EMERGENT PATTERNS: THE LIVING FOSSIL MENAGERIE AND THE CONCEPT OF STASIS

The moniker ‘living fossil’ and its congener terms have been applied to viroids, ribozymes, proteins, genes and gene families, organelles, cell types, species, taxonomic groups with few to many species, even gene pools of human ethnic groups—a menagerie of exotic entities across domains of life and many levels of the biological hierarchy. More than 150 years of discussion has yielded no more than a conceptual conundrum against a background of expectations. But what are those expectations; which of the many varied parameters of living fossils and stasis have shared scientific meaning beyond rhetoric; of these, which can be quantified and tested? To address these questions, we examined nearly 400 scientific papers from Darwin’s Origin in 1859 through today. Living fossils and stasis are explicitly comparative concepts, and patterns emerging from our study reveal areas of conceptual confusion most critically in need of revision, especially attribution of taxonomic stasis vs. character stasis, whether historical entities in a comparison share a common relationship to a specific higher level (or part of a level) in a biological hierarchy, reflecting a common genealogical history, and which defining parameter (or several) has valid scientific meaning. Living fossil concepts are more often a categorization, whereas the conceptual components of stasis play an evidentiary role. Our results lead us to conclude that no one concept of living fossils or stasis will do. Inevitably, these concepts are always contextual. Defining an entity as a living fossil or example of stasis requires defining the conceptual parameters as well.