Why Rome actually fell: plagues, slavery, & ice age — Kyle Harper

Kyle Harper 0:00 To me, a very plausible counterfactual is that a more or less Mediterranean core of the Roman Empire could have survived east and west, really all of Italy, Africa, and probably Spain, if you hadn't had this double shock of climate change and plague. The Romans don't have technology improvements that are really self-sustaining, and the reason they don't have that is because they don't have science. Their science sucks. They have, like, the most advanced financial markets in the world before, like, the 17th or 18th century.

Dwarkesh Patel 0:28 20% of the population is enslaved.

Kyle Harper 0:30 Yeah.

Dwarkesh Patel 0:30 Why aren't there more slave rebellions?

Kyle Harper 0:32 Evolution is just creative and weird and contingent and unpredictable. Billions and billions and billions of microbes constantly seeing if you manage to lock that door, and they're just looking for a way to break in.

Dwarkesh Patel 0:45 Today, I have the pleasure of chatting with Kyle Harper, who is a professor and provost emeritus at the University of Oklahoma, and the author of some really interesting books, The Fate of Rome, Plagues Upon the Earth, Slavery in the Late Roman World, w- an upcoming one called The Last Animal. The reason I wanted to have you on is because I don't think I've encountered that many other authors who can connect, um, biology, economics, history, climate into explaining some of the big things that have happened through human history in the way you can. The most recent reason I r- I wanted to have you on is I interviewed David Reich, uh, the geneticist of ancient DNA, and some of the questions we were discussing, he kept emphasizing this overwhelming role and surprising role that diseases have had in human history, not just in the recent past, but g- I mean, in his work going back, like, thousands of years, tens of thousands of years. And he's like, "You gotta have Kyle on." I emailed him afterwards, like, "Wh- who, who should I interview next?" And he's like, "You gotta have Kyle on." Um, you have this graph in, uh, The Fate of Rome. Yeah, you show human population over the last few thousand years. I assume that these two down spikes are both the bubonic plague, Yersinia pestis, right?

Kyle Harper 1:55 Yeah, yeah.

Dwarkesh Patel 1:56 And so, this is not, like, some small little nudge you can see. Like, the overwhelming, I mean, other than the hyper-exponential growth in human population, the (laughs) overwhelming, not just one, but the overwhelming two major features in human population, going back the last (laughs) 10,000 years is this one bacteria.

Kyle Harper 2:14 Yeah.

Dwarkesh Patel 2:14 Right? One of the things you discuss in the book is that the collapse of the Roman Empire was a result of this one particular event.

Kyle Harper 2:21 Well, I mean, my... The period that I normally work on is sort of from the High Roman Empire, so like the, the glory days of the Pax Romana in the first or second century, which is usually where I start, through what we call the, the late antique or early medieval period, so the sixth or seventh century. And at the beginning of this period, Rome dominates this Mediterranean empire. It's what you think of when you think of, uh, ancient Rome. Um, it's the largest city in the world. It's, it's the center of this huge network. Um, and then by the end of this period, the city of Rome has, you know, we don't know, 50 to 100,000 people. Um, it's a tenth or twentieth of its former size, and I think we now can say pretty clearly that environmental factors like climate, but also especially diseases play a part in that, in that really big transformation. And well, there's a problem because we don't have the same kind of modern government mortality statistics-

Dwarkesh Patel 3:16 Mm-hmm.

Kyle Harper 3:16 ... that we do for, like, COVID or even for the last century or century and a half. You know, we have to piece together from clues, but it's pretty clear that the, the bubonic plague events, whether you're talking about the Black Death of the 14th century, the Plague of Justinian in the sixth century, um, these events are capable of, of causing death rates temporarily that are just orders of magnitude beyond what we're accustomed to. Um, and even in these ancient societies, the reason why these were so shocking, in a world where the death rate's always pretty high, probably, you know, um, you know, s- several percent of the Roman population, three, four percent a year maybe dying in a normal year.

Dwarkesh Patel 3:55 Mm-hmm.

Kyle Harper 3:56 Um, and so for them to just be utterly shocked, uh, by the death rate already tells you that it's some, some multiple of what they're, they're accustomed to.

Dwarkesh Patel 4:05 Yeah. I think you discuss in the book the possibility that the death rate might have been close to s- or even over 60%, uh, wherever the Black Death... So this is not just like... Th- this is, like-

Kyle Harper 4:16 Yeah.

Dwarkesh Patel 4:16 ... literally the most significant thing.

Kyle Harper 4:17 Yeah, it's, it's mind-blowing. And I mean, I, uh, you know, in the Black, the case of the Black Death in the 14th century, it's pretty clear. It kills 50, 60% of the population-

Dwarkesh Patel 4:26 Yeah.

Kyle Harper 4:26 ... in entire regions.

Dwarkesh Patel 4:29 Yeah.

Kyle Harper 4:29 You know, we don't necessarily think that it killed 50, 60% of the whole continent, although that's actually not impossible.

Dwarkesh Patel 4:35 Right.

Kyle Harper 4:35 But even the fact that it's killing 50% of the people in cities, in provinces, in countries-

Dwarkesh Patel 4:42 Yeah.

Kyle Harper 4:42 ... is just beyond the damage that other plagues do.

Dwarkesh Patel 4:46 Right, and do you think that were it not for this not- this, like, 60% mortality event plus the fact that I think we haven't even discussed yet, this super severe cold snap, do you think that the Roman Empire might have otherwise just kept going? Because you discuss, like, there's been, there were these two previous other big pandemics.

Kyle Harper 5:08 Yeah.

Dwarkesh Patel 5:08 The empire still survives. Um, the, uh, I think Will Durant had this quote that the r- uh, the ro- the Roman Empire fell for longer than most empires have lasted.

Kyle Harper 5:16 (laughs)

Dwarkesh Patel 5:17 (laughs) Um, so do you, do you think, like, you know, it'd be similar to China maybe? There were...

Kyle Harper 5:21 Yeah.

Dwarkesh Patel 5:21 Maybe a dynasty collapses, but fundamentally, the same sort of, um, cohesive nation reemerges.

Kyle Harper 5:27 Yeah, I mean, that's, that's a great comparison, right? And not just sort of, like, decline and fall of dynasties, but also, like, geographic changes in the configuration, that parts get added and parts get, get cleaved off, but you still kind of think of it as fundamental continuity in the core. Like, that, to me, is a very, very plausible counterfactual. Like, Justinian, the, the emperor in the 540s, he reigns from the five 20s to the 560s. He's, he's on a path of success. He's retaken Africa. He's mostly retaken Italy.... when the, the plague hits. Like, to me, a very plausible counterfactual is that a more or less Mediterranean core of the Roman Empire, um, could have survived east and west. So, it does sort of survive in the east. But even including-

Dwarkesh Patel 6:17 Mm-hmm.

Kyle Harper 6:18 ... um, really all of, of Italy, Africa and probably Spain, that would have been like a, to me, a very, very reasonable, uh, outcome of the 6th century if you hadn't had this, this kind of random shock.

Dwarkesh Patel 6:31 Yeah.

Kyle Harper 6:32 That there would be this... You know, the Roman Empire would keep going and then remember, it does, and it calls itself the Roman Empire until the 15th century. But we would think of it as maybe more sort of like really the Roman Empire if it still included the western Mediterranean and was this major powerful urbanized polity that resists invasion from the, from the south east, as happens in the 7th century. So, um, so yes. The answer is like I think that the Roman Empire absolutely could have had another turn sort of as the, the thing that we kind of mean when we say the Roman Empire, this pan-Mediterranean powerful urbanized empire.

Dwarkesh Patel 7:07 Right. Yeah. Okay,

Dwarkesh Patel 7:08 so one of the things I found really interesting, uh, was you were discussing the firsthand accounts as this big... And by the way, feel free to explain the cold snap as well as it's happening. But, um, the firsthand accounts of people who are experiencing this, um, some of whom come from this burgeoning Christian faith, which already lends itself to millenarianism and apocalyptic thinking. I'm curious basically how did different people try to make sense of, like, this once in a thousand year event, uh, that's super kind of like just intense.

Kyle Harper 7:42 Yeah. Clearly, people, people have to try and explain, um-

Dwarkesh Patel 7:47 Yeah.

Kyle Harper 7:47 ... within the, the elements of a world view that they have how something like this could happen. And they don't have, they don't have modern science. They don't have germ theory, you know. They don't think of it in terms of a, a biological event or climatic event. Um, and since that's come up and you've invited, I'll, I'll say a little bit about that. But this is one of the other really exciting frontiers where we're learning new things about the human past that we just didn't know, um, 10 or 15 years ago, that, um, in this case, we now have really, really cool paleo climate data that helps us understand that this period of the 6th and 7th century was also a period of really abrupt and significant natural climate change.

Dwarkesh Patel 8:32 Mm-hmm.

Kyle Harper 8:33 Um, and so we're all familiar with like anthropogenic climate change, the carbon emissions stay in the atmosphere, trap heat. Humans are changing the climate. It's a big problem. We can talk about it if you want. I'd, I'd just like to clarify that like that view is not incompatible with the reality that the climate does also change for natural reasons on every time scale, um, from like really long geological time scales to much shorter time scales. So, we live in the Holocene. The last 11,700 years have been pretty stable, pretty warm. It's an interglacial. We're literally between ice ages right now. And, um, it's been really stable in the big picture. And yet even within that stability, there are smaller scale climate variations and climate changes.

Dwarkesh Patel 9:19 Mm-hmm.

Kyle Harper 9:19 And because we need to understand how the earth system works, how the climate system works in order to be able to model, um, what's happening, we need, we need an empirical record of what the climate has done. So, for historians, this is like great news because now we have a huge number of sometimes even pretty high resolution climate reconstructions for historical periods across the Holocene. And so we now know, like we did not know this 20 years ago when I started graduate school say, um, that the, the Roman period experienced these, some really abrupt episodes of climate change. And in this case, the 6th century, we know the cause, that there was a series of really significant volcanic eruptions. Volcanoes are a very powerful short term climate forcing mechanism. They eject sulfur into the stratosphere. It aerosolizes and sort of creates a reflective shield, um, that scatters the radiation entering the, the atmosphere. And so it leads usually to short term cooling. And in this case, you had a series of really significant volcanic eruptions that cooled the climate for several decades and in some ways, the later series of eruptions even like a century and a half. And it wasn't just a little bit cooler. It was like a degree to two degrees cooler, which we all kind of know now like two degrees, this isn't weather. This is climate. So, like two degrees doesn't affect your, your day. But two degrees globally is a pretty different globe. And so all of a sudden in the late Roman world, it's much, much cooler. Probably areas that had been wetter are now drier. Places that are drier may be wetter. I mean, it changes the, the hydrological cycle as well, which is more complicated. But in addition to the, the shock of the plague, you have this simultaneous and probably not unrelated shock to the climate system. And so we know that it was essentially challenging for agricultural, agriculturalists, that, um, when the, the sun is blocked and it's really, really cold and the wheat doesn't grow-

Dwarkesh Patel 11:31 Mm-hmm.

Kyle Harper 11:32 ... your society then starves. And so the Romans get this like wham bam double shock of climate change, famine, and plague. And so back to how people explain this, yes, like apocalyptic thought is one of the principle sort of ways people frame it. They, to them, nature's going crazy, you know. Huge amounts of the population are dying of this horrible sudden disease and the crops don't grow. And you don't have microbiology and you don't have climatology, so you explain it in the, with the resources of the world view you have. And-... there's a, a huge burst of like apocalyptic thought in the sixth and seventh century, which is always kind of there. I mean, you mentioned that Christianity is eschatological. It is, yes, fundamentally, but like that comes out in different ways with different sort of emphases and different time periods, and this is a period, the sixth century, when there's a really sharp emphasis on eschatology in Christian thought.

Dwarkesh Patel 12:35 Mm-hmm. I found your early chapters in the book about, um, what the Roman economy was like in this happy period quite interesting. Um, uh, so there's, there's a bunch of questions I have about this. I- if you read Gibbon in like the 17- writing in the 1770s, I think he says in the 1770s that like the happiest, if you want to look at the happiest time in human history, you go back to this period you're talking about. Um, that, so this was true at- at least according to him as of like a couple centuries ago, you're s- this is still like, um, uh, peak civilization. Uh, and you discuss the complexity of the Roman economy, uh, the fact that millions of tons of wheat and other products have to make their way to Rome and the trade networks and everything. Um, and then I think you basically say like, "Look, they, they were experiencing productivity gains. The wages were increasing. Population was increasing. But they were still not at the level at which it was plausible that, save for these climactic and biological factors, they might have had an in- industrial revolution." And so I'm curious why you think like, basically, yeah, paint a picture for me of what like the Roman world looked like as of this happy period and why that's- was still like counterfactually not, you know, couldn't have just saved us 1,000 years of history if they-

Kyle Harper 13:46 Yeah.

Dwarkesh Patel 13:46 ... they, uh, were on the right track.

Kyle Harper 13:47 Yeah, I mean, first of all, like I think this is, this is like the sort of question that historians ought to worry about all the time, like to, we've got to be thinking about why didn't the, the Roman economy catalyze the takeoff? Because in some ways it, it was so precocious, um, for its time period, and it seems not utterly impossible, right? The Roman world is still a pre-industrial economy so agriculture is the dominant sector. The majority of people work in agricultural pursuits, and, uh, productivity is low. They don't have modern mechanized traction. They don't have modern synthetic fertilizers. They don't have the modern, you know, Green Revolution yields, all the things that have made agriculture stupendously productive. So, just like the primary sector is fairly limited in terms of its productivity because of the- the sort of limitations on technical inputs, um, and, you know, we can think of the- the inputs to an economy are going to be capital, labor, and ideas. And what the Romans, they've got people (laughs) . They have some investment, but like they just, they don't have technology. They don't have ideas. It's- it's a late Iron Age civilization. And, um, I do think there's productivity growth and that productivity growth comes from markets, from trade, where you get, you know, comparative advantage. In Egypt, I'm really good at growing wheat. Um, you can make glass in-

Dwarkesh Patel 15:12 Mm-hmm.

Kyle Harper 15:12 ... Syria and then we'll trade. Um, and the urbanization of the Roman world certainly facilitates that. Cities are- are these sort of like hubs of productivity-

Dwarkesh Patel 15:22 Yeah.

Kyle Harper 15:22 ... and- and exchange. Um, and there's some technology. I mean, the Romans, you know, if you look really, really hard over like five or six centuries, there's certainly like economies of scale where the production process and manufacturing is- is sort of moved from artisanal to sort of, you know, um, industrial scale, but there's not really ... there's no takeoff because they don't have science. Uh, they don't have research and- and engineering that drives continuous productivity gains. So I think they go like precociously far in a pre-industrial setting where you take trade really far. They have good institutions in terms of, you know, there's- there's strong property rights. There's relatively reliable contract enforcement. Um, there's- there's financial markets. They have like the most advanced financial markets in the world before like the 17th or 18th century.

Dwarkesh Patel 16:15 Mm-hmm.

Kyle Harper 16:15 There's impersonal financial intermediation, so like it's not like you have to know me and come ask me for a loan if you wanna go, you know, build a ship and go trade something. There are banks that take money from depositors and, you know, keep- keep balances and then lend out to, um, to debtors who want to go and do entrepreneurial things. So they have like so much potential, but there's just no, there's no spark. Um, you never see these sustained productivity increases, and I would just say ultimately it's because the Romans don't have technology improvements that are really self-sustaining, and the reason they don't have that is because they don't have science. Their science sucks. Um, I'm offending some of my colleagues, I'm sure. Like Galen is great. Ptolemy's incredible. Um, you know, I love Pliny the Elder's encyclopedia, but like if you look in the big picture, the- the contribution that the- the Roman Empire makes to our knowledge of how nature works and then the applied technology that comes out of that is really pathetic-

Dwarkesh Patel 17:18 Mm-hmm.

Kyle Harper 17:18 ... for 5, 600 years. Um, and so they go as far as you can with Smithian advantages to- to market exchange and specialization, um, to- to banks and finance, but without the kind of creative destruction of new technologies that improve productivity, you're eventually gonna run out of improvements.

Dwarkesh Patel 17:39 Mm-hmm. If you're like Augustus or some other Roman emperor and you're like, "Look, we've got this big good economy, but I want to see productivity gains," um, and you want to make it happen somehow, what is it exact- is there something you c- like at- at- from a t- um, top-down perspective you could have done? I mean, in Britain, you know, the- the government subsidizes the- the royal, uh-

Kyle Harper 17:59 Yeah. That's-

Dwarkesh Patel 17:59 ... um, uh, arts and so forth and the, the-

Kyle Harper 18:01 That's what I was gonna say.

Dwarkesh Patel 18:02 Yeah, yeah. The p- the longitude prize and so forth, but-

Kyle Harper 18:04 Yeah.

Dwarkesh Patel 18:04 ... yeah.

Kyle Harper 18:04 That's exactly what I was gonna say is, I mean, this happens first in France and then Britain, but you, you get royal societies for science where you're, um, you're doing really, I would say, I would say there's like-... three things that are essential there. One is, like, the promotion of what we would call basic or fundamental science. So it doesn't all have to be, like, immediately practical or commercialized-

Dwarkesh Patel 18:28 Mm-hmm.

Kyle Harper 18:28 ... but you're, like, promoting deep knowledge of nature. Um, two, you're doing it in an empiricist way, and this is something very important in the 17th century that the Romans, by contrast, don't have, is you have like the spirit of Francis Bacon that, um, that we need to ground our knowledge in experiment and observation, not just believe whatever authorities or Aristotle said. And it's very much the spirit of places like The Royal Society is we don't take things on anybody's word-

Dwarkesh Patel 18:57 Mm-hmm.

Kyle Harper 18:57 ... especially like Aristotle's. Um, and so, um, you need, you need basic science. You need empiricism, like this rigorous and self-correcting. Uh, and then third, you need a sense of useful knowledge, and that's the other thing that really comes together in the 17th century is not just the basic and abstract science, but the, the application. And the, the 17th century language for that is useful knowledge. Um, and that is something that doesn't ever get wired together in the Roman Empire. There are tinkerers and engineers, but they're not talking to the, the mathematicians and the physicists. And so if you were from on high to, like, design, um, self-sustaining innovation, I think you would, you would wanna bring those elements-

Dwarkesh Patel 19:41 Mm.

Kyle Harper 19:41 ... into proximity. And, uh, Augustus, you know, unfortunately for them, didn't do it.

Dwarkesh Patel 19:46 (laughs)

Kyle Harper 19:46 Probably good for the world. The Romans are pretty, pretty nasty people-

Dwarkesh Patel 19:49 Yeah.

Kyle Harper 19:49 ... in a lot of ways. Um, I definitely, um, am of the opinion that sort of the, the high science matters, that like Isaac Newton is not a tinkerer, right? He's not building, like, pumps.

Dwarkesh Patel 20:00 (laughs)

Kyle Harper 20:00 But the guys who are, are like his friends.

Dwarkesh Patel 20:04 Right.

Kyle Harper 20:04 And they're in and around The Royal Society, and they're absolutely... I mean, look at Denis Papin, who's a French engineer, who's like very much in the circle of like Leibniz and the, the like very high abstract mathematics, is trying to build like vacuum pumps.

Dwarkesh Patel 20:19 Mm.

Kyle Harper 20:19 Um, and the, the proximity of like high math, high science, very abstract, with the what is ultimately gonna be the sectors that lead to mechanization where then you can harness this new source of energy or this... Not new source of energy, this, um, this sort of source of energy that is there all along but hasn't been tapped in coal. Um, that's what catalyzes the big positive cycle of positive feedbacks. So what the Romans don't have is that. What the Romans do have is the, the kind of specialization. And like now that we look for it, it's there. Like when you, when you look at, you know, food processing, which is a huge sector, the way that they build mills, like there's definitely improvements.

Dwarkesh Patel 21:04 Mm-hmm.

Kyle Harper 21:05 Um, but there's never like the, the catalytic change where you get runaway positive feedbacks.

Dwarkesh Patel 21:11 That's right, yeah. So a previous guest of mine, Nat Friedman, um, I don't know if you saw this, but he launched this challenge called the Vesuvius Challenge.

Kyle Harper 21:19 Oh yeah.

Dwarkesh Patel 21:20 There, this library at Herculaneum in 79 AD was buried under the, uh, the ashes of Mount Vesuvius when the volcano erupted, speaking of volcanoes (laughs) . Um, and now they figured out with, uh, modern techniques how to read the burned scrolls. And it is supposedly the biggest library of classical text, uh, ever. Like it would, like double the amount of, um, classical text we have. What, as a scholar of ancient Rome, what would you personally find most fascinating? What are you exci- e- excited to find from this data?

Kyle Harper 21:55 Well, I, I mean, I'm super interested in the, the history of math. Like it'd be-

Dwarkesh Patel 21:59 Huh.

Kyle Harper 21:59 ... it'd be sort of like what, what happens after Euclid? Because it's, it's very hard to say that you get like these really interesting people like pop up like Diophantus who's later. He's in the Roman, early Roman Empire. But like there's still like really interesting math going on. And I mean, Euclid is incredible. Like that is... The Greek like experiment in, in math and science is the one that I think had like the better chance of sparking sustained-

Dwarkesh Patel 22:25 Mm.

Kyle Harper 22:25 ... takeoff. Um, and it didn't. And, um, it'd be interesting to know more about like why. Why does, why did things stall? Because these people aren't... You know, like, like Euclid is not just like a towering genius who comes out of nowhere.

Dwarkesh Patel 22:40 Mm-hmm.

Kyle Harper 22:40 He's very much a product of the, the culture and the questions that are being asked in the generations before.

Dwarkesh Patel 22:45 Mm.

Kyle Harper 22:46 But it just sort of feels like, um, you know, after him you fail to get that kind of sustained continuous progress and advance. So maybe, um, maybe sort of back to that, that big question that we were asking before. Like what, what is it that, that prevents the kind of breakthroughs-

Dwarkesh Patel 23:05 Mm.

Kyle Harper 23:05 ... that we see in the, in the modern world?

Dwarkesh Patel 23:07 What, um, what is the population of Greece during their golden age?

Kyle Harper 23:10 Well, I mean of like the greater Greek world or like individual city-states like Athens? I mean, we think of Athens as being like a couple 100,000 people.

Dwarkesh Patel 23:19 Right.

Kyle Harper 23:20 Like not massive. It's-

Dwarkesh Patel 23:21 So I wonder if it's, um, like the Greeks had the science but not the people-

Kyle Harper 23:25 Yeah.

Dwarkesh Patel 23:25 ... e- uh, to sustain a modern economy. Or not a modern, but even a sort of like-

Kyle Harper 23:30 Yeah, growth.

Dwarkesh Patel 23:30 ... industrial economy. And then the Romans had the people but not the science.

Kyle Harper 23:33 Yeah. Yeah, there's, there's probably something to that, that like there's just not the, the critical mass of, of educated-

Dwarkesh Patel 23:41 Yeah.

Kyle Harper 23:41 ... people of like sheer cognitive power to like keep it-

Dwarkesh Patel 23:45 Right.

Kyle Harper 23:45 ... keep it going, yeah.

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Dwarkesh Patel 24:39 Let's turn to another one of your books, um, uh, the one about slavery in the Roman world. Uh, I did not realize before I read that one how central s- I mean, how much Rome was a slave society. I guess that just, like, isn't a salient thing when it, um, in a sort of, like, conventional understanding of Rome. Yeah, why: why don't you paint, paint us a picture of the-

Kyle Harper 25:01 Yeah.

Dwarkesh Patel 25:01 ... how much slavery was involved in Roman world?

Kyle Harper 25:03 I mean, slavery, slavery, you know, tragically is a, a really important institution throughout history.

Dwarkesh Patel 25:09 Yeah.

Kyle Harper 25:10 We sometimes tend to, to think of it as, like, a distinctly modern phenomenon-

Dwarkesh Patel 25:14 Yeah.

Kyle Harper 25:14 ... but that actually misses the, the deeper picture. And in fact, it obscures the importance of modern slavery because modern slavery is uniquely important and it's uniquely tied up with certain kinds of, of market exchange and certain kinds of production, certain kinds of racial ideologies. There's, like, things about modern slavery that's really important to understand those are different, but not just because slavery is there. Like, slavery has this longer history and, um, and slavery is more important in some societies than others and we wanna try and understand that, um, to ask why and then what implications does that have for understanding those societies? Rome is one of those societies. Slavery is really a prominent institution in Rome from the late republic. As the, the Romans conquer other parts of the Mediterranean, they start taking captives as slaves en masse and they build a, an economy that really relies on slave labor in important sectors of the economy, so plantations where commodities like wine, olive oil are produced for market exchange that allow landowners to amass enormous amounts of wealth. So slavery becomes this, this really important institution that's entangled in the, the development of the Roman economy from, you know, maybe the third or second century BCE and then with ups and downs and really important changes along the way for, for centuries and centuries.

Dwarkesh Patel 26:37 Mm. And so you're pointing towards, like, from the supply side, all the Roman conquests lead to all this surplus labor that they could make use of and on the demand side, these cash crops.

Kyle Harper 26:46 Yeah.

Dwarkesh Patel 26:47 Yeah.

Kyle Harper 26:47 Exactly. I'm very big, uh, proponent of the idea that it, you have to have both, right? You have to have a source of slaves and after the conquest stops, the Romans figure out other sources of slaves.

Dwarkesh Patel 26:57 Mm.

Kyle Harper 26:58 Um, and if anything, the demand is, is equally or perhaps even more important because if there's not a, a mechanism, if there's not institutions that let you, um, turn this kind of exploitation into, into cash flow (laughs) , um, the institution's not gonna go very far. And so it really is the, the institutions, the presence of markets where you can, you can take labor, um, and turn it into, to profit that's the, the most important element.

Dwarkesh Patel 27:26 Mm. One of the fi- things that I find interesting is in the age of colonization, we, we're used to thinking about r- uh, slavery in terms of, uh, race but also, like, maybe, like, religion and other things which more obviously demarcate free and slave populations. Um, in the Roman world, it doesn't seem that that's clearly the case, yet there's no abolition movement, uh, the way that, like, emerges out of, you know, England in like, the 19th century or something or maybe even before that. So... And the reason that's mysterious is, like, look, if you were, like, literally descended from slaves, if you were like, "My grandfather was a slave, but then we were freed," and th- they're like basically just like you, you would think that there would be more of a sense of like, not everybody would be an abolitionist, but at least some people would be, like, writing about abolition and something.

Kyle Harper 28:11 Yeah.

Dwarkesh Patel 28:11 Um, abou- And then you've got, like, Ch- Christianity and so forth, uh, burgeoning and they didn't seem to have a problem with it. Like-

Kyle Harper 28:18 Yeah.

Dwarkesh Patel 28:18 ... why is there no abolition movement ge- despite the sort of, like, um, heterogeneous nature of the slave population?

Kyle Harper 28:24 Yeah. Um, it's, it's sort of, like, disturbing in a way, isn't it, that, like, humans have, have the, the ability to, to convince themselves that it's okay to, to own other human beings-

Dwarkesh Patel 28:39 Yeah.

Kyle Harper 28:39 ... as property through a variety of different kinds of ideological justifications? And you see even in the ancient world there's different models that people use to, to th- say that slavery is okay. I mean, Aristotle develops a theory of natural slavery that actually some people deserve to be slaves by their very nature and that it's actually good for them, um, to be in bondage.

Dwarkesh Patel 28:58 Mm-hmm.

Kyle Harper 28:58 What's really interesting though is tha- that doesn't actually ever seem to be, like, the dominant ideology. The Roman ideology of slavery is not racialized. It's not like the Romans think that the Greeks or the Germans are, like, you know, some fundamentally separate kind of human that, that justifies their, their exploitation. Um, the, the Roman ideology of slavery is really rooted in the law of property and status, so they think that slaves are people who've been conquered and rather than killed, they've been spared, um, and they've been sold and-

Dwarkesh Patel 29:31 Mm-hmm.

Kyle Harper 29:31 ... to the condition of being somebody else's property. And this seems to, to mentally explain to them, um, where their slave system comes from and why it's justifiable. And so you have different kinds of criticism of the, the slave system from within, but remember, most of what we have written is from the, the slave ownership class. It's not like w- (laughs) you know, I don't think the, the slaves were themselves, um, um, you know, believing this ideology. And there must have been sort of what we would think of as abolitionist movements or spirit-

Dwarkesh Patel 30:04 Yeah.

Kyle Harper 30:04 ... um, that we just don't have really good, good records of.

Dwarkesh Patel 30:08 Yeah.

Kyle Harper 30:08 Um, but, um, but it is, like, this curious thing that, that, um, the Romans are able to, to build this huge system that's really brutal and really violent, um, but, um, has this kind of flimsy ideology where they, they, um, tell themselves these stories, but the deeper, the deeper lesson of that is that humans can create these, these systems of belief-

Dwarkesh Patel 30:31 Mm-hmm.

Kyle Harper 30:32 ... um, that will exclude others and justify-... almost any form of exploitation-

Dwarkesh Patel 30:36 Oh, yeah.

Kyle Harper 30:36 ... and convince themselves that it's okay.

Dwarkesh Patel 30:38 I hope your next book about The Last Animal discusses the, uh, potential parallels with back-to-farming.

Kyle Harper 30:43 Uh, well, there's, there's some, uh, there's a pretty gruesome chapter. I'll say that.

Dwarkesh Patel 30:47 Yeah. I, I, I don't know if you mentioned, uh, I, w- what numbers you said, but like I think it was like 10% to 20% of the population under the Roman Empire was enslaved, um, or what- whatever the number is there. But given that larger size of a slave population, it's surprising to me that there's so few slave revolts not only in Rome but even throughout history. Like there's Spartacus in-

Kyle Harper 31:08 Yeah.

Dwarkesh Patel 31:08 ... 71 BC. Then there's the Haitian Revolution, I forget when, but like probably late 18-

Kyle Harper 31:14 Yeah, that was 17-

Dwarkesh Patel 31:15 ... to... Yeah, okay.

Kyle Harper 31:15 Yeah.

Dwarkesh Patel 31:15 What, yeah, w- what, you know, if like 20% of the population is enslaved-

Kyle Harper 31:19 Yeah.

Dwarkesh Patel 31:19 ... um, wh- like how is this a sustainable... You know, if you're like running a farm (laughs) and there's like-

Kyle Harper 31:24 Yeah.

Dwarkesh Patel 31:24 ... 4,000 slaves and then, like, the next farm over also and like-

Kyle Harper 31:27 Yeah.

Dwarkesh Patel 31:27 ... um, why aren't there more slave rebellions?

Kyle Harper 31:29 Yeah. (laughs) Right? Why, why not? I mean, w- why, how did they, how did they do this? I mean, they, they have a really elaborate system of, of repression. They're worried about it. Um, and probably the, the parts of Roman society where there are 20%, 30%, 40% slaves are pretty, pretty limited to, to certain regions and certain-

Dwarkesh Patel 31:52 Mm-hmm.

Kyle Harper 31:52 ... time periods. Um, and partly because once you cross some kind of threshold, the, the challenges of repressing sort of direct violent resistance. Um, but it's, you know, it's a system of exploitation. That means there's, there's always a mix of, of carrots and sticks, (laughs) um, to put it crudely. Like the Romans, um, um, extract people's labor partly through, you know, physical violence but also partly through like systems of manumission that try and incent people to, um, to obey and not to, to rebel in order to earn their freedom. Um, and, um, you know, they're, they're using everything from literal chains, um, to like enticements to try and keep, um, rebellion from ever sort of coalescing in a way that can-

Dwarkesh Patel 32:40 Mm-hmm.

Kyle Harper 32:40 ... can turn into collective violence. But yeah, I mean, it's a little bit, it's a little bit, um, challenging for us to look back and say, I mean, we know, like in Pompeii, the, the slave population in Pompeii is huge. It must be 30%.

Dwarkesh Patel 32:50 Mm-hmm.

Kyle Harper 32:50 Um, and not all of these people would have been like plantation, you know, workers who were lashed every day and, you know, worked to, to the physical bone. A lot of them are nurses and textile, you know, workers and, and maids and tutors and, um, all sorts of things that are sort of quasi-embedded in households as well where there's always this weird psychological dimension, too. I mean, part of the, the, the strangeness of slavery is how, how it's deeply embedded in domestic institutions as well.

Dwarkesh Patel 33:22 Mm-hmm.

Kyle Harper 33:22 And so there's ideologies in which the paterfamilias is sort of the, the father and the master-

Dwarkesh Patel 33:27 Mm-hmm.

Kyle Harper 33:28 ... um, that, that, um, sort of brainwashes, tries to brainwash people against, um, resistance. But it's this, like the important thing to recognize it's just like a pervasive system that, that tries to colonize people's minds and pervasively tries to keep them from, from resisting.

Dwarkesh Patel 33:44 Yeah. And I wonder if we can close the loop with the question we began with which is, why didn't Rome have an industrial revolution? Um, I don't know if it's a plausible explanation that cheap slave labor reduced the incentives for mechanization and engineering and other crafts or if, if not. I don't know.

Kyle Harper 34:03 It's definitely an argument that's been made. Aldo Schiavone who's an Italian, um, historian has argued that. It's kind of a, it's like a neo-Marxist tradition that argues this. It's an interesting argument. I don't buy it at all.

Dwarkesh Patel 34:15 Mm-hmm.

Kyle Harper 34:15 Um, but, you know, the, the good version of that argument would just be that, um, that the Roman Empire is using in fact slaves in many of the most forward elements of the economy, too. We tend to, I think because we think we know slavery is bad and we think progress and economic-

Dwarkesh Patel 34:32 Yeah.

Kyle Harper 34:32 ... growth and innovation is good, we tend to think that those things don't go together. But in reality, it's like the most economically advanced sectors of the Roman economy-

Dwarkesh Patel 34:43 Huh.

Kyle Harper 34:43 ... that have the most seri- you know, a high degree of organization, productivity, that tends to employ slaves. And so, um, in the, in the Roman world, like you could make the argument that if the, the labor in those sectors had been free, there would have been more opportunities for, for positive feedback loops. The way the argument's usually made is just that, um, you know, the Romans got rich without really thinking about productivity. They just wanted to extract, um, labor, extract wealth rather than create wealth-

Dwarkesh Patel 35:16 Mm-hmm.

Kyle Harper 35:17 ... um, you know, which I don't think is, is like a terrible argument. But I just, ultimately I don't think it's the, the system of labor that keeps the, the Roman world from, from industrializing. And there are lots of sectors in the Roman world where slavery is not-

Dwarkesh Patel 35:29 Yeah.

Kyle Harper 35:30 ... a dominant institution. It's not like they're more productive or like flirting with-

Dwarkesh Patel 35:33 Mm-hmm.

Kyle Harper 35:34 ... some kind of breakaway. So it's an interesting argument, but not one I've, I've ever found all that persuasive.

Dwarkesh Patel 35:41 Final question about Roman slavery. What did Gladiator get right and wrong about? W- will they just abduct you in front of your house and-

Kyle Harper 35:47 You know, I haven't seen-

Dwarkesh Patel 35:47 ... you know, make you a slave?

Kyle Harper 35:48 ... the second one. So you mean the-

Dwarkesh Patel 35:49 The first one, yeah.

Kyle Harper 35:50 ... the first one? The first one got right, um, that when you're making a movie, you should more, worry more about making a good movie-

Dwarkesh Patel 35:57 (laughs)

Kyle Harper 35:57 ... than a sort of actually... The first one's a great movie. And if it was like completely historically accurate, it would have been much more boring. Um-

Dwarkesh Patel 36:06 (laughs)

Kyle Harper 36:06 So, uh, so I'm not, uh, gonna be critical of, of that movie. Like it, it plays very loose with the facts of high politics-

Dwarkesh Patel 36:15 Mm-hmm.

Kyle Harper 36:15 ... um, around Commodus and the creation of this character. But who cares? I mean, Russell Crowe's incredible.

Dwarkesh Patel 36:20 (laughs)

Kyle Harper 36:20 And it, um-

Dwarkesh Patel 36:20 But on, on slavery in particular.

Kyle Harper 36:22 On slavery in particular, I mean, I think actually that's one of the strong suits of the movie-

Dwarkesh Patel 36:26 Yeah.

Kyle Harper 36:26 ... is you see this like, um, this like completely, uh, you know, exploitative, um, system that brings people from very different parts of the world-

Dwarkesh Patel 36:38 Yeah.

Kyle Harper 36:38 ... who, uh, have very different backgrounds and then the, the system of like urban spectacle is very real. Um, and the, the use of slave labor in that-... is certainly a part of it. So, um, so the movie actually gets, like, some really important things about that right.

Dwarkesh Patel 36:53 Mm.

Kyle Harper 36:53 And that makes it totally forgivable that it has to create a, a kind of high politics storyline.

Dwarkesh Patel 36:58 Yeah. Okay, I think that covers all the questions about Rome. Uh, we can get back to your most recent book about, um, Human History in Plagues.

Dwarkesh Patel 37:06 Uh, what, what do you make of the, um, the general, like, argument that people have often made that we were living in a sort of Eden before, uh, agriculture? Especially given your, um, you know, you, you've explained that all these diseases that we're sort of stuck with are, like, actually quite new. Um, if we, if, if we take that s- perspective seriously, was, was, you know, was life before human population exploded and we had agriculture just much more pleasant, at least in comparison?

Kyle Harper 37:37 Homo sapiens is two to 300,000 years old.

Dwarkesh Patel 37:40 Yeah.

Kyle Harper 37:40 We emerge in Africa, um, and, and disperse, multiply, but we spend 90, 95% of our history as foragers. So people who are hunter-gatherers, who take energy from wild food sources, rather than sedentary farmers who've domesticated plants and animals and live a sedentary lifestyle where you, you're enslaved to this wheat or rice, um, but it gives you reliable calories. Um, that is, along with the Industrial Revolution, and then whatever this thing we're about to go through-

Dwarkesh Patel 38:12 (laughs)

Kyle Harper 38:13 ... that is the biggest change in the history of our species-

Dwarkesh Patel 38:15 Yeah.

Kyle Harper 38:15 ... other than those others. Okay, so the shift from foraging to farming, it affected everything. It affected our beliefs. It affected our genetics. We're, we're all basically genetically different-

Dwarkesh Patel 38:29 Mm-hmm.

Kyle Harper 38:31 ... um, adapted to live, um, in a different kind of environment with different kinds of diets. Um, it, it affected, uh, our societies, it affected inequality, it affected culture in every possible way. And of course, it affected our health in really basic ways. It affected our labor regimes, so doing the same kind of labor over and over every day is very different from running around as a hunter chasing deer-

Dwarkesh Patel 38:58 Right.

Kyle Harper 38:58 ... or whatever. Um, which sounds quite nice.

Dwarkesh Patel 39:00 (laughs)

Kyle Harper 39:01 Um, it had changed... So it changed our labor regimes. It changed our diet, most of all. Hunter, foragers tend to eat high protein, high fat-ish diets, um, with no refined carbohydrates, but, like, limited carbs. Um, and it's a very varied, highly varied diet. So sedentary farmers tend to eat more monotonous diets and they tend to be, like, dependent on grains and starches. So, like, very narrow spectrum, um, for your calories. Um, so changes in labor regime, changes in the diet, uh, and then changes in lifestyle, being sedentary and living in big populations that then puts you in proximity to other humans, puts you in proximity to, to human waste.

Dwarkesh Patel 39:54 Okay.

Kyle Harper 39:54 Um, so feces are a major, major conduit of infection and it puts you into proximity to the air that they breathe, um, which is conducive to respiratory diseases. So this transition, which by the way, takes thousands of years, right? It's one of these things that's, that's more of a process than an event. Um, but it has massive implications for, for human health, including the, the infectious disease environment that we inhabit. So it's not like hunter-gatherers were living in paradise. Like, the infectious diseases that they had were seriously burdensome. They sucked and probably most people died of infectious disease. They... You know, malaria is a really, really old disease. Lots of diseases existed in pleis- in the Pleistocene, in like our Paleolithic past.

Dwarkesh Patel 40:46 Mm-hmm.

Kyle Harper 40:46 Um, so it's not like it was Eden, um, but there is this idea that the transition from foraging to farming, I mean, Jared Diamond called it humanity's biggest mistake.

Dwarkesh Patel 40:55 Yes.

Kyle Harper 40:56 Um, (laughs) and, um, the, you know, certainly it, these changes entailed, um, some things that, that, like, were not positive net for humanity. And, um, one of them is that it definitely increased the infectious disease burden. So simply as our population multiplies and as we're in contact with feces and as we're sharing the air through which respiratory pathogens can spread, diseases are constantly trying to take advantage of this. That's just how nature works. Energy is scarce. Everybody's trying to steal it from everybody else, including microbial parasites. And so the disease burden of humans over time definitely increases. Um, and the, the burden of infectious disease on humans goes up over time. So very broadly across these thousands and thousands of years, the, the diseases that are suffered by, say, people t- by the time of the Roman Empire are absolutely much worse than what had been-

Dwarkesh Patel 41:58 Mm-hmm.

Kyle Harper 41:59 ... you know, the case in, in Stone Age times.

Dwarkesh Patel 42:02 Uh, James Scott has an in- interesting theory in Against the Grain.

Kyle Harper 42:05 Yeah.

Dwarkesh Patel 42:06 I don't know if it originates with him, but, um, he argues that one of the reasons that the early agriculturalists who were so successful, and David Reich, by the way, uh, uh, if you've seen his stuff about like the Yamnaya 4,500 years ago, the conqueror of all of Eurasia, but before then, the, um-

Kyle Harper 42:23 Yeah.

Dwarkesh Patel 42:23 ... the Anatolian, uh, the initial hunter-

Kyle Harper 42:26 First farmers, yeah.

Dwarkesh Patel 42:26 ... farmers, like, th- they're the ones who, like, displaced the initial hunter-gatherers-

Kyle Harper 42:29 Yeah.

Dwarkesh Patel 42:29 ... across, uh, uh, Europe and Asia. Anyway, so he argues that initial wave was so successful because of these first, I guess, um, diseases that the farmers were, um, had created the conditions to engender and... Basically, the relationship we had... Sorry. The relationship these farmers had with respect to the foragers that they were taking over from was similar to the relationship the Europeans had to the Native Americans where inadvertently, um-... that the disease is just, like, a significant player in why you were able to dominate them. Um, I don't know how plausible you find that.

Kyle Harper 43:06 I mean, I would f- first thing, say, like, it's important, I think you were starting to get at this, that there's never, like, a generation of humans that has the opportunity to make this choice once and for all. Like, should we, (laughs) should we stay, like, hunting-

Dwarkesh Patel 43:22 (laughs) .

Kyle Harper 43:22 ... uh, you know, mammoths or should we become sedentary farmers with, like, basically torturous dentistry-

Dwarkesh Patel 43:29 Right.

Kyle Harper 43:29 ... um, and die by diarrhea, like... This happens over thousands of years through an evolutionary process where nobody can... It's a story of unintended consequences, right?

Dwarkesh Patel 43:37 Yeah.

Kyle Harper 43:37 I mean, the mammoth are gone because, partly because we killed them all. Um, and so people start, like the first livestock that are domesticated are goats and nobody says, like, "Hey, let's become goat farmers." The goats are wild, they're ibexes, and people are hungry and so they start managing them to only kill the males to make sure that they can reproduce and they start pinning them and they start killing the wolves who are trying to attack them and over very, very, very long periods of time this becomes this tight mutualistic relationship where all of a sudden we're goat farmers, you know? (laughs)

Dwarkesh Patel 44:10 Yeah.

Kyle Harper 44:10 Um, but no generation makes that whole decision for anybody, um, so that's part of it is that it's unintended consequences that are made in very, very incremental steps. And then two is, like, I definitely agree that there's some kind of, like, um, cultural selection here where the- the farming groups are simply so much more, uh, adapted to extract energy efficiently from the environment, right? It's all about energy. You want to multiply, you want to grow, you want to survive, um, it's all about energy. And so the, you know, foragers require huge landscapes to extract enough energy-

Dwarkesh Patel 44:50 Yeah.

Kyle Harper 44:51 ... to feed themselves and grow and reproduce, whereas farmers per, per unit of land can extract, um, such higher rates of- of energy that then can be, you know, through photosynthesis is captured and turned into edible sugars that we can metabolize. Um, and so those populations are just growing faster, um, that- that they, you know, quote-unquote out-compete the- the hunter-gatherer populations, say, of- of Europe that are largely but not completely, um, displaced. Now, on top of that, so just like the energy story alone is- is a big piece of it, but then on top of that you probably do have some kind of, um, population difference in, uh, in the- the exposure and possibly even immunity to infectious diseases, so I definitely think that early farmers, the first farming societies that are starting to live sedentary lifestyles where you have aggregations... These are not cities, these are villages-

Dwarkesh Patel 45:50 Yeah.

Kyle Harper 45:50 ... um, but still that's more than, like, a hunter-gatherer band-

Dwarkesh Patel 45:55 Right.

Kyle Harper 45:55 ... and your childhood is then gonna be constant exposure to- to a series of pathogens. Um, those kinds of populations, when they're then migrating into Europe, were probably carrying these- these pathogens with them that may have had a kind of further effect that, on top of just being able to extract more energy and multiply faster, um, drives up the mortality of the- the existing populations.

Dwarkesh Patel 46:17 Yeah. The point you made about fertility is, uh, interesting. I can't remember where I saw this, and it might be wrong, but I vaguely remember reading that for, um... It's not just the fact that you're not, like... the energy density is lower, it's that you're also moving around a lot.

Kyle Harper 46:33 Right.

Dwarkesh Patel 46:34 And so that, um... Because of that you're spacing out kids much more so than if you were just, like, in the same place and I think, like the fert- like... The actual fertility for foragers is, like, not, is like sort of like a reasonable, um... I don't know if sustainable is the right word because I don't mean like in an ecological sense but more so in a like, uh, um, c- like keeps your population constant

Narrator 46:52 Yeah.

Dwarkesh Patel 46:52 level.

Kyle Harper 46:52 I mean don't s- don't, like, make me swear but it's like more like four than six, like, b- because-

Dwarkesh Patel 46:57 Right.

Kyle Harper 46:58 ... because women who are, who are, you know, moving with the foraging bands-

Dwarkesh Patel 47:03 Right.

Kyle Harper 47:03 ... you know, miles and miles on foot on average a day, um, and also carrying kids-

Dwarkesh Patel 47:09 Right.

Kyle Harper 47:09 ... right, um, are- are gonna have very different, uh, life history than sedentary populations.

Dwarkesh Patel 47:15 Yeah.

Kyle Harper 47:16 And that's- that's very clear.

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Dwarkesh Patel 48:26 One thing I'm really curious about is what effect these diseases through history have had on the cognitive functioning of people. I mean, yeah, you discuss this in like the more, the chapter about like more recent history of the Great Diversions-

Kyle Harper 48:41 Yeah.

Dwarkesh Patel 48:41 ... and probably like contributed to the productivity of Europe, um, that they were able to have public, uh, health earlier. But literally go- uh, if you go back thousands of years, you mention for example that like Caesar was 5'5" and that was considered tall during his period. Did the same diseases and malnutrition, whatever it was that caused these physical health effects also mean that like the average IQ was much lower a-... um, uh, just because of, like, you know, you're, like, the- when you're-

Kyle Harper 49:10 Yeah.

Dwarkesh Patel 49:10 ... a kid, you're sick and that steals away nutrition for brain growth or something?

Kyle Harper 49:14 Yeah. Short answer, yes. Long answer, um, we know that in the- the modern world, like say over the last 250 years, um, first in Western European societies and their settler offshoots and then more globally and more rapidly globally, um, there have been really deep physiological changes-

Dwarkesh Patel 49:32 Mm-hmm.

Kyle Harper 49:33 ... in the average human, right? So, we're talking about populations with distributions. Um, and, um, what's happened is really two things. One is there's more energy per capita, um, so people eat more, they eat more calories and they eat better calories. They eat lots of bad stuff too but like-

Dwarkesh Patel 49:51 (laughs)

Kyle Harper 49:51 ... people- people eat more. Um, and two, the burden of infectious disease has been lowered. And, um, growth, the growth for a human is a very complicated trait that's influenced by genetics so, you know, I was never destined to be, you know, super tall, um, but it's also affected by environment which includes, but is not limited to, um, what you put in, nutrition, and then what you spend either doing labor or what you spend fighting infectious disease. Infectious disease imposes a huge burden on the body. The immune system is extremely metabolically expensive and so if your childhood is spent just fighting infectious diseases, you're going to struggle to invest energy in growth.

Dwarkesh Patel 50:39 Yeah.

Kyle Harper 50:39 So, there's massive increase in the size of populations over the last 250 years and even though it's a- a even more complicated trait, this improves, um, people's cognitive abilities.

Dwarkesh Patel 50:54 Right.

Kyle Harper 50:54 People are smarter. Like, may not feel like it-

Dwarkesh Patel 50:58 (laughs)

Kyle Harper 50:58 (laughs) But, uh, but, uh, and it, I think it is, uh, has rapidly leveled off, uh, but, you know, people- people are more intelligent today than they were 100 years ago. Their brains, um, are- are better nourished and, um, they spend less... their bodies spend less time fighting pathogens. So, I think there's no doubt that pre-industrial populations, and again, populations, so you still have (laughs) , you know, you still have your Isaac Newtons, um, who whatever infected him as a kid, uh, didn't slow him down, but-

Dwarkesh Patel 51:27 Right.

Kyle Harper 51:27 ... Um, but at the population level, I think there's no doubt that not only were pre-industrial populations, um, shorter, this is just a total fact that we know from their bones, um, but they probably also, on average, um, had s- had sort of a lower distribution of cognitive abilities.

Dwarkesh Patel 51:45 Mm.

Kyle Harper 51:45 But with a big distribution.

Dwarkesh Patel 51:47 Yeah, so you have this- a great profile in the book about, like, living in London in the 18th century and just, like, how disgusting it was.

Kyle Harper 51:53 It's pretty disgusting.

Dwarkesh Patel 51:54 (laughs) Um, but at the same, like, l- literally at the same time, in that city, you were just mentioning-

Kyle Harper 51:59 Yeah.

Dwarkesh Patel 52:00 ... there's these scientists and, um, people with, like, towering intellects who are basically figuring out how the universe works-

Kyle Harper 52:06 Yeah.

Dwarkesh Patel 52:06 ... and how to make all these machines and so forth. And so, um, I mean, one answer is just, like what you just said, like, "Look, the distribution was lower," but that- that's still, like, maybe Newton would've had an- had an IQ a standard deviation higher (laughs) and, um-

Kyle Harper 52:19 Yeah.

Dwarkesh Patel 52:19 ... if- if he was born today. Um, but it just, like, seeing that from the small population, you're seeing so much genius. Yeah, I guess the question is, how is that still... how could you have had this much of a deleterious impact on cognitive functioning and still had enough spare, um, geniuses f- to kick off the Industrial Revolution?

Kyle Harper 52:40 Yeah, I mean, obviously it, uh, it didn't, uh, didn't keep them from- from discovering some pretty amazing (laughs) things.

Dwarkesh Patel 52:46 Right.

Kyle Harper 52:46 So, um, so it couldn't have been, it couldn't have been, you know, completely destructive, but, you know, that's what's- one of the things that's interesting about the early modern period in the 17th and 18th century in particular is it's sort of this between period where, um, where you have sort of the- the pre-industrial and the modern that are still, like, mixed together in these really interesting ways. And so, you know, the example I use in the book is the very famous, uh, diary of Sam- Samuel Pepys, who's this incredible figure and is, like, very close to Newton in that social group and, um, you know, his name is on the- the first edition of the Principia, right? I mean, these people are like, this close to each other.

Dwarkesh Patel 53:27 Yeah.

Kyle Harper 53:27 But like, you know (laughs) , the stuff that I evoke, I won't- I won't, uh, you know, this is- this is a family podcast.

Dwarkesh Patel 53:34 (laughs)

Kyle Harper 53:34 I don't want to say it, but like, you know, the stuff that Pepys does, um, bodily functions, is like mind-blowing to us. It's-

Dwarkesh Patel 53:41 Right.

Kyle Harper 53:41 ... it's vile and disgusting. Uh, but at the same time, like, you know, right down the- the way, um, you've got people who are making the most fundamental discoveries about the nature of- of the universe (laughs) and-

Dwarkesh Patel 53:53 Right.

Kyle Harper 53:53 ... uh, inventing machines that will- will improve productivity and ultimately economic output. Um, so that's what- that's what's precisely so weird and interesting about that particular period-

Dwarkesh Patel 54:03 Right.

Kyle Harper 54:03 ... is you have this kind of mingling of the old and the new.

Dwarkesh Patel 54:07 Yeah. When I had Joseph Henrich on, you know, one of the things he discusses is if you look at... I mean, cultural evolution has figured out some remarkable things, right? If you look at the cuisines of different cultures, apparently the, um, the spices they use match the antimicrobial and antifungal properties you need-

Kyle Harper 54:25 Yeah.

Dwarkesh Patel 54:25 ... in that particular biome. At the same time, you're like watching... I mean, uh, reading that part of the book I'm like, "Okay, I get in some cases they just genuinely did not have the resources to invest in public health and so forth," but like, come on (laughs) , I mean like, I don't know if I should mention some of these things as well but like, you're just like sleeping in your own vomit and, um, uh, so forth. Like, the- why didn't cultural evolution or some like force just be like, "Hey, like this we can sort of like do without"?

Kyle Harper 54:52 Yeah, I mean, it- it's a deep question and what I think we don't think enough about is like how, like how, in a really fundamental way, how hard are some problems to solve?

Dwarkesh Patel 55:06 Yeah.

Kyle Harper 55:06 Like, some problems are just like very, very hard to solve.

Dwarkesh Patel 55:09 Mmm.

Kyle Harper 55:09 And even though the incentive is really there, um, you think-... ah, that took a really, really long time to figure out-

Dwarkesh Patel 55:16 Yeah.

Kyle Harper 55:16 ... even though if you'd only known, like, it would've made your life so much-

Dwarkesh Patel 55:20 Right.

Kyle Harper 55:20 ... so much better. Um, and like, you know, it, and it also, like, there's tons of trial and error, right? So, um, the, the example that comes to my mind is, is the invention of vaccination-

Dwarkesh Patel 55:34 Yeah.

Kyle Harper 55:34 ... um, which is, like, one of the great human achievements, like of all the public health improvements is the most important one. Um, public health is never perfect. It's this, like, system of, like, six or seven really critical tools that involve clean water, personal hygiene, vaccines, antibiotics, um, um, eh, m- different kinds of therapeutic interventions or ??? therapy. And, mm, we're still, we can't, like, fend off all the germs. Like, you have to have all of that and you can-

Dwarkesh Patel 56:07 Right.

Kyle Harper 56:07 ... sort of, like, achieve this, this equilibrium state where you mostly have it under control. Vaccination's, like, the most important one, and it took forever-

Dwarkesh Patel 56:17 Right.

Kyle Harper 56:18 ... to find the first vaccine. And it took this huge period of, like, all kinds of weird trial and error, like inoculation with the actual smallpox, which is very, very dangerous. Not vaccination. Vaccination uses cowpox, the, the lymph of an infected cow, um, to, to intentionally cause the immune reaction-

Dwarkesh Patel 56:38 Yeah.

Kyle Harper 56:38 ... of humans. Before that people would inoculate a person with actual smallpox, which is just giving somebody smallpox. You do it through the skin.

Dwarkesh Patel 56:46 (laughs)

Kyle Harper 56:46 But, like, you're giving somebody smallpox. But it was absolutely in, like, a utilitarian way it was the rational thing to do. It had these horrific death rates, right?

Dwarkesh Patel 56:53 Right.

Kyle Harper 56:53 It would never, it would never get FDA approval.

Dwarkesh Patel 56:54 (laughs)

Kyle Harper 56:55 Uh, but in a world where, like, 10, 20% of kids die of smallpox, it's this horrible decision but you, you'd be rational to do it. And so that, we actually don't know where that comes from. It may come from Africa, it may come from China. It spreads for, like, a century or more before Jenner discovers vaccination. So, like-

Dwarkesh Patel 57:15 Yeah.

Kyle Harper 57:15 ... it's clearly, like, really hard to figure that out.

Dwarkesh Patel 57:18 Right.

Kyle Harper 57:18 And then even after Jenner, it's, like, another, you know, 60 years, 70 years before Pasteur kind of systematizes it and says, "Hey, we could do this for everything."

Dwarkesh Patel 57:29 Yeah.

Kyle Harper 57:29 Right? So, um, so some of these, some of these discoveries and innovations take, they're really, really hard to discover. But then the beauty of cultural evolution is that we can store that information and you and I don't have to figure out any of that. We can go on to the next problem-

Dwarkesh Patel 57:46 Yeah.

Kyle Harper 57:46 ... because that's now been, like, collectively stored in the library of, of cultural evolution.

Dwarkesh Patel 57:52 Yeah.

Kyle Harper 57:52 It's known. You know, we don't even think about it, uh, most of the time until it's controversial. But (laughs) um, but, like, what a blessing to, you know, to live after people like Jenner and Pasteur-

Dwarkesh Patel 58:04 Right.

Kyle Harper 58:04 ... who figure that out.

Dwarkesh Patel 58:05 Yeah. Um, there, there's this great blog post by the author Slime Old Time where he's discussing-

Kyle Harper 58:09 Wait, author what?

Dwarkesh Patel 58:13 (laughs)

Kyle Harper 58:13 (laughs)

Dwarkesh Patel 58:13 You don't know internet culture, you know.

Kyle Harper 58:14 I, I live-

Dwarkesh Patel 58:15 There's a bunch of weirdos out there. (laughs)

Kyle Harper 58:16 I live in a different world, sorry. What, what'd you call them? (laughs)

Dwarkesh Patel 58:21 (laughs) Um, Slime Old Time. (laughs)

Kyle Harper 58:24 You can't just drop them, like, I'm gonna let that one slide. Okay. I got some homework.

Dwarkesh Patel 58:30 Anyways, so he has a, uh, blog p- they have a blog post about, uh, scurvy and why it took so long to discover. And he was discussing all these sort of, like, it's sort of like an epistemic conundrum because you can, like, use lime and you realize, like, "Oh, it works." But, but then if you use lemons, which have much less vitamin C or maybe it's the other way around, they just w- work much, uh, way, um, way worse. And then there's, like, certain kinds of fruit which have vitamin C, certain kinds which don't. So it's, like, it's, uh, it's a-

Kyle Harper 58:58 Yeah.

Dwarkesh Patel 58:59 ... it's actually hard to kind of figure out, like, what is it if you don't have a mechanistic explanation about how you solve this problem. And I think they had once figured it out and then they lost the knowledge until it was rediscovered again.

Kyle Harper 59:09 Yeah. Yeah.

Dwarkesh Patel 59:10 Um, but it makes it all the more mysterious that the kinds of things that Henrik discusses, uh, forager societies having figured out. Like, literally there's, like, this 10-step process for how to process a certain kind of bean so that you don't get cyanide poisoning. Um, and if you mess up any one of those 10 steps, you're gonna get cyanide poisoning. But, like, a society just figures out-

Kyle Harper 59:32 Yeah.

Dwarkesh Patel 59:32 ... you know, like, the right taboos and traditions to process beans. But, like, you can figure that out, but this thing which is causing 20% mortality, you only get, like, in the 17th, 18th century.

Kyle Harper 59:42 Yeah. Yeah, but it's, we need to think more about, about, like, the computation that's, that's happening. Like, what, you me- you said it takes, like, 10 steps to figure out, you know, how to process this one particular kind of food. But, um, but I'm guessing, like, it is, it is just really hard to figure out infectious disease. Um, it's a really, really steep mountain.

Dwarkesh Patel 1:00:05 Mm.

Kyle Harper 1:00:05 And n- once you get, like, up to a certain-

Dwarkesh Patel 1:00:08 Right.

Kyle Harper 1:00:08 ... plateau, then the discoveries, like, come really, really fast. They become systematic, um, and they become more fundamental. But it was really hard to get there.

Dwarkesh Patel 1:00:17 Yeah.

Kyle Harper 1:00:17 Um, it, you know, not that many societies really scaled it, not even within the societies that did. Like, it was just a handful of people at first. Um, but, but they did get there.

Dwarkesh Patel 1:00:28 Yeah. Okay, and then

Dwarkesh Patel 1:00:30 asking about where different countries were at around this time, what evidence do we have about what was actually happening in India before, um, the British or the Mughals? Because it does seem to be this sort of black box in terms of historiography. But, like, do we know if there were these huge plagues? Uh-

Kyle Harper 1:00:48 Yeah, it's such a, it's a tricky problem because, okay, start with the third plague pandemic in the late 19th century.

Dwarkesh Patel 1:00:56 Yeah.

Kyle Harper 1:00:57 Um, we know that, that that's in India.

Dwarkesh Patel 1:01:00 Yeah.

Kyle Harper 1:01:01 Um, and India's a big part of its history. Um, it's in fact where the, the plague bacillus is discovered by Alexander Yersin. Um, it's called Yersinia pestis in his honor. Japanese scientist finds it exactly the same time, gets left out of the nomenclature. But the-

Dwarkesh Patel 1:01:19 It's a special kind of honor to- (laughs)

Kyle Harper 1:01:21 Yeah, to be-

Dwarkesh Patel 1:01:22 ... have the deadliest agent in history. (laughs)

Kyle Harper 1:01:22 The worst, the worst pathogen ever. Um, immortality.

Dwarkesh Patel 1:01:27 (laughs)

Kyle Harper 1:01:27 The plague is definitely in India in the 17th century.

Dwarkesh Patel 1:01:31 Yep.

Kyle Harper 1:01:31 And we know that from contemporary written records that are pretty unambiguous about the, the presence of the disease. What we don't know is was it there before that? And if not, why not? Because it kind of actually seems like it's not.

Dwarkesh Patel 1:01:45 Mm.

Kyle Harper 1:01:45 At least not in this, like, same explosive way. Um, and that's pretty curious. Like, we don't have a great explanation of that because, you know, India's connected to the, to the Central Asian world, um, where the, the plague is endemic. There's plenty of trade. Um, it would had plenty of chance to move to-

Dwarkesh Patel 1:02:08 Yeah.

Kyle Harper 1:02:08 ... to the subcontinent. So, we don't understand that. And then if you go back even further, you know, that's the Black Death. You go back even further to the late antique period, we ... it's like a total mystery. And the, the Indian sources from the even the fifth and the sixth century are not great.

Dwarkesh Patel 1:02:25 Mm.

Kyle Harper 1:02:25 Um, they're hard to use. This is totally outside my language abilities. They require, um, totally different expertise. Um, I've worked with some people who think that there are, like, oblique references that may be interpreted as epidemic. But one of the interesting things is we actually think that the plague moves through India to get to Rome.

Dwarkesh Patel 1:02:50 Hmm.

Kyle Harper 1:02:50 This is not definite, but the plague's en- enzootic, it's like natural animal reservoir, is the Tian Shan Mountains where China, Kazakhstan, and Kyrgyzstan meet. And, um, and we can actually, you know, in the scheme of things, kind of identify a pretty small region where the pandemic lineage comes from. And we know that it doesn't go overland, so it doesn't, it's not like the Black Death which goes across the Steppe, the Mongol trade networks, military networks carry it. In the sixth century, probably, the plague goes south through India, um, and maybe, like the, the ports in Gujarat or along the West Coast-

Dwarkesh Patel 1:03:36 Mm.

Kyle Harper 1:03:36 ... that are still pretty connected with the Roman world-

Dwarkesh Patel 1:03:41 Right.

Kyle Harper 1:03:41 ... with East Africa, with Arabia, with the Red Sea, that the plague travels on ship across the Indian Ocean because it shows up, the Plague of Justinian shows up in the Red Sea. Um, and so that is a clue that it probably is imported on this seaborne commerce. But how it, you know, how it got from Central Asia to Gujarat is, is a hard question.

Dwarkesh Patel 1:04:05 Huh. And, I mean, I know the way we found that the Yersinia pestis existed in these Yamnaya 4,500 years ago is by... Didn't they just find like the f- uh, I don't know how, but if you can figure that out, why can't you look at the fossils of people 500 years ago or-

Kyle Harper 1:04:26 Yeah.

Dwarkesh Patel 1:04:26 ... 1500 years ago and just see if they have Yersinia pestis in them?

Kyle Harper 1:04:29 There's two things. First of all, you have to look.

Dwarkesh Patel 1:04:30 Yeah.

Kyle Harper 1:04:31 So there is, at present, not nearly the same amount of ancient DNA laboratory work that's happening on remains from ancient India.

Dwarkesh Patel 1:04:44 Mm-hmm.

Kyle Harper 1:04:45 Um, so, if you're not looking, you're definitely not gonna find it-

Dwarkesh Patel 1:04:48 Yeah.

Kyle Harper 1:04:48 ... and people aren't looking.

Dwarkesh Patel 1:04:50 Yeah.

Kyle Harper 1:04:51 Secondly, it takes a lot of luck for it to preserve. So the DNA molecule starts degrading.

Dwarkesh Patel 1:04:57 Mm-hmm.

Kyle Harper 1:04:57 The second you die, just starts falling apart. Um, and even in the best of cases where we're getting it from, usually you're getting it from, if it's pathogen, usually getting it from the dental cavity.

Dwarkesh Patel 1:05:11 Mm-hmm.

Kyle Harper 1:05:12 If it's human DNA, you're getting it from the, the inside of the skull. But it takes a lot of luck for it to preserve because the soil conditions will affect the degradation.

Dwarkesh Patel 1:05:22 Mm-hmm.

Kyle Harper 1:05:22 The temperature will affect the degradation. And just in a crude sense, heat is bad-

Dwarkesh Patel 1:05:27 Mm.

Kyle Harper 1:05:28 ... um, and so it's why there's more DNA, ancient DNA that's preserved at more northern latitudes-

Dwarkesh Patel 1:05:34 Yep.

Kyle Harper 1:05:35 ... so far. But it has as much to do with the fact that people aren't looking, um.

Dwarkesh Patel 1:05:39 Yeah.

Kyle Harper 1:05:40 But we should be looking, um, and if you've got skeletal materials from an ancient mass grave in India, call me.

Dwarkesh Patel 1:05:50 (laughs)

Kyle Harper 1:05:50 (laughs) We can, we can definitely look. (laughs)

Dwarkesh Patel 1:05:53 And just to be clear for the context. (laughs)

Kyle Harper 1:05:56 Ancient, ancient, ancient, uh...

Dwarkesh Patel 1:05:59 Um, going

Dwarkesh Patel 1:06:00 forward to the future a little bit, um, speaking of future technology, maybe the one that's more relevant than AI is synthetic biology, and there's a worry that you can potentially create diseases which the, maybe the evolutionary gradient is, um, one that is, like, not catastrophic where diseases are incentivized to be transmissible but keep you at a chronic level of infection that doesn't necessarily kill you immediately. Uh, actually it's interesting why the b- bubonic plague diverges from that, uh-

Kyle Harper 1:06:32 Yeah.

Dwarkesh Patel 1:06:33 ... this selection pressure which maybe you can answer. But, um, yeah, wh- wh- what do you think about the potential that with synthetic biology people can make diseases that have the transmissibility of measles but also the deadliness of something like Ebola? Is that, given your understanding of biology and whatever-

Kyle Harper 1:06:49 Yeah.

Dwarkesh Patel 1:06:49 ... is that, how plausible is that?

Kyle Harper 1:06:51 Well, let me, let me start with the plague where I'm a little, a little more-

Dwarkesh Patel 1:06:54 Yeah.

Kyle Harper 1:06:54 ... comfortable as, and I can say something as a, as a knowledgeable person. But the, but I think it's relevant because you said, like, it's weird that the plague seems to sort of evade some of these evolutionary constraints, and l- it's worth just, like, saying what these are. Like, a pathogen, you know, is a disease-causing organism, a microbe, usually a virus or a bacterium but also fungi and single-celled organisms like protozoans that-... that cause disease in a host. But like, they're not trying to cause you disease. COVID doesn't hate you, you know.

Dwarkesh Patel 1:07:29 Mm-hmm.

Kyle Harper 1:07:29 Plague doesn't hate you. It's just evolution. It's just trying to steal energy or-

Dwarkesh Patel 1:07:35 Right.

Kyle Harper 1:07:35 ... hijack your cells to reproduce its genes. And, um, and in fact, it has incentives to try and do that as well as possible while doing the least possible damage. Um, and so it's always kind of trying to thread that needle or to, to find the right balance because if a pathogen just kills you instantly, there's nothing to steal and it can't transmit its genes into the next generation. Um, and so it's a really, every pathogen has these like basic evolutionary problems. How do I get from one host to the next? And how do I evade my host's immunity, which our immune systems are incredible, um, for long enough to, to multiply?

Dwarkesh Patel 1:08:16 Mm-hmm.

Kyle Harper 1:08:16 Um, and so most pathogens, you know, this is clunky. There's not like a perfect equilibrium but they have to like explore this space where there are these, these various constraints. And, um, and they find all sorts of weird ways around it. Um, and evolution is really, really good and really, really creative, uh, unfortunately for us.

Dwarkesh Patel 1:08:37 (laughs)

Kyle Harper 1:08:37 Um, and just like the tricks that they find to like hide inside your immune system, um, or to, to like fake it out, um, are really, really wild. But, um, one of the... there's, I think there's two reasons why plague is so weird. Um, and like we don't completely understand why plague is so weird but I think there's two basic reasons. One is that it's vector borne, which means that it's transmitted through, um, uh, another organism that is the, the intermediate.

Dwarkesh Patel 1:09:09 Mm-hmm.

Kyle Harper 1:09:10 Uh, and arthropod or insect vectors are really annoyingly, you know, helpful to, to certain pathogens. And most, there's, there's actually a relatively small number of diseases that are transmitted through a vector like this, but they tend to be really, really nasty, um, like malaria.

Dwarkesh Patel 1:09:33 Mm-hmm.

Kyle Harper 1:09:34 Um, typhus. And they can kind of get away with it because even if like you're dying, um, you know, a mosquito can come and bite you and transmit malaria to me. Plague is a vector borne disease.

Dwarkesh Patel 1:09:47 Mm-hmm.

Kyle Harper 1:09:48 And it's very, very well adapted to transmit, particularly by fleas but we think also maybe by lice and other biting organisms, but really by fleas. It's really, really good at transmitting by fleas.

Dwarkesh Patel 1:09:58 Mm-hmm.

Kyle Harper 1:09:59 Um, and that's evolution. Actually, this is one of the cool things with ancient DNA we've been able to like piece together at the like absolute molecular level, the, the genetic changes that let it make this protein that like have this effect in fleas. It's really weird, it forms this biofilm in the, in the gut of the flea that like chokes it and makes the flea feel like it's starving.

Dwarkesh Patel 1:10:21 Mm-hmm.

Kyle Harper 1:10:21 And so the flea just starts feeding and feeding and feeding and meanwhile it's regurgitating bacteria. Um-

Dwarkesh Patel 1:10:27 Sorry, can I, can I, can I ask a question about that?

Kyle Harper 1:10:30 Yeah.

Dwarkesh Patel 1:10:30 Why is it the case... 'cause there's diseases that hijack the flea's mind or ant's minds or something. Are there like... why, why isn't there a disease that makes humans zombies?

Kyle Harper 1:10:40 (laughs)

Dwarkesh Patel 1:10:40 Is it just the human brain is like so complicated that it's like-

Kyle Harper 1:10:42 Lemme, lemme come back to this.

Dwarkesh Patel 1:10:43 (laughs)

Kyle Harper 1:10:43 Lemme come back to this. (laughs) We can talk about zombies but that's a...

Dwarkesh Patel 1:10:47 (laughs)

Kyle Harper 1:10:47 We need to-

Dwarkesh Patel 1:10:47 Okay.

Kyle Harper 1:10:48 We need to wind up for that.

Dwarkesh Patel 1:10:49 (laughs)

Kyle Harper 1:10:49 Uh, okay, so one, flea... so the plague is vector borne and it's really, really good-

Dwarkesh Patel 1:10:54 Yeah.

Kyle Harper 1:10:54 ... at like manipulating the fleas and that's just evolution. Two, I, I said this before but it's an animal disease. We're like collateral damage.

Dwarkesh Patel 1:11:05 Mm-hmm.

Kyle Harper 1:11:05 We're totally irrelevant to the, to the like really core evolutionary history. The plague just wants to infect rodents. Of course, I'm anthro... you know, it's not really like wanting to do this.

Dwarkesh Patel 1:11:16 Yeah, right.

Kyle Harper 1:11:16 The plague makes a living, it survives out there in, in burrowing rodent colonies.

Dwarkesh Patel 1:11:24 Mm-hmm.

Kyle Harper 1:11:24 We're like tertiary. I mean, we-

Dwarkesh Patel 1:11:27 Right.

Kyle Harper 1:11:27 It doesn't care at all. And so it has no evolved incentive to modulate its virulence to be able to transmit sustainably. Plague never sustains itself in human populations.

Dwarkesh Patel 1:11:38 Yeah.

Kyle Harper 1:11:38 It can transiently infect human populations but then it always dies out. It becomes extinct, that lineage.

Dwarkesh Patel 1:11:44 And, and then what hap- what, why, what is the reason that like you have this one, these 1,000 year, like what, what... cycles basically where-

Kyle Harper 1:11:53 Yeah.

Dwarkesh Patel 1:11:53 ... you know, why does it, why is it now 500 years? Why is it now 10 years? Why is it like, um-

Kyle Harper 1:11:57 Yeah, we're-

Dwarkesh Patel 1:11:58 What, what causes it go dormant? What causes this to reemerge?

Kyle Harper 1:12:00 Yeah, this is... you need to ask me in five years because, um, we've learned so much and now this is like the thing that would fall in the category of like almost a new question now that we can ask because now that we have the Neolithic lineages and the Bronze Age lineages, we're starting to like piece together this fuller history but we still don't even like totally understand the boundaries of when is the plague really sort of not circulating in human populations, um, and what are the factors that cause it to, to be so explosive? Like is it evolution of the bacterium? Is there something about the genetics of the lineages that, that escape from the animal reservoirs that are like especially transmissible? Is it human ecology like that we put rodents like black rats, you know, in the, in the right place to get the disease? Is it there's something about the, the climate stress that-

Dwarkesh Patel 1:12:57 Yeah.

Kyle Harper 1:12:57 ... renders the pop- We don't, we don't have a great understanding-

Dwarkesh Patel 1:13:00 Yeah.

Kyle Harper 1:13:01 ... of like why the plague comes and goes. So that's scary. And the, the... connecting it to the, your other question about like these super bugs, I mean, what's interesting in the very big picture about the, the plague to me is like even like the, the history of infectious disease is like on the one hand, like there's a real core of it that's just like basic principles of ecology and evolution.... right? I mean, we do certain things in the environment that creates the conditions that pathogens can evolve and take advantage of. But on top of that, like evolution is just creative and weird and contingent and unpredictable, and it's those little, those little like contingent facts that can end up having these really, really huge effects. And so in the case of the plague, like you would never... If you were like really, really knowledgeable about the basics of ecology and evolution of disease, you would never be like, "I think that, you know, every now and then-"

Dwarkesh Patel 1:14:01 (laughs)

Kyle Harper 1:14:02 "... a rodent disease from Central Asia is gonna wipe out half of the continent."

Dwarkesh Patel 1:14:06 (laughs)

Kyle Harper 1:14:06 Like, that shouldn't, that's not predictable.

Dwarkesh Patel 1:14:08 Right.

Kyle Harper 1:14:08 That shouldn't be happening. Um, and, and actually that one's kind of an outlier, but like infectious diseases always kind of like that. I mean, tuberculosis has probably killed more people maybe than any other infectious disease, like this horrible disease.

Dwarkesh Patel 1:14:20 Yeah.

Kyle Harper 1:14:20 It's just this... We don't really understand it. Now we really don't understand where it came from-

Dwarkesh Patel 1:14:26 Yeah.

Kyle Harper 1:14:26 ... because it doesn't look like it is an animal host before it has humans. And it's just a weird disease. It's just a bacterial pathogen that, uh, in the, the huge world of bacteria, this one is very, very good at hiding.

Dwarkesh Patel 1:14:41 Mm-hmm.

Kyle Harper 1:14:41 And so it gets in your chest and, and it just lurks.

Dwarkesh Patel 1:14:46 Yeah.

Kyle Harper 1:14:46 And then it'll just waste you away, particularly if you're, you're poor and you're stressed. Um, and so like you, there's some core principles there, but then there's... It's just like something weird about it. It's just like this terrible luck that makes it, um, what it is. And, and so to me, like there's going to be another pandemic, you know, maybe bird flu, maybe something else. Um, but like it's the real, real outliers and the weird ones that we should, we should maybe worry about a little bit more than we do. Like-

Dwarkesh Patel 1:15:19 Mm.

Kyle Harper 1:15:20 ... if you want to go to zombies, like I'll, I'll (laughs) -

Dwarkesh Patel 1:15:22 (laughs)

Kyle Harper 1:15:22 ... I'll go there. You don't have to twist my arm too hard.

Dwarkesh Patel 1:15:24 (laughs)

Kyle Harper 1:15:24 But like, you know, like prion diseases or like fungal diseases where we don't have the, the same, nearly the same infrastructure and level of knowledge-

Dwarkesh Patel 1:15:33 Yeah.

Kyle Harper 1:15:33 ... biomedical research as we do for like bacterial and viral diseases, you know, something, if we create the incentive, evolution is going to find some weird ways to, to exploit it. And it's not just transmissibility and virulence. Those are like two really basic parameters. But, um, you know, when you look at even COVID-19, part of what made it insidious is it just has just the right parameters to be latent for just long enough.

Dwarkesh Patel 1:16:03 Mm-hmm.

Kyle Harper 1:16:03 And like the first COVID SARS-CoV-1 2003, slightly more virulent, and in fact, it was just more virulent enough that it made you sick pretty quick. And just that little difference was enough to contain it because you could figure out who was sick.

Dwarkesh Patel 1:16:17 Yeah.

Kyle Harper 1:16:18 COVID-19 was impossible to contain because it took, you know, several days before you really-

Dwarkesh Patel 1:16:24 Yeah.

Kyle Harper 1:16:24 ... presented with clinical illness. And it's just that little quirk that, that made it totally impossible to, to control through non-pharmaceutical interventions early on.

Dwarkesh Patel 1:16:35 Right.

Kyle Harper 1:16:36 And so like, you know, follow that train of thought, if pathogens are going to find ways to, to take advantage, um, and there may be, you know, pathogens that push the limits on latency-

Dwarkesh Patel 1:16:50 Yeah.

Kyle Harper 1:16:50 ... that can be very, very hard, um, to control. So I think that's like one of the takeaways of the big evolutionary history of our pathogens, is evolution is very weird, very contingent, very creative at exploiting whatever weakness we give it. It's because there are billions and billions and billions of microbes-

Dwarkesh Patel 1:17:07 Yeah.

Kyle Harper 1:17:08 ... in this room. Um, you know, I don't know how many tens to hundreds of millions of species of microbes are in this room. Most of them are n- not even remotely pre-evolved to, pre-adapted to be pathogenic, but like lots are, and they're constantly-

Dwarkesh Patel 1:17:22 Yeah.

Kyle Harper 1:17:23 ... you know, they're constantly seeing if you managed to lock that door.

Dwarkesh Patel 1:17:26 Right.

Kyle Harper 1:17:26 Um, and they're just looking for a way to, to break in.

Dwarkesh Patel 1:17:28 Yep. Yep. Um, okay, just a couple more rapid fire questions for

Dwarkesh Patel 1:17:32 you. Have you found tools like Deep Research useful for especially your kind of work where you just have to compile insights from many different fields? If you throw in a question, the kinds of questions you honestly investigate, and now maybe they can rely on you as a citation for those particular questions about what effect did climate have on the fate of Rome or something-

Kyle Harper 1:17:51 Yeah.

Dwarkesh Patel 1:17:51 ... but if you just had a different question, which like maybe you'd write a book about in the future, how well do they do at synthesizing this kind of literature and coming up with a thesis the way you do?

Kyle Harper 1:17:59 Yeah, I mean, amazing-

Dwarkesh Patel 1:18:01 Mm.

Kyle Harper 1:18:02 ... but not yet, not yet, um, like completely displacing, um, or like totally threatening the, the kind of work that, that a historian does. Um, the... But at this point, like I can't, I can't even conceive of what a research project would look like without using-

Dwarkesh Patel 1:18:22 Really?

Kyle Harper 1:18:22 ... AI. I mean, it's just a-

Dwarkesh Patel 1:18:23 Oh, really? That fast?

Kyle Harper 1:18:24 ... a constant-

Dwarkesh Patel 1:18:25 It's like become so central to your work?

Kyle Harper 1:18:26 Yeah. But like for, you know, for just like, it's just like a constant conversation partner when you're-

Dwarkesh Patel 1:18:32 Mm.

Kyle Harper 1:18:32 ... when you're doing research, when you're writing, you know, you can go back to that PDF and ask like, you know, whatever, "How many species are there in this taxon?" Um, or you can just ask the AI. Um, and you still have to check it, but it's getting, obviously it's getting-

Dwarkesh Patel 1:18:48 Right.

Kyle Harper 1:18:48 ... more and more reliable really, really quickly.

Dwarkesh Patel 1:18:50 Yeah.

Kyle Harper 1:18:50 Um, but I think it, it hasn't yet like... You know, it, it... In some of the deeper research, um, it's not the equal of humans yet. And then in the synthesis, it's really not.

Dwarkesh Patel 1:19:02 Mm-hmm.

Kyle Harper 1:19:02 Um, there's still that creative element of synthesis that is where conceiving of the question is as important as the answer.

Dwarkesh Patel 1:19:10 Yeah.

Kyle Harper 1:19:11 Um, and it's, it doesn't feel like it's like right around the corner, but, um-

Dwarkesh Patel 1:19:16 Yeah.

Kyle Harper 1:19:17 ... but it's changed.

Dwarkesh Patel 1:19:17 Have, have you used Deep Research?

Kyle Harper 1:19:18 Oh, yeah.

Dwarkesh Patel 1:19:19 Yeah. Okay.

Kyle Harper 1:19:19 It's... I started using it like two weeks ago or so.

Dwarkesh Patel 1:19:22 (laughs)

Kyle Harper 1:19:22 I don't know how long it's been arou- how long has it been around? Somebody told it, told me about it.

Dwarkesh Patel 1:19:24 It's not that much longer. Yeah.

Kyle Harper 1:19:25 Okay. Somebody told me about it like eight-... I think it was like less than two weeks ago.

Dwarkesh Patel 1:19:29 Yeah.

Kyle Harper 1:19:30 Um, and yeah, it's incredible. I mean, it's really incredible.

Dwarkesh Patel 1:19:34 Yeah. And then, uh,

Dwarkesh Patel 1:19:35 I wanna touch on your next book that isn't out yet, The Last Animal. One question I have is, basically how worried should we be about extinction given that we're on the cusp of technologies which will make it possible for us to reanimate many lost species? I assume if you have their genome or something, you know, our descendants will be able to, like, make more wooly mammoths and saber-toothed tigers and so forth. So, um, yeah, sh- should we, like, discount the value of endangered species as a result?

Kyle Harper 1:20:04 Uh, I, I would say no. We, (laughs) we should still-

Dwarkesh Patel 1:20:08 (laughs)

Kyle Harper 1:20:08 We should still be concerned with extinction for, for a couple reasons. One is, I mean, absolutely this is, this is a legitimate, serious scientific field to, like, understand the genomics of extinct animals. And there is, like, a, you know, small but, uh, but serious enough science of de-extinction.

Dwarkesh Patel 1:20:27 Yeah.

Kyle Harper 1:20:27 And it's, it's feasible that some, um, organisms could be targeted for, for serious de-extinction efforts. Um, at the same time, like, a couple of, a couple of thoughts. One is, like, I'm not that optimistic that it will work, not because I think it's necessarily impossible, although it's not yet, totally feasible, particularly for animals that don't have, like, very similar modern descendants. Um, but it's, i- it's because a species isn't just a genome. A species is an organism that inhabits a food web and an ecosystem.

Dwarkesh Patel 1:21:02 Mm-hmm.

Kyle Harper 1:21:03 And, um, you know, we could bring the wooly mammoth back, but there's nowhere for them to live. You know, the, the, the mammoth steppe where they need, that they need to, to thrive is not there.

Dwarkesh Patel 1:21:14 Mm-hmm.

Kyle Harper 1:21:14 Um, and, you know, there's, there's really very little point in bringing an animal back from extinction just to put it in a, a box at a zoo, um, to sorta, like, you know, satiate our curiosity about it. So, um, without the ecosystem, you can't have the, the species. And really part of the, one of the themes that I try and get at in the, the book that I'm trying to finish is, like, we need to think about living systems, ecosystems.

Dwarkesh Patel 1:21:42 Mm-hmm.

Kyle Harper 1:21:42 Um, and the extinction question is very much a question of, like, what kinds of systems will exist on the planet? And I think, you know, whatever happens technologically in 100 years, 1,000 years, um, the, the impacts that humans have on biodiversity is gonna be very, very long-lasting. We're part of a species that has been impacting biodiversity for over 10,000 years, and there's things we can't do. Uh, I mean, there's things we can't undo. Um, we can't, there's things we can't change about the past. But, um, we're making decisions right now that will be binding on the future whether our descendants like it or not. And so we need to think very hard about, like, what choices do we wanna make to, to keep intact, um, the kind of variety and vibrancy of living systems that in 1,000 years, 10,000 years, um, that will be a huge part of our legacy. Like, the impact that we make on the stream of, of macroevolution will be one of the really big things that our species does. And it can sometimes be very hard to recognize that in, like, our individual lives, but collectively, it will absolutely be part of our forever legacy on Earth. And so we need to, to think very carefully about the choices that we make.

Dwarkesh Patel 1:22:57 Uh, I think that's an excellent note to close on. Just to plug one more time, we've been discussing Plagues Upon the Earth, uh, which is the history of disease going back through the Neolithic, um, to modern times, Fate of Rome, which discusses the plagues and just, like, ro- h- history of the Roman Empire considering climate and biology. We also discussed, um, what was the name of the s- book on slavery? The, uh, Slavery in the Late Roman World?

Kyle Harper 1:23:22 Slavery in the Late Roman World.

Dwarkesh Patel 1:23:24 Yep. And the upcoming book is The Last Animal.

Kyle Harper 1:23:27 The Last Animal.

Dwarkesh Patel 1:23:28 Um, all linked in the description below. And where else can people find you?

Kyle Harper 1:23:32 Um, in your... (laughs) in your descriptions.

Dwarkesh Patel 1:23:35 (laughs)

Kyle Harper 1:23:35 That's it. (laughs) I'm not on social media, sorry.

Dwarkesh Patel 1:23:37 Okay, got it. Well, you can find him here on this podcast. So- (laughs)

Kyle Harper 1:23:40 Oh, yes.

Dwarkesh Patel 1:23:40 ... j- j- just begin again. (laughs)

Kyle Harper 1:23:40 Exclusively. (laughs)

Dwarkesh Patel 1:23:42 I hope you enjoyed this episode. If you did, the most helpful thing you can do is just share it with other people who you think might enjoy it. Send it to your friends, your group chats, Twitter, wherever else. Just let the word go forth. Other than that, super helpful if you can subscribe