Fulfilling the Criteria for Early Life on Earth

Abstract

The ‘burden of proof’ needed for the demonstration of the earliest cellular life is very great indeed. Compelling proof requires the demonstration of multiple, in situ and mutually supporting lines of evidence to fulfil the aforementioned criteria: for a wellconstrained age and context; evidence for a morphology unique to biology; and more than a single line of geochemical evidence for metabolic cycling; together with falsification of the null hypothesis of plausible non-biological origins (see for example Brasieret al., 2004, 2005, 2006 and references therein). This section of the book points the reader to the best areas of the world in which to search for signs of early life and the types of rocks to look for, before Chapter 5 discusses the techniques to use to analyse these rocks.