Newton's life after doing science when he became the boss of the mint and hunted down counterfeiters in London. These are human stories, what can I tell you? Newton was a pretty bloodthirsty guy, to be perfectly honest. Anyway, Tom's most recent book is called "So Very Small: How Humans Discovered the Microcosmos, Defeated Germs-and May Still Lose the War Against Infectious Disease." It's a history book, a science book, a storytelling book about the various ways that we got from Van Leeuwenhoek looking through a little microscope and seeing that there were critters moving around, to Pasteur saying, "I can figure out how to defeat these guys." And not everyone agreeing with them along the way. In fact, some people fighting hard against them. And at some point you have to say, a lot of lives could have been saved if people had just faced up to the scientific reality. Lessons for contemporary issues, left for you to decide. So with that, let's go.

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0:04:02.4 SC: Tom Levenson, welcome to the Mindscape Podcast.

0:04:04.8 Tom Levenson: Thank you for having me, Sean. This is great.

0:04:07.2 SC: It is great, but nevertheless, the very first page of your new book, kind of frightened me a little bit. You start talking about the bubonic plague in Oregon in 2024. You rushed to say, "Don't worry, they tamped it down because we have modern medicine now." But it did raise the question, how many of these old timey terrible sounding diseases are still lurking around out there. We'll be more systematic later in the podcast, but I just had to ask that one right away.

0:04:37.8 TL: All of them are out there except smallpox. Smallpox is the only disease I love this factoid. The only human infectious disease that has been rendered extinct in the wild. There is no more virus out there except in a couple of freezer lockers, which is kind of nervous making that they're there. But essentially there's no smallpox circulating, hasn't been since at least 1980. And that's a remarkable thing 'cause it used to be the leading killer. And one in three of people who caught it would die most often terrible disease. But the rest of them, tuberculosis, consumption, the disease that took all those figures, the poet Keats and Henry David Thoreau and everybody else, that's still causing a million deaths a year worldwide. It's not prevalent in the developed world, but it's still very much out there and it's actually becoming an increasingly deadly threat. We can go into why later on.

0:05:50.0 TL: Cholera still pops up. And in fact, I saw a recent report that there's some cholera. Clearly we know about measles. As we talk, there is a still uncontained outbreak in Texas, and I understand now it's in, measles cases have been identified in something, 20 or something additional states. Three people have died so far in that one, and you can keep going on down the list. Polio has been on the very teetering edge of eradication for decades now, but it's not quite extinct. And there are cases that pop up, including in the United States as recently as 2022, 2023, and if we aren't careful, that could also break it's current very narrow bounds and become a major problem again. So yeah, they're all still out there.

0:06:45.6 SC: Well, it's interesting because your book is about the historical context. We have a lot of fascinating stories about how we got to germ theory and vaccines and fighting it and so forth. But constantly, there's a refrain of, it wasn't easy. [laughter] The scientist invented some stuff and then there was politics and there was establishment pride. And on all those things, and you can't help but read it and go, yeah, I guess those things are still around a little bit.

0:07:16.1 TL: Very much so. The book, so very small, began as a question from an editor like, "Can you think of decisive moments in science?" There were these, my UK editor came to me and more than a decade ago and said, "I'm doing this series on decisive moments where we're doing things like Picasso's Guernica or Handel's Messiah, the first performance, that kind of thing." He says, "But we have no science. What would be good idea. What would be good breakpoints in science or coffee." And I thought of a couple and I said, well, Einstein going up the mountain in Mount Wilson and seeing the evidence that the universe is not static, is a break point. The world is different or the cosmos is different before and after that moment. And I said I could do that, but I don't wanna do that, 'cause I've written about Einstein a lot.

0:08:08.4 SC: Yeah.

0:08:08.8 TL: And enough. And I said, I don't know anything about it, but germ theory strikes me as this really striking moment. And germ theory is this idea that was definitively established in the 1870s and '80s, and it basically says that infectious disease is not caused by some derangement of the body or environmental disturbance, a miasma or what have you, bad air, bad water, whatever. In a sort of general sense, it's caused by microbes. And crucially, each different disease, cholera, typhoid, whatever it might be, battlefield infections, all these kinds of things, each specific condition was caused by a single specific microbe. That was an essential element of the idea. And I said, before that, you have and a much looser and vaguer understanding of disease. And after it, you have this very precise definition of what's involved in infectious disease. There are, it gets very precise. There are these things called Koch's postulates, which are a list of rules about how to make sure that you have identified the correct sequence from pathogen to disease. And it involves isolating the bacterium as viruses, as these were being worked out, viruses had not yet been observed.

0:09:42.9 TL: The first one was observed in the 1890s. And so, you identify the bacterium in a diseased organism, you isolate it, you culture it, you give it to another healthy organism and you reproduce the same disease. There are these rules that sort of how you establish that this is in fact the pathogen. That all happens in this last quarter of the 19th century. And there's a before and after. And with that knowledge, there are all kinds of things you can do, that are also part of the story I tell in the book. You have ideas about public health were already advancing in this period that I call germ theory without germs. When it's recognized that there are pathogens, but it's not of some sort, but it's not understood what they are, and how the dynamic happens. But even that lets you do some very important things. That's the cholera story with, and all that. But afterwards you can do targeted public health.

0:10:54.8 TL: You understand why you're doing clean water systems and so forth, and making sure the sewage system doesn't interact with the water supply. All these kinds of basic, really good things. You develop vaccines. There was one vaccine that existed, the Jenner's cowpox vaccine to prevent smallpox, that was discovered essentially empirically or developed empirically in the late 18th century, 1790s, but there were no other vaccines. And then, with germ theory, particularly pushed by Louis Pasteur in that early period. But as with anything in science, lots and lots of other people are involved, but that's when you start getting vaccines against a much wider range of diseases. And of course finally, third in the sequence, historically, you get chemical compounds that are discovered or developed that can attack an infection that's already lodged in the body. Vaccines are sort of like the wall around the castle. If something gets through the wall, whether it's your skin or a vaccination or what have you, then you've got an infection and you do something about it. You wanna do something about it. And that's where antibiotics come in. And we got all those things out of germ theory.

0:12:13.8 TL: But what really struck me as I first sort of, I said, germ theory, there's a before and after, and it's great and there's a decisive moment and everything's grand. And that's all true. But you and I both know that science is not usually simply a case of a eureka moment that changes everything. [laughter] And so, I started looking into it a little bit more. I told my editor, that he should find somebody who actually knew about medicine and the history of microbiology and all that sort of stuff to write it. And then I wrote two other books while this idea was still bouncing between us. And finally he said, "You better write it." And I said okay, I better write it.

[laughter]

0:12:55.0 TL: And along the way, I discovered something that turned it into a book that really sort of spoke to the way I think about the world. And that was, it should have been obvious at the time, I guess, but it took me a while. I'm slow. It took me a while to get there. The microbial world, there is actually a decisive, singular moment when it was discovered. Microbes are not visible with the naked eye. You needed to develop instruments. The instrument in question is the microscope. That comes about early in the 17th century. And people look at all kinds of things with it, but they don't, partly because the early microscopes weren't that powerful and partly because it takes a while to realize that with this instrument, it's not just that you can see more detail on things you already know are there. You look at a bee's wing and so forth. One of the very famous early books is sort of reports on microscopy. Is this on the life of bees, that was written by two Italians. And there are these beautiful drawings of these magnified insects. And it's really cool. But that really took a step forward when Antonie van Leeuwenhoek, and I hope I apologize to my Dutch friends for my butchering that, but he was a Dutch cloth merchant, a draper in Delft. And cloth merchants of time used lenses to inspect the fabric for flaws or whatever.

0:14:36.9 TL: And he became interested in that that magnified world. And he almost certainly saw a copy of Robert Hooke's Micrographia, which was in some ways the first great popular science text. This book of magnificent microscope studies of both materials, points of needles and so forth, but lots of living things. But again, he had pictures of a flea and the compound eye of insects and so forth. He saw in greater detail things that were again, perceivable by in some ways by human eyes and didn't penetrate deeper into the invisible realm, the invisible to us. And that seems to have inspired Leeuwenhoek and he became, it turned out he wasn't meticulous craftsman. He made these great single lens microscopes, these little drops of glass, that were incredibly powerful for the day. He was almost certainly making the most powerful instruments in Europe at the time. And this work of his started 1673 or so, and by 1676 he was really sort of feeling his oats and pointing this his instrument or using his instrument on a wider and wider range of subjects. And he looked at a drop of pond water, and in that pond water, he saw what he called animalcule, animalcules. Little animals.

0:16:16.5 SC: I love the name. Yeah, it's great.

0:16:18.7 TL: And he saw some things that are probably planaria or rather fairly large multicellular microscopic organisms. But then he looked long enough and hard enough and his microscopes were good enough, that he actually saw single celled bacteria. And we know he did, not just 'cause he reported it and described it and you can see descriptions. But I think the earliest surviving of his drawings, he was a meticulous draftsman. He drew pictures of lots of stuff that he studied, comes from 1682 and there are four or five bacteria drawings on it and they are present day identifiable as at least, to families of bacteria, if not the specific strain. And those experiments have been replicated. Historian of science, made a single lens microscope and did it again and said yes, he could have seen what he said he saw. So yeah, he really saw a bacteria. And again, he saw them for the first time in 1676. And then he kept observing them. And one of the really interesting things to me is, within a very few years, he looked at it in pond water, he looked at it in other liquid sources.

0:17:39.6 TL: He infused peppercorns in water. And 'cause he was interested to see what would happen with the peppercorns. But he also saw microbes there. But at some point, he took gunk, between his own teeth and looked at that through the microscope and saw more bacteria. And why is that significant? At least it's significant to me. And the answer is because that's when, that's the first recorded example of recognizing that microbes live inside us.

0:18:08.0 SC: Yeah.

0:18:09.6 TL: Gunk between teeth is not very far inside us, but still it's there. And we can cohabit in the literal sense of the word with this whole microbial universe.

0:18:24.0 SC: That might have been Eureka moment, but it was certainly also a very creepy moment, don't you think? [laughter]

0:18:28.8 TL: Oh, yeah. But what's interesting is, so the question for the book was, all right, that's 1676. And the Robert Koch's demonstration that anthrax is caused by a bacillus, B. Anthracis, a single microbe. Which was the first end to end account of demonstration that anthrax is caused by a pathogen. It's this pathogen and you can replicate it and it's a living microbial, it's a bacterium. All that was set Koch did that from two or three days before Christmas in 1876. Two or three weeks into January, he'd created a chain of infection with these you take some B. Anthracis, give it to a rabbit, then when that rabbit got sick, he'd harvest blood and isolate the bacteria again and give it to the next rabbit. And he created this chain of infection and he isolated the bug and did all those good. And he even also traced the life cycle of anthrax, which he caught them in their spore stage and he was able to activate motile bacteria from the spores. He nailed it all in the space of three to four weeks. But that's 200 years after Van Leeuwenhoek.

0:19:54.2 TL: And while it is I think, formally impossible to say with certainty why something doesn't happen, that's still a long time. And I wondered why it was so long. What were the impediments to figuring that out? That's really where the book got started. And what became exciting as I wrote the book, is it became clear to me at least, and I hope I persuade readers, is that the broad outlines of why it was difficult to go from the first observation of microbes to recognizing that they actually matter to us in really important ways, that lens, helps us understand why we're currently in trouble with infectious disease, why many of the advances of the last century and a half, are now at least at risk, if not already really compromised.

0:20:46.1 SC: Maybe you can help us understand what would have been the mindset of the people in the pre-germ theory era. You've already mentioned miasma theory, but we knew that disease was infectious, or at least infectious diseases are infectious. I'm guessing that people had ideas about how diseases were spread either by touch or breathing or whatever. Was there some consensus as to what they thought happened before they said it was little microbes?

0:21:19.1 TL: Well, that's for the philosophy of science. That's what's so interesting about this case. How does a theory get replaced? Well, there there's the big broad outlines and there's you can turn to Thomas Kuhn or you can turn to people who've argued with Kuhn or whatever. But something that I've, I really think is true in a bunch of different domains, is that the easy conventional sort of high school version that theories change when a fact comes along that the theory can't accommodate. That's tricky on so many levels. We could talk a lot about that if you wanted. But the problem for... One of the problems for making the connection between microbes and disease, is that there was already a pretty coherent theory of disease, that didn't particularly predict things, but it accurate or it adequately described what was observed. So when you have something like the plague, there were two questions. What is a disease? What's happening when you get sick? And how does a disease move from one person to the next?

0:22:49.4 TL: Those are obviously related questions, but they're, you can distinguish between them. And there were a variety of detailed accounts of disease. And certainly, the more people observed different conditions, people recognized the plague as something other than other fevers that you might encounter. And in part, they recognized it because the plague has some characteristic markers, like the buboes of bubonic plague. These lesions that burst on your skin and so forth. And even though they, that's not a universal symptom of the plague, it's common enough that there are ways to recognize it as the plague, and not as what we would now call typhoid or something else. Now recognized as typhoid. There were some... People in the past are not dumber than we are. They have less information or different information, but they're not stupid. And so, there were detailed observations, and people obviously wanted to know what was going on, when you had a terrible event like the plague. But the basic idea, is that there is that healthy bodies are in a form of balance.

0:24:09.6 TL: There was humoral theory, the four humors that have to be in balance. But there are sort of other broader, you could sort of generalize that. You didn't have to be a Galenist and say, "No, it's the humorous." There were what were called chemical physicians, which were people who are looking at more detailed accounts of the substances that make us up. And people were beginning to be aware of bodily systems. This was William Harvey working out the system of blood circulation, is not just important for that one story. It sort of gives you a way to think about how the body works. That was distinct from what went before. But overall, the idea is when you're healthy, your body's in balance, and ill health is some derangement of that balance. And if you think about it, as a sort of broad statement, it's still true.

0:25:05.6 SC: It's a metaphorical way of talking about what's going on. Yeah.

0:25:08.1 TL: Look, think about diabetes. It's a problem, insulin regulation. Well, when your insulin regulatory system is working as it should, you don't have diabetes, and when it isn't, you do. That's a form of imbalance. It's not a crazy concept. It's a perfectly understandable one. And it adequately described what was observed with the naked eye. And similarly with the spread, the origins, where does the first case come from? And then how does it spread? There were a range of possible sources. Ultimately the source was God. God was expressing judgment on individuals or societies. And this judgment, the judgment was expressed through the events that happened to you in life, including illness. But it was well established that people live in the material world and divine judgments and the devil's blandishments, et cetera, occur through natural means. There was a scientistic approach to understanding both satanic and divine regulation of the world or interaction with the world. And so, you look for things, and that's where miasmas come in.

0:26:30.1 TL: It's literally bad air. It could come from an emanation from the earth. It could be the foulness as you move forward in time, the idea is that the bad city conditions, unhygienic conditions, produce these miasmas that are deranging. You don't need to have some sort of supernatural or origin for these things. They can be perfectly straightforward. And again, when you think about it, and this is sort of skipping ahead in the book, this is where some of the critical ideas of the 19th century came in. You don't need to know about germs specifically to recognize the correlation between fetid odors and decaying flesh and so forth. As not great things to raise your kids immersed in.

[laughter]

0:27:23.9 TL: So you have all this knowledge and you have a persuasive. And the great thing about miasmas is, you don't have to invent a mechanism for carrying them from place to place. Because if it's in the air or if it's somehow in the environment, it can move from person to person. And there was the idea of contagion which comes from the root to touch.

0:27:45.8 TL: So obviously, handling somebody diseased was understood as a risk for the person doing the work. But also, contagion as a concept sort of grew more indirect. I had the image in my head of the old 1950s early slush box automatic transmissions, the Hydra-Matic, where the gear changes are carried through water. You don't actually have a direct mechanical connection between bits of metal. The idea of early disease contagion being kind of Hydra-Matic contagion. Sorry. Struck me as a sort of a plausible metaphor. But all that, you can look at the Great plague of London, which is sort of where the book proper starts, and you've got a sufficient explanation. Now, you did have people who were looking both for specific treatments that might actually help with the plague, and they had no idea. And the things that were proposed were ineffective though, in some cases may have made people more comfortable when they were asked to drink more alcohol or something. But you also had some attempt to think about, what kind of substance, what seeds of disease, in the language of the time, might be going from what was in the miasma, what was the active ingredient, as it were?

0:29:15.6 TL: And again, all that is fully plausible. And you can squint just right and see in this concept of seeds of disease, a precursor, something, an idea that could lead you to microbes. But there was nothing in the thinking of the time that required them.

0:29:37.0 SC: Right.

0:29:37.4 TL: And there was no indication that whatever these seeds might be, they could be inert, they could be sort of gaseous, they could be almost anything. There's no pointer towards some specific identifiable living element. Of course, during the great plague of London, this was 10 years before Leeuwenhoek first saw microbes. But there were diseases that went, the diseases didn't stop in 1676, obviously.

0:30:12.5 SC: But this is something that's interesting that comes out in the book. It is quite a span of time in between Van Leeuwenhoek and then the acceptance of the germ theory of disease. But not only were people fighting disease at the time, they were doing so, at least sometimes in ways that in retrospect, make perfect sense if you believe the germ theory of disease. So in the book you talk about, John Snow is a famous guy, Florence Nightingale as the nurse, and a lot of modern methods of being clean and well behaved. But the one I have to ask about, since we don't have infinite time, is Cotton Mather, who is more famous for other reasons, but apparently he was quite the experimental medical doctor.

0:30:57.1 TL: Well, I wouldn't... He's more of an eager magpie than an actual rigorous experiment. So Cotton Mather, of course, is a Puritan minister. He's most famous for his role in the Salem witch trials, in which he deeply believed in the truth of the testimony of those who are accusing people of being witches and believed in sort of dream evidence. I dreamed this happened and thought that that was how Satan would communicate, and was thus directly implicated in the deaths of a lot of people who were clearly shouldn't have been killed. And at the same time, and he was part of this. He was not just a pure, any Puritan minister. He was, if there can be such a thing. He was part of the Puritan aristocracy. His father and uncles and his whole family was basically in the business of being Puritan leaders. And he's a very funny character. He apparently, when he was a student at Harvard back in the day, he apparently had some inclination to become a doctor to study medicine. But of course, the pull of the family business was too strong.

[laughter]

0:32:21.6 SC: The family business being a minister?

0:32:24.6 TL: Yeah, exactly. He was ordained in and gave his first sermon at his father's church, which was the leading church in Boston. When he was ordained, something like 20% of the population of Boston was in the audience. It was like, he was a big deal. His family was a big deal, in that line of work. He was clearly also both intellectually ambitious and interested in the natural world. And so, 20, 30 years after the witch trials, he started writing to the Royal Society in London with these sort of American curiosities. And some of these things were just bonkers. The Royal Society early on was itself ranged from this incredibly serious, important stuff to, you look at it and you laugh. Robert Boyle, the great sort of patron saint of chemistry, very early on in the Royal Society history, read a paper to the assembled fellows, about a monstrous calf. It ranged, truly their interest range all over the map and Mather presented these sort of American wonders.

0:33:39.4 TL: Some of them very real interesting bits of natural history, some of them these sort of legends that he seems to have accepted credulously. And the Royal Society loved him and published him and made him a Fellow of the Royal Society. And he was also, really as part of his ministry as much as, and his intellectual life, very interested in all things related to medicine and health. And he collected anecdotes, he collected recipes that people had for cures or nostrums. And he really, I think had a sense that it was sort of his duty as a minister and essentially a representative of God on earth, to do what he could for the health and well being of both his Community, but sort of by communicating with the Royal Society or whatever, the world at large. And he was in fact, genuinely one of the pioneers of vaccination. Being one of the earliest proponents of smallpox in inoculation, or variolation, as it's sometimes called, where you take smallpox material from somebody who's suffering from a hopefully mild case of the disease, and you scratch marks into a healthy person's arm or arms, they often did it in multiple limbs. And you mix this stuff in, and the idea is to give the person a mild case, a very, hopefully very mild case of smallpox. And thus confer on them what had already been observed to be the result of a smallpox infection if you survived, which was lifelong immunity to any further cases of the disease.

0:35:31.3 SC: And it's not literally vaccination, you've not developed a vaccine. But inoculation is sort of the broader category of which vaccines are an example.

0:35:40.7 TL: Right. And this is the earliest attempts in Western Europe and the Americas, to engineer immunity to a naturally occurring disease. And that to me is the distinction that's key, 'cause vaccines are a particular way to engineer that immunity.

0:35:58.4 TL: Mather learned about this technique first from his slave, an African man who had been gifted to him by members of his congregation, who to told him about undergoing this procedure in Africa. And then when in the mid 1710s, the Royal Society published two papers from doctors working in the near East in Turkey, and one was from definitely in Turkey. I'm trying to remember where the other one was working. I can't off the top of my head. Anyway, that also described the use of this inoculation, smallpox inoculation in Turkish medicine. Mather wrote to the secretary of the Royal Society, having seen this paper, and said, "I can attest that my servant, as he called him, his slave, had already told him about this and that he'd followed this up with conversations from other people with knowledge of Africa." And that, this seemed to him such a promising preventative for this really deadly, horrible scourge of a disease, that should smallpox visit Boston again, he said, I will attempt to get this method used. And sure enough, a few years later, in 1721, smallpox comes back to Boston. And Mather tries to persuade Boston's medical community to do inoculation. Only one member of that community agrees to do so. Others vehemently oppose him.

[laughter]

0:37:40.6 SC: A common theme in the book, like we said.

0:37:42.6 TL: Right. Well, and the interesting thing, is they oppose him for multiple reasons. One, certainly there's risk and there are dangers involved. You're doing... Sure, the Human Subjects committee might have had some words to say. But the other reason is, this was a proxy for a battle over power, sort of professional power. Who had the right to do medicine, not Puritan ministers, God damn it. There was a one European trained M.D in Boston at the time, who clearly bitterly resented the incursion into his prerogatives, but also was more broadly part of a broader power struggle in Boston, where a number of people, up to and including James Franklin, Ben Franklin's brother, who was the publisher of the first independent, non-censored newspaper in the colony, are saying, "We've got to reduce the influence of Puritan ministers." And this is a club to beat Mather with and by extension, the Puritan establishment. And so, there was this significant resistance up to the point of a direct attack on Mather's life. Somebody threw a bomb through his window, which fortunately didn't explode, but no joke.

0:39:02.8 SC: Yeah.

0:39:04.0 TL: And so, ultimately they were able to inoculate a few hundred Bostonians, with almost entirely good results. While several thousand Bostonians got sick and something like 14% of them died. And the question was, those were lives that could have been saved.

0:39:31.6 SC: Right. So the inoculated people essentially all survived?

0:39:36.8 TL: Essentially. There's a bit of controversy 'cause a few died. And the question was, were they already ill or had they died of something else?

0:39:44.2 SC: Sure.

0:39:44.7 TL: And the person who was doing the inoculation said, "Yes, they were all, wasn't me." And it's hard to say exactly, but the proportion of people who suffered serious. A huge proportion of Boston got sick, of a substantial chunk of them. And it was a relatively mild strain of smallpox clearly, 'cause a 14% death rate was below the average. But still, that's...

0:40:10.5 SC: A lot of people.

0:40:12.4 TL: Yeah. Boston was under 10,000 people. I think again, I'm pulling. I should look at the book right now. Something like 900 people died. So that's a big chunk of Boston.

0:40:21.8 SC: Yeah.

0:40:23.8 TL: And the objections to this inoculation campaign were sort of the prototype for what would come after. Some legitimate medical concerns and a lot of other stuff going on at the same time. Political issues, cultural reluctance to attempt whatever was going on, specific social enmity.

0:40:50.4 SC: Right.

0:40:50.6 TL: All those things mix in. And that's not what you think of usually as an explanation for why some scientific event doesn't happen.

0:40:57.8 SC: You do if you've read some science. You do if you know a little bit about the history. So that's not surprising to me. Speaking of personalities and conflicts and things like that, let's leap forward to the real germs. And Louis Pasteur I guess, is the first person to talk about. Obviously from your book, I get the impression that on the one hand, he deserves as much credit as he gets. He really did do a lot of other things. On the other hand, just like the more familiar examples to me, of Newton and Leibniz, there were rivalries and jealousies and bitter priority disputes going on.

0:41:33.5 TL: Absolutely. Just to put a mark in, I hope we can cycle back to the story of childbed fever, 'cause that's a really classic and important case in this. I think it sets up some of what we're seeing now.

0:41:47.5 SC: Oh, we can talk about childbed fever. Let's do it. Yeah, we're not gonna run out of electrons.

0:41:51.8 TL: Okay. So childbed fever, puerperal fever, is an infection. There are actually a number of different bacteria that can produce it's symptoms. And it happens to women who have just given birth. And it can be devastating. It's very frequently fatal. And what's interesting is, there's a whole sort of social history dimension to it. Puerperal fever is described in ancient Pythagorean texts even. So people knew about it in antiquity. And it clearly is a disease that didn't just pop up in Europe in the 16th, 17th century. But there was a change that happened, up until sometime in the 16th or 17th century. Childbirth had been largely the province of women. It was handled by midwives or and it's very local. So if you wouldn't have, in a village, 12 women giving birth in the same week. That's not usually how it worked. And reports of puerperal fever are sparse from that period. And partly they're sparse because, this was not, that community was not a writing community. There weren't journals of midwives and so forth and so on.

0:43:28.8 TL: But as European cities grow and power centralizes and you have things like increasingly formal associations of medical of experts, in some sense, doctors. Childbirth becomes increasingly sort of overtaken by male doctors, and at least in the cities, happens in hospitals where you do get a lot of women in the room at the same time giving birth. And that's when you start to see, not just individual cases of puerperal fever popping up from time to time, bad luck there is. The wrong bacteria happen to be in the lying in chamber. That could happen. But when it happens in a lying in hospital, you have the perfect conditions for the bacteria, the pathogens to move from patient to patient. And that's what happened, as very early on in the history of the hospital. You have stories, you have reports of essentially epidemic puerperal fever.

0:44:44.4 SC: The problem with hospitals is they're full of sick people. [laughter] It's a terrible place to go.

0:44:49.1 TL: They're full of sick people. And if you have a person delivering, attending a delivery, and then wiping their hands off and moving on to the next person, you can see where the problem might arise. So over the course of the 17th and 18th century, there are repeated reports of outbreaks of puerperal fever, where dozens or more women will suffer and many die from this condition. And you start seeing conditions, you might have sort of a two or three year run where there's just this ongoing transmission of puerperal fever. And again, up there were a whole bunch of different theories adduced as to how this might happen. It didn't appear to be a contagious disease. 'Cause if a woman n a hospital falls sick, and then a woman in a home fall sick, unless you notice that the same person attended both births, it doesn't appear that there's any connection, right?

0:46:03.6 SC: Right.

0:46:04.1 TL: The two people don't touch each other, all that sort of stuff. So there was no urgent need to try and identify a sort of course of causation. But people did notice that the sort of explanations for how some derangement of how the milk was being expressed or other issues that might attend a difficult childbirth. That didn't really explain why you'd get clusters of cases in a place and time. And so, in 1795, well before the conventional story is, this is all worked out in the 1840s in Austria. But no, in 1795, this doctor in that well known center of medical research Aberdeen, Scotland in 1795, a local doctor started delivering babies, and took notes on the midwives who were delivering babies. And there was this ongoing chain of infections, and people suffering and dying of puerperal fever. And he tried a couple of different explanations. He looked at weather reports to see if there was a correlation with weather conditions. Again, there was no base of knowledge or theoretical insight that drove this, purely empirical what's going on. So he looked for correlations, and eventually he started noticing that there was... It didn't take him that long.

0:47:46.9 TL: He started noticing that there were sequences of infection. Both he and the midwives would go from patient to patient to patient, and those patients would in sequence come down with this terrible debilitating, too often fatal condition. And he wrote it up and he said, "Basically, we are the cause." He didn't say it basically, he said it explicitly. He said, it shocked him to realize that he had been the source of his patient suffering. And he wrote this and published it in 1795, and nothing happened.

0:48:22.4 SC: Nothing. [laughter]

0:48:23.7 TL: Yeah, he was basically driven out of town. The midwives were furious at him for suggesting that they might be killing their patients. It didn't get picked up in London.

0:48:33.7 SC: So something happened. But not acceptance of his ideas?

0:48:37.2 TL: Yeah. And a few years later, he died of I think, tuberculosis and was basically lost to history. And there's no, but the idea was there and the knowledge, if you looked at that and you could say, "Okay, there is something that is moving from patient to patient, on the doctor's hands or on the midwives hands, and we need to interrupt that. You could... That was not a difficult leap to make, but it didn't get made.

0:49:06.9 SC: And science didn't know about microbes of that era?

0:49:09.7 TL: They did not. They knew about microbes existing.

0:49:12.1 SC: Yeah.

0:49:12.5 TL: They did not connect them with disease.

0:49:14.5 SC: Right.

0:49:15.6 TL: I know we're sort of looping and looping. One of the most interesting things in the book, one of the things I found most surprising, was that Cotton Mather, in the 1720s. Cotton Mather, Witchburner, actually wrote down a suggestion that Leeuwenhoek's animalcules, might be the cause of diseases. And he even guys says, different animalcules could cause different diseases. This he wrote it down. The book he wrote it down in, was a manuscript at his death and wasn't actually published until the 1970s. And he almost certainly derived the idea from somebody else. A doctor who wrote in this one brief mention in a British paper. And again, these ideas were thinkable. People could imagine it. Clearly, we have we have that absolute existence proof. But it struck no chord and the idea essentially disappeared for well over 100 years, which is still to me. I try to explain it, I think I do explain it, but when you just stop and think about it for a minute, it's mystifying and incredibly saddening when you think about how much loss and pain and suffering, derive from the fact that nobody picked up on that.

0:50:34.7 SC: Well, there's a lot of ideas in the history of science that nobody picks up on. But here's something where it's kind of obviously important to make progress on this, and you might hope that people are responsibly searching around for every possible hypothesis to go test.

0:50:54.3 TL: You would. And one of the things to... If people listening to this take one thing out of it, the truly remarkable thing, that Leeuwenhoek did, is he revealed not just more information about something, but a whole new realm of material existence that no one had suspected existed before. Up until that moment, we didn't know about the microbial world, the microcosmos, and it's there. And we now know how incredibly rich and important it is and how deeply embedded in the history of life on Earth, and all the different things we can now say about microbes. But it seems to me analogous to the impact that we would feel, if we got definitive proof of life on another planet.

0:51:54.8 SC: Right.

0:51:55.5 TL: It's that revelatory. And you would have thought that that would have led to more speculation. Again, to sort of push the analogy, think of all the writing from people in the 19th century and on, about life on other planets. That very early movie of the Lumiere brothers, Journey to the Moon. The idea of, clearly the existence of other worlds beyond our own is enormously stimulating the imagination. Well, here was a whole nother world, wholly unsuspected, teeming with creatures that are unlike the creatures we see with our naked eye, that have different shapes and different means of locomotion, that have apparently whole societies, ecosystems, interactions going on, that have been there all along beyond the limits of our senses. And now they're there. I am a little perplexed why that wasn't crazier. Why that didn't make people jump more.

0:53:02.2 SC: Yeah.

0:53:02.9 TL: But just as, I know I rabbit on too long about such stuff, but just to sort of round off the puerperal fever story, flash forward to Boston in the 1840s. Oliver Wendell Holmes, senior mediocre poet, Boston Brahmin and medical doctor at that point, a young medical doctor. And he at a meeting of a local medical society, somebody raised the question about how you can explain a then ongoing puerperal fever outbreak. And Holmes took it on himself to try and study it. Unlike this doctor in Scotland, Holmes was not, he didn't have an OB practice. He wasn't delivering babies. He was a young and relatively inexperienced doctor at that point. And he just did this from the records, case records. And he tracked this, tracked the births cases of puerperal fever deaths and attendance. And he, in a relatively short period of time, he reported back to the medical society, that yeah, in fact there are patterns of infection and the common element is the doctor. And what needs to happen is the doctor has to make sure, or the midwife, the medical person attending the birth needs to make sure that they are fully cleansed of whatever is going on between births.

0:54:36.5 TL: And he published this, as well as giving it as a society talk. And again, not only did sort of nothing deeply change, he got a severe and actually contemptuous pushback from established senior American OBGYN practitioners. And the one that really stuck in mind, was this perhaps the top such doctor in the U.S at the time, a Philadelphia doctor named Meigs or Meigs. M-E-I-G-S. Again, I'm not sure how it was pronounced, responded that it was, that Holmes writing was the monitorings of a sophomore and that what he concluded, couldn't be true because, and I quote, "A gentleman's hands are clean."

0:55:29.6 SC: There you go. Q E D.

0:55:33.1 TL: And then the story sort of concludes with the most well known one, which is Ignaz Semmelweis working in the Vienna General Hospital with the two wards where there's one ward handled by midwives, who do not do pathology, do not dissect the bodies of women who have died of puerperal fever. And the other ward run by doctors and male medical students who do in fact, this is part of the great transformation of medicine into a science. You do pathology, you study the diseases in the body by dissecting and analyzing the corpses. And mostly, this was this enormously rigorous and productive advance in the way you teach and think about medicine, leads to all kinds of good stuff, but not here.

[laughter]

0:56:19.2 TL: So you dissect somebody who dies of puerperal fever and guess what you have on your hands and body and clothes, if you don't sterilize yourself. And so, lots and twists and turns in the story, but Semmelweis figures out that this is the meaningful distinction between the two outcomes. The midwives ward has a very, very low rate of puerperal fever, and as many as 10% of the patients in the other ward fall victim to it.

0:56:48.0 TL: So it's a big deal. And he says, "Okay, we're gonna stop this. He puts a chlorine solution next to the autopsy room and says, "You can't go back to the ward until you wash your hands thoroughly, until there's no smell left." Again, didn't know about germs. He didn't know what it was. He just said, there's these cadaverous particles, and you got them, they're associated with death, so you've got to wash the stink of death off you. And that turned out to be enough, long enough, enough sterilization, so that the, when that was done, the doctor's ward very rapidly approached the same levels of infection that the midwives had already achieved. So it was again, he had no idea what just cadaverous particles. He had no idea what was causing the disease, what the pathology of the disease was, how it developed, what the chemical, biochemical mechanism, none of that. All he knew is that, when medical students and doctors walked from cutting up a corpse to delivering a baby, bad things happened.

[laughter]

0:57:58.0 TL: Let's stop those bad things. Let's just put a wall between them. And again, the tragedy is he was not, though his ideas got some traction in some places, broadly his conclusions were rejected both within the German speaking world and beyond. And it took several more decades before the idea of proper sterile conditions really took hold.

0:58:27.5 SC: Well, and when Pasteur does eventually come along and sort of put things together and put the germ theory on a proper footing, his inspiration or his route into it was not through trying to cure diseases. That was a clear thing to try to do, but he was just trying to make sure that you made wine correctly and reliably. [laughter]

0:58:50.2 TL: He did refer to it. It was sort of a term at the time, diseases of beer and wine. [laughter]

0:58:55.5 SC: Okay, good.

0:58:56.1 TL: There was this metaphor clearly in his mind. But yeah, the first real demonstration of a bad thing happening because of the metabolic, in the metabolic work of a bacterium, was Pasteur's study of making beet juice. So he had went, this was in the 1860s. He had a, maybe it might have been late 1850s. Excuse me, I misspoke. He had a student, he was a young professor of chemistry. He was not a biologist and he was certainly not a physician. He was teaching chemistry at the University of Lille. And one of his students was the son of a local manufacturer who made beet alcohol, among other products. And they were having a bad run at the time where, instead of producing alcohol, they produce this foul smelling, useless substance. And they wanna know why.

0:59:56.1 TL: And Pasteur agreed to take a look and eventually identified a lactic acid bacterium. So instead of yeast metabolizing sugar and water into alcohol, you had lactic acid bacteria metabolizing their inputs into this foul smelling, nasty, industrially useless lactic acid, hence the name, within the beet juice. And he was able to say basically, you wanna make sure your vats of beet juice are free of these bacteria before you go in. And gave them some insight into industrial processes. But that was the first insight where he saw that two things really, that bacteria free floating in the atmosphere, microbes free floating in the atmosphere, could reach and affect substances like beer, wine, beet juice, soup, whatever. So there's this notion that there is this the potential pathogens that we are surrounded by all the time, and that these microbes actually do have meaningful large scale physical effects on the scale that human beings occupy. And there are a whole series, he did, there was... That insight took him in a bunch of different directions. It included finally his often regarded as the definitive and final destruction of the concept of the spontaneous generation of life.

1:01:37.2 SC: Right.

1:01:38.3 TL: But it also took him through into a bunch of different aspects of infection and this sort of just microbial role in biochemical processes more generally.

1:01:50.9 SC: Well, that's what I learned from that part of the book. Was that, an important aspect of it, because it's always hard when we know or we think we know now what is going on, like why didn't they know? It's not that hard. But the existence of the microbes was known. But the idea that they could have an effect was less clear. People thought that for the wine thing there were chemical reactions, sure. But the idea that these little beasties are contributing to those chemical reactions was apparently a little bit of a barrier.

1:02:21.4 TL: It was, yeah. It took a long time, it took a long time even to associate yeast with the fermentation. And then, the idea that you have yeast that are doing fermentation but these bacteria, which are yet smaller and simpler organisms, can muck it up, can produce different fermentations that lead to results we don't want. That was another big step. But I think this is where one of the theme, this is where I argue something that I think is I hope one of the bits in the book, that people engage with. They feel free to disagree. But asking the question, why did it take so long? You are ultimately asking for cultural and social reasons. And a gentleman's hands are clean is one example of essentially hierarchical thinking. There is a social order and people at the top of the order are not capable of, and certainly not responsible for bad things happening lower down. Well, there's a broader sense of that and I think it starts in religion, but certainly doesn't just stay there.

1:03:30.9 TL: This notion the scala naturi in Latin, scale of nature and often referred to as the great chain of being, which was titled one of the classic books in cultural history, Lovejoy's, The great chain of being. But it's this notion, and you see it in the first chapter of Genesis that there is God, there are heavenly creatures, and then there's humankind. And all the rest of creation is given into our dominion, explicitly in the text of the that first chapter of Genesis. And this gets elaborated in a bunch of different ways. And you get by the Middle Ages and later you get these beautiful elaborate drawings showing an old white haired gentleman sitting on a throne at the top and angels with their wings. And then people, and then all the way down to rocks and dirt. Through the ranges, some hierarchically organized view of the kingdom of life and so forth. And one of the things that that structure, I think makes it easy to believe and hard to disbelieve, is that authority goes from the top down and not the authority and agency, and not the other way.

1:04:52.7 SC: Right. Perfect.

1:04:53.5 TL: So I think, and again, you see those ideas, it doesn't have to be divine or the divinity and the explicitly religious framing of it can become, can drift very far into the background. The idea that humankind is superior to the animals is one that you can believe without needing to have the authority of Genesis. The idea of white people are entitled to rule others is certainly one that was persuasive to an awful lot of people for a long, long time. And perhaps to some of some folks still. The idea that there is a hierarchy of agency and authority, is one that persists in lots of different domains. And I think it mattered here. I think it was very, very hard to imagine that microbes, which were delightful to look at and it's wonderful to be a tourist in the microcosmos, the idea that they could turn around and have agency or impact on us crowns of creation. It's a very hard thought to think. You need to, I think and that's one of the things I think I chronicle in the book. You need to accumulate a lot of ideas and specific instances where you see something is going on in the disease process that needs explanation, to really kind of let go of the idea that in some sense, the bad things that happen to humans, humans do to each other.

1:06:35.5 SC: Yeah.

1:06:36.3 TL: That's an easy idea, easy idea to master. But to extend that and say, well, despite our big brains and our opposable thumbs and our tool, using these single celled simple creatures, can really mess us up. That takes some thinking.

[laughter]

1:06:56.3 SC: Okay. And do we properly give Pasteur credit for finally saying that out loud clearly for everyone to see? I know there was some controversy.

1:07:06.9 TL: Yes, I think Pasteur and Robert Koch are the two people who are most associated as the major founding figures in germ theory. And yes, they did. They were enormously, they had enormous impact. They made major discoveries. They were rivals. Pasteur really did try to undermine Koch's sort of claim of unique discovery with the anthrax bacterium. Probably, Pasteur did important stuff with anthrax, including coming up with an anthrax vaccine. But he certainly overstated and he did mess with Koch. Koch did not take that well and responded really in very hostile and even more belittling terms to Pasteur. Most of that just doesn't matter. It didn't matter at the time. Both people went on and had had the careers they had without really impediment. It just clearly pissed them both off. [laughter] And there was an enormous at that point, also remember there's an enormous Franco-German rivalry.

1:08:24.6 SC: Exactly, yeah.

1:08:25.9 TL: Stomped France in the war of 1870. So there was that nationalistic animus as well. But again, it's important to realize that, I think one of the... Pasteur seeded some of the first major derivatives of germ theory. News of his work on yeast and fermentation reached just Lister, a doctor practicing in Scotland. And Lister realized that if these bacteria lurking in the air, could contaminate beet juice or beer or what have you, then they could also perhaps explain the terrible problem of surgical wound site infections, which were basically made much surgery impossible to do and many surgeries very dangerous. And you would have a compound fracture of a limb and more often than not, surgeons would amputate rather than treat because the likelihood of infection was so high, that kind of thing. And Lister invented essentially sterile surgery and showed that you could in fact, if you did originally very elaborate work to try and wall off the wound site from bacteria, you could in fact, perform surgeries that had previously been fraught with danger or simply unthinkable.

1:09:56.4 SC: I do wanna... Go ahead.

1:09:58.2 TL: I'm sorry, go ahead. I was just saying, that happened in the 1860s.

1:10:01.5 SC: Yeah.

1:10:01.9 TL: Tragically, it happened just after the Civil War.

[laughter]

1:10:05.3 TL: So you have this...

1:10:06.8 SC: Civil War was tough.

1:10:07.7 TL: Yeah. And...

1:10:09.8 SC: If you got hurt. [laughter]

1:10:12.4 TL: Yeah. More people died of disease and wound infections than died of immediate battlefield trauma.

1:10:19.6 SC: Right.

1:10:19.9 TL: By like 2:1.

1:10:21.4 SC: Well, the chronology is definitely interesting, so I wanted to again, skip to the highlights here, but vaccination, now real vaccination becomes a real thing. But it did predate, again Pasteur, but he had a famous experiment with the sheep that I really love. Even though, it's famous in some circles. But let's pretend that not everyone listening has heard about it.

1:10:44.0 TL: Okay. So, as I said, Pasteur invented an anthrax vaccine. Again, one of the reasons why it's always fraught to say. Well, Pasteur was this great giant colossus astride. So people had identified a bacterium with anthrax cases before that, these rod-shaped bacteria were showing up, and people actually explicitly wondered if they were simply a correlate. You get sick with anthrax and that makes your body less able to defend itself against the slings and arrows of outrageous fortune and these bacteria are opportunistically making their home in your bloodstream, that kind of thing. Nobody actually sort of definitively established these bacteria were the pathogen until Koch did it. But there was this, it was certainly known that this bacterium was present in essentially all cases of anthrax by a decade or more before Pasteur started working, two or three decades before Koch got his interest going. So Koch identifies and established. And nobody, it's now clearly the correct answer, that this one particular bacterium is in fact the source of the symptoms of the disease, when they infect an animal or a person.

1:12:16.4 TL: And Pasteur works to, his basic method was to try and pass the bacteria through repeated animals until it was attenuated, keep recycling it. And he tried different, aging them in cultures. And there are lots of different ways that he worked to try and create less pathogenic versions of the microbe. And he eventually got it. Again, there's a little controversy. Did he in fact have a live attenuated vaccine by the time he did this famous experiment, or had somebody worked on actually a killed version where they actually fixed the bacteria in some chemical. There's the notebooks are a little funky there. And he announced that he had a vaccine, and an anti-germ theory doctor said, "Prove it." And challenged him to this test where he was gonna take... There would be two groups of sheep and I think there were a couple of goats involved as well, and they're gonna separate them up and half of them, all of them were gonna get injected with anthrax. So given the disease. And then half would be, but half would have been previously injected with the vaccine and half would not.

1:13:47.6 TL: And Pasteur said, okay, and took his vaccine to this farm, not that far out of Paris, and did the test. And it was one of those, like they draw it up kind of experiences, where basically all the control group that went unvaccinated died, and all the vaccinated animals were happily gambling around the fields. And it was regarded and presented certainly in the popular press, which Pasteur was really good at representing himself in, as this sort of clear triumph and clear demonstration of the truth of germ theory.

1:14:26.8 SC: It's one of the things we didn't... You wrote a long book. I'm sorry, Tom, but we didn't get to talk about all the cool stuff. People should buy the book. But one of the themes that comes through, aside from the sort of establishments always resisting you, is the effectiveness of good science communication, and in particular graphic design. Florence Nightingale, Jon Snow, and certainly Pasteur was a master of publicity. They got their points across, not always by just having the better data or theory, but by being a little... There's some showmanship involved as well.

1:15:03.6 TL: Absolutely. And that's no surprise.

1:15:08.6 SC: No surprise at all, when you say it that way. Yeah.

1:15:10.0 TL: Yeah, it's just I guess what's surprising to us with our presentist bias, is that they figured that out back then. But again, Robert Hooke, that book Micrographia?

1:15:21.7 SC: Oh, yeah.

1:15:22.2 TL: He wrote that book to sell, and it did. But yes, it is interesting to me that, as you say, Nightingale, with her essentially the invention of polar diagrams. Nightingale was a formidably intelligent and gifted person. She had an unusual education for aristocratic young women or elite women of her time. She did have some training in mathematics and she really had a gift for data representation that Tufti would have been proud of I think.

1:16:01.9 SC: You don't think Florence Nightingale, graphic designer, but very much that was in her wheelhouse.

1:16:08.1 TL: And she was able to, these lovely circular, she called them cockscomb 'cause they were supposedly vaguely like that thing on top of a rooster's head. But you could really see the change in death rates from before and after introducing proper hospital hygiene in the Crimean War. And similarly, Jon Snow's sort of gift for graphical representation, map-based, geographical. I'm sorry, not graphical, geographical representation of data. Again, made his case that small. Not smallpox. Cholera was a disease of some specific contaminant in water. Very, very difficult to argue with. And people did, but still, it was a very persuasive case.

1:17:00.0 SC: Yeah. Just so people know, these are maps of block by block, house by house in London. These people got it, these people didn't. Here's the water supply. Draw your own conclusions. [laughter]

1:17:09.0 TL: Right. And it even sort of accommodated the fact that London's streets are this ridiculous tangle.

1:17:19.0 SC: Exactly, yeah.

1:17:20.0 TL: Because Snow was able to show that even though some of the cases of cholera that were centered on this one bad source of water, the broad street pump, that some of those seem to be quite far away, and there were other houses nearer that weren't affected. But he was able to show that even though the crows, the crow's flight, bird's flight distance was greater to those places, the actual distance through the streets to the water supply, all the cases were in houses, where the closest water supply was that one pump on this street in Soho. He was good.

1:18:03.9 SC: And despite all of this human genius, we can wind it up by coming to the present day. Not everyone is convinced. Maybe before explaining that not everyone even in the present day is convinced of, not just the efficacy of vaccines, but even I hesitate to say it, but some people are a little skeptical of the germ theory of disease right now. But let's just remind ourselves how effective vaccines have been, in making the world a better place. You paint a vivid picture. Not just, you say you cure disease, that sounds good, but a wholesale change in life expectancy and demographics more generally that we kind of take for granted now.

1:18:47.2 TL: Yeah, the one message I'd like to leave with anyone listening to this is, our release from the fear of infectious disease is in historical terms, incredibly recent. People are familiar with the story of public health infrastructure. You create clean water, you create, you get clean air, you reduce the incidences of all kinds of diseases enormously. If you just did that, it would be a huge change. But the combination of vaccines and antibiotics means, that for at least people in the developed world and increasingly in the rest of the world, diseases that were once inescapable are now preventable or curable really readily. And in London as late as 1900, there was still a significant rate of infant and child mortality. And that basically is not a problem. The fact that the U.S child mortality, infant mortality, is worse than the rest of the developing world, is a fact and a serious problem, and has social and political roots, not medical ones. We know we can prevent these maternal and child deaths, and the fact that we don't, is in fact a social choice, even if we're not conscious of making it.

1:20:21.5 TL: But broadly speaking, in 1952, there was a terrible polio outbreak in the United States, and thousands died and more were affected with lifelong consequences. And two or three years later, the first polio vaccine came out. And that threat, our parents or our grandparents were terrified to let their kids go to the swimming pool in the summertime, in the '40s and '50s. That's no longer an issue. The vaccines against common childhood illnesses. There were a few, couple done before the war, before the Second World War, but most of them emerged between 1950 and the end of the 1960s. That's not very long ago. It's recent enough so that I am though, I'm sure you wouldn't think to look at me, old enough so that I was a kid before the rubella vaccine, which was the last in the list to show up, was available. And I caught a case. German measles it was also called. And it was really unpleasant, and I was lucky because there are possible lifelong consequences for rubella and I didn't get them. So that's great. But this is living memory. And now however, or up until very recently, measles was declared eradicated in the U.S around 2000.

1:21:55.0 TL: It's back. Up until very recently, no one, no parent had to seriously worry that their child would be killed or damaged by diseases that for almost all of human history were devastating companions. Just things that you had to live with. And again, I think there are a lot of different reasons for this. There are explicit political reasons. There are just the fact that amnesia, this lack of experience means it's very hard to credit that the threat exists. That's a human, perfectly normal human reaction to things. If you've never seen it, it's hard to believe it's real. But the anti-vaccine movement and more broadly, the sense that public health in general, not just vaccine regulations, but the other things we might do, like wear masks and physically separate during COVID. These are seen by I think too many as unwarranted intrusions into the individual liberties of everyone. And that's not precisely the same as the kind of hierarchical chain of being kind of stuff I associate with the difficulty of getting to germ theory. But it's clearly a kissing cousin. There is a sense that there is a still a hierarchy of agency. My choice is inviolate.

1:23:43.1 SC: Right.

1:23:43.7 TL: And you see that happening in our politics right now. RFK Jr. Is, his HHS is rewriting vaccine guidelines to emphasize that vaccines are an individual choice and that there are complications and all that sort of stuff, there are risks to vaccines, et cetera, et cetera. And this is very much locating the choice and decision making power over the sort of creation of these ecological niches for infectious disease. It's locating that in your choice and my choice and everybody else's choice. And if the consequences of those choices were confined to the individual, that would be one thing. But one of the things about infectious disease is, it is, wait for it, infectious, it moves from person to person. So those choices have impacts beyond the individual. And that's something that we find in our society right now, and in our politics right now. Something that's very, very difficult to accommodate.

1:25:00.4 SC: And it's also a case where you can believe whatever you want, but at some point as a scientist, I do believe there are objective facts out there about how the world operates. But there are crucial differences in the time scales and tangibility of those facts. You can think, you can walk through a door, but if you try it, you will instantly figure out you don't. You can think that vaccines cause more harm than good, and you can get away with it for a while. For months, years, whatever. Other people are being affected, I'm not being affected. And so, it's just so much harder to overcome all of the human foibles in the equation when there's that much wiggle room in something. A complex system like society, politics, medicine.

1:25:50.3 TL: Absolutely. And I should emphasize the, one of the things that's happened, there was vaccine hesitancy from the very beginning and in earlier times there was generally more reason behind it. There was these vaccine like any other technology, has advanced and improved over time. But one thing that's really different in 2025 than was true in 1970 or 1920 or 1850, is an understanding of sort of disease and immunity down to the molecule or atomic level. These are extremely well characterized. It's not that you know everything. There's lots and lots of stuff that is not known about specific mechanisms and pathways and all kinds of stuff, but an enormous amount is known and the mechanism by which vaccines have their impact. The reasons why some vaccines are confer lifelong or extremely long lasting protection and others do not, is part of the interaction between vaccine and pathogen. All these kinds of things, these are understood, they've been well characterized and there's no room for doubt anymore about the fact that A, vaccines work, B, how they work and see what their limitations are. And D, what the consequences of rejecting all that can be.

1:27:28.0 TL: It can be, one of the things that happens is, if polio were to escape, I've seen model studies that show that it could very, very rapidly produce extremely large scale outbreaks. Because the global state of polio vaccination has been waning since polio has been eradicated.

1:27:49.6 SC: Why do you need to be vaccinated? Yeah. [laughter]

1:27:50.8 TL: It's gone everywhere in Afghanistan or Pakistan. And the only reason you'd vaccinate now is if a case showed up.

1:28:00.1 SC: Yeah.

1:28:02.3 TL: So the the risks are real and growing, and one of the things you'll see is, as I suggested earlier in the book, that some of the issues in thinking about microbes were unrelated to anything to do with the science of microbes or the natural history of microbes at that time, but to well established social and cultural predispositions. Well, similarly right now, a lot of the anti-vaccine stuff is now has sort of left the bounds of say, the autism community where they were terribly misled by that early paper that suggested falsely, that there was a connection between vaccines and autism. Now it's left the bounds. But I think for an awful lot of people, being anti-vaccine is not actually a statement about what you know or believe about how the immune system works. It's an affinity marker of, I'm with this group and this group has included as part of it's political catechism, that vaccines are a bad thing.

1:29:12.8 SC: Yeah, we just talked about that literally with recently with political scientist Lilliana Mason. And you and I both know that 10 years ago, if you said it's so annoying that conservatives are denying science like climate change or whatever, you would get the response. But the liberals deny vaccines or modern medicine and so forth and it's shifted quite a bit for obvious reasons.

1:29:37.5 TL: It has. And again, it's not surprising. All of us offload some of our knowledge and judgments to, we don't have time to become masters of many things, much less everything. So if people we admire and respect say, the sun rises in the East, we don't actually need to go out there with a compass and make sure of it ourselves. And that's true for all kinds of things. So when too many political leaders make political hay out of opposing vaccines or what have you, it's not surprising that large sections of their followers would say, "Okay, well I don't need to go study that myself." Joe Rogan or whoever says this and he wouldn't lie to me on the radio or whatever. Robert F. Kennedy says that, he's the secretary of Health and Human Services, he's not going to lie to me, et cetera, et cetera. And you just go on about your business. And again, it's not surprising, it's very human. We all do some variation of that. But in this case, it has tragic and fatal consequences.

1:30:49.6 SC: So don't take it personally, Tom. But after the podcast is over, I'm gonna go wash my hands. [laughter] You put the cleanliness into our heads. But Tom Levenson, thanks very much for being on the Mindscape Podcast.

1:31:01.1 TL: Thank you so much for having me, Sean.

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