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

1. 0:00 – 7:08

   Plague's impact on Rome's collapse

   1. KHKyle Harper0:00

      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.

   2. DPDwarkesh Patel0:28

      20% of the population is enslaved.

   3. KHKyle Harper0:30

      Yeah.

   4. DPDwarkesh Patel0:30

      Why aren't there more slave rebellions?

   5. KHKyle Harper0:32

      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.

   6. DPDwarkesh Patel0:45

      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?

   7. KHKyle Harper1:55

      Yeah, yeah.

   8. DPDwarkesh Patel1:56

      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.

   9. KHKyle Harper2:14

      Yeah.

   10. DPDwarkesh Patel2:14

       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.

   11. KHKyle Harper2:21

       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-

   12. DPDwarkesh Patel3:16

       Mm-hmm.

   13. KHKyle Harper3:16

       ... 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.

   14. DPDwarkesh Patel3:55

       Mm-hmm.

   15. KHKyle Harper3:56

       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.

   16. DPDwarkesh Patel4:05

       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-

   17. KHKyle Harper4:16

       Yeah.

   18. DPDwarkesh Patel4:16

       ... literally the most significant thing.

   19. KHKyle Harper4:17

       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-

   20. DPDwarkesh Patel4:26

       Yeah.

   21. KHKyle Harper4:26

       ... in entire regions.

   22. DPDwarkesh Patel4:29

       Yeah.

   23. KHKyle Harper4:29

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

   24. DPDwarkesh Patel4:35

       Right.

   25. KHKyle Harper4:35

       But even the fact that it's killing 50% of the people in cities, in provinces, in countries-

   26. DPDwarkesh Patel4:42

       Yeah.

   27. KHKyle Harper4:42

       ... is just beyond the damage that other plagues do.

   28. DPDwarkesh Patel4:46

       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.

   29. KHKyle Harper5:08

       Yeah.

   30. DPDwarkesh Patel5:08

       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.
2. 7:08 – 12:35

   Rome’s little Ice Age

   1. DPDwarkesh Patel7:08

      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.

   2. KHKyle Harper7:42

      Yeah. Clearly, people, people have to try and explain, um-

   3. DPDwarkesh Patel7:47

      Yeah.

   4. KHKyle Harper7:47

      ... 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.

   5. DPDwarkesh Patel8:32

      Mm-hmm.

   6. KHKyle Harper8:33

      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.

   7. DPDwarkesh Patel9:19

      Mm-hmm.

   8. KHKyle Harper9:19

      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-

   9. DPDwarkesh Patel11:31

      Mm-hmm.

   10. KHKyle Harper11:32

       ... 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.

3. 12:35 – 24:39

   Why did progress stall in Rome’s Golden Age?

   1. DPDwarkesh Patel12:35

      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-

   2. KHKyle Harper13:46

      Yeah.

   3. DPDwarkesh Patel13:46

      ... they, uh, were on the right track.

   4. KHKyle Harper13:47

      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-

   5. DPDwarkesh Patel15:12

      Mm-hmm.

   6. KHKyle Harper15:12

      ... 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-

   7. DPDwarkesh Patel15:22

      Yeah.

   8. KHKyle Harper15:22

      ... 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.

   9. DPDwarkesh Patel16:15

      Mm-hmm.

   10. KHKyle Harper16:15

       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-

   11. DPDwarkesh Patel17:18

       Mm-hmm.

   12. KHKyle Harper17:18

       ... 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.

   13. DPDwarkesh Patel17:39

       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-

   14. KHKyle Harper17:59

       Yeah. That's-

   15. DPDwarkesh Patel17:59

       ... um, uh, arts and so forth and the, the-

   16. KHKyle Harper18:01

       That's what I was gonna say.

   17. DPDwarkesh Patel18:02

       Yeah, yeah. The p- the longitude prize and so forth, but-

   18. KHKyle Harper18:04

       Yeah.

   19. DPDwarkesh Patel18:04

       ... yeah.

   20. KHKyle Harper18:04

       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-

   21. DPDwarkesh Patel18:28

       Mm-hmm.

   22. KHKyle Harper18:28

       ... 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-

   23. DPDwarkesh Patel18:57

       Mm-hmm.

   24. KHKyle Harper18:57

       ... 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-

   25. DPDwarkesh Patel19:41

       Mm.

   26. KHKyle Harper19:41

       ... into proximity. And, uh, Augustus, you know, unfortunately for them, didn't do it.

   27. DPDwarkesh Patel19:46

       (laughs)

   28. KHKyle Harper19:46

       Probably good for the world. The Romans are pretty, pretty nasty people-

   29. DPDwarkesh Patel19:49

       Yeah.

   30. KHKyle Harper19:49

       ... 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.
4. 24:39 – 37:06

   Slavery in Rome

   1. DPDwarkesh Patel24:39

      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-

   2. KHKyle Harper25:01

      Yeah.

   3. DPDwarkesh Patel25:01

      ... how much slavery was involved in Roman world?

   4. KHKyle Harper25:03

      I mean, slavery, slavery, you know, tragically is a, a really important institution throughout history.

   5. DPDwarkesh Patel25:09

      Yeah.

   6. KHKyle Harper25:10

      We sometimes tend to, to think of it as, like, a distinctly modern phenomenon-

   7. DPDwarkesh Patel25:14

      Yeah.

   8. KHKyle Harper25:14

      ... 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.

   9. DPDwarkesh Patel26:37

      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.

   10. KHKyle Harper26:46

       Yeah.

   11. DPDwarkesh Patel26:47

       Yeah.

   12. KHKyle Harper26:47

       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.

   13. DPDwarkesh Patel26:57

       Mm.

   14. KHKyle Harper26:58

       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.

   15. DPDwarkesh Patel27:26

       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.

   16. KHKyle Harper28:11

       Yeah.

   17. DPDwarkesh Patel28:11

       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-

   18. KHKyle Harper28:18

       Yeah.

   19. DPDwarkesh Patel28:18

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

   20. KHKyle Harper28:24

       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-

   21. DPDwarkesh Patel28:39

       Yeah.

   22. KHKyle Harper28:39

       ... 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.

   23. DPDwarkesh Patel28:58

       Mm-hmm.

   24. KHKyle Harper28:58

       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-

   25. DPDwarkesh Patel29:31

       Mm-hmm.

   26. KHKyle Harper29:31

       ... 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-

   27. DPDwarkesh Patel30:04

       Yeah.

   28. KHKyle Harper30:04

       ... um, that we just don't have really good, good records of.

   29. DPDwarkesh Patel30:08

       Yeah.

   30. KHKyle Harper30:08

       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-
5. 37:06 – 48:26

   Was agriculture a mistake?

   1. DPDwarkesh Patel37:06

      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?

   2. KHKyle Harper37:37

      Homo sapiens is two to 300,000 years old.

   3. DPDwarkesh Patel37:40

      Yeah.

   4. KHKyle Harper37:40

      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-

   5. DPDwarkesh Patel38:12

      (laughs)

   6. KHKyle Harper38:13

      ... that is the biggest change in the history of our species-

   7. DPDwarkesh Patel38:15

      Yeah.

   8. KHKyle Harper38:15

      ... 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-

   9. DPDwarkesh Patel38:29

      Mm-hmm.

   10. KHKyle Harper38:31

       ... 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-

   11. DPDwarkesh Patel38:58

       Right.

   12. KHKyle Harper38:58

       ... or whatever. Um, which sounds quite nice.

   13. DPDwarkesh Patel39:00

       (laughs)

   14. KHKyle Harper39:01

       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.

   15. DPDwarkesh Patel39:54

       Okay.

   16. KHKyle Harper39:54

       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.

   17. DPDwarkesh Patel40:46

       Mm-hmm.

   18. KHKyle Harper40:46

       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.

   19. DPDwarkesh Patel40:55

       Yes.

   20. KHKyle Harper40:56

       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-

   21. DPDwarkesh Patel41:58

       Mm-hmm.

   22. KHKyle Harper41:59

       ... you know, the case in, in Stone Age times.

   23. DPDwarkesh Patel42:02

       Uh, James Scott has an in- interesting theory in Against the Grain.

   24. KHKyle Harper42:05

       Yeah.

   25. DPDwarkesh Patel42:06

       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-

   26. KHKyle Harper42:23

       Yeah.

   27. DPDwarkesh Patel42:23

       ... the Anatolian, uh, the initial hunter-

   28. KHKyle Harper42:26

       First farmers, yeah.

   29. DPDwarkesh Patel42:26

       ... farmers, like, th- they're the ones who, like, displaced the initial hunter-gatherers-

   30. KHKyle Harper42:29

       Yeah.
6. 48:26 – 1:00:30

   Disease’s impact on cognitive function

   1. DPDwarkesh Patel48:26

      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-

   2. KHKyle Harper48:41

      Yeah.

   3. DPDwarkesh Patel48:41

      ... 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-

   4. KHKyle Harper49:10

      Yeah.

   5. DPDwarkesh Patel49:10

      ... a kid, you're sick and that steals away nutrition for brain growth or something?

   6. KHKyle Harper49:14

      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-

   7. DPDwarkesh Patel49:32

      Mm-hmm.

   8. KHKyle Harper49:33

      ... 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-

   9. DPDwarkesh Patel49:51

      (laughs)

   10. KHKyle Harper49:51

       ... 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.

   11. DPDwarkesh Patel50:39

       Yeah.

   12. KHKyle Harper50:39

       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.

   13. DPDwarkesh Patel50:54

       Right.

   14. KHKyle Harper50:54

       People are smarter. Like, may not feel like it-

   15. DPDwarkesh Patel50:58

       (laughs)

   16. KHKyle Harper50:58

       (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-

   17. DPDwarkesh Patel51:27

       Right.

   18. KHKyle Harper51:27

       ... 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.

   19. DPDwarkesh Patel51:45

       Mm.

   20. KHKyle Harper51:45

       But with a big distribution.

   21. DPDwarkesh Patel51:47

       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.

   22. KHKyle Harper51:53

       It's pretty disgusting.

   23. DPDwarkesh Patel51:54

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

   24. KHKyle Harper51:59

       Yeah.

   25. DPDwarkesh Patel52:00

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

   26. KHKyle Harper52:06

       Yeah.

   27. DPDwarkesh Patel52:06

       ... 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-

   28. KHKyle Harper52:19

       Yeah.

   29. DPDwarkesh Patel52:19

       ... 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?

   30. KHKyle Harper52:40

       Yeah, I mean, obviously it, uh, it didn't, uh, didn't keep them from- from discovering some pretty amazing (laughs) things.
7. 1:00:30 – 1:06:00

   Plague in India and Central Asia

   1. DPDwarkesh Patel1:00:30

      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-

   2. KHKyle Harper1:00:48

      Yeah, it's such a, it's a tricky problem because, okay, start with the third plague pandemic in the late 19th century.

   3. DPDwarkesh Patel1:00:56

      Yeah.

   4. KHKyle Harper1:00:57

      Um, we know that, that that's in India.

   5. DPDwarkesh Patel1:01:00

      Yeah.

   6. KHKyle Harper1:01:01

      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-

   7. DPDwarkesh Patel1:01:19

      It's a special kind of honor to- (laughs)

   8. KHKyle Harper1:01:21

      Yeah, to be-

   9. DPDwarkesh Patel1:01:22

      ... have the deadliest agent in history. (laughs)

   10. KHKyle Harper1:01:22

       The worst, the worst pathogen ever. Um, immortality.

   11. DPDwarkesh Patel1:01:27

       (laughs)

   12. KHKyle Harper1:01:27

       The plague is definitely in India in the 17th century.

   13. DPDwarkesh Patel1:01:31

       Yep.

   14. KHKyle Harper1:01:31

       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.

   15. DPDwarkesh Patel1:01:45

       Mm.

   16. KHKyle Harper1:01:45

       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-

   17. DPDwarkesh Patel1:02:08

       Yeah.

   18. KHKyle Harper1:02:08

       ... 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.

   19. DPDwarkesh Patel1:02:25

       Mm.

   20. KHKyle Harper1:02:25

       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.

   21. DPDwarkesh Patel1:02:50

       Hmm.

   22. KHKyle Harper1:02:50

       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-

   23. DPDwarkesh Patel1:03:36

       Mm.

   24. KHKyle Harper1:03:36

       ... that are still pretty connected with the Roman world-

   25. DPDwarkesh Patel1:03:41

       Right.

   26. KHKyle Harper1:03:41

       ... 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.

   27. DPDwarkesh Patel1:04:05

       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-

   28. KHKyle Harper1:04:26

       Yeah.

   29. DPDwarkesh Patel1:04:26

       ... 1500 years ago and just see if they have Yersinia pestis in them?

   30. KHKyle Harper1:04:29

       There's two things. First of all, you have to look.
8. 1:06:00 – 1:17:32

   The next pandemic

   1. DPDwarkesh Patel1:06:00

      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-

   2. KHKyle Harper1:06:32

      Yeah.

   3. DPDwarkesh Patel1:06:33

      ... 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-

   4. KHKyle Harper1:06:49

      Yeah.

   5. DPDwarkesh Patel1:06:49

      ... is that, how plausible is that?

   6. KHKyle Harper1:06:51

      Well, let me, let me start with the plague where I'm a little, a little more-

   7. DPDwarkesh Patel1:06:54

      Yeah.

   8. KHKyle Harper1:06:54

      ... 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.

   9. DPDwarkesh Patel1:07:29

      Mm-hmm.

   10. KHKyle Harper1:07:29

       Plague doesn't hate you. It's just evolution. It's just trying to steal energy or-

   11. DPDwarkesh Patel1:07:35

       Right.

   12. KHKyle Harper1:07:35

       ... 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?

   13. DPDwarkesh Patel1:08:16

       Mm-hmm.

   14. KHKyle Harper1:08:16

       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.

   15. DPDwarkesh Patel1:08:37

       (laughs)

   16. KHKyle Harper1:08:37

       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.

   17. DPDwarkesh Patel1:09:09

       Mm-hmm.

   18. KHKyle Harper1:09:10

       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.

   19. DPDwarkesh Patel1:09:33

       Mm-hmm.

   20. KHKyle Harper1:09:34

       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.

   21. DPDwarkesh Patel1:09:47

       Mm-hmm.

   22. KHKyle Harper1:09:48

       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.

   23. DPDwarkesh Patel1:09:58

       Mm-hmm.

   24. KHKyle Harper1:09:59

       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.

   25. DPDwarkesh Patel1:10:21

       Mm-hmm.

   26. KHKyle Harper1:10:21

       And so the flea just starts feeding and feeding and feeding and meanwhile it's regurgitating bacteria. Um-

   27. DPDwarkesh Patel1:10:27

       Sorry, can I, can I, can I ask a question about that?

   28. KHKyle Harper1:10:30

       Yeah.

   29. DPDwarkesh Patel1:10:30

       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?

   30. KHKyle Harper1:10:40

       (laughs)
9. 1:17:32 – 1:19:35

   How Kyle uses LLMs

   1. DPDwarkesh Patel1:17:32

      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-

   2. KHKyle Harper1:17:51

      Yeah.

   3. DPDwarkesh Patel1:17:51

      ... 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?

   4. KHKyle Harper1:17:59

      Yeah, I mean, amazing-

   5. DPDwarkesh Patel1:18:01

      Mm.

   6. KHKyle Harper1:18:02

      ... 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-

   7. DPDwarkesh Patel1:18:22

      Really?

   8. KHKyle Harper1:18:22

      ... AI. I mean, it's just a-

   9. DPDwarkesh Patel1:18:23

      Oh, really? That fast?

   10. KHKyle Harper1:18:24

       ... a constant-

   11. DPDwarkesh Patel1:18:25

       It's like become so central to your work?

   12. KHKyle Harper1:18:26

       Yeah. But like for, you know, for just like, it's just like a constant conversation partner when you're-

   13. DPDwarkesh Patel1:18:32

       Mm.

   14. KHKyle Harper1:18:32

       ... 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-

   15. DPDwarkesh Patel1:18:48

       Right.

   16. KHKyle Harper1:18:48

       ... more and more reliable really, really quickly.

   17. DPDwarkesh Patel1:18:50

       Yeah.

   18. KHKyle Harper1:18:50

       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.

   19. DPDwarkesh Patel1:19:02

       Mm-hmm.

   20. KHKyle Harper1:19:02

       Um, there's still that creative element of synthesis that is where conceiving of the question is as important as the answer.

   21. DPDwarkesh Patel1:19:10

       Yeah.

   22. KHKyle Harper1:19:11

       Um, and it's, it doesn't feel like it's like right around the corner, but, um-

   23. DPDwarkesh Patel1:19:16

       Yeah.

   24. KHKyle Harper1:19:17

       ... but it's changed.

   25. DPDwarkesh Patel1:19:17

       Have, have you used Deep Research?

   26. KHKyle Harper1:19:18

       Oh, yeah.

   27. DPDwarkesh Patel1:19:19

       Yeah. Okay.

   28. KHKyle Harper1:19:19

       It's... I started using it like two weeks ago or so.

   29. DPDwarkesh Patel1:19:22

       (laughs)

   30. KHKyle Harper1:19:22

       I don't know how long it's been arou- how long has it been around? Somebody told it, told me about it.
10. 1:19:35 – 1:24:12

    De-extinction of lost species

    1. DPDwarkesh Patel1:19:35

       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?

    2. KHKyle Harper1:20:04

       Uh, I, I would say no. We, (laughs) we should still-

    3. DPDwarkesh Patel1:20:08

       (laughs)

    4. KHKyle Harper1:20:08

       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.

    5. DPDwarkesh Patel1:20:27

       Yeah.

    6. KHKyle Harper1:20:27

       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.

    7. DPDwarkesh Patel1:21:02

       Mm-hmm.

    8. KHKyle Harper1:21:03

       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.

    9. DPDwarkesh Patel1:21:14

       Mm-hmm.

    10. KHKyle Harper1:21:14

        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.

    11. DPDwarkesh Patel1:21:42

        Mm-hmm.

    12. KHKyle Harper1:21:42

        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.

    13. DPDwarkesh Patel1:22:57

        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?

    14. KHKyle Harper1:23:22

        Slavery in the Late Roman World.

    15. DPDwarkesh Patel1:23:24

        Yep. And the upcoming book is The Last Animal.

    16. KHKyle Harper1:23:27

        The Last Animal.

    17. DPDwarkesh Patel1:23:28

        Um, all linked in the description below. And where else can people find you?

    18. KHKyle Harper1:23:32

        Um, in your... (laughs) in your descriptions.

    19. DPDwarkesh Patel1:23:35

        (laughs)

    20. KHKyle Harper1:23:35

        That's it. (laughs) I'm not on social media, sorry.

    21. DPDwarkesh Patel1:23:37

        Okay, got it. Well, you can find him here on this podcast. So- (laughs)

    22. KHKyle Harper1:23:40

        Oh, yes.

    23. DPDwarkesh Patel1:23:40

        ... j- j- just begin again. (laughs)

    24. KHKyle Harper1:23:40

        Exclusively. (laughs)

    25. DPDwarkesh Patel1:23:42

        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 on YouTube and leave a five-star review on Apple Podcasts and Spotify. Check out the sponsors in the description below. If you wanna sponsor a future episode, go to dwarkesh.com/advertise. Thank you for tuning in. I'll see you on the next one.

Episode duration: 1:24:12