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The Ecological Context: Summaries

How Systems Work
Richard Levins PhD, Harvard School of Public Health

 

Physics was the paradigmatic science of the 19th and early 20th centuries. Its subject matter consisted of a relatively small number of  kinds of things, each with an enormous number of replicates. And it was enormously successful at solving the problems it posed. It also prescribed a methodology and aesthetics for all of science. But the paradigms of physics also mislead when applied to more complex systems where a large number of kinds of objects belonging to very different domains, each with few or no replicates, interact in real historical time. The major failures in epidemiology, agriculture social and economic development came about from construing problems too narrowly, out of context, ahistorically, statically, within too many a priori constraints.        

The paradigmatic sciences of the 21st century will be ecology and organismic biology, including neurobiology. They are above all sciences of complexity. At times complexity seems to be overwhelming. But this is more due to unfamiliarity than to any intrinsic impossibility of understanding complex systems. In what follows some of the guidelines and key concepts for understanding complex systems will be presented and applied to problems of health, agriculture, environment and development.

The truth is the whole. Therefore pose the problem big enough to fit a solution, and always ask “where is the rest of the world?” The epidemiological transition. The Eco-social Distress Syndrome.

The common convenient dichotomies  into which we divide the world are not truly mutually exclusive: biological/social, nature/nurture, scholarship/activism, physiological/psychological, environmental/life style, random/deterministic. Therefore look for how they interpenetrate. Human biology is a socialized biology. The interpenetration of “organism” and “environment”. Commodities as ecological conditions of things.           

Things are snapshots of processes in which opposing forces balance long enough to give a temporary equilibrium and warrant a name.

Things are the way they are instead of a little bit different: the problem of homeostasis, the networks of negative and positive feedbacks. Schmalhausen’s Law. Why pesticides increase pest problems.

Things incorporate their history, but with different rates of erasure of the past. The half-life of experience. Measures of recent and long term nutrition.

Things are the way they are instead of very different because the same networks of feedback also destabilize. The world climate system.

All of the above applies to ourselves as well. We need the self-critical processes that ask why is our science the way it is, why do we do what we do and think about what we think about, and exclude other kinds of questions? Where are we most likely to be mistaken?

       

Symptoms of Distress: Emerging Diseases
Mary E. Wilson MD, Harvard Medical School

New infectious diseases continue to emerge throughout the world. Many of them are zoonoses, infections of animals that have transferred to humans. RNA viruses, which are extremely mutable and adept at adapting to multiple different species, are overrepresented among pathogens causing these new infections. By far the most important infection to emerge in the last century is HIV/AIDS. Ongoing close contact of humans with other primates as pets and through hunting and trade in bushmeat predisposes to transfer of primate viruses to humans.

Emerging infections are heterogeneous in mechanisms of transmission and include infections that are vector-borne, food or water borne, and transmitted directly from person to person. Others are acquired directly from animals or from environmental sources or food contaminated by microbes from animals. So far, with the important exception of HIV, most of the microbes causing these infections have not become easily transmissible from person to person, a characteristic that would allow them to globalize.

Avian influenza is a contemporary example of an infection whose emergence and spread has been fueled by a world with industrial farming (and billions of birds raised for food each year), widely distributed backyard poultry in many countries, and multiple intersecting connections of biota through travel, trade, and migration, leading to a vast and growing animal-(wild and domestic) human interface. A synergy between movement of avian species by migration and trade provides multiple possible routes of entry into new geographic areas of viruses carried by animals.

Many features of the world today: population size, density, location (low latitude), mobility, vulnerability, and demographics coupled with environmental change create an unstable situation that favors the replication and potential emergence of pathogens that are transmissible to and among humans.