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

**Dwarkesh Patel** (0:00)
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, 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 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 wanted to have you on is I interviewed David Reich, 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 in his work going back like thousands of years, tens of thousands of years. And he's like, you got to have Kyle on. I emailed him afterwards, who should I interview next? And he's like, you got to have Kyle on. You have this graph in 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 or syniapestis, right? 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 overwhelming, not just one, but the overwhelming two major features in human population, going back the last 10,000 years is this one bacteria, 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** (1:36)
Well, I mean, the period that I normally work on is sort of from the high Roman Empire, so like the glory days of the Pax Romana in the first or second century, which is usually where I start, through what we call the late antique or early medieval period, so the sixth or seventh century. At the beginning of this period, Rome dominates this Mediterranean Empire. It's what you think of when you think of ancient Rome. It's the largest city in the world.
It's the center of this huge network. Then by the end of this period, the city of Rome has, we don't know, 50 to 100,000 people. It's a tenth or twentieth of its former size. I think we now can say pretty clearly that environmental factors like climate, but also especially diseases, play a part in that really big transformation. Well, there's a problem because we don't have the same kind of modern government mortality statistics that we do for COVID or even for the last century or century and a half. We have to piece together from clues, but it's pretty clear that the bubonic plague events, whether you're talking about the Black Death of the 14th century, the plague of Justinian in the 6th century, these events are capable of causing death rates temporarily that are just orders of magnitude beyond what we're accustomed to. And even in these ancient societies, the reason why these were so shocking, in a world where the death rate is always pretty high, probably several percent of the Roman population, three, four percent a year may be dying in a normal year. And so for them to just be utterly shocked by the death rate, it already tells you that it's some multiple of what they're accustomed to.

**Dwarkesh Patel** (3:20)
I think you're discussing in the book the possibility that the death rate might have been close to, or even over 60 percent, wherever the Black Death. So this is not just like, this is like literally the most significant thing.

**Kyle Harper** (3:32)
Yeah, it's mind-blowing. And I mean, in the case of the Black Death in the 14th century, it's pretty clear it kills 50, 60 percent of the population in entire regions. And we don't necessarily think that it killed 50, 60 percent of the whole continent, although that's actually not impossible. But even the fact that it's killing 50 percent of the people in cities, in provinces, in countries, is just beyond the damage that other plagues do.

**Dwarkesh Patel** (4:01)
Right. And do you think that we're not for this, this like 60 percent mortality event plus with 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, the empire still survives. I think Will Durant had this quote that the Roman Empire fell for longer than most empires have lasted. So do you think like, you know, it would be similar to China, maybe. There were maybe a dynasty collapses, but fundamentally the same sort of cohesive nation re-emerges.