Plagues Upon the Earth by Kyle Harper

Reviewed by Ian Lipke

Kyle Harper has written a history, a most unusual history. He does not tell of events that occurred at some specific date but chooses to write in a grand sweep that places events in non-specific contexts such as ‘Mammals in a Microbe’s World’, or he stirs readers’ imaginations in defining the transition from hunting and gathering to farming as ‘Where the Bloodsuckers Aren’t’. While the humour is brash, (‘the worm is in more ways than one, a fluke’ (75)) the author takes his readers on a wild ride through geography, ecology, evolution, and history, and enthralls with the addition of information that, before reading, was not even guessed at.

We shudder when we think of COVID-19, but have forgotten so much of previous pandemics. From Harper, we learn that millennia ago today’s pathogens did not yet exist. We contemplate, when informed, that we have a distinct disease pool and accepts Harper’s mantra that we are part of nature not living apart from it. The central theme of the book is: “human history shapes disease ecology and pathogen evolution; disease ecology and pathogen evolution in turn shape the course of human history. Our germs are a product of our history, and our history has been decisively patterned by the battle with infectious disease” (5).

Harper’s history is an unconscious indictment of mankind’s need to live in clusters. He observes a world infected, through the eyes of our germs. He argues that a human being is simply a host, a means of nourishment and transport, and the human disease pool a bi-product of our success as a species. “The trajectory of human history has been deeply influenced by the patterns of infectious disease” (9). “The flow of energy through ecosystems ensures that rates of population change are controlled by density-dependent mechanisms” (59). Unlike other species, we are unaffected. Our germs are a product of our history.

The book is organised around four energy revolutions, identified as the mastery of fire, the invention of farming (farm animals were regarded as the source of new diseases. That story is incomplete), the regular crossing of the Atlantic Ocean, and the harnessing of fossil fuels. Each revolution is described in exhaustive detail, in complexity that has the reader pondering. Each idea appears new (and often is), and exciting and stimulatory of further serious consideration. The self-regularity of simian populations, the devastation inflicted on mammalian creatures, and ultimately man, by such uncomplicated organisms as the snail, the deeper effects of evolution that science has known about but not seen expressed with such clarity – ‘the deep history of Schistosoma is thus full of contingency across multiple timescales’ (74) – appear as samples of deep scholarship in this remarkable book.

For the deep-grained medical expert, jealously guarding his/her territory, Harper’s book presents a veneer of science. The evidence supporting this view is thin. For the general reader and the non-specialist scientist, Harper provides answers that satisfy. Intellectualism, that formerly dwindled through the regurgitation of stale concepts, now receives an injection of fresh and fertile ideas. Harper’s invoking of genetics and his ‘tree-thinking’ (which studies the evolution of micro-organisms) and his ‘time travel’ or palaeogenetics, wherein he investigates aDNA — ancient DNA, makes exciting reading. The use of genetics provides readers with a view of the history of disease from the point of view of the pathogen.

Harper does not treat in any depth the practice geneticists adopt as an extension of the ‘time travel’ conceptualization. I refer to ‘tracking’. Built on the thousands of genomic sequences gathered from many parts of the world comes the ability to track diseases across space and time. However, Harper refers only obliquely to this issue under the discussion of globalisation.

A planetary perspective helps to untangle the relationship between disease and globalization, Harper proposes. (11) Globalisation is a major theme in the history of disease, he alludes, because transportation technologies and human movements have repeatedly intersected the evolution and transmission of infectious diseases. While this may be true enough it is only part of the story and in not addressing the rest, Harper does his argument a disservice. Not mentioned, perhaps not known, is the extent of disease before the arrival of Europeans – other research has shown that pre-contact lineages are extinct. The question to what extent is ancient endemicity responsible has never been resolved.

Harper lists the typhoid and paratyphoid diseases as “quiet, persistent killers” that “for millennia” have haunted human communities. He suggests that these diseases emerged as a specialist human pathogen in Europe around the time of pig domestication — in other words, as much as 10,000 years ago. This statement has been disputed, some scientists counter-arguing that current “tree thinking” indicates that the strain of Salmonella Harper refers to, diverged from strains circulating in pigs sometime around the late ninth century.

For our purposes, since scientists will always argue about specialized bits of knowledge, our focus must remain on Harper’s contribution to the history of mankind on earth through specific means not normally invoked. Harper notes that “Covid 19, of course, has changed the stakes and made itself evident that infectious diseases retain the capacity to upend our lives…The story of disease can help us understand how we came to be where we are, and possibly help us to decide where we want to go” (15). Few would disagree.

Completing the reading of this book leaves one with more than a feeling of satisfaction. Admiration for a major task that was written in an engaging style that retains a facile elegance throughout its 700 pages, that presents comprehensive and detailed information as though it were the sort of material that readers come across every day, is what one might not expect, but welcomes, in a serious work of this size.

A fine publication.

Plagues Upon the Earth


by Kyle Harper

Hardback (B315) | Dec 2021 | Princeton University Press | 9780691192123 | 696pp | 234x155mm | GEN | AUD$49.99, NZD$57.99

NewSouth Books


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