Dwarkesh Podcast Episode Summary: "Why Rome Actually Fell: Plagues, Slavery, & Ice Age — Kyle Harper"

Host: Dwarkesh Patel
Guest: Kyle Harper, Professor and Provost Emeritus at the University of Oklahoma
Release Date: April 24, 2025

In this enlightening episode, Dwarkesh Patel hosts renowned historian Kyle Harper to delve into the multifaceted reasons behind the fall of the Roman Empire. Harper, author of The Fate of Plagues upon the Earth, Slavery in the Late Roman World, and the forthcoming The Last Animal, offers a comprehensive analysis that intertwines biology, economics, history, and climate science to uncover the complex tapestry of factors that led to Rome's decline.

I. The Overwhelming Impact of Plagues on the Roman Empire

Timestamp: 00:00-03:20

Harper introduces the critical role of infectious diseases in shaping human history, particularly emphasizing their devastating effects on populations. Referencing his work and discussions with geneticist David Reich, Harper highlights two significant pandemics—the Plague of Justinian (6th century) and the Black Death (14th century). He states:

"It's pretty clear that the bubonic plague events... are capable of causing death rates temporarily that are just orders of magnitude beyond what we're accustomed to." (01:11)

These pandemics resulted in catastrophic mortality rates, with Harper estimating that the Black Death may have killed 50-60% of populations in affected regions, drastically reducing Rome's population and weakening its societal structures.

II. Climate Change and Environmental Shocks

Timestamp: 04:01-11:50

Beyond plagues, Harper discusses the significant impact of abrupt climate changes on the Roman Empire. Volcanic eruptions in the 6th and 7th centuries led to a cooling period of 1-2 degrees Celsius, disrupting agricultural production and leading to widespread famine. Harper explains:

"You have this simultaneous and probably not unrelated shock to the climate system. And so we have this huge burst of apocalyptic thought in the 6th and 7th century." (06:22)

This environmental stress compounded the effects of plagues, creating a perfect storm that destabilized the empire both economically and socially.

III. The Potential for Rome's Continuity Without Pandemics and Climate Crisis

Timestamp: 03:33-06:22

The discussion pivots to a counterfactual scenario where Rome might have survived had it not been for these catastrophic plagues and climate shifts. Harper posits that the Roman Empire had the structural and economic foundations to endure and even thrive further:

"A very plausible counterfactual is that a more or less Mediterranean core of the Roman Empire could have survived east and west." (04:42)

He suggests that without these massive shocks, Rome could have maintained its status as a powerful, urbanized empire resisting invasions and continuing its legacy.

IV. The Roman Economy: Complexity and the Absence of an Industrial Revolution

Timestamp: 11:50-34:56

Harper provides an in-depth analysis of the Roman economy during its zenith, highlighting its sophistication through extensive trade networks, advanced financial systems, and significant productivity gains driven by specialization and markets. However, despite these advancements, Rome never experienced an Industrial Revolution. Harper attributes this stagnation to the lack of sustained technological innovation and scientific advancement:

"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." (16:54)

He contrasts this with the later emergence of Royal Societies in France and Britain, which fostered basic science, empiricism, and useful knowledge—key elements that drove the Industrial Revolution.

V. Slavery in the Late Roman World

Timestamp: 24:18-34:56

In Slavery in the Late Roman World, Harper explores the integral role of slavery in the Roman economy. He explains that as Rome expanded its territories, it amassed a vast number of slaves through conquest, which fueled plantations and allowed landowners to accumulate wealth. Key points include:

• Supply and Demand: Continuous conquests provided a steady supply of slaves, while markets and agricultural demands ensured high demand.

"If there's not a mechanism, if there's not institutions that let you turn this kind of exploitation into cash flow, the institutions aren't going to go very far." (26:01)

• Ideological Justifications: Unlike modern racialized slavery, Roman slavery was primarily justified through legal status and property rights rather than inherent racial differences.

"The Roman ideology of slavery is really rooted in the law of property and status." (27:39)

• Low Rebellion Rates: Despite high slave populations, Rome maintained control through a combination of repression and incentives for manumission, preventing large-scale rebellions.

Harper challenges theories that cheap slave labor hindered technological progress, arguing instead that the lack of scientific advancement was the more significant factor in preventing an industrial revolution.

VI. The Intersection of Disease, Nutrition, and Cognitive Function

Timestamp: 36:52-51:55

Harper extends the discussion to the long-term effects of diseases on human development and cognitive abilities. He posits that high disease burdens in pre-industrial societies likely impeded physical growth and cognitive development:

"In the modern world... there have been really deep physiological changes in the average human." (48:29)

Harper asserts that better nutrition and reduced disease exposure have historically contributed to increases in human height and cognitive capacities, factors that were likely constrained in ancient populations affected by rampant diseases.

VII. Agricultural Societies and the Rise of Infectious Diseases

Timestamp: 36:52-42:21

Transitioning to the broader scope of human history, Harper discusses the shift from foraging to agriculture—a transformation that significantly increased population densities and, consequently, the spread of infectious diseases. He challenges the notion of a "Golden Age" before agriculture, emphasizing that hunter-gatherer societies were also plagued by numerous diseases:

"The transition from foraging to farming... increased the infectious disease burden." (36:52)

This transition set the stage for societies like Rome to become vulnerable to pandemics due to dense populations and sedentary lifestyles.

VIII. Historical Plagues in India: Gaps in Historiography

Timestamp: 60:03-63:44

Addressing global perspectives, Harper touches upon the enigmatic history of plagues in India. While evidence exists for significant outbreaks like the third plague pandemic in the late 19th century, earlier instances such as those during the Plague of Justinian remain obscure due to limited ancient records and challenges in ancient DNA research:

"We actually think that the plague moves through India to get to Rome. This is not definite." (60:33)

Harper highlights the need for more comprehensive research to uncover the presence and impact of plagues in ancient Indian societies.

IX. The Future of Infectious Diseases and Synthetic Biology

Timestamp: 63:44-76:43

Looking ahead, Harper explores the potential risks associated with synthetic biology, including the creation of engineered pathogens with enhanced transmissibility and lethality. Drawing parallels with historical plagues like Yersinia pestis, he warns of unforeseen consequences:

"Evolution is very weird, very contingent, very creative at exploiting whatever weakness we give it." (69:57)

Harper emphasizes the unpredictable nature of pathogen evolution and the importance of robust public health infrastructures to mitigate future pandemics.

X. The Role of AI in Historical Research

Timestamp: 76:43-78:49

In a brief interlude, Harper discusses the integration of AI tools like Deep Research into historical scholarship. While acknowledging the impressive capabilities of AI in synthesizing literature and aiding research, he maintains that the creative and analytical nuances of human historians remain irreplaceable:

"It's really not... like right around the corner, but it's getting more reliable really, really quickly." (77:14)

XI. De-extinction and Conservation Concerns

Timestamp: 78:49-82:43

Concluding the episode, Harper addresses the contentious topic of de-extinction—reviving extinct species through advanced technologies. He argues that while the scientific pursuit is valid, the ecological implications render de-extinction efforts largely impractical:

"A species is an organism that inhabits a food web and an ecosystem. And we could bring the woolly mammoth back, but there's nowhere for them to live." (79:42)

Harper underscores the importance of preserving existing biodiversity to maintain ecosystem integrity, cautioning against overreliance on technological solutions to address extinction.

Conclusion

Kyle Harper's insightful discussion on the downfall of the Roman Empire intricately weaves together the devastating impacts of plagues, climatic shifts, economic structures, and slavery. By examining both historical patterns and future implications, Harper provides a nuanced understanding of how interconnected factors contribute to the rise and fall of civilizations. This episode serves as a compelling exploration of history's lessons, emphasizing the enduring relevance of studying past pandemics, economic systems, and societal structures to navigate present and future challenges.

Notable Quotes:

• Kyle Harper: "The Black death... is just beyond the damage that other plagues do." (03:33)

• Kyle Harper: "Ultimately it's because the Romans don't have technology improvements that are really self-sustaining." (16:54)

• Kyle Harper: "Humans can create these systems of belief that will exclude others and justify almost any form of exploitation." (27:39)

• Kyle Harper: "It's no wonder that pre-industrial populations... probably also had a lower distribution of cognitive abilities." (48:29)

• Kyle Harper: "Evolution is very weird, very contingent, very creative at exploiting whatever weakness we give it." (69:57)

This episode not only sheds light on the intricate causes behind Rome's decline but also offers profound reflections on human societal development, the burden of disease, and the ethical considerations of modern technological advancements.