The Making of Paleontological Time

Abstract

Usually, the notion of time shared by paleontologists is an arrow. Hence, time is a synonym of duration, either when discussing questions relevant to one thousand years or to a billion years. Geological time, or “deep time”, is a simple concept. This concept of time has been built from lithology and from the study of faunas and floras inside these lithologic layers, or, differently said, from fossils. Stratigraphy, as a science, rests on lithology and fossils. Modern methods which produce radiometric dates (absolute ages) confirmed two centuries of stratigraphers’observations and speculations. Nevertheless, comparison of the linear time of geology and the branching time of living beings is a source of severe difficulties. Although they seem familiar, the relationships between life and time, between differentiation and duration, or between evolution and chronology are rather complex. Time and fossils are less secure allies than usually thought. The deployment of living beings in the temporal dimension creates multiple parallel durations and independent developments. Hence, the historical reading of the tree of life and the interpretation of geological time are not immediate. The notions of hierarchical time and of temporal paralogy developed in this paper, demonstrate these difficulties, often underestimated.