A History of Humanity in Which Humans Are Secondary

A new book tells the story of our past from the perspective of the bugs that have shaped it.

Person made out of DNA strands
Paul Spella / The Atlantic; Wikimedia

Most accounts of humanity’s origins, and our evolution since, have understandably put Homo sapiens center stage. It was our ingenuity, our tools, our cultural savvy that enabled our species to survive long past others—that allowed wars to be won, religions to blossom, and empires to rise and expand while others crumbled and fell. But despite what the schoolbooks tell us, humans might not be the main protagonists in our own history. As Jonathan Kennedy argues in his new book, Pathogenesis: A History of the World in Eight Plagues, the microscopic agents behind our deadliest infectious diseases should be taking center stage instead. Germs and pestilence—and not merely the people who bore them—have shaped inflection point after inflection point in our species’ timeline, from our first major successful foray out of Africa to the rise of Christianity, to even the United States’ bloody bid for independence.

Three years after the outbreak of a devastating infectious disease with a staggering death toll, spending time with a book that vividly details the microbial richness of human history might not rank high on most people’s must-do lists. But those with enough of an epidemiological appetite to pick up Kennedy’s new book will be gratifyingly—if not necessarily cheerfully—rewarded with the knowledge that their read was at least well timed. Epidemics, Kennedy reminds us, are not aberrations in our overstuffed, interconnected, climate-change-fractured world. And when the next one arrives, as it surely will, our response to it will be better if we remember, and avoid, the many mistakes of the past.

Kennedy’s book isn’t meant as revisionism; the broad strokes of history remain intact. But it gently sidelines humans—and, in doing so, humbles them. In the grand scheme of things, he writes, we have far less influence over the fate of our own species than we might like to think: “Very often we don’t make history in circumstances of our own choosing, but in circumstances created by microbes.” Humans aren’t alone, even in their own tale. We’re constantly being puppeteered by our viral, bacterial, and parasitic passengers—simply riding a narrative arc that’s been constantly bent by our bugs.

Consider, for instance, the vanishing of the Neanderthals, one of the early human species that lived alongside and interbred with ours. Neanderthals were once perceived as brutish and dumb—intellectual inferiors who whimpered out after our ultra-brainy species spread over the globe. Decades of scientific findings now exist to refute that notion, showing that Neanderthals were extraordinarily sophisticated—painting caves, lighting fires, even making use of medicinal plants. What snuffed them out wasn’t their lack of smarts but a lack of immunity to the (likely viral) diseases that Homo sapiens introduced to them as the two species mingled.

That same tragic motif plays out repeatedly over some 60,000 years, as Kennedy points to the cast of microbes that played startlingly prominent roles in several otherwise-familiar chapters of our history. Neolithic farmers may have edged out their hunter-gatherer predecessors with the help of hepatitis B, tuberculosis, measles, and a bevy of mosquito-borne viruses; diseases such as typhus and smallpox may have helped turn the tide against Athens in the Peloponnesian War. Spanish conquistadors appear to have been aided in their obliteration of the native populations by smallpox—an inadvertent weapon at least as powerful as any tool forged by hand. And although it’s clear that various sociopolitical factors were key to the ultimate founding of the United States, it’s also a bit fun to cheekily consider malaria-carrying mosquitoes as among the “founding mothers of the United States,” as the historian John McNeill once put it. The parasitic disease—which established itself in the American South prior to the Revolution—killed eight times more British troops than did American guns, potentially enough to substantially tilt the odds.

Other societal forces such as religion and politics have infectious roots too. Horrific bouts of plague, Kennedy writes, were major catalysts for the global spread of both Islam and Christianity—religions that were able to find massive audiences only after large sectors of the global population had died off, and survivors had begun to lose faith in the efficacy of local religious practices. Perhaps Christianity offered a more soothing balm for mortality than paganism at a time when painful deaths were terrifyingly common. And maybe “the lethal effects of Yersinia pestis,” the bacterial pathogen behind the plague, truly were what helped Islam develop into “a major religion practiced by almost a quarter of the world’s population.”

There was little awareness of the deus ex microbe as these events unfolded—which is understandable, given that it took until the end of the 19th century for germ theory to gain traction among leading scientists. But Kennedy makes a compelling case that historical ignorance has left behind some pretty sinister vestiges. Neanderthals, ravaged by disease, are still regularly cast in modern terms as dumb brutes; the native peoples of South America, technologically advanced but beaten down by foreign epidemics, imagined themselves disfavored in the eyes of the gods, who instead took the side of the colonizers who ravaged them with diseases.

Pathogenesis even implicates infectious disease in the reinforcement of—maybe even the genesis of—certain racial stereotypes. West Africans trafficked to the Americas initially labored alongside white slaves and indentured servants. But when diseases ferried over from Africa began to obliterate those lighter-skinned people, the darker-skinned people who’d already built up immunity were spared—leaving a population of almost entirely Black slaves. Abruptly, the region’s conceptions of slavery became linked to melanin, a stereotype that has insidiously stuck. It was a horrible irony: The movement of pathogens put a premium on protection against them—but ended up saddling survivors with horrific consequences. Our notion of superiority over certain groups, Kennedy suggests, is at least as misguided as our smugness about our supremacy as a species in this world.

Kennedy’s point isn’t that we’re powerless against infectious disease. (Nor are microbes unilateral villains: The opening to Pathogenesis painstakingly details the many ways in which the benign ones have benefited us—including aiding the evolution of the placenta, a vital mammalian organ that is thought to have co-opted genetic material from an ancient virus that infected our ancestors.) But, he suggests, humans will remain vulnerable to pathogens’ formidable powers if we continue to ignore them and not learn from the past responses of people in similar circumstances. The ongoing coronavirus pandemic, after all, is not the first time that people have concertedly pushed back against calls for face masks; nor is it the first time the public has bought into lethal misinformation. As Kennedy writes, the cholera outbreaks in 19th-century Europe sparked rumors that the public-health officials and doctors trying to enforce quarantines, travel restrictions, and isolation for the sick were a front—a plot to “poison the urban poor.” Locals rebelled, and governments capitulated, abandoning the very interventions that might have saved countless more lives.

Those missteps are important to keep in mind as we look ahead. Our modern habits are technologically advanced but epidemiologically dangerous. As the globe’s population has grown, infections have gotten easier to spread; as we’ve domesticated animals, we’ve carved new conduits for microbes to travel across species lines. Climate change is also pushing wild creatures into new habitats, where they’re more likely to encounter us. Disease spillovers into humans will keep happening; in just the past two decades, three have occurred with coronaviruses alone. That’s a grim fact to consider. And yet, Kennedy’s book manages to end on a somewhat hopeful note. Yes, our trajectory is defined by microbes. But it’s also influenced by our reactions to them—and our acknowledgment of their power. This current pandemic may be tilting toward a slow end. As much as we may want the crisis to disappear in the rearview, the coda of one outbreak is an ideal time to prepare for the next, inevitably on its way.

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