That post was one of our ten most popular links of 2018, she is very good at what she does.
From the Los Angeles Review of Books:
THERE HAS BEEN a lot of imperfect thinking about disease the past two
years. As the world has collectively experienced a throwback to an era
without the protections of effective medical interventions, more broadly
conceived histories — true pandemic histories — are hard to find. Many
of the bigger questions have gone unanswered, and sometimes unasked.
Where do infectious diseases come from? When and how do they disappear?
Have there been times or circumstances when disease burdens were heavier
or lighter? Where do we, in our present COVID-19 moment, sit within
that history?
Billed as “a monumental history of humans and their germs,” Plagues Upon the Earth: Disease and the Course of Human History
by Roman economic historian Kyle Harper offers an opportunity to
consider what “good thinking” in disease history might look like.
Harper’s background as a Classicist, as well as his demonstrated interest
in the new ways climatology and genetics enable reinvestigation of
Roman history, would, one might expect, situate him as a welcome new
interpreter of humans’ encounters with disease. Plagues Upon the Earth is
a book meant to impress. The notes run to nearly 60 of its 700 pages,
the list of references to nearly 90. In all, over 2,100 references are
cited. Surely this is the global history the world has needed.
Presumably, we will find a story that differs significantly from the
half-century-old accounts of Alfred Crosby and William McNeill,
who wrote in the pre-AIDS 1970s about infectious diseases as
history-altering forces. Given the extraordinary strides in global
historical thinking in the same half-century, one would especially hope
to see framings beyond a European focus. These hopes are only partially
fulfilled.
Harper’s thesis is simple: “Our germs are a product of our history.”
By that, he means that different infectious diseases have arisen at
different inflection points in humans’ collective journey on the planet,
often due to human behaviors themselves. The oldest diseases, such as
gastrointestinal parasites, date from our time as hunter-gatherers.
Sedentism and domestication of animals brought other types of pathogens,
as did the new respiratory environments of increasingly crowded urban
communities in the Bronze and Iron Ages. The interconnected world of
medieval trade intensified disease spread in Eurasia and Africa, while
the unification of the world’s tropical zones during the age of European
colonialism allowed additional diseases to spread intercontinentally.
Finally, new sources of energy and new transportation technologies of
the 19th and 20th centuries allowed the speed of spread to increase
nearly a hundredfold, even as urban communities (the ultimate microbial
playgrounds) grew ever larger.
Figure
1: A fragment of the Hippocratic oath on the third-century CE Papyrus
Oxyrhynchus 2547, Wellcome Library (Image via Wikimedia).
The history of infectious diseases is one of the more difficult
fields within the history of medicine. The documentary record on which
it is grounded has inherent limitations. In, say, the Hippocratic Corpus
or Ayurvedic traditions (composed in a pre-laboratory age when
observation of microorganisms was impossible), the disease conceptions
differ so much from germ theory conceptions that, in the absence of very
precise symptom descriptions, it is impossible to translate past
categories into modern terms. This is known as the problem of
retrospective diagnosis.
For the material history of disease, paleopathologists (a sister
subspecialty within physical anthropology) can look at lesions created
on bones or teeth by chronic health conditions, such as malaria or
sustained malnutrition. But microorganisms are impossible to discern
even with a microscope, since they (like most soft tissues) are
destroyed as postmortem decay sets in. A quick-killing disease like
plague could never be assessed from ocular examination of the bones
alone.
Riding the crest of a decade-old shift in infectious disease
research, Harper exploits a new generation of scholarship that engages
openly with data yielded by genetics. Why genetics? Harper cutely
describes the twin contributions of this field as “tree thinking” and
“time travel.” Nicknames notwithstanding, this is high-tech science of
the first order.
“Tree thinking” is phylogenetics, which analyzes either whole genomes
or partial genomic sequences to find common variants in different
lineages of pathogens. Simply put, it studies the evolution of
microorganisms. Tuberculosis (TB), for example, has nine known lineages,
each with many localized strains. Analyzed one against another, these
variants allow construction of phylogenetic trees — family trees
showing, for example, how closely related a strain of tuberculosis in
India might be to a strain in the Philippines or Ethiopia. (It’s a pity
that a book with more than two dozen images, figures, maps, and tables
couldn’t have offered a single figure showing how visually-oriented “tree thinking” analysis works.)....
