[This is the seventeenth of seventeen finalists in the book review contest. This one was chosen out of the reviews I somehow missed the first time around. There were four other such essays, which you can see ina supplementary runners-up packet here. I’ll make a post about how to vote tomorrow. - SA]

Biological evolution was hijacked by cultural evolution; tools and language allowed humankind to upset the ecological balance in incredible ways. We should all know the story by now. Human grunts to other human and they agree to kill a wooly mammoth together and then grunt and agree to share the meat and then grunt and learn to make a spear and grunt and form a complex society and worldwide dominant species.

Parasites and viruses are invisible and hard to grunt about. A lion, in contrast, is difficult not to grunt about.

This book, Plagues and Peoples written by William H. McNeill in 1976, frames the entirety of human history and prehistory in the context of humankind’s relationship with microparasites and viruses. Communication, culture, tools, clothes, and shelter allowed humans to hunt dominantly, live anywhere, and deal with most ecological challenges- but microparasites remained elusively hard to deal with until modern times. This uneasy relationship with the invisible unconsciously shapes where human’s live, how civilizations form, and how societies are organized.

At every step of humanity’s evolution, McNeill sees microparasites and viruses being one of the ‘fundamental parameters and determinants of human history.’

Out of Africa

McNeill does not think it is coincidence that the cradle of humanity also has the most variety of human parasites and remains one of the most balanced ecosystems in the world. Humans evolved into the ecosystem, along with the parasites and wildebeests and lions.

“…the extraordinary variety of human parasites that exist in Africa suggests that Africa was the principal cradle for humankind, for nowhere else did the adjustment between human and nonhuman forms achieve anything like the same biological elaboration.”

Even when humans could grunt about predators and prey, parasites were there to put an exploding population in check. McNeill points to trypanosome, which causes sleeping sickness, and is carried by antelope, transmitted by the tsetse fly. The parasite does not affect antelope or the fly, but causes “drastic debility” in humans- McNeill calls this “an example of a stable, well-adjusted, and presumably very ancient parasitism.” To this day “within the tsetse’s range, something resembling a pre-human ecological balance survives.”

Many parasitic worms and protozoa in Africa do not provoke immune reactions. When too many humans get together they spread these parasites more and suddenly the population drops again. This ecosystem that ancient humans evolved into had a population check that even language and spears and fire could not overcome.

Until some enterprising early humans discovered the Mediterranean and the comparative lack of parasites in global temperate climates. Clothes and shelters, fires and families allowed humans to flourish in new climates. Leaving Africa allowed human’s cultural hijacking of biological evolution to truly become dominant because humanity left most of those pesky tsetse flies in Africa. That’s when humans decimate macro fauna populations across the globe, entirely disrupting most every ecosystem that is touched by human’s cultural ingenuity from roughly 40,000 to 10,000 BC. When you kill all the wooly mammoth and giant sloth and buffalo, you keep walking and find more to kill. Until humanity experiences maybe it’s first resource depletion and needs a new way to find, or maybe grow, food.

Ebbing and Waning

As society gets more complex, so does the relationship with microparasites.

The ecological population check of anciently co-evolved parasites in Africa didn’t work when humans left Africa. After killing all the big game in the world, people (independently across the globe) decided to domesticate an animal and grow some vegetables in their backyard. Eventually humans decided that instead of dealing with weeds and unpredictable backyard gardens, they will collaborate and build irrigation systems and monoculture. Humans escaped the tropical jungle to eventually settle down in warm, wet, dense irrigation farms.

Here McNeill points to the blood fluke that causes schistosomiasis, “a nasty debilitating disease, affecting as many as 100 million people today.” Mollusks and humans are the fluke’s hosts, which swims around in water looking for the next snail or farmer. In humans, the disease is debilitating in childhood and is less acute, although still semi-debilitating, thereafter. Again, like trypanosome (and also malaria), blood flukes’ very complex life cycle seemingly indicates a lengthy evolution in respect to humans. Maybe blood fluke emerged from tropical Africa, but it spread widely through irrigation farming.

Here, it starts to get interesting.

“It seems reasonable to suspect that the despotic governments characteristic of societies dependent on irrigation agriculture may have owed something to the debilitating diseases that afflicted field workers who kept their feet wet much of the time, as well as to the technical requirements of water management and control…. The plagues of Egypt, in short, may have been connected with the power of the Pharaoh in ways the ancient Hebrews never thought of and modern historians have never considered.”

What if Seeing Like a State misses what the Hebrews missed? Farming grains indeed allowed a storable and quantifiable good to be taxed, but the blood fluke made it so it was easy to take away from the sickly farmers.

If you have enough blood fluke sickly irrigation farmers to rule, you can start to sustain a city. And then viruses become a problem.

Diseases of Civilization Par Excellence

Viruses really have two options- spread to a new host or die. When they infect a host, immune response will eliminate the virus or eliminate the host. For a virus to spread prolifically it will need, more or less, an ever growing population of hosts that have not had the virus. McNeill calls infectious viral diseases that pass directly from human to human the “diseases of civilization par excellence; the peculiar hallmark and epidemiological burden of cities and of countryside in contact with cities.”

Probably all viruses transferred to humans from animal herds. There have been uncountable false starts when the human hosts or invading virus die out locally and cut off the chain of infection. But at certain thresholds of human population, growth, and density allow re-infection rate to sustain and the virus to evolve interesting abilities to sustain further re-infection, such as latency.

Chicken pox (related to cow pox) infects kids and all the other kids in their kindergarten. They are itchy for a while and then the virus retreats to the tissues and is dorman for fifty years, only to reappear as shingles. This is genius on the part of chicken pox. By then there are plenty of new kindergarteners to infect. McNeill, again, points out that ‘the mildness of the disease for most people and the remarkable latency pattern it exhibits suggests this is an old viral infection among humankind.”

Establishing this type of diffusion of disease, he says, requires several thousand years. Through statistical analysis of the modern spread of measles, McNeill claims that the minimum population size to keep a virus going is about half a million people. Coincidentally, the world’s oldest civilization, the ancient Sumeria population was approximately half a million.


The host-parasite relationship mirrors subject-government relationship. “The entire process of adjustment between host and parasite may be conceived as a series of wavelike disturbances to pre-existing biological equilibria.” As McNeill paints the complexly evolving relationship between humans and parasites, he introduces government as humanity’s macroparasite.

McNeill again,

“Only when civilized communities had built up certain level of wealth and skill did war and raiding become an economically viable enterprise. But seizing the harvest by force, if it led to speedy death of the agricultural workforce from starvation, was an unstable form of macroparasitism.”

The violent ‘macroparasites’ had to learn how to coexist with their agricultural workforce ‘hosts’. There have been many wavelike disturbances in the evolution of this relationship. Achieving this political balance of growing enough surplus to feed an army while not effectively starving your farmers also took thousands of years and multiple false starts and population thresholds. I personally like this framing.

McNeill extends the metaphor maybe a bit too much describing how successful governments immunize their rent paying subjects by protecting them from other macroparasites. “Disease immunity arises by stimulating the formation of antibodies and raising other psychological defenses to a heightened level of activity; governments improve immunity to foriegn macroparasitism by stimulating surplus production of food and raw materials sufficient to support specialists in violence in suitably large numbers and with appropriate weaponry.” Both micro and macro parasites are burdensome but also guard against sudden lethal disasters.

Early humanity’s macroparasites used to be lions and tigers and bears. Apex predators would take your child but probably not your whole family. In a similar way humans evolved into an ecosystem alongside microparasites in Africa, there were macroparasites in the system as well. Using language, technology, and culture let us escape the micro and macro parasitism that humanity evolved into, but at a certain scale of society these micro and macro parasitic ‘forces’ came in new forms. Viruses instead of parasites and human violence instead of apex predators.

These new forces share a similar attribute- human ingenuity does not guard against them. Viruses (and other microparasites) because they were hard to see and understand until recently. Human violence, and government control thereafter, because human ingenuity creates a positive feedback loop that strengthens the ability of human violence and government control. This framing of why government macroparasitism is such a sticky problem is a very solid fundamental reason to find importance in freedom of speech, rule of law, and other cultural checks on macroparsitic power. Once agricultural city states started to pop up, humanity stumbled between avoiding too much microprasitic malay and macroparsitic violence.

It just sucks if you’re the farmer finding a balance between the microparasites, viruses, and the macroparasite government, both taking just enough energy to hopefully not kill you while you’re still useful. The systems evolving until the hosts and parasites find mutually tolerable accommodation.

Finding that Balance as a Chinese Rice Paddy Farmer

Around 600 BC extensive farming started in the Yellow River Valley. It took enormous collective engineering effort to build canals, irrigation systems, and flood controls to turn the vast flood plain into a productive carpet of rice paddies. Chronic warfare ended around 200 BC with consolidation of power in the Han Dynasty. This introduced a double layer of macroparasitism: private landowners and the Emperor both demanded taxes be paid. This was still better than tumultuous chronic warfare. This coincided with another powerful factor in the macroparasistic balance: Confucianism. The ideals propagated “a culture among imperial officials and private landowners internalized an ethic that strenuously restrained arbitrary or innovative use of power.”

This system seemed to work. “A remarkably stable and long-lasting balance was achieved within Chinese society between peasant farmers and the two social classes most directly parasitic upon them. This balance survived, with some important elaborations but not real structural breaks, until the twentieth century. The system flourished throughout the Yellow River Valley, and eventually beyond.

Yellow River Basin

The Han Dynasty never made it very far south towards the Yangtze. Political and military obstacles were relatively unimportant, and the climate and land meant longer and more productive growing seasons for agriculture. The Yangtze also has more predictable and manageable flood plains. Yangtze Valley is prettier too. Why not extend civilization southward?

In McNeill’s words “for in moving southward and into better farming regions, Chinese pioneers were also climbing a rather steep disease gradient!” The climatic gradient is steep, like New England to Florida, in a shorter geographic distance. For a Chinese peasant, the mutually tolerable accommodation with the state and with the microparasites of the Yellow River Valley was maintainable. But more microparasitic intensity made the balance unmaintainable. The Han Dynasty and Confucianism really only worked at a certain latitude.

By the way, guess which major Chinese city is on the Yangtze? (You can look back at the map.)

In contrast to the Ganges Valley in India, with a civilization and farming starting around 600 BC but remained unstable and never consolidated. The Ganges Valley is hugely productive agriculturally but also warmer and wetter than China’s southern Yangtze Valley. “Classical Indian civilization thus took form under climatic and (presumed) disease conditions that the early Chinese found too much to bear.”

It took a long time for China to populate the Yangtze River basin- biological accommodation to a microparasitic climate will take a long time. By that time, around 1200 AD, there is also evidence the Sung Dynasty was a less powerful and less demanding macroparasite. “To achieve such a mass population [100 million by A.D.1200] two things were needed: a suitable microparasistic accommodation to the ecological conditions of the Yangtze Valley and regions farther south, and a regulated macroparasitism that left enough of their product with the Chinese peasants so that they could sustain a substantial rate of natural increase over several generations.”

Epistemic Status: A convincing narrative with zero evidence

McNeill explicitly and regularly reminds the reader that this overarching thesis has little to no evidence. But it does have lots of examples. It’s the same problem that most overarching histories of humanity face: lack of documentation. Except this time it’s lack of documentation 10,000 years ago of something we discovered existed 300 years ago and is invisible without a microscope. In some way, though, this complete lack of documentation makes his case stronger- the invisible forces are stronger than the visible ones.

We all kind of knew the narrative that the Spanish decimated the Aztecs and Mayans with help of smallpox. I just never extended that logic towards humanity’s escape from Africa, the march of civilizations into the countryside, and what type of social structures worked best at certain ‘disease gradient’ latitudes. The documentation of the conquistadors was almost adequate to infer disease as a massive influence. But earlier medical records and writings lack such detail. When McNeill contrasts this force of microparasitism balancing with and against the adequately vague force of macroparasitism, it’s hard not to nod your head and agree.

McNeill provides as much detail and admits lack of detail as possible. The book is about on fifth footnotes. But the most convincing arguments for his narrative is the sum of parts that make up the narrative. I’m going to just list a few more examples that fit his framework because they are all interesting and also paint a more convincing picture of the importance microparasitism played in human history.

  • The way that Europeans decimated Native Americans with smallpox blankets has been a key driver in ancient civilization expansion. The moment the city folk come in contact with tribes, smaller towns, anyone in the countryside they also bring the city folk diseases. This makes civilization expansion fundamentally easier.

  • India’s caste system is a relic of living in a high disease gradient area and cohabitating between city folk, farmers, and others. The ‘untouchables’ makes a lot of sense in that framework.

  • Many weird religious things that you’ve probably heard of fit in this framework like not eating pork and washing hands. In the year 2245 Martian kids will wonder why members of Church of the Crypto Spaghetti Monster on Earth all wear cloth over their mouths in public.

  • Mongol caravans introduced the plague to rats and then spread the plague rats across the world. The plague probably existed in say Yunnan, China where the locals had developed a complex set of myths and traditions to say, not eat rats. When the Mongols came they trapped the rats, got the plague and spread it in China. China’s population decreased from around 123 million in 1200 to around 65 million in 1331. Then the Mongols brought the rats to Europe 1346.

  • The long term effects of the plague in Europe include anti semitism, less use of Latin, better painting, good European sensibilities of government, and more religious rigidity. No, I do not want to explain further.

  • Since the Mediterrean is relatively disease free and overall pleasant, the Roman civilization ended up relatively top heavy and parasitic. It was too top heavy when epidemics arrived and the microparasites disrupted the balance.

  • Certain religions and forms of government evolve in certain disease gradients.

  • Australian rabbit populations provide a fascinating view of virus-host evolution in fast forward.

  • An entirely new pace of urban growth coincides with dramatically improving medical practices.

William H. McNeill versus Jared Diamond

I never read Guns, Germs, and Steel , but constantly wondered how parallel Diamond and McNeill thought about diseases. Luckily, they had a public debate! McNeill criticizes GGS , Diamond responds, and then McNeill further replies! How lucky we are.

McNeill’s opening paragraph includes “Not bad for an ameteur historian” and “…is not an intellectual success.” I am unsure how self aware McNeill is when he criticizes Diamond for being a ‘big picture historian.’ I am pretty sure McNeill is jealous of Guns, Germs, and Steel’s success though. All these punches are really to describe Guns, Germs, and Steel as overly geographic deterministic. An ‘East-West Axis’ as the penultimate factor in Eurasia’s success is too broad of a claim. McNeill also quibbles that continents should not be the unit of analysis.

Diamond responds that he is answering adequately broad questions like: Why was there civilization in Europe and not in Australia? Closing with “Historians’ failure to explain history’s broadest pattern leaves us with a huge moral gap. In the absence of convincing explanations, many (most?) people resort, consciously or unconsciously, to racist assumptions: the conquerors supposedly had superior IQ or culture.”

McNeill responds “that some few historians are trying to do so [explain history’s broadest patterns], among them myself, and with more respect for natural history than Diamond has for the conscious level of human history. He wants simple answers to processes far more complex than he has patience to investigate. Brushing aside the autonomous capability of human culture to alter environments profoundly—and also irreversibly—is simply absurd.”

Where Diamond sees geography first, McNeill sees biogeography’s interaction with culture first. As far as big picture histories go, I think McNeill has a very convincing and important narrative. However, framing governments versus diseases with individuals in the middle, while interesting, seems to not give the individual too much agency. McNeill could make his narrative more convincing by, at least sometimes, shrinking his ‘unit of analysis’ closer to individuals.

A lot of these big picture histories of humanity start with sometimes conflicting premises. How happy were hunter gatherers? In Sapiens Yuval Noah Harrari frames humanity as a slow deterioration of individual happiness at the expense of building a greater society starting from the carefree hunter gather and ending in the far AI future of civilizational greatness and individual obliteration. Jared Diamond calls agriculture “the worst mistake in the history of the human race.” Other narratives paint individuals crawling out of the dark neanderthal caves into utopian agricultural societies and everyone is more or less getting happier as modernity progresses. The distinction is foremost a narrative tool which seems to have important implications, but I have been unresolved on which side I adhere to. Plagues and Peoples kind of has it both ways in a way that seems truer. Human individuals are constantly finding the balance between their environment and society towards something… mutually tolerable.

I wonder what McNeill versus Yuval Noah Harrari would look like.

Ok, now I’ll talk about COVID-19

I happened across this book last summer, literally on the floor of Buckeye Bend Books in Greenbrier County, West Virginia. An overarching history of humanity framed through the importance of viruses written in 1976 was exactly what I needed. Something to put the year 2020 in context and not hitting refresh on the John Hopkins’ virus tracker. While reading with the intent of relating everything to COVID-19, not too much really correlates super well.

Buckeye Bend Books

Plagues and Peoples does not talk too much about the flu. But his remarks are both prescient and a bit gloomy.

“Another sort of epidemic disease whose future among mankind remains at least potentially significant is well illustrated by the influenza epidemic of 1918-19. Influenza has been around a long time.*” His ninetieth footnote indicates that “no fewer than ninety-four epidemics of influenza between 1173, the earliest he [August Hirsch] thought he could identify, and 1875. Of these he calculated at least fifteen had been pandemic, i.e., effected Asia as well as Europe… There is no reason to suppose that influenza was new in 1173, however… the history of the disease remains irrecoverable.”

It really drives home what we all knew but did not want to talk too much about: COVID-19 and it’s mutations will be around for a long time. With public health, modern medicine, massive quarantining, and a vaccine in production we have quickly found what might be called a mutually tolerable relationship already. At least a bit more tolerable than in 1918 when the flu infected almost the entire world’s population and killed over twenty million people. The tricky part is that this virus is not mutating or evolving towards becoming ‘more mutually tolerable’; the virus just mutates at random and sometimes it is more deadly and more contagious. We could easily, it seems, have a COVID-24 pandemic.

The idea of disease gradients is interesting in the geographic variabilities of COVID-19. India has ten times less of a death rate than the United States, to which a Mayo Clinic Professor recently pondered “cross reactive immunity from prior corona virus and other infections” as a main reason. Another interesting parallel to ponder is how humans have had such trouble adapting to microparasites because they were invisible and how that mirrors some of today’s issues of how our society deals with COVID-19.

The microparasite-macroparasite balance is also a good frame to see what is happening. When COVID-19 is destroying the productivity and ability to afford food, governments have not only taken less taxes but immediately started giving us money. I would say that governments were surprisingly quick to counterbalance societies’ mutually tolerable position. One could use this framework to argue governments will all trend ‘less parasitic’ in at least the mid-term. mRNA vaccine production, once fully operationalized, could tip the balance towards much more tolerable relationship.

The book does not offer explicit expectations of what comes after COVID-19. He talked about European life after The Black Death but most of the implications were because of such a substantial amount of death, not because Europeans couldn’t go to bars. Through his telling of history there is not a huge correlation between plagues and technological progress or social progress. Reading the book, though, offers some solace. Humans have struggled, coped, and evolved with parasites and viruses since before humanity. This relationship is not new. As powerful of a force COVID-19 seems today, microparasites of the past have definitely been more influential on human history. At least now we know what they are. McNeill makes an adequately vague prediction about the future:

“For the present and short-range future, it remains obvious that humanity is in course of one of the most massive and extraordinary ecological upheavals the planet has ever known. Not stability but a sequence of sharp alterations and abrupt oscillations in existing balances between microparasitism and macroparasitism can therefore be expected in the near future as in the recent past.”

Meta Micro/Macro Parasitism

The themes from this book that I keep coming back to are not so much in the COVID-19 framework, but more in a Daniel Schmachtenberger way of systems thinking. Thinking a bit more meta about micro and macro parasitism gives a decently coherent model of the world. There are weaker forces and things that when outnumbering an individual extract a certain amount of energy. And there are stronger forces and things that a group of individuals may outnumber but still extract some energy. This eventually looks like a dynamin hierarchy. Millions of virions can make a person sick while millions of people will pay taxes to a government.

This model is enticing because it seems, in McNeill’s narrative, persistent since the dawn of humanity. It also seems a bit Marxist. Like any overarching model of reality, it will overfit and underfit. Regardless, models can be useful or at least beautiful. When picturing this dynamic, oscillating system I keep coming back to a Ranier Maria Rilke poem translated by Joanna Macy:

Widening Circles

I live my life in widening circles
that reach out across the world.
I may not complete this last one
but I give myself to it.
I circle around God, around the primordial tower.
I’ve been circling for thousands of years
and I still don’t know: am I a falcon,
a storm, or a great song?

The most interesting part of this model is how a human, or humans, adapt to these forces. Collaboration and innovation propelled us out of the biological ecosystem dynamic. Once societies reached a density threshold to harbor viruses, customs and religions practices evolved to help control the spread. Once technology created a macroparasitic positive feedback loop by creating forms of control and violence oppression, eventually concepts of democracy and human rights evolved. Eventually collaboration- collective acceptance of human rights or wearing masks- is more important than the newest technology. A collective narrative- a convincing model- is what seems to elevate humanity into a more ‘mutually tolerable’ situation.