American Scientist

THE STOCKHOLM PARADIGM: Climate Change and Emerging Disease. Daniel R. Brooks, Eric P. Hoberg, and Walter A. Boeger. 409 pp. University of Chicago Press, 2019. Cloth, $120; paper, $40.

At first glance, The Stockholm Paradigm: Climate Change and Emerging Disease, by Daniel R. Brooks, Eric P. Hoberg, and Walter A. Boeger, may seem to be just one more in a spate of books about human impacts on the environment. But in fact, it is a singular hybrid: a critical history of science, describing paths taken and not taken; a technical work of analysis and theoretical synthesis; an agenda for research and for policy; a critique of institutionalized science (and of scientists); and a confessional exploration of the interplay of inquiry with fear and hope.

Brooks, Hoberg, and Boeger are parasitologists, and their field of study includes not just the traditional macroparasites (worms and arthropods) but all pathogens, including viruses. They have undertaken to write this book, they say, because we are in a mess: Emerging diseases are increasing, we are massively ignorant of potential pathogens, and we are in denial about the extent of the threat we face.

The book takes as its departure point a failure: More than a century has passed since the germ theory of disease became widely accepted, but only recently have scientists begun to consider parasites and infectious agents in ecological and evolutionary terms, after long neglecting to do so. When Charles Darwin explicated the dynamisms of evolution, he stressed intraspecific competition; he thus concluded that hosts and parasites evolved separately, rather than through a struggle resulting in mutual modification. At the same time, biomedical scientists, including early bacteriologists, were so fixated on pathogenicity that they defined parasite species in terms of their hosts, ignoring both ecology and evolution altogether. The authors note that the medical press, and even parasitology journals, took little notice of Darwin’s death.

Later on, the theorists who began to take up the evolution of parasite-host relations emphasized the coevolution of parasites and hosts, characterizing them as being engaged in an “arms race” in which each becomes more specialized in its adaptation to the other, leading to a relatively benign coadaptation. These theorists have depicted parasites as “extreme ecological specialists,” who, as they coevolve with their hosts, become less able over time to switch readily to a new host—an inability that serves as a “fire wall” against emerging disease. In addition, the view of classical geneticists that mutations are random, and that virulent varieties simply appear, has led these theorists to assume “that a pathogen can colonize a new host (emerge) only if it experiences genetic mutations that allow it to adopt the new host.” This coevolutionary paradigm is flawed, however. There is no fire wall: Host-switching is happening all of the time in altering habitats, and climate change is accelerating it. An alternative explanatory framework—a new paradigm—is therefore needed to resolve this “parasite paradox.”

The authors have come up with such a framework—a complex reconceptualization of host-pathogen relations that they refer to as the Stockholm Paradigm. They never define the term precisely or explain how they chose the name. But they do demonstrate that the framework leads to predictive successes, can be used to transform anomalies into expected phenomena, and can serve as a source of suggestions for research-based action.

Their new paradigm takes into account natural-historical data on parasite evolution, parasite-host relations, and the nature of the parasite itself—data that have been confirmed by genomic mapping. The paradigm has an ecological agenda and adopts a distinct perspective: the point of view of the parasite, which needs to find hosts, because hosts are among its “conditions of life.”

Pathogens and parasites respond to their situation with two types of activity: exploitation of existing hosts and exploration, the seeking of new hosts (behavior that is especially evident in eras of environmental change). Rather than being tightly adapted to a single host, parasites have capacities that make it possible for them to exploit many different hosts, even ones to which they may not be optimally adapted. In other words, their fitness space (the environment in which they can survive and reproduce) is what the authors refer to as sloppy. When conditions change, the parasite needs to be able to explore the new circumstances in which it finds itself in order to locate new viable fitness space. By oscillating between exploitation (specialization and isolation) and exploration (generalization and expansion), the pathogen occupies a maximum amount of available fitness space. At the heart of the Stockholm Paradigm, therefore, is the authors’ claim that “the evolutionary potential of pathogens is immense, and they can take advantage of opportunities rapidly under a variety of conditions.”

The book opens with two introductory chapters that are diagnostic and historical. The next five chapters present and defend the new paradigm. The final three chapters concern our plight (unpreparedness for emerging diseases) and possible actions we can take (we can accept unpalatable truths, make plans, develop infrastructure, inventory and surveil pathogens, make lifestyle changes, and cooperate with one another).

What makes the book unique is the depth and breadth of the authors’ criticisms and reflections. They acknowledge that science has been “an essential source of solutions,” but they criticize its institutions and practices for having impeded progress. They object to structures that promote individual achievement over cooperative response, and to criteria that value the specialized over the general. In classic failing-paradigm language, the authors reflect on knowing more and understanding less at the end of the 20th century. They blame disciplinarity and rivalry. They deplore stove-piping, a narrowing of audiences for one’s work that leads to “lack of communication and collaboration among research programs with common interests.” They criticize scientists, too, for mongering gloom rather than taking action, and for cynically treating crises as funding opportunities.

The book’s three closing chapters transition from the descriptive to the normative—from “how the world is” to “What shall we do?” Although any application of science involves making such a transition, these authors don’t just follow the common practice of focusing on what policy makers must do; they also make the exploration personal, turning it into a dialectic between looming doom—“an existential crisis”—and a feverish “hope” that “breeds” new science. Calling on biologists like themselves to be “the adults in the room,” they seek to walk the fine line between immediacy and panic. Given the intrinsic adaptability of parasites and pathogens and its acceleration by climate change, they predict that “our species is going to experience a population correction” from epidemic disease.

The Stockholm Paradigm was published six months before the start of the current pandemic. The authors’ sobering projection of the effects of a return of a Spanish flu–like virus was timely, but it also reminds us that COVID-19 is not as lethal as the next new flu may be.

An explanatory framework is needed to account for the fact that pathogens in altering habitats are switching hosts at an increasing pace. 

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The authors chastise the complacency of many: the world, for ignoring the warnings in the 1972 report The Limits to Growth; clinicians, for just treating “flu-like” symptoms rather than systematically culturing agents; and unnamed “conservation biologists,” for ignoring “the evolutionary nature of the biosphere” and focusing instead on “a perceived need to preserve existing diversity”—or on trying to return the biosphere to some mythical former pristine state.

The authors warn of the dangers of common activities such as air travel and visiting urban green spaces—activities that place one in proximity to pathogens and parasites hosted by other mammals or by birds. In addition, they call for a global campaign of surveillance: parasite hunting, with follow-up genomic assessments to anticipate especially dangerous unions with hosts in time to intervene.

Their enthusiasm for such a program is coupled with an admission that it is a long shot and does not quell despair. The authors admit to having passed through Elisabeth Kübler-Ross’s well-known stages of grief over our impending deaths (ending in acceptance), even as they deplore the defeatism of a “Cassandra Collective” of late-career environmental scientists who have lost hope and left public life. In many ways then, the book goes beyond “existential crisis” to become a work of scientific existentialism (although it is hard to imagine Jean-Paul Sartre putting a flow chart on the penultimate page of a book, as these authors have done).

As a challenge both to science and to scientists, this book is impressive in its ambition. As a historian, I am most impressed with its reconstruction of the roads not taken, the disjunct of medical from biological science, the aloofness of health specialists toward evolution. The Stockholm Paradigm itself seems to me to be confirmed. It is common nowadays to recognize that genomes are rich with capacities that may be expressed only in certain situations— capacities that make possible the sort of exploration by pathogens that the book describes. On matters of response, I commend the authors both for their forthrightness in voicing inconvenient truths about science and scientists, and for recognizing personhood as the ultimate ground of public action.

Yet ultimately the book is not broad enough. The limitations are both in sensibilities and in analyses. Given the vehemence of the attack on stove-pipe disciplinary perspectives, it is both striking and disturbing that the authors’ response is disciplinary. The prose with which they present their campaign mixes broad participation (“grassroots and bottom up”) with military metaphors, from “boots on the ground” to command and control (“everyone must contribute”), thereby evoking a “dictatorship” led by parasitologists.

Nothing so sinister is on offer, however. Taking one’s own medicine is no easy matter. Disciplines do discipline, determining the ways we see and interact. Here we see a particularly expansive parasitological view. We see too the history of the unique and sometimes ambiguous field of parasitology, lying at the interface between ecology and the applied health and agricultural sciences. The ambiguity is evident here as a tension between ecological assessment and practical action. The authors endorse the view (expressed in the 1930s by Russian parasitologist Aleksandr Aleksandrovich Filipchenko) that “parasite” is not a natural kind, and that an organism should not be defined in terms of its relation to another (the host); yet they later declare that, for them, “the world is populated by two kinds of species—pathogens and hosts.” And a biocentrism such as Filipchenko’s would forbid the lack of consistency the authors display in treating plant-eating insects as parasites while treat ing plant-eating people only as the hosts of other parasites. Fortunately, disciplinary context does have the advantage of making the authors’ grand campaign seem less menacing: Coordinated surveys relying on lay volunteers are common in natural history; birding is the exemplar.

The authors’ attempts to reach beyond parasitology are commendable, but fragmented. Their 89-page bibliography consists mainly of parasitology articles. Institutions, both formal and informal, have important roles to play and would seem to be the only means by which analysis can avoid despair, but they receive little attention here. The authors’ main excursions into the history of ideas (the legacy of Kant, philosopher Susan Neiman’s revisionist history of theodicy in Evil in Modern Thought) are unhelpfully broad and are no substitute for a discussion of the loci of power, the intricacies of making and implementing policy, the bases of community action, and the historical record of public health. The authors depict scientists’ inaction in terms of the evolutionary heritage of primates, comparing it to freezing in one’s tracks on sensing a big cat. That’s a vivid analogy, but it hardly suffices as explanation: It ignores postwar policies that shaped scientists’ career structures and public roles. Likewise, to blame crotchety postmodernists for failure to respond to the Limits to Growth report ignores political and economic interests, and contestation from countervailing cornucopian models. Lacking such analyses of the political economy of science, the authors’ critique of science and scientists might be too easily dismissed as sour grapes from an underappreciated discipline, or as a simple venting of familiar frustrations.

Perhaps the largest absence is of public health itself. Long before disease vectors were recognized, towns were responding to approaching plague with rodent removal campaigns, and persons in malarial areas were covering their skin and avoiding evening outings. Although greater surveillance of pathogens may be valuable, to hope for deliverance through informed preemption may be too high a bar. The thrust of the Stockholm Paradigm proposals will be to increase the number of variables relevant to the study of pathogen-host relations; what will limit the number of variables is less clear. The authors do not get far into the complexity of gene expression, nor do they go into matters of horizontal gene transfer, such as those that affect cholera virulence. Fortunately, generic public health practices are not incompatible with continued investigation. And as has been repeatedly noted with regard to climate change, the call for more complete knowledge need not be a barrier to taking action.

Caveats aside, The Stockholm Paradigm is a groundbreaking book with regard to both genre and substance. We do not expect reflection, much less despair, from scientists; “personal” accounts are usually fluff. Will the book be read? As a hybrid, it will necessarily challenge readers used to familiar genres. I hope, however, that this mix of sophisticated theory and profound reflection will go far to set a paradigm of its own.