Thursday, September 28, 2006

The Phanerozoic fallacy

«   Part 7 of the series, Genesis for the rest of us   »

Plague bacteria

The Phanerozoic eon encompasses the 545 million years of geologic time since the emergence of diverse hard-shelled animals. The Phanerozoic takes its name from the Greek term meaning visible life and refers to the large size that organisms have attained since the Cambrian explosion.

The term Phanerozoic can also describe the assumption that environmental law begins and ends with protection of only those things visible to the naked human eye. Genesis' listing of plants and animals involved in the creation reinforces and arguably inspires this fallacy. In addition to "great sea monsters and every living creature that moves" in the seas Genesis mentions only flowering plants, birds, and cattle, "creeping things," and "beasts of the earth."

The failure to account for invisible life generates a massive register of shortcomings in environmental law and risk regulation. And because salient evidence dominates human assessments of risk and value, we remain what journalist Jay Ingram has called "slaves of the macroscopic" who "fail[]to appreciate the overwhelming domination of the microbial." This failure puts us in extreme peril, not only as a scientific matter, but also as a matter of simple survival.

The smallest life forms express the greatest variety, often through minute genetic differences. Consider Yersina pestis, the bacterium responsible for bubonic plague. (It's depicted above under 2000x magnification and fluorescent staining.) Y. pestis evolved from and is very closely related to Y. pseudotuberculosis, a bacterium that causes a much milder enteric illness. Y. pestis is transmitted to humans by fleas that have fed on infested rodents, while Y. pseudotuberculosis is transmitted through contaminated food and water.

The major difference between the two bacteria appears to be an extrachormosomal gene coding an enzyme in Y. pestis that enables this bacterium to thrive in the flea's midgut. Plague arises when a bite from an infected flea delivers a large number of Y. pestis bacteria into the bloodstream. See generally Mark Achtman et al., Microevolution and history of the plague bacillus, Yersinia bacillus (2004).

The point is not that Y. pestis deserves protection from human activities -- quite the opposite -- but that humans have great difficulty perceiving biological variation on a small scale, let alone articulating politically persuasive reasons for preserving it. Each human hosts 500 to 1000 microbial species, yet the precise interaction between humans and bacteria eludes complete understanding. See Michael S. Gilmore & Joseph J. Ferretti, The Thin Line Between Gut Commensal and Pathogen, 299 Science 1999 (2003).

Next in this series: Mother superior.


Anonymous Patrick S. O'Donnell said...

The points raised in the last paragraph may go some way in accounting for the initial resistance to acknowledging the bacterium Helicobacter pylori as the primary cause of peptic (gastric and duodenal) ulcers. For a provocative discussion that relies on the discovery of H. pylori and the hypothesis that these bacteria routinely colonize human stomachs as a case study, see Paul Thagard's How Scientists Explain Disease (1999).

And might this be related to what others have termed our penchant for reliance on 'basic-level categories.' As Lakoff and Johnson have noted (Philosophy in the Flesh: The Embodied Mind and Its Challenge to Western Thought, 1999; I find the subtitle a bit pretentious), our reliance on such categories reveals an optimal fit of sorts with our bodily experience of entities and salient differences that exist in the natural environment (i.e., the 'folk version of biological genera'). They account for this, for example, by claiming that basic-level categories are consonant with the ease with which we can form the relevant mental images (e.g., in one direction: you can get a mental image of a chair, but not one of generalized furniture). While I'm not always fond of the philosophy of mind assumptions at work here, I think there is something to this account of how we routinely generate categories and concepts from our earliest 'bodily' encounters with objects in the world in a way that inhibits our ability to do such things as 'perceive biological variation on a small scale.' In addition, common cognitive heuristics might play an explanatory role here....

9/28/2006 7:29 PM  
Blogger Toonzie said...

If you haven't yet I recommend you read a book called Tears of the Cheetah by Stephen J. O'Brien. It tells a series of stories about the ways in which molecular biology and genetics have been use to understand and address the problem of endangered species.
You can read more about it Here.
If you are interested I'll be happy to loan you my copy.

10/01/2006 12:54 PM  

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