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 "failto 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.