Published by EH.Net (February 2022).

Kyle Harper. Plagues Upon the Earth: Disease and the Course of Human History. Princeton: Princeton University Press, 2021. x + 686pp. $35.00 (hardback), ISBN-13 978-0691192123.

Reviewed for EH.Net by Eric Jones, Senior Fellow, University of Buckingham.


Deep in the endnotes to this hefty text, Kyle Harper nails his colours to the mast. It is a slightly obscure place to fly them, given that he is so persuasive about the value of economic history. He draws on the subject for the framework of his final chapters because economic historians do try to find general causes of change, whereas historians of medicine and public health emphasize particularity. We lose sight of the real thrust of change, he says, by focussing on the particular, whether or not it is philosophically acceptable to lump ideas together as ‘Enlightenment medicine,’ ‘public health’ or ‘germ theory’. Because most Western societies successfully adopted similar public health measures, carping that the constructs are artificial is in Harper’s words, ‘to miss the forest for the trees.’

This is a first point about an impressive book. A second point may be less comforting for economic historians, unless they are willing, as he is, to invest heavy-duty effort in understanding the symptoms and medical basis of a number of diseases – it is far from our comfort zone, true, and not for the faint-hearted. Fortunately, a third point is that the accounts of waves of disease are more fluently summarised than I have ever seen in such a long and technical volume. He is a master of the telling phrase (‘mosquitoes are vampires with wings,’ vaccines are ‘externalising the immune system’). I was tempted to think he must have a factory of elves passing him material at the University of Oklahoma, where he is professor of classics, but, no, all 500 pages are his own work.

We are unusual apes, the ‘sneezing ape,’ with an especially heavy load of parasites. Why then are there so many more of us than of other primate species? Harper sees beyond even this puzzle. He asks why it took us so long (in terms of the grand periods he likes to study) to achieve our numerical predominance? These are nice, fundamental questions not addressed in such terms in our usually short-period research, which inclines to take its cues from the interests of contemporary economists. A classicist like Kyle Harper is needed to suggest that we economic historians might find our comparative advantage in broad studies. If one has a hammer, everything starts to seem like a nail. Harper has the hammer of medical history and might be accused of battering all human experience into that shape (for instance, he sees the Thirty Years’ War as an ‘epidemiological event’). That would be a travesty, for no one is better at handling detailed cases while still conveying the broad sweep and discerning penetrating questions about it. If one wants to find fault, he takes at face value one or two fashionable shibboleths, such as that mechanisation was a reflex to high real wages, but they are incidental to his whole scheme.

Harper adopts a wide perspective, even including knowledgeable sections on plant and animal diseases. Some themes stand out but only the scantiest selection can be mentioned here. He points out that introduced European diseases did not have a uniform impact on Native American populations, contrary to the impression given by many sources. He notes that some diseases, endemic in larger places, were actually identified where they arose only intermittently, as with measles epidemics in the Faroes (rubella was first recognised in Australia in a similar fashion). Although it is not a novel insight, he treats the plague as pan-Eurasian but adds that domesticating the horse was the ‘epidemiological fact of the first order’ which made possible the fatal integration of the World Island. Similarly he recognises the disease unification of the tropics, and observes that the knock-on effects of the nineteenth-century globalisation of transport caused gains in life expectancy to stall. Class differences in health had widened between 1650 and 1850, but thereafter social and biological status converged, rather more through a confluence of improvements in public health than the growth of personal incomes. It is a topic where the mindset that elevates economic growth above administrative reform proves misleading.

Economic historians will find it both obvious and disconcerting that, as this book shows, simple economism will not do. As Harper says, diseases come upon us by choice and chance. The latter reflects the haphazard and scarcely predictable arrival of hostile organisms which get through our defences. Choice is a result of how society is set up, its distribution, contacts, age structure, population density and so forth, elements little able to be altered in the very short run but nevertheless deriving from human decisions. Even today there is ten years’ difference in life expectancy between poor and prosperous regions of the United Kingdom, something that could be amended by economic policy without fresh medical interventions. Health and wealth were both part of our ‘Great Escape’ from many earlier scourges but if there was anything like a silver bullet, it was the betterment of habitats and social arrangements. These improvements were partly unintended: the European marriage pattern is credited with helping to raise life expectancies, as was the spread of brick housing. On the other hand, the enforcement of quarantines by larger nation-states was a matter of policy.

The economic consequences of health emergencies may certainly be traced, as is abundantly done here, but although the initial enabling conditions may be detected too, the incidence of disease, notably epidemics, cannot really be predicted in a way that is of practical use. Medical advances have been astonishing but there is no getting away from the fact that our species is tossed by forces substantially beyond our power to forecast or control. Medicine and economic growth have become delinked: life expectancy worldwide has risen far above gains in income. Sadly, there are limits to the economic historian’s professional omniscience. This book extends the range we must consider. It is outstandingly well-written and enlightening.


Eric Jones is a Senior Fellow at the University of Buckingham and the author of Barriers to Growth: English Economic Development from the Norman Conquest to Industrialisation (Palgrave Macmillan, 2020) and Landscape History and Rural Society in Southern England: An Economic and Environmental Perspective (Palgrave Macmillan, 2021).

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