Pathogenesis by Jonathan Kennedy review – in sickness and in health

A fascinating account of how diseases have shaped humanity, from the neolithic to Covid-19

The Covid-19 pandemic has wreaked extraordinary destruction and misery, killing nearly 7 million people worldwide thus far and devastating the lives of many more. And yet, viewed through the long lens of human history, writes the public health sociologist Jonathan Kennedy, “there is little about it that is new or remarkable”. Previous pandemics have killed many more, both in absolute numbers and as proportions of populations, and so may future ones. Covid should be a wakeup call that helps us manage deadlier plagues in the future. But will we heed it?

Our very existence and success as a species, Kennedy argues in this fascinating book, has been shaped by bacteria and viruses. Where, for example, did all the other species of humans go? At one time, early Homo sapiens shared the Earth (and interbred with) the stronger, larger-brained and equally artistic Neanderthals, as well as the hobbit-like Denisovans. What happened to them? It could be, as some argue, that we simply killed them all, or that they were somehow less well able to adapt to climate change. But Kennedy explores the possibility that roving Homo sapiens from Africa, who had acquired strong immune systems on their travels, might have simply infected the already settled Neanderthals of Europe with a novel pathogen that they couldn’t fight off – just as the colonising Spanish, tens of thousands of years later, decimated the Aztec population with smallpox as much as with weapons.

A similar dynamic repeats itself over and over in human history, in Kennedy’s telling, even if some of the details remain speculative. Why, for example, were dark-skinned Neolithic hunter-gatherers such as the celebrated “Cheddar Man”, who first settled the British Isles after the last ice age, replaced throughout Europe by light-skinned farmers of Mediterranean origin? “The most likely answer,” the author suggests, is that the farmers carried infectious diseases to which they had, over time, become immune, but which devastated the indigenous populations. Those farmers were in turn almost completely replaced by another wave of migrants, shepherds from the Eurasian steppe – thanks, perhaps, to a Neolithic wave of bubonic plague in Europe. Kennedy does not shy away from emphasising the point most relevant to modern politics: “Contemporary Europeans are neither genetically ‘pure’ nor are they the region’s indigenous people.” Modern genetic analysis shows that even the people who built Stonehenge were completely wiped out and replaced by a new wave of migration. As Spinal Tap so clairvoyantly put it: “The druids. No one knows who they were, or what they were doing.”

We can be more confident, at least, about the geopolitical effects of disease once we enter the era of written history. An epidemic of either typhus or smallpox devastated Athens from BC430, which “undermined Athens’s capacity to fight against the Spartans and had a profound impact on the course and outcome of the Peloponnesian War”. A series of plagues beginning in 65AD, meanwhile, might have weakened the Roman empire to an extent that contributed to its eventual fall. Medieval waves of the Black Death, it is salutary to be reminded, killed astonishing numbers of people – as much as 60% of the entire population of Europe succumbed in a single decade of the 14th century.

The subsequent introduction of rules of quarantine and cordons sanitaires, Kennedy argues, can be seen as marking the beginnings of the modern state, extending as they did its power into ordinary human life in unprecedented ways. Meanwhile, the shortage of agricultural labour caused by devastating recurrences of the plague was perhaps instrumental in the collapse of feudalism in favour of a capitalist system of flexible employment. Later on, the susceptibility to malaria of northern soldiers in the American civil war “probably delayed victory by months or even years”, possibly giving Lincoln time to come round to the idea of abolishing slavery.

The book thus performs that satisfying trick of encouraging the reader to think differently about familiar topics, though its ideas are inevitably variable in their persuasiveness. Among the most conjectural, for example, is the suggestion that the rise of Christianity in the imperial Roman era might itself have depended on the prevalence of disease, because of its consoling message. “The Christian faith skyrocketed because it provided a more appealing and assuring guide to life and death than paganism during the devastating pandemics that struck the Roman empire in the second and third centuries CE,” Kennedy suggests. Well, maybe. But the conversion of Constantine, briefly mentioned on the same page, was surely the nearer and sufficient cause.

There is, too, occasionally a slightly po-faced attitude to Kennedy’s discussions, as when he cites the “What have the Romans ever done for us riff” from Life of Brian. (There is “something unsettling about a group of white, Oxford- and Cambridge-educated men extolling the virtues of colonialism, albeit for comedic effect,” he complains piously.) And the depredations of “capitalism” come to figure, in this story, as a villain as evil as any virus. The economic growth driven by the Industrial Revolution, Kennedy claims, did not, as is usually thought, increase welfare through improved living standards, though here his disagreement seems to be merely about timescales. (It didn’t overall at first because many of the new cities and working environments were filthy and unsanitary, but it sure did in the long run.)

The author seems to approve considerably more of capitalism with Chinese characteristics, celebrating the undoubted improvement in living standards of many millions of people in China over the last few decades. He is also curiously happy to accept the official Chinese figures on Covid death rates in order to argue that the US and “liberal democracy” in general are not obviously superior systems.

Kennedy is convincing, though, in his emphasis on the way that disease can intersect and interact with social inequality, both globally – most sub-Saharan Africans remain unvaccinated for Sars-Cov-2, the rich countries having kept multiple doses for their own citizens – and within countries, where health outcomes are shockingly dependent on socioeconomic status. What is sometimes called “shit life syndrome” will harm you as surely as many infectious diseases, and “pathogens thrive on inequality and injustice”.

So what will we do now? Perhaps, as Kennedy suggests, the recent, comparatively mild pandemic will cause us to rethink “how humans see their place in the world”, to stop creating super-pathogens with our incontinent use of antibiotics, and to realise that “if we Homo sapiens don’t strive to live in balance with the other living things on our planet, we face a very bleak future”. That, however, is a tall order, and not just politically. Bacteria alone make up an estimated 13% of the biomass of Earth, while humans represent a mere 0.01%. In the war against disease, we are massively outnumbered.

• Pathogenesis: How Germs Made History is published by Torva. To support the Guardian and Observer order your copy at Delivery charges may apply.


Steven Poole

The GuardianTramp

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